1986 B2 2.9L acceleration hesitation

[Jbrownjr]

Muchas Gracias for all the help in getting this beast to run! Next challenge: acceleration hesitation.

She'll start right up. Idles pretty well on it's own. (It's been sitting for months, and stale fuel is a potential. We added high-octane fuel about a month ago to hopefully help; but putting that out there.

Under the hood, when we push the throttle, it'll rev a bit, but almost immediately chokes as if it's fuel or air-starved.
Since we've been here before (trying to solve this very problem), I did notice a recommendation to replace the Engine Temperature Control (ETC) sensor. It's months old.
IAC has been changed within the past year as well (although it's idling alright). We've replaced quite a few components under the hood trying to get her to run well enough to drive.
About 6 months ago we ran into a wall and took it to a local (ex-Ford-dealership) mechanic. He spent a few weeks on it, and fixed a few things, but it was running about as good as it does now. It limped home about 10 miles from that 'hospital' stay.

(Funny story...she'd backfire now and again, and about a mile from home actually caught fire on the underside. Fire dept put that out, and she drove home the next day. Exhaust hangers melted, fuel vapor line melted; but otherwise no real damage.)

So back to basic troubleshooting...where would y'all suggest we look first to troubleshoot this acceleration hesitation?

 

[Tiha]

So it will die if you are just holding the throttle open?
Or do you have to be driving?

Will it come out of it? Or continues to be a dog?

What about plugged exhaust? No idea jut threw it out there.

 

[L\Bronco]

Muchas Gracias for all the help in getting this beast to run! Next challenge: acceleration hesitation.

She'll start right up. Idles pretty well on it's own. (It's been sitting for months, and stale fuel is a potential. We added high-octane fuel about a month ago to hopefully help; but putting that out there.

Under the hood, when we push the throttle, it'll rev a bit, but almost immediately chokes as if it's fuel or air-starved.
Since we've been here before (trying to solve this very problem), I did notice a recommendation to replace the Engine Temperature Control (ETC) sensor. It's months old.
IAC has been changed within the past year as well (although it's idling alright). We've replaced quite a few components under the hood trying to get her to run well enough to drive.
About 6 months ago we ran into a wall and took it to a local (ex-Ford-dealership) mechanic. He spent a few weeks on it, and fixed a few things, but it was running about as good as it does now. It limped home about 10 miles from that 'hospital' stay.

(Funny story...she'd backfire now and again, and about a mile from home actually caught fire on the underside. Fire dept put that out, and she drove home the next day. Exhaust hangers melted, fuel vapor line melted; but otherwise no real damage.)

So back to basic troubleshooting...where would y'all suggest we look first to troubleshoot this acceleration hesitation?

You mentioned in the other thread that you pulled codes, I suggest that you do a key on engine running test with your scan tool (Or whatever method you are using to read the codes.) The KOER test checks the functionality of many control systems on the engine (Fuel control, idle control, spark control, ect... It can often give very large clues to running issues.
I agree with Tiha, exhaust restriction is a possibility for sure, also check the MAP sensor and the vac hose that feeds it. The sensor is difficult to check, (I don't want to load the parts cannon, but trying a known good one is the easiest way to verify MAP) The map sensor tells the pcm how much load is on the engine, If the MAP isn't reporting load, the mixture will go extremely lean and wont recover.
A bad TPS can give a hesitation, but it usually only lasts a moment as the throttle is moved, The engine will recover if the throttle is held still.
Hope that helps
Cheers

 

[goodO1boydws]

Just thought of something that I don't remember seeing in the troubleshooting saga.

Have you thought of the knock sensor possibly having gone bad, or checked to see if its connection is good? It's something that is usually so reliable one can last practically forever and be something that most people overlook.

But a bad one can cause hesitation.
And backfiring, which you just wrote about AGAIN as happening before the fire-which was from underneath.

Another problem stemming from a failed/non-functioning knock sensor is potential catalytic convertor problems, as its failure default is usually to have the engine run rich, which can lead to clogging and extreme temperature rises in the cat and the exhaust system in front of it.

