1989 5.0 Will not go in to closed loop, bogs when accelerated, no codes

[Dadpool]

Greetings fellow Bronco owners.

I have a 1989 with the 5.0 AOD that my son and I have been fighting for about 3 years after putting in a new engine. I won't go through all the details but will list the most recent that we are running in to.I

I gave up after a couple of years and sent it to 2 different mechanics. The first one back burnered it because it was taking too much time to diagnose.
I took it to another recommend one and they found a bad ECT, replaced but it was still running rich. After checking seveal other item they replaced the ECM and it started running correctly and not rich. They sent it home with us and my son drove it for a month and it started running rich again. We took it back in december and they relooked over everything and came up with the injectors we got were wrong causing it to not go in to closed loop. They were a set of reman ones from AutoZone. I know they are not known for reliable parts but its what we could afford. After double, tripple checking their site, in store I wasn't convenced that the injectors were the issue, but I got the manager to warranty them and got another set of the same type for them to try. It still was running rich and not going in to closed loop. They back burnnered it. I suggested that they try a set of know good injectors I had out of an 88 302 from a Crown Vic that I put in my Falcon. They agreed, so I pulled them and gave them to the mechanic. A month later they still haven't tried them, so I brought it home and put them in.Other than a couple of broken O rings they went in with no issues, and I did replace the O rings.
It started and seemed to be doing ok, but still rich and not going in to closed loop.

I since replaced the ECT again ( I had a spare new one for my Falcon) still no change. I attempted to test the sensor but giving the location, it is difficult to get a reading once at temp. I tried with it running under hot water and it seems to be within specs, I don't remember the values off hand. I decided to run a new line to the ECM for the ECT, keeping the original wires in the loop since I seen it provides grounds to the TPS, MAP and several others.
Now as of this weekend with a cleared ECM it will start, it calibrates a bit after reaching temp then tries to go in to closed loop, but then jumps back in to closed loop, bumping the idle to 1000 rpm. When trying to drive it, it bogs down at low RPMs, but smooths out at around 2500 to 3000. Once it is shut off, it is hard to start again.

To the best I can tell by spraying some carb cleaner on it (before it warms up) there are no vacuum leaks in any vacuum lines, which have all been replaced from the plastic lines. No leaks on the TB and between the upper and lower intake.

Fuel pressure when KOEO is around 30ish and holds steady, so I don't believe the the injectors are leaking. Fuel pressure seems good when running, but there is no change in how it runs if the vacuum line is removed from the FPR. Research found maybe a weak or back fuel pump. The one on the frame is making noise, but with a auto stethoscope to the tank, I can not hear it buzz when key is turned on.

Timing is at 10 btdc with spout unplugged and advances to around 20 at idle.
Parts replaced that could be causing the issues, and slightly inconclusive test results
TPS, IAC, ECT Multiple times, MAP, ACT, FPR during the install of the engine. It does have a knock that was not replaced.

I have reverted back to the stock wiring for the ECT, verified all ground and pin outs from sensor connectors via continuity, and that they are all getting the 5v ref power.

This does have the emissions removed, so we get a TAD and TAB code, but that is expected. Otherwise, just 11, system pass.

I will be verifiying the in tank pump again and getting that replaced this weekend, if NAPA will order in the pump before I bring them the old one to warranty.

Plugs and plug wires, cap and rotor are new. Reman Dizzy, so TFI module or PIP could be suspect but not likely.

Any other ideas I can try on this thing?

 

[Tiha]

First thought is, you said it ran good for a month after new ECM,

How did you determine ECM was bad last time, and why could that not have failed again in the same way?

 

[Dadpool]

First thought is, you said it ran good for a month after new ECM,

How did you determine ECM was bad last time, and why could that not have failed again in the same way?

Thanks for the reply. Mechanic #2 decided it was worth a try to put in a new ECM. I did forget to add that they ordered in 2 additional ECMs from 2 different companies to try after I took it back with no change in closed loop status. Another thing, they were monitoring open/closed loop from the O2 sensor with a lab scope.

 

[L\Bronco]

Hey Dadpool, (…I love that!)
A couple things to start, how are you verifying open loop/ rich?
2nd have you tried a key on engine running self test? They can often unlock problems that evade diagnosis.
Last, try plugging the throttle body with your hands (tubes removed)
If it stays running or takes a long time to stall, it indicates un-metered air. (Vac leak)

(When trying to drive it, it bogs down at low RPMs, but smooths out at around 2500 to 3000. Once it is shut off, it is hard to start again.)

