911 diag help needed

[thebronc]

Ok so i have a 86 full size with a 302 efi. I have prob i nor any other techs who helped can figure out. I will attemp to explain theproblem and symptoms. But please dont let how i explain the symptoms pidgion hole what is actually the prob. And then i will tell things i checked also codes.

The biggest symptom is when driving and u get to about 45 or 50 mph when i let off the gas completely the truck will kinda bog back and fourth between free coast and a sensation that feels as if i lost all spark or like engine braking or torque conv is locking and unlocking (no pidgion holing. Just trying to best explain) this will happen till gets to like 20 or 25 mph and what feels like the trans shifts and goes back to normal

other symptoms that may or may not be related. Engine no longer goes into high idle warm up. Once started it has low irratic idle. Also vehicle always now holds irratic iddle. And once warm the idle is always high. In park its at 1300rpm . When does the back and fourth bogging u can smell excess gas. Every once in a great great while when starting engine will only turn and possibly has no spark then after 3rd try or so will fire right up as it always does. When idle ever gets low in park or nutral and then shift into gear engine will surge as if it is properly detecting load but trans doesnt go to gear right away. Sometimes when driving at various speeds it will like huge cough like momentarilly lost spark and give u one big **** and then all is ok.

Codes

koeo. 31. Egr (evp/ept) circuit out of range

koer. 44. Thermactor air system not working

koer. 34. Egr (evp) closed valve signal to high

koer. 13. Cant control rpm during low rpm check

Things checked and tried and changes noticed

checked for vaccume leaks with water and propane. None found at this time

pulled plugs#8 has a little oil and is darker then rest but is burning hot enough and is burning it all off no prob. But still i cleaned pluged and swapped it with #7 plug. Things changed.now 90% of the time instead of back and fourth bogging. When let off the gas now at same speed of 45 to 50 the truck will just do the same bog sensation as previously explained but now its just constant. No back and fourth. Untill bout 25 and kicks out like it shifted and all is ok again.

Replaced iac. No change.

All cylinders compression at 150 except #9 at 145. Top half of motor i rebuilt a year ago.

All plug wires new. Rebuilt distributor. New o2 sensor. New msd ignition coil. Replaced tfi when it went out year and half ago.

Cant tell if its engine or tranny or both

When truck is under power it does great. Plenty of power plenty of get up and go. Shifts good. Did power brake and slowly gave more and more gas and heard no miss fire.

Need all help as this is my daily driver and its killing me in gas worse than ever and switching jobs soon and need it dependable again.

Not to mention its putting a hault on my sas plans for next summer haha

Thank u for any and all help

 

[miesk5]

yo,

What's your name bud?

and, WELCOME!

OK< so you have a new IAC; we'll fo thru the drill and then read what Nelbur did...

DTC 13 Cannot control RPM during ER Self-Test, low RPM & Possible Causes;

vaccum leak, use garden hose section to listen for leak noise;

TB base idle off- Idle Air Control (IAC) Sludge; Poor Idle TSB 91-25-07 for 85-92 Bronco & F Series & many others; "...Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions. Hard Cold Start, Stall On Initial Start-Up, Stall During Idle, Stall During Decel, Rough Idle, Rolling Idle, Hesitation During Acceleration. A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only. It eliminates the need to clean the majority of past model throttle body applications. Cleaning is not required on sludge tolerant throttle body designs released for 1991 and newer model years..."