(I once had a clogged one getting so hot it was literally red hot, but the smell of melting/cooking undercoating and paint alerted me in time. )
-------------------------------------------

And to clarify what L/Bronco just wrote:

"A bad TPS can give a hesitation, but it usually only lasts a moment as the throttle is moved, The engine will recover if the throttle is held still."

If its ONLY a bad TPS, the engine will usually recover/run normally if the throttle is anywhere OTHER THAN IN the TPS's bad spot.

(The most common range for the TPS to be cutting out is in the rpm range where the engine spends the greatest amount of time-which is usually just off idle or fairly low in the rpm range.)

 

[Jbrownjr]

So it will die if you are just holding the throttle open?
Or do you have to be driving?

Will it come out of it? Or continues to be a dog?

What about plugged exhaust? No idea jut threw it out there.

It shudders a bit, but won't die. We haven't driven it yet...remembering the last time it behaved like this, we ended up doing 15-20mph around the neighborhood. It drives, but really lacked power.

Troubleshooting the exhaust (clogged cat?) I removed the cat. It's a little crumbly at one end, but not completely shattered. No longer part of the equation at this point.

 

[Jbrownjr]

You mentioned in the other thread that you pulled codes, I suggest that you do a key on engine running test with your scan tool (Or whatever method you are using to read the codes.) The KOER test checks the functionality of many control systems on the engine (Fuel control, idle control, spark control, ect... It can often give very large clues to running issues.
I agree with Tiha, exhaust restriction is a possibility for sure, also check the MAP sensor and the vac hose that feeds it. The sensor is difficult to check, (I don't want to load the parts cannon, but trying a known good one is the easiest way to verify MAP) The map sensor tells the pcm how much load is on the engine, If the MAP isn't reporting load, the mixture will go extremely lean and wont recover.
A bad TPS can give a hesitation, but it usually only lasts a moment as the throttle is moved, The engine will recover if the throttle is held still.
Hope that helps
Cheers

KOEO: 87 (I am grounding the fuel pump at the ODBI connector to get the pumps to run. Initially I suspected the Fuel pump relay, and we're still bypassing it, so I have a feeling that code is confirming the obvious)

KOER: "3" KOEO codes start with the baseline 'flicker', then repeat the code twice, then the ending 'flicker'. KOER...no repeats. I have to catch this right after it's started, and I only get a "3". I'm wondering if that means "30"? If so I found "Cylinder #3 failed balance test"
Based on this video (

) it doesn't seem that hard to diagnose. (I already confirmed with a noid light cylinder 3 injector is receiving a pulse. Unless something else jumps at at you guys...we can check the plug/wire tomorrow night.

While testing for a bad spot on the TPS (manually moving the throttle) it would actually level out after I paused at a certain distance. Still a little rough, but it would hold at various RPM levels. That seems to jive with you comment: "A bad TPS can give a hesitation, but it usually only lasts a moment as the throttle is moved, The engine will recover if the throttle is held still."?

I'm still suspicious about the fuel quality. We did add some higher octane fuel about a month ago, so maybe letting it run a while is getting that circulating through improving ever-so-slightly?

 

[Jbrownjr]

Just thought of something that I don't remember seeing in the troubleshooting saga.

Have you thought of the knock sensor possibly having gone bad, or checked to see if its connection is good? It's something that is usually so reliable one can last practically forever and be something that most people overlook.

But a bad one can cause hesitation.
And backfiring, which you just wrote about AGAIN as happening before the fire-which was from underneath.

Another problem stemming from a failed/non-functioning knock sensor is potential catalytic convertor problems, as its failure default is usually to have the engine run rich, which can lead to clogging and extreme temperature rises in the cat and the exhaust system in front of it.

(I once had a clogged one getting so hot it was literally red hot, but the smell of melting/cooking undercoating and paint alerted me in time. )
-------------------------------------------

And to clarify what L/Bronco just wrote:

"A bad TPS can give a hesitation, but it usually only lasts a moment as the throttle is moved, The engine will recover if the throttle is held still."