This part sounds a lot like when the in tank low press pump fails.
Pull the inlet line off of the hi press (frame) pump, then unplug the hi press pump, cycle the key and see if you get fuel delivery. (Should make a quart in 30 sec.
Hope that helps
Cheers!

 

[Dadpool]

Hey Dadpool, (…I love that!)
A couple things to start, how are you verifying open loop/ rich?
2nd have you tried a key on engine running self test? They can often unlock problems that evade diagnosis.
Last, try plugging the throttle body with your hands (tubes removed)
If it stays running or takes a long time to stall, it indicates un-metered air. (Vac leak)

(When trying to drive it, it bogs down at low RPMs, but smooths out at around 2500 to 3000. Once it is shut off, it is hard to start again.)

This part sounds a lot like when the in tank low press pump fails.
Pull the inlet line off of the hi press (frame) pump, then unplug the hi press pump, cycle the key and see if you get fuel delivery. (Should make a quart in 30 sec.
Hope that helps
Cheers!

Hey L\Bronco! Thanks, I made it up as a way of trolling my oldest son on games that we both play on line

The mechanics were using a lab scope. Since I don't have one, I have been using the idle pattern and unburnt exhause as my guide. My process is:
Clear the ECM by battery disconnect for 15 to 30 minutes.
Hook the battery back up and start the engine. It does the high idle at start for the first minute or so then drops to the the normal 700 - 800 RPM
I let the truck sit and idle for 5 to 10 minutes, keeping any eye exhaust color, RPM's and temp. When I can feel the warmth coming from the radiator I know the idle is about to change, going up to 1000 RPM. This is when I am saying it is trying to go into closed, but something stops it and then it goes back in to closed look and starts using defaule vaules to keep it running. Is this the exact science, probably not, but thats how I am working it.

I did think about doing the KOER, but for me it usually brings up false codes if you don't get the steering wheel turned at the right time and snap the throttle at the right time. If I had the niffty Snap-On Scanner that would be a simple process. I can do this test and post the results. It can't hurt at all.

I am pretty sure that I have found that the in tank is not making noise, and will reevaluate tonight with another pressure test, and listening to the in tank with the rail pump power disconneted, and try the removal of the line if it is still inconclusive.

 

[L\Bronco]

For KOER, turn the wheel hard 1/4 turn and back and stab the brake once shortly after it flashes 4 times. Goose the throttle immediately after the single flash, (it should be about 30 sec to a min or so after the 4.)
Good luck!
Ill be watching for data.
Cheers

 

[Dadpool]

Hey L\Bronco! Thanks, I made it up as a way of trolling my oldest son on games that we both play on line

The mechanics were using a lab scope. Since I don't have one, I have been using the idle pattern and unburnt exhause as my guide. My process is:
Clear the ECM by battery disconnect for 15 to 30 minutes.
Hook the battery back up and start the engine. It does the high idle at start for the first minute or so then drops to the the normal 700 - 800 RPM
I let the truck sit and idle for 5 to 10 minutes, keeping any eye exhaust color, RPM's and temp. When I can feel the warmth coming from the radiator I know the idle is about to change, going up to 1000 RPM. This is when I am saying it is trying to go into closed, but something stops it and then it goes back in to closed look and starts using defaule vaules to keep it running. Is this the exact science, probably not, but thats how I am working it.

I did think about doing the KOER, but for me it usually brings up false codes if you don't get the steering wheel turned at the right time and snap the throttle at the right time. If I had the niffty Snap-On Scanner that would be a simple process. I can do this test and post the results. It can't hurt at all.

I am pretty sure that I have found that the in tank is not making noise, and will reevaluate tonight with another pressure test, and listening to the in tank with the rail pump power disconnet25ed, and try the removal of the line if it is still inconclusive.

Codes are as follows for KOER
44
13
25
Attached are vacuum levels at idle and 2500 rpm. It moves slightly with the rough idle, but stays steady.
There is buzzing directly from the tank, but ran out of time to test pressure from it. My son bought the wrong tester to test the rail pressure, so we will try again tomorrow night. We also tested temp before and after the catalytic converter, in the 400s before and low 300s behind. Possible clogged cat?

 

[L\Bronco]

Codes are as follows for KOER
44
13
25
Attached are vacuum levels at idle and 2500 rpm. It moves slightly with the rough idle, but stays steady.
There is buzzing directly from the tank, but ran out of time to test pressure from it. My son bought the wrong tester to test the rail pressure, so we will try again tomorrow night. We also tested temp before and after the catalytic converter, in the 400s before and low 300s behind. Possible clogged cat?