Now read this;

Idle Air Control (IAC) Modification in an 86; "...I have spent some time this week trying to set up an air bypass around the IAC valve by cutting away some of the gasket between the IAC in and out air holes, rather than pay big bucks for Fords spacer kit. I cut away the center of the original IAC gasket from the outside of each hole to the outside of the other hole, giving about 1/2" gap for the air to pass through. I noticed an immediate improvement in the engines starting behavior, but it would still die occasionally. For most of my trucks life it has been dying when it was started hot. It would rev up and then drop the idle so low it would die unless I would catch the idle with the accelerator. It would never die when cold as the IAC would keep the idle speed up, and it never died at stop lights. Now it's worst situation seems to be when it has been shut down for a half hour or so, and restarted. I wonder if the heat soak is fooling the ETC into thinking the engine is warmer than it really is. I decided that more improvement could be had if I had a thicker gasket, because the original IAC gasket was very thin (0.018"). I had some 0.030" gasket material so I made my own with the same 1/2" cut out. This gave enough bypass to noticeably raise the idle speed and almost eliminate the dying. After maybe 50 starts in the last few days, it only died twice. After so many years of catching it with the accelerator it is darned hard to leave my foot off it. It is clear to me that by trial and error one can tune the air bypass without the need for the expensive Ford kit. I may combine the two gaskets for more bypass, but the idle is about as fast as I would want now, especially for driving in snow..."; miesk5 Note, Tomco makes an idle plate P/N 8491 = to Ford, P/N F2PZ9F939A; Like Ford’s service kit, Tomco’s spacer plat e (arrow) is installed between the air bypass valve and its mounting boss using two gaskets. The two holes in the plate are for bleeder screws, which provide a minimum air rate adjustment independent of the throttle opening.

Source: by Nelbur at Ford Bronco Zone Forums

http://broncozone.com/topic/22150-fast-idle-problem/page__pid__115710#entry115710

=========

DTC 311 - Thermactor air system inoperable. "...The computer determined that for some reason the fresh air injection from the Thermactor system was not present. There are several components that make up this system. The initial component is the smog pump. The first checks I would make are the hoses and plumbing from the smog pump back to the diverter valve (behind the pass. cylinder head) and then on to the crossover pipe at the back of the heads and down to the catalytic converter. The check valves that are at the center of the cross over pipe and the top of the metal tube from the cat are often the culprits as they can and do snap in half as the get old. If the plumbing looks to be in good order we can discuss the slightly more complicated aspects of the system. The diverter valve also has two vacuum lines running to it. Make certain they are in place and intact. (Computer needs to be able to control the flow of fresh air by the Thermactor system)..."

Source: by greystreak92 (

DTC 31 "...This code could be caused by several different factors. If the pintle position sensor (Ford calls it the EVP sensor) is shorted or open, you could have a code set. If the EGR valve becomes carboned up and does not seat fully, the EVP sensor gives a high reading and a code is set. If the diaphragm of the EGR valve is bad, then it, too, is flagged

DTC 31 EVP (EGR position sensor) mounted on top of the EGR valve. Testing & Operation; Source: by Ryan M (Fireguy50) at

http://oldfuelinjection.com/?p=35

three wires; 1) VREF 5 volt reference

2) SIG RTN ground (via PCM)

and 3) EVP sensor output to the computer.

Vacuum Pump; AutoZone has a Hand Operated pump in their Loan-A-Tool® service, part number OEM27010 with a Refundable deposit

================

DTC 44

Possible causes for these faults are:

Vacuum hoses leaking, blocked or kinked.

Secondary air injection valve inoperative.

Secondary air injection solenoid defective or blocked.

Check for correct vacuum hose routing to AIRB/AIRD solenoids and by-pass diverter valve. See Vehicle Emission Control Information (VECI) label. Check for kinked or blocked vacuum hoses. Check for kinked or blocked air hoses. Check for disconnected vacuum hoses.

AIRB/AIRD solenoids are oftan called the TAB & TAD;

Thermactor Air Bypass Solenoid (TAB, AIRB, AM1); Miesk5 Note, the TAD & TAB are Identical & Static Resistance Value for both is 50 to 100 ohms

Thermactor Air Diverter Solenoid (TAD, AIRD, AM2)); Miesk5 Note, the TAD & TAB are Identical & Static Resistance Value for both is 50 to 100 ohms

TAB & TAD Location in Self Test Video in an 86; the "right side" (passenger) near the AC/Ventilation Systems Vacuum Tank (black plastic ball type)

Source: by JKossarides ("The Bronco", Jean) at http://www.supermotors.net/registry/media/742200

KOER; Right Thermactor Inoperative; "...I had a similar issue that turned out to be the vacuum line to the Thermactor Air Bypass Valve. No CEL, just a code; 1. First check that the two vacuum lines are connected to the Vacuum Reservoir (coffee can) and the resevoir is in good repair with no leaks on the bottom. Frequently the can leaks or the vacuum lines are accidentally knocked off. Check the vacuum hose to the bottom of the Bypass Valve. Check the vacuum hose to the Diverter Valve. Check the vacuum hoses to the TAB/TAD Solenoids. Then check your TAB/TAD Solenoids. These are common easy to miss problems. Once these are ruled out all that is left is: Thermactor Air Supply Hoses. One-way Check Valves. Main TAB/TAD Valves..."

Source: by Seattle FSB

===========

DTC 34 - EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the ****** side of the EGR by mouth. the egr is not closing properly which can cause detonation. remove the egr and clean off any carbon built up on it with carb cleaner and a brush if necessary.

Source: by miesk5 at Ford Bronco Zone Forums

======

 

[nelbur]

I believe what you call bogging is a change in idle speed when you have your foot off the accelerator, which changes the engine braking, making it feel like a downshift. My '86 does this and I am no happier with it than you are. My father had an '86 F 150 with the same problem, and the dealer persuaded him that the transmission was downshifting. They did a bunch of work on the tranny, but there was no change. The '86 302 was the first full year of Fords EFI, and I think there are peculiarities with the idle control on this model. During the heat of summer my truck has a surging idle when I start it up after it has been shut down for, say 15 to 30 minutes. It used to drop so low that the engine stalled until I bypassed some air using a cut away IAC gasket. It still surges but doesn't stall now. If your IAC is working you should have a high idle briefly when you start up in the morning.

When my truck was new and under warranty I would periodically take it in and explain that it was stalling. They would clean the injectors and tell me to stop using cheap gas. I think they were also cleaning the throttle body. It would be better for awhile, but before long it would be back to it's old tricks. I still have the original injectors (230,000 miles) but I understand that a new self cleaning injector was used in later years. I am not sure when that happened.

 

[thebronc]

Hello. My name is Ben.

Im not actually new to hear I use to have an account a couple years ago but I forgot the password and username.

Okay so I'm going to try to cover both responses and I thank you both for responding.. where to start.. I'm writing this on the phone and it doesn't show me what you guys wrote so its off of my memory. if I miss anything I'm sorry

I already check for vacuum leaks water and propane and did not find any but I did not check the charcoal canister at the bottom where it rusts out. I will atemp to check that tomorrow on my lunch. I also checked the bellow on my egR valve with water propane and brake clean and it seemed to be good but just in case I'll hook up the vacuum tester to it. I have not check for carbon buildup by the idle air control or the throttle body but it was on my list to do and will try to do that as soon as possible.

To the second reply on here. Again sorry I don't know your name it doesn't show me right now. I know it's not the downshifting of the tranny that you're speaking of because now it is to the back and forth to bogging and free coasting. Plus the symptoms changed when I switched the spark plugs.

I also know it's not the idle air control gasket because I've always had the same gasket on there and it's never been a problem. Also my truck no longer goes into high idle warm up when first started. It does not have a rough start.. starts right up just idles and low and irratic.

I will also try to check and see if the pintle on the E G R valve is stuck. And will also check all the metal tubing and tubes on the air system even though I checked them a year ago when I rebuilt the top half of the motor and they were all okay but will still check.

That's all I can remember from your replies for now I will post this and then go back and read and see if I missed anything

thank you both for your replies now I have somethings to check

 

[Rons beast]

Hey TB, welcome,

I had similar problems with my 96. The upper plenum and the EGR port was all gunked up. A thorough cleaning, and new EGR cured the problem.

