Diagnosis needed TIA

[demarpaint]

Thanks for the info it is something that will also have to be addressed.

There was a TSB about the TB gasket which was addressed, but the TB is the factory original unit. I'd have to search for one. I'm not sure how one coming from a wreck would be though, this van is pushing 24 years old. Borrowing one unfortunately is no longer possible, my brother sold his F-150 a while ago.


Is there anything I can do with the TB I have? I mean something like putting 1/4 turn on a screw for the sake of argument? At this point there would be no out of pocket expense, or pulling a part from a wreck that is worse than what I already have.

It almost does exactly what a bad accelerator pump would do.

 

[mechanicx]

Well if you had the tools to do the factory specified base idle adjustment that would be good. If you turned the screw say a qtr of a turn and tested it out and could put it back to where it is I don't see any harm. I do agree with you that it acts just like an accelerator pump problem or more precise a transition circuit. I do wonder about your base ignition timing with the spout disconnected. Also does this application have a MAP? If so the MAP along with the TPS fills the role off the idle transition and accelerator pump. if you unplug the MAP maybe that will show something.

 

[demarpaint]

Base timing was/is properly set, the MAP sensor was swapped with my brothers. The last tech that had it confirmed the base idle was properly set, but am I 100% certain? Not really anymore! i'm only as certain as he was. LOL, at this point I don't know. Which is why I asked about tweaking it. I could make a mark and return it to the current setting.

If I start playing with 1/4 turns do I start with clockwise or counter clockwise turns? Is a 1/4 turn to much? I can just as easily do 1/8 turns. At this point I'm tossing Sh!t against the wall. This thing has quite a few people scratching their heads, and as you and others can tell I do take beer breaks and don't give up! LOL

I'm headed out for a bit I'l check back later.

Thanks guys!

 

[mechtech2]

A 'tip off' stumble is usually lean or retarded ignition advance.
I'd clean your MAF and recheck those vacuum connections. The intake gaskets often leak. But even a leaky valve cover gasket can cause some running problems. And of course, check the ignition timing. Dirty injectors are another thing to check.

One often overlooked point is that that car was not designed for E10 fuels - it is automatically at a disadvantage. Ad this to the stone age controls on the engine, and people often have problems.

 

[demarpaint]

It might be something I have to continue to live with!

 

[OVERKILL]

Base-idle reset for an EEC-IV Ford is this:

Get the engine warm.

Unplug the IAC.

The engine should BARELY idle; RPM should be around 500-600. Plug the IAC back in, it should pop up to ~850 IIRC.

ECM shoots for a static idle value. But when the TPS is much above a volt, you will just end up with a high idle as the TPS is out of range.

Anything between .86-.98 is fine for TPS voltage. The lower end is actually like .68, and the high end is 1.13 IIRC, but use the range I've given to keep things "safe". This is KOEO.

 

[demarpaint]

Originally Posted By: OVERK1LL
Base-idle reset for an EEC-IV Ford is this:

Get the engine warm.

Unplug the IAC.

The engine should BARELY idle; RPM should be around 500-600. Plug the IAC back in, it should pop up to ~850 IIRC.

ECM shoots for a static idle value. But when the TPS is much above a volt, you will just end up with a high idle as the TPS is out of range.

Anything between .86-.98 is fine for TPS voltage. The lower end is actually like .68, and the high end is 1.13 IIRC, but use the range I've given to keep things "safe". This is KOEO.


I had the van at operating temp. I unplugged the IAC and had a base idle of about 525. Plugged in I think the idle is about 800 or a touch higher, I can check that in the morning. TPS voltage was a little under 1. The TPS this van has is fixed there is no adjustment.

Another thing comes to mind. When it is hot out, and you flip on the AC the engine will sometimes search for an idle speed, up and down, and then settle when you tap the gas. This is another intermittent quirk worth mentioning.

 

[OVERKILL]

Sounds like base idle is dead-on.