If its ONLY a bad TPS, the engine will usually recover/run normally if the throttle is anywhere OTHER THAN IN the TPS's bad spot.

(The most common range for the TPS to be cutting out is in the rpm range where the engine spends the greatest amount of time-which is usually just off idle or fairly low in the rpm range.)

No, the knock sensor hasn't come up yet. I read in another forum that I should see a code if that's going/gone bad?
Seems like we're getting very close thanks to all the contributors here!

 

[L\Bronco]

KOER: "3" KOEO codes start with the baseline 'flicker', then repeat the code twice, then the ending 'flicker'. KOER...no repeats. I have to catch this right after it's started, and I only get a "3". I'm wondering if that means "30"

Code "3" at the beginning of a KOER test shows as 30 on an old Ford STAR (self test automatic readout) tester (it counted the flashes for us and gave us a digital readout.)
Code 30 indicated that the PCM was for a 6 cylinder (8's were a 4 or 40 and 4's were a 2 or 20) The flicker was the fault codes coming in the data stream, (Fast codes)
during the 30 it should rev up to around 1500 RPM and run a series of tests, while that is going on, you are supposed to turn the steering wheel rapidly half a turn back and forth (To activate the p\S press switch, step on the brake pedal and release, (once only) and cycle the O\d cancel switch if equipped. After about 30 to 40 seconds you should get one flash (10), This is a dynamic response request, Stomp the throttle to the floor and release quickly, (This tests the knock sensors) immediately after the goose test (as we called it) the fault codes will flash, if it passes you should get a 1-1 (11) no faults. Usually the list of flash codes during KOER was long.
Hope that helps
Good luck
Cheers

 

[Jbrownjr]

Code "3" at the beginning of a KOER test shows as 30 on an old Ford STAR (self test automatic readout) tester (it counted the flashes for us and gave us a digital readout.)
Code 30 indicated that the PCM was for a 6 cylinder (8's were a 4 or 40 and 4's were a 2 or 20) The flicker was the fault codes coming in the data stream, (Fast codes)
during the 30 it should rev up to around 1500 RPM and run a series of tests, while that is going on, you are supposed to turn the steering wheel rapidly half a turn back and forth (To activate the p\S press switch, step on the brake pedal and release, (once only) and cycle the O\d cancel switch if equipped. After about 30 to 40 seconds you should get one flash (10), This is a dynamic response request, Stomp the throttle to the floor and release quickly, (This tests the knock sensors) immediately after the goose test (as we called it) the fault codes will flash, if it passes you should get a 1-1 (11) no faults. Usually the list of flash codes during KOER was long.
Hope that helps
Good luck
Cheers

Wow...that sounds like a college freshman initiation challenge.

Seriously, let me confirm:

1. during the 30 it should rev up to around 1500 RPM and run a series of tests [I assume this test is after it's warmed up, and the rpms are back to ~1,000, so the ECU will rev back up to 1,500 RPM?]
2. While that is going on, you are supposed to turn the steering wheel rapidly half a turn back and forth (To activate the p\S press switch) [Only once?]
3. Step on the brake pedal and release, (once only)
4. Cycle the O\d cancel switch if equipped
5. After about 30 to 40 seconds you should get one flash (10), This is a dynamic response request
6. Stomp the throttle to the floor and release quickly, (This tests the knock sensors) immediately after the goose test (as we called it)
7. The fault codes will flash, if it passes you should get a 1-1 (11) no faults. Usually the list of flash codes during KOER was long.
   

 

[L\Bronco]

Wow...that sounds like a college freshman initiation challenge.

Seriously, let me confirm:

1. during the 30 it should rev up to around 1500 RPM and run a series of tests [I assume this test is after it's warmed up, and the rpms are back to ~1,000, so the ECU will rev back up to 1,500 RPM?]
2. While that is going on, you are supposed to turn the steering wheel rapidly half a turn back and forth (To activate the p\S press switch) [Only once?]
3. Step on the brake pedal and release, (once only)
4. Cycle the O\d cancel switch if equipped
5. After about 30 to 40 seconds you should get one flash (10), This is a dynamic response request
6. Stomp the throttle to the floor and release quickly, (This tests the knock sensors) immediately after the goose test (as we called it)
7. The fault codes will flash, if it passes you should get a 1-1 (11) no faults. Usually the list of flash codes during KOER was long.

That's pretty much it, yes. We used to call it the pedal dance, or the ford hokey pokey!

(It should be at operating temp first or you will get a coolant temp out of range code.)
Yes yank the wheel back and forth once. (fairly aggressively)
The ECU will bring the RPMs up after the test starts using the IAC valve. (The base idle setting and fast idle is checked at this point.)
That's from memory, I haven't had to do one of those on an OBD-1 in a long time. (hopefully I didn't miss anything.)
It's a very in depth test, Ford did this because there was no way to view live data on a Ford back then.
Hope that helps.
Cheers

 

[Jbrownjr]

Season 2, Episode ?

Thanks to @L\Bronco we managed to 'do the dance' and get KOER codes:

25 “Knock not sensed during dynamic response test”
41 “Oxygen sensor circuit indicates system always lean”

• Knock Sensor
  • Tested the 'patch' between the main wiring harness and the knock sensor. Found the wires at the sensor bare for about 1/4". Taped them (in case there was shorting between the wires. No change.
  • Tested the yellow wire for voltage while KOEO. 2.5v. (I read elsewhere that should be 5v?)
  • Next time we'll try banging on the exhaust manifold (near the knock sensor) and see if it responds.
• Oxygen sensor
  • Checking the obvious - the O2 sensor was replaced last year sometime, connector looks great. (Mind you the cat is removed for now)
  • Checked a few plugs. Carbon 'fouled' but clean where it sparks. (Not symptoms for lean conditions)

I mentioned earlier we've been manually grounding the fuel pump circuit, suspecting the fuel pump relay. We replaced that under warrant and found no improvement. Suspecting the wiring between the relay and the computer led us to the passenger floorboard where we have an ECU from a donor '86 B2. On a whim, we swapped computers. 1) fuel pumps came on during KOEO with the 'old' ECU. 2) Engine ran worse with the 'old' ECU. So two bad computers, but defective in different ways (of course) Taking the 'refurbished' ECU back to O'Reilly's we found the 1 year warranty expired 3 months ago. :-( The kids who helped us ordered another from Cardone, and recommended I return tomorrow when the managers are working. (See if they feel inclined to make an exception) I'll plead my case tomorrow.

Curiously...if the ECU is defective at the FP Relay circuit, obviously we can override that by grounding the FP Relay; but I wonder if there's any more 'intelligence' in the ECU that might adjust fuel pressure/flow based on feedback from the FP relay circuit? (Long shot...)

So she still idles well, but won't accelerate worth a darn. Took her for a test drive this evening (been months since she left the garage), but she's running as rough as she was when the mechanic gave up (about the time she caught fire )

In your collective experience, would one of these codes be more likely to contribute to the poor acceleration? Of course the goal is to resolve both, but we'd sure be more encouraged to get her drivable first.

 

[L\Bronco]

Congrats, getting through the dance is half the battle sometimes.
first the 25. It simply means the PCM didn't see the A\C voltage from the knock sensor at the moment the TPS went to WOT. This will happen if the engine doesn't ping, if the base timing is below the 10 deg that it should be, (Premium fuel can do it too) or if the sensor is defective.
No knock sensor signal will usually only cause the pcm to NOT R E T A R D the timing when the engine pings, so it's very unlikely that it is your issue.
There should be 5vdc on the knock sensor wire with the sensor unplugged and 2.5vdc plugged in. If you hit the block near the sensor, you should see A/C voltage briefly.
The 41 (sys lean code) could mean its actually lean which would explain your hesitation. but it also sets when the sensor is not sending a signal at all, or the sensor ground has high resistance. An exhaust leak ahead of the sensor can cause it as well as fresh air gets drawn into the exhaust system momentarily every time an exhaust valve closes.
The KOER test will force the system rich and then lean and watch for a corresponding signal from the O2 sensor. anything below 450mv is seen as lean by the PCM.
(We are way down the rabbit hole now.)
The list of causes for a KOER 41 is long.
If ford would have given us access to the datastream of those old OBD 1's this would be much easier.
If you can tap into the O2 sensor signal wire with a voltmeter and measure from there to ground while its hesitating, you will be able to see if there is in fact an O2 signal and if its lean (below 450mv DC)
Note: don't poke any O2 sensor wires on the sensor harness (they are covered with a hard plastic insulation. Sometimes the sensor actually samples outside air through the wires{breaths})
If you have a 3 wire sensor, There should be 2 whites and one black, Black is signal. (the 2 white wires are the heater circuit)
I think Id resolve the PCM issue first though, If the calibration is off or corrupt it could simply be mis-measuring the air and adding the incorrect amount of fuel.
Hopefully that's enough for a start.
Good luck
Cheers

 

[Jbrownjr]

Congrats, getting through the dance is half the battle sometimes.
first the 25. It simply means the PCM didn't see the A\C voltage from the knock sensor at the moment the TPS went to WOT. This will happen if the engine doesn't ping, if the base timing is below the 10 deg that it should be, (Premium fuel can do it too) or if the sensor is defective.
No knock sensor signal will usually only cause the pcm to NOT R E T A R D the timing when the engine pings, so it's very unlikely that it is your issue.
There should be 5vdc on the knock sensor wire with the sensor unplugged and 2.5vdc plugged in. If you hit the block near the sensor, you should see A/C voltage briefly.
The 41 (sys lean code) could mean its actually lean which would explain your hesitation. but it also sets when the sensor is not sending a signal at all, or the sensor ground has high resistance. An exhaust leak ahead of the sensor can cause it as well as fresh air gets drawn into the exhaust system momentarily every time an exhaust valve closes.
The KOER test will force the system rich and then lean and watch for a corresponding signal from the O2 sensor. anything below 450mv is seen as lean by the PCM.
(We are way down the rabbit hole now.)
The list of causes for a KOER 41 is long.
If ford would have given us access to the datastream of those old OBD 1's this would be much easier.
If you can tap into the O2 sensor signal wire with a voltmeter and measure from there to ground while its hesitating, you will be able to see if there is in fact an O2 signal and if its lean (below 450mv DC)
Note: don't poke any O2 sensor wires on the sensor harness (they are covered with a hard plastic insulation. Sometimes the sensor actually samples outside air through the wires{breaths})
If you have a 3 wire sensor, There should be 2 whites and one black, Black is signal. (the 2 white wires are the heater circuit)
I think Id resolve the PCM issue first though, If the calibration is off or corrupt it could simply be mis-measuring the air and adding the incorrect amount of fuel.
Hopefully that's enough for a start.
Good luck
Cheers

OK, ECM replaced. (Cardone replacement under warranty from O'Reilly)
No change...except the Fuel pumps come on at KOEO like they are supposed to.

So the next step is to measure mv DC on the O2 sensor circuit. Tomorrow morning we'll take that on.
Looking at the wiring diagram..."Heated Exhaust Gas Oxygen Sensor" has 3 legs: ECU (#29), Blk/Lt Grn to EEC Power relay, Gry/Yel to the Ignition switch (20 GA Dk Blu fusible liink). Unless you can advise a better point to tap into that circuit, we'll trace wires and find a spot.

 

[L\Bronco]

The Blk\lt grn goes to ground, that is the one by the battery we suggested you check in the last thread, it is also the ground for the eec power relay
Grey/ yellow will be power for the heater, the third wire that goes to the pcm is the one you want to measure.
I realized last night, a long time ago I had one that would start to lose spark, only under load, and it was a weak ign coil. (it worked fine until the cylinder pressure went up.)
Just a thought.
Cheers

 

[goodO1boydws]

OK, ECM replaced. (Cardone replacement under warranty from O'Reilly)
No change...except the Fuel pumps come on at KOEO like they are supposed to.

So the next step is to measure mv DC on the O2 sensor circuit. Tomorrow morning we'll take that on.
Looking at the wiring diagram..."Heated Exhaust Gas Oxygen Sensor" has 3 legs: ECU (#29), Blk/Lt Grn to EEC Power relay, Gry/Yel to the Ignition switch (20 GA Dk Blu fusible liink). Unless you can advise a better point to tap into that circuit, we'll trace wires and find a spot.

Glad to hear that you're getting closer, and the fuel pumps are coming on how they should now.

Touching on something L/Bronco wrote earlier:

An old school way that may work for you to tell whether the hesitation is coming from an actual too-lean condition, even if it comes and then shortly goes away, or is from an ignition system related issue, is to manually add a very small amount of fuel for a very short amount of time WHILE its hesitating. (or when it would "normally' be hesitating)

In essense you become an accelleration pump-just like those on carburetors, the ones that don't begin adding fuel when the throttle first starts to move.

(This is only feasible if the hesitation is consistent and predictable, and if it still happens even when the engine is not under load.)

While its parked you could work the throttle linkage by hand, get the rpms up to just before the hesitation point, and then right at the hesitation-starting-moment (or at the precise throttle position) spray a very short blip of carb cleaner directly into the throttle body and see if there's any change in the established pattern of hesitation. Obviously do it several times with and without the added fuel to be sure.

If the coil is weak or the timing (for whatever reason) is whats causing the hesitation it shouldn't change what happens-or the degree of what happens, the instant the blip of fuel is added.

If, while accellerating, the fuel is either insufficient or the engine is already getting too much (which can make it stumble slightly resembling hesitation), or if the gas is simply BAD, it should change things.

If its not getting enough, by adding more at just the right time the hesitation should decrease. If its already getting too much fuel for efficient combustion, adding more would make it act worse.

 

[Jbrownjr]

The Blk\lt grn goes to ground, that is the one by the battery we suggested you check in the last thread, it is also the ground for the eec power relay
Grey/ yellow will be power for the heater, the third wire that goes to the pcm is the one you want to measure.
I realized last night, a long time ago I had one that would start to lose spark, only under load, and it was a weak ign coil. (it worked fine until the cylinder pressure went up.)
Just a thought.
Cheers

"Strange things are happening at the Circle K"

Blk/lt grn - confirmed as you described. (It increases confidence when I can match the drawing, advice and visual observation)
Gry/Yellow - identified and discounted.
Green/blu - 3rd "signal" wire identified and traced to the top-end where we pierced the plastic casing and measured mv.

"-35" is about what we saw on average. A few times I observed 150...175; but despite careful probing, those were only glimpses. Confirming our reader was set to "200mv" setting. Even if we were off by a decimal (i.e. 350), it's definitely reading under 450mv even when accelerating.

Ignition coil has been replaced (twice in the past year...thanks to the O'Reilly's warranty and our limited troubleshooting knowledge last year. More recent testing suggests it's good. (I recall a ~1" spark during our last test)

I think the EEC relay is one of two electrical components we haven't replaced, but as I understand it the engine wouldn't run if it were at fault.

Next thing to check?

 

[Jbrownjr]

Glad to hear that you're getting closer, and the fuel pumps are coming on how they should now.

Touching on something L/Bronco wrote earlier:

An old school way that may work for you to tell whether the hesitation is coming from an actual too-lean condition, even if it comes and then shortly goes away, or is from an ignition system related issue, is to manually add a very small amount of fuel for a very short amount of time WHILE its hesitating. (or when it would "normally' be hesitating)

In essense you become an accelleration pump-just like those on carburetors, the ones that don't begin adding fuel when the throttle first starts to move.

(This is only feasible if the hesitation is consistent and predictable, and if it still happens even when the engine is not under load.)