Good Luck

 

[thebronc]

Ok so everyone keeps saying my egr is stuck. So my goal is tomorrow to remove and check and clean it. I only get small amounts of time to work on it as i cant work on it at my apts and all my tools are at work anyways.

Question. My truck has what looks like a aftermarket charcoal cannister. Should it hold pressure. I did find vaccume leaks in the lines. Which i will fix tomorrow. Dumb question but are the lines to it a big part of the vacuume system and a big deal? Also if i plug off one port to the cannister and blow into or **** on the other. Should it hold pressure in it. Cause mine does not at all

 

[Rons beast]

Hey The B.

How about posting a pic so we can be sure of what you are speaking.

If there is straight vacuum to the canister and it holds none....there is a problem. However you may be confusing a charcoal canister with another part. Any vacuum leak is a big part of the whole working engine management system.

If the EGR is original,or more than 5 years old, replace it, you will be glad you did. Cleaning rarely works.

Good Luck

 

[thebronc]

No pic at this time but im for sure its the carcoal canister. Ni vacuume pressure can be held inside of it from either line.

Here are some recent updates from today

removed the egr. Was stuck closed possible. Clean. Its perfectly free moving and diafram is good and hold perfect vacuume.

I found some vacuume leak in the lines off the charcoal can to the throttle body. Fixed those. No changes.

Fixed vacumme lines to egr and acv. No dice

discovered when i rebuilt top half of motor i switched the egr and acv vacuume lines. Oops. Well switched back. Still no change what so ever.

Disconnected all electricle to vacuume solonoids. Dumped lots if gas. But still same probs. Which kinda eliminates stuff but not really haha.

So plan now is to re do every vacuume line. Well the crappy hard lines anyways. Replace egr valve even though i dont think thats the prob.

Had my ford mech buddy drive and he said it kinda does feel like a intermitten miss.

My two questions are one... Is it possible i have a bad injector leaking internally and flooding a cylinder causeing the miss and ir boggyness.

Two. What else can be going in with the iac that its nit giving right info to computer. We are leaning twards its git a miss. Bad injector. Or the comp is not getting right info from iac or something. Idk. Jit really narrowed down. But closer than i started haha.

O also throttle body and iac port is all stupid clean.

What bout throttle position sensor????

 

[miesk5]

yo BEN,

Suggest buying a vacuum gauge, best low cost test and MPG helper you can spend $ on;

Mount it inside cab; run hose thru clutch blank on firewall w/proper size grommet (buy grommet when buying gauge & hose); connect other end to vac "tree" atop intake manifold.

Vacuum Gauge Diagnosis by CRAIG

http://www.classictruckshop.com/clubs/earlyburbs/projects/vac/uum.htm

Also check vac lines for AC, heater, defroster, vent control ckt & vacuum tank (plastic ball type), under dash & lines to heat/blend/etc. doors; power brake booster, & HVAC vacuum reservoir

Check vac hose to Diverter valve (behind the pass. cylinder head); use mirror to see it

---

Throttle Position Sensor (TPS) Testing

=========

Fuel Injectors; Deposit Resistant Injectors were installed between mid-90 and 92

Injector Diagnosis TSB 88-17-11 for 85-88 Bronco, F Series & many others

ISSUE: Port fuel injected vehicles that have cold hesitation, lack of power, rough engine idle or a surging condition at steady speeds may be caused by dirty fuel injectors. When no-detergent fuel is used, deposits form on the fuel metering surfaces of the fuel injectors. The deposits that form reduce the fuel flow resulting in a lean condition.

ACTION: To correct this, follow normal diagnostics as shown in the Engine/Emissions Diagnosis Manual, Section 2. If you get to a step that instructs you to replace a fuel injector, FIRST try cleaning the injector with the Rotunda Tester/Cleaner, 113-00001. If the condition still exists after cleaning, the injectors should be flow tested to make sure they are functioning properly. If the flow test indicates lean injectors, a second cleaning may be necessary because of severe injector fouling. Refer to the diagnostic chart for step-by-step instructions.

CAUTION: NEVER ATTEMPT TO FLOW TEST INJECTORS WITH THE CLEANING SOLUTION MIXTURE. THIS WILL PRODUCE FALSE TEST RESULTS. ONLY USE CLEAN GASOLINE.

In cases where fouled injectors were the cause of the driveability concern, it should be recommended to the customer that a better quality gasoline be used. The Owner Guide, Maintenance Schedule and Operating Guide address the fuel quality issue.

NOTE: IT IS VERY IMPORTANT THAT THE CORRECT CLEANING SOLVENT IS USED WITH THE ROTUNDA TESTER/CLEANER. THE CORRECT CLEANING SOLVENTS ARE:

Power Flush Injector Fluid E6AZ-19579-C

Carburetor and Combustion Chamber Cleaner D9AZ-19579-BA

DO NOT USE

Injector and Fuel System Cleaner E6AZ-19579-A

 

[thebronc]

Thank u all for ur posts and responses.

Miesk5. Please please dont get me wrong here. I am in no way trying to be a d bag ot anything. and i thank u for ur posts and responses. But im kinda looking for more first hand personal experience knowlege and actuall possibilities. im askin questions about things and it seems ur kinda just cutting anf pasting hiw to check those things. And alot of things u post dint even follow my symptoms or issues. I can test everything. Eventually but im not at that point yet. Im trying to do what makes most sense first. Like i asked if a bad injector is likely and could cause my prob or a tps could. U gave how to test. The reason im foing this way instead of just testing all is cause im limited wgen i can work on it. My tools are at work and cant work on cars in my apartments and limited use allowed at work to. So i try to get best use of my time. Again im sorry if i sounded rude. Im just trying to fig this out as fast and best as possible

gonna hook up a vac guage today hopefull and watch and record info while driving. Also gonna try the occiloscope this weekend

 

[thebronc]

Did a running vacuume check and a running fuel pressure check and both checked out ok. At all speeds and and rpms and even when the prob is occurring on decel bog. So eliminated thise two from the list

 

[Rons beast]

Hey Ben,

From what you are telling us, you suspect a stuck injector, or intermittent miss. Those 2 have totally different symptoms.

If an injector is stuck open, it won't be stuck intermittently. So that would show up as a constant miss.

You would be able to tell there was a cylinder not pulling it's weight.

You said you power braked the ride and no miss showed up. That indicates the secondary side of the ignition is good.

Your symptoms sound alot like a vacuum leak, and very possibly a leak that is effecting the transmission.

If it were my ride I would get a good flashlight and get under the truck and look for anything that may have gotten pinched , or loose in or around the trans. Then work my way forward, and search for any loose or cracked hoses.

You should not have any open vacuum to the charcoal canister. It's there to store fumes from the gas tank and it is purged when the engine is started, BUT should not allow free and open vacuum.

After you dillegently look for any vacuum leaks, and if none are found, try closing off any vacuum lines to the canister and see if your problem persists.

Good Luck

 

[thebronc]

Its getting worse. Last three times it had trouble starting. And i almost forsure feel a miss now. So tomorrow i will block off vacuume to the charc can. Gonna change my tfi modual as i have a extra already. Gonna run a multi meter on my plug wires. Gonna put a new plug in the cylinder in question. And also check in the cap for any burning or arching marks. Hoping i can sneak my truck on the oscilloscope on sat but might not he able to as i think the snitch is working then

other than possible vacuume can. I dont have vacuume leaks as i ran vacuume checks. Checked with water. Checked with propane. And rebuilt most of the the vacuume lines yesterday.

Its not a leaking injector either as when the guage was hooked up and key was on. Pressure would of dropped of but didnt..