That AC issue is a triggered lean or rich condition. Surging is an indication of the ECM trying to compensate for it. VERY common on modified EEC-IV Mustangs. Not so common on a stock 300 I6, LOL!!!!! Normally, you tune it out with a chip on the 'stang. I'm thinking that shouldn't be necessary with your van

How many inches of vacuum does it pull at idle?

 

[punisher]

Originally Posted By: OVERK1LL

That AC issue is a triggered lean or rich condition.


.......or someone did not set idle strategy correctly during all of the work done.

EDIT: Seriously time to find some shop with an old 60 pin adapter and an SBDS/Service Bay Diagnostic System.

 

[brianl703]

Originally Posted By: mechtech2

One often overlooked point is that that car was not designed for E10 fuels - it is automatically at a disadvantage. Ad this to the stone age controls on the engine, and people often have problems.


E10 fuel isn't new. A 1988 vehicle was certainly designed for it. It was available back then, especially in the midwest.

 

[demarpaint]

OVERK1LL I don't have off the top of my head the vacuum reading but I know it was well within normal.

Punisher the idle strategey was set by disconnecting the negative terminal, for about 30 minutes then turning the headlights on, or leaving a door open to so a light would stay on. Then the light was shut, door closed and battery reconnected. Engine started and ran for 2 minutes IIRC and then the was AC flipped on. At that point I took it for a typical drive for that vehicle, which is about 5 minutes to the parkway. Three stop signs, three lights, and a nice on ramp. During that time, I turned the AC on and off for a short time, over a minute.

I'm pretty sure the idle strategy is properly set. Don't these vehicles relearn the strategy on their own if they get messed up because of a dead battery or something?

Thanks!

 

[punisher]

Originally Posted By: demarpaint

I'm pretty sure the idle strategy is properly set. Don't these vehicles relearn the strategy on their own if they get messed up because of a dead battery or something?

Thanks!


You did it by the book. It does take longer than you think for the idle to sort itself out if the strategy isn't set correctly the first time. I replaced the batt in the Grand Marq 2 months ago, and just got in a rush and forgot to go through the setup. Took more than a month for it to stabilize with the AC on. Its a measure of my stubbornness (and laziness) that I decided to wait it out instead of disconnecting the batt again and resetting it.

Life is tough for a tech when he runs across a problem like you have. I remember my last week on the line I inherited a T-Bird (4.6 2V) from another dealership that had an off idle stumble like yours. Problem was it would only occur in the first 30 seconds after a cold startup. Unfortunately that wasn't enough time for the DCL to communicate with the PCM so there was no way to get a snapshot of the problem. Fuel pump had been replaced (twice) under warranty, no fix, MAF, no fix, PCM, no fix, fuel pressure regulator, no fix,ACT, no fix, ECT, no fix, vapor purge control valve, no fix etc. Ford had paid big bucks to have a tech throw parts at it, and I really couldn't fault the tech all that much. Sometimes you have to take a guess, usually not that many, but you have to. We finally snagged an identical vehicle from the used car dept, and I had my helper start swapping parts, until something changed. One evening he swapped out coil packs before he went home, and behold it started up the next morning and no hesitation. Let it set, tried it again, OK. Let it cool, test drove it OK. Conversely the used car we swapped parts with inherited the miss, so we knew the answer. Swapped out one coil pack to see which one it was and turned out the Bank 1 coilpack had a problem for the first 30 seconds on cold start. Passed all resistance tests, output voltage was OK, no EDM problems indicated, no visible connector problems. That d****d coil just had cold problems, which is exactly the opposite of what one would expect in that situation. I remember now why I retired, that and working on Expeditions and Navigators to I guess.

 

[demarpaint]

Sometimes in cases like mine you have to know when to fold'em, or say uncle. I'm thick headed though!

As a side note about 75-100 miles ago I had my brother make a plate to block off the EGR valve to rule that out once again. I tested it but never blocked it off. It is OEM Ford with about 10,000 miles on it. Changing it did nothing! Blocking it gave me more power, understandably so. