Forum newby needs troubleshooting help(long)

[lbperry4227]

Just got my car running but it’s not running right.
It’s got a stock 302 EFI out of an ‘88GT. I’ve removed the EGR and plugged fordfuelinjection.com’s three resistor module into the EGR connector. I’ve put the resistors into TAD and TAB circuit. I cleaned out the IAC pretty thoroughly (before that it wouldn’t idle at all).
Symptoms: It idles pretty well at 900 – 1000 when cold. It hunts a little when warmed up.
When I hold the throttle at a constant position pretty much anywhere in the range, the rpm will stay steady for several seconds (~3-5) and then the engine will start choking down. If I press slowly on the gas, it will bog worse and the rpm will drop until it dies. I can prevent the dying by blipping the throttle. The symptoms improve slightly as it gets up to temp but it still occurs. The plugs are sooty black with the top of the center electrode and a thin ring around the tip a light tan.
I ran the KOEO and KOER with the following results:
KOEO:
67 – Neutral Safety Circuit failure (I’ve got the transmission harness unplugged.
11 – System Passes
KOER:
94 – Thermactor Air Injection inoperative (left side)
44 – Thermactor Air Injection inoperative (right side)
33 – EGR valve opening opening not detected
1 - ??
3 - ??
The 94, 44, and 33 on the KOER are almost like I don’t have the TAD, TAB, and EGR resistors in place. If the last two are a 13 instead of a 1 and 3 then that translates to "Cannot control RPM during ER Self-Test low RPM check".
Sorry for such a long thread but I’d really appreciate any ideas you might have to solve my problem(s).
Thanks for any help you can provide,
Lawrence Perry

 

[Camman]

This is going to be a little difficult to diagnose over the internet. From purely the symptoms you are describing my first inclination would be unmetered air is entering the motor. Check for vacuum leaks. As far as the egr thing I am not familiar with it. But... y would you want to remove it? It costs you no power

Also I am suprised your car ran the koer codes with a 67... mine never will

Also, set your timing to stock and see whats up. Do you have a vacuum gauge? Can you tell me what it looks like at idle as well as when you give it gas.

Let me know if this is any help at all, and if not I will do my best to help you trouble shoot it.

 

[HISSIN50]

Welcome to the board LP!

Just to clarify (I think you were just tossing out lots of info at once), the EGR and TAB/TAD systems are separate.

Camman's idea with the vac gauge is great. If I did not think it was an engine management issue, the bogging you describe, while holding the throttle, almost sounded like an exhaust restriction or funkyness with the EGR, if you had one.

Did you mention what your warm idle setting is?

If you have not already, perhaps take a cruise through the 'Surging idle checklist' by Jrichker at the top of the sub-forum page. Perhaps a piece of info is in there that can help.

Good luck.

 

[lbperry4227]

Thanks, guys. You gave me some things to look at. I'll check for vac leaks first and then put a vac gauge on it. I've never used a vac gauge on an EFI engine before so I'm not sure what I'm looking for (I'm an old school carb guy just getting back in the game)but I'll try it and see if anything jumps out at me. There's probably some good info on this forum that'll point me in the right direction. I'll do some searches.
Camman, timing is stock. I think. I'll double check.
I removed the EGR, air pump, etc, to clean up the top of the engine as much as possible. EFI engines just aren't as clean looking as a carb setup.
Thanks again for the help. I'll report back progress.
Lawrence Perry

 

[HISSIN50]

With the vac gauge, it is much like a carbed vehicle. Look for 15-20" hg at idle, and a nice steady signal (no fluttering or drop off in the reading). A diminishing reading can be an exhaust restriction.

Good luck.

 

[Camman]

if your familiar with troubleshooting a carbed vehicle with a vacuum gauge then you are good. The efi motor is EXACTLY the same as far as vacuum is concerned. The motor is still the same, just instead of a carb there are injectors.

 

[lbperry4227]

I replaced the IAC since the old one still had quite a bit of carbon in it even after I cleaned it twice. That helped the idle somewhat but it still hunts a little. It did help the coughing, bucking problem in that it only happens below 2000 rpm now instead of throughout the range.
I put a vacuum gauge on it and at idle it's a solid 18" - 22" and drops pretty much as you'd expect when the throttle is opened.
I did find one thing that may be a clue. I replaced the TPS when I first got the car running and set it to about .96 volts. I went back and double checked it and go it to about .98 volts which is about all I could get in sensor rotation. I decided to check the TPS reading through the throttle range and as the throttle was opened it went to about 2 volts and then went dead, not 0 volts, just no reading at all. I think I remember reading somewhere that I was supposed to get a reading up to 5 volts at WOT. Is this correct?
Do you think that I just got a bad TPS? Could the readings I got cause the problems I'm seeing?
Thanks for your help,
Lawrence Perry

 

[HISSIN50]

The TPS should see a baseline of ~0.97 volts and see a linear elevation as the throttle is opened, ending at ~4.5 volts (just like you said). THe fact that you dont have this does suggest that the TPS is a little off. New ones are not expensive and it might be worth replacing (usually I say to check wiring, but since it functions normally at other times, it seems like a TPS issue).

Good luck.

 

[lbperry4227]

Disregard previous post. I just realized I had voltmeter on 2 volt scale so when it got to 2 volts it quit.
Am double checking everything now.
Sorry for false alarm.
Lawrence

 

[lbperry4227]

TPS now at .97V initial and goes to 4.7V at WOT. It looks OK.
DANG! Thought I had found the silver bullet fix.
Well, back to the drawing board.
Thanks,
Lawrence

 

[HISSIN50]

Nice work - diagnosing diagnostic tools is a HUGE part of the game. I recall spending some time troubleshooting a dead circuit, only to find my test light had crapped out. Now I bench test the meter/light before beginning.

Good luck with it!