 

[Rons beast]

Also clear your trouble codes. Then see what may show back up, after your changes.

That will give a better indication what may be the problem.

 

[miesk5]

I can only go by the Codes and the other checks & tests you have perfomed

I do cut & paste because it is easier than re-typing the Ford DTC Code tests and especially that For TSB

In my first reply I addressed the EGR DTC 34 - EGR voltage above closed limit - Failed sensor, carbon between EGR pintle valve and seat holding the valve off its seat. Remove the EGR valve and clean it with carbon remover. Prior to re-installing see if you can blow air through the ****** side of the EGR by mouth. the egr is not closing properly which can cause detonation. remove the egr and clean off any carbon built up on it with carb cleaner and a brush if necessary.

Source: by miesk5 at Ford Bronco Zone Forums

--

In my first reply I addressed some of your main issues; "let off the gas completely the truck will kinda bog back and fourth"

here it is again since you are using a phone to communicate here;

DTC 13 Cannot control RPM during ER Self-Test, low RPM & Possible Causes;

vacuum leak, use garden hose section to listen for leak noise;

TB base idle off- Idle Air Control (IAC) Sludge; Poor Idle TSB 91-25-07 for 85-92 Bronco & F Series & many others; "...Hard cold starts, hesitation and stalls on initial start-up or during idle or decel may be caused by sludge in the throttle body and/or idle by-pass valve. Sludge deposits or oil film on the throttle body bore and plate or the idle air by-pass valve may cause one or more of the following conditions. Hard Cold Start, Stall On Initial Start-Up, Stall During Idle, Stall During Decel, Rough Idle, Rolling Idle, Hesitation During Acceleration. A new idle air by-pass service kit (F2PZ-9F939-A) is now available for service use to correct sludge contamination concerns of the throttle bore and plate only..."

Now read this;

Idle Air Control (IAC) Modification in an 86....

use a multi meter on DC Volts to ensure battery voltage of at least 10.5v.

back probe the harness connector wires



Test by Charlie Probst

Check that IAC gasket is it deformed?

As Nelbur mentioned, his gasket mod helped.

Has anyone tried to adjust the idle stop *****? If not, do not turn it.

 

[thebronc]

Iac is new along with a new gasket which matched the previous one that never had a problem before. Battery is new and good

no vacuume leaks other than possible charc can which will eliminate today even though i know its nit the prob.

Idle ***** has nit been touched

egr is clean. And good.

RON. Curious. I used to hook the scanner up to my truck and would power up just fine with trucks power through the rear plug ins. Now it wont. I have to hook up a power cord to the cig lighter. Does that mean anything about my computer? Also i tried to clear the codes and it wouldnt let me. I forget what it said but i will try again today

 

[miesk5]

test voltage @ IAC harness connector as shown above

Scan Tool Won’t Initiate Self-Test

 

[thebronc]

Iac is new along with a new gasket which matched the previous one that never had a problem before. Battery is new and good

no vacuume leaks other than possible charc can which will eliminate today even though i know its nit the prob.

Idle ***** has nit been touched

egr is clean. And good.

RON. Curious. I used to hook the scanner up to my truck and would power up just fine with trucks power through the rear plug ins. Now it wont. I have to hook up a power cord to the cig lighter. Does that mean anything about my computer? Also i tried to clear the codes and it wouldnt let me. I forget what it said but i will try again today

 

[Rons beast]

Hey Ben,

Knowing the scan tool is having a problem, ( actually the truck is having a problem with the tool.)

The entire problem could be a grounding problem. Your ground strap from battery - to the frame and engine and body MUST be good and clean. I have encountered many problems that eventually got traced to a bad ground.

You have a 26 year old vehicle...I bet it never had the grounds cleaned and inspected in it's history. If your battery cable is looking tired at all do yourself a favor and change it. Check and clean all the grounds. It may take some boring time to search them down, but it will be well worth it.

Good Luck