Hey Dadpool
44 is air injection system non functional (Which is removed)
25 is Knock sensor signal not received during goose test. You either missed the timing of the throttle in the test, or it didn't ping when you rapped the throttle. (could be premium fuel or lower than spec compression, or something like that. Probably not our issue)
13 means it was unable to lower the idle to base during the test, (525RPM) indicating un metered air or base idle too high.
Unplug the IAC when idling , warmed up, A\C off, in neutral. it should drop to just above 500. If it stays high, try my plugging the throttle body bores test I described earlier.
I would look at the idle speed symptom first, a big vacuum leak will give you the drivability issue you have for sure.
If it stalls right away, check for wear in the throttle plates\bore, or a sticking IAC valve.
If it was stuck rich, you would have seen a code 42, if it was way too lean you would have a 41.
As far as the cat goes, If I'm following your vac readings correctly, vac improved by 2 ish"hg at 2500 compared to idle. That is the test for an exh restriction. It passes.
Your idle vacuum is pretty low at idle though. You mentioned a new engine, is the cam stock?
More to follow...
Cheers

 

[Dadpool]

Hey Dadpool
44 is air injection system non functional (Which is removed)
25 is Knock sensor signal not received during goose test. You either missed the timing of the throttle in the test, or it didn't ping when you rapped the throttle. (could be premium fuel or lower than spec compression, or something like that. Probably not our issue)
13 means it was unable to lower the idle to base during the test, (525RPM) indicating un metered air or base idle too high.
Unplug the IAC when idling , warmed up, A\C off, in neutral. it should drop to just above 500. If it stays high, try my plugging the throttle body bores test I described earlier.
I would look at the idle speed symptom first, a big vacuum leak will give you the drivability issue you have for sure.
If it stalls right away, check for wear in the throttle plates\bore, or a sticking IAC valve.
If it was stuck rich, you would have seen a code 42, if it was way too lean you would have a 41.
As far as the cat goes, If I'm following your vac readings correctly, vac improved by 2 ish"hg at 2500 compared to idle. That is the test for an exh restriction. It passes.
Your idle vacuum is pretty low at idle though. You mentioned a new engine, is the cam stock?
More to follow...
Cheers

We will try those tonight and report back.
It was a stock long block, so I would imagine it is a stock cam.
On the cat though, from my research, the exhausing side should be higher than the intake correct? With it being 100 deg difference, wouldn't that point to a failing cat?

 

[L\Bronco]

We will try those tonight and report back.
It was a stock long block, so I would imagine it is a stock cam.
On the cat though, from my research, the exhausing side should be higher than the intake correct? With it being 100 deg difference, wouldn't that point to a failing cat?

That is true on the cat, (sorry, but I'm going to throw another however in)
On the old stuff youd have to do a decent drive on the hiway for 5 or 10 min to see the 100 deg.
The old stuff barely lights off at 2500 rpm for 5 min.
The temp deal only tells you the catalyst is functioning. not much to do with back pressure.
The vacuum increase tells you the engine can breathe.
The best check is a backpressure gauge in the O2 sensor hole at 2000 rpm. But you can trust a pass with the vac gauge.
Heading to Pomona for the Winternationals tomorrow, so I may not get to reply till tues or so.
Cheers

 

[Dadpool]

That is true on the cat, (sorry, but I'm going to throw another however in)
On the old stuff youd have to do a decent drive on the hiway for 5 or 10 min to see the 100 deg.
The old stuff barely lights off at 2500 rpm for 5 min.
The temp deal only tells you the catalyst is functioning. not much to do with back pressure.
The vacuum increase tells you the engine can breathe.
The best check is a backpressure gauge in the O2 sensor hole at 2000 rpm. But you can trust a pass with the vac gauge.
Heading to Pomona for the Winternationals tomorrow, so I may not get to reply till tues or so.
Cheers

Just putting this out there. Here is vacuum with O2 removed. It looks to be breathing a lot better on the gage.
Also, blocking the intake made it die instantly.

 

[L\Bronco]

Just putting this out there. Here is vacuum with O2 removed. It looks to be breathing a lot better on the gage.
Also, blocking the intake made it die instantly.

Ok cool, did you get a chance to unplug the IAC valve at hot idle and look for 500 rpm?

 

[Dadpool]

Ok cool, did you get a chance to unplug the IAC valve at hot idle and look for 500 rpm?

Yes there was no change so I got it replaced under warranty. Idle is smooth as butter with new iac and o2 unplugged, still bogs under acceleration though. My aone was too busy at work to get the right gage to test fuel pressure of in tank pump so will test tomorrow. Enjoy your trip! I am feeling good new will be waiting when you return.