While its parked you could work the throttle linkage by hand, get the rpms up to just before the hesitation point, and then right at the hesitation-starting-moment (or at the precise throttle position) spray a very short blip of carb cleaner directly into the throttle body and see if there's any change in the established pattern of hesitation. Obviously do it several times with and without the added fuel to be sure.

If the coil is weak or the timing (for whatever reason) is whats causing the hesitation it shouldn't change what happens-or the degree of what happens, the instant the blip of fuel is added.

If, while accellerating, the fuel is either insufficient or the engine is already getting too much (which can make it stumble slightly resembling hesitation), or if the gas is simply BAD, it should change things.

If its not getting enough, by adding more at just the right time the hesitation should decrease. If its already getting too much fuel for efficient combustion, adding more would make it act worse.

Tried the carb/choke cleaner test. While idling as I accelerate sprayed into the throttle body. No difference.
As for bad gas? We actually pumped 10 gallons out and added fresh fuel 2 days ago. Definite improvement, but still rough at acceleration. And to clarify, there's no specific 'rough spot'. It just stumbles. I mean it'll increase in RPMs, but still doesn't sound 'smooth', but it's even more rough during the acceleration motion.

 

[L\Bronco]

Ok, quick question, does it seem better on initial start up, and gets worse as it warms up? Or is it bad right from the start?
The O2 sensor needs to be warm (200deg) before it can make a good signal, it needs to run for a min or 2 before you read it.
That being said, the pcm ignores it for the first couple min, and any time you hit WOT, (its called open loop control)
If the O2 signal is the problem, it should run ok at startup and full throttle.
If its bad all the time, its really lean, fuel pressure is normal, (35-45) is this the case while its hesitating?

 

[L\Bronco]

Sorry, your last reply came in while I was typing. If extra fuel didnt change it, then we are looking at ignition or base engine. The O2 sensor might not have been warm enough during your check.
Sounds like everything in the ign system has been changed.
It sounds a bit (from your last description) like a cracked spark plug or plug/coil wire leak. (Arcing) but not if everything is new.
Is the capacitor on the coil power wire still there? It should be bolted to the coil mount frame and plugged into the grey one wire connector that connects to the red on the coil. (It controls voltage spikes from the ignition coil in the primary (12v) side)
Did you check for a partially restricted exhaust as Tiha suggested earlier?
Use a vacuum guage on a manifold port (the one on the fuel press reg will work)
Read it at idle and then around 2000rpm in neutral, (get it to run as smooth as you can when its revved up.) the vac should be 1-3”hg better at 2000 eg. 18”hg @idle and 21”hg at 2000.
If it drops and was running smooth, you probably have A plugged muffler or resonator.
If it wont run fairly smooth, dont trust the vacuum reading.
Good luck
Cheers

 

[goodO1boydws]

Now that you've done so much to eliminate possibilities:

If its still not running smoothly through MOST of the rpm range and only gets WORSE when accellerating, I'd suspect either a fairly significant cylinder (or cylinders) misfire or incorrect**** INITIAL timing. Both are easy to check.

(I forgot if you said the heads have ever been off that you know of, or the timing chain and gears replaced. If either have not, they could both potentially contribute to the problem.)

(Again, I misremember:
If you haven't already done so, double check a piston mechanically to see if TDC on the timing mark comb is where its supposed to be.)

Follow the adjustment procedure and try backing the distributor off a couple degrees at a time and after each adj, see if it has any effect. Then advance it back to where you started. Now move it forwards a couple degrees at a time and see how that effects it.

Even new wires can be marginal or less-than-optimally-routed, and possibly causing or helping to cause misfiring or cross firing.

Use a timing light on every sparkplug wire, stare into it and watch for a steady flashing rate at idle and also as you accelerate. Any misfiring will be seen as a break in the steady rate of flashing, which it should have (no matter what is going on fuel-wise) and would tell you where to concentrate.

****After XYZ thousand miles (especially if its been burning any significant amount of oil), there could be enough build up of deposits in the combustion chambers of some or all cylinders to raise the compression rate in those cylinders to the point that the "normal" ignition setting isn't what they want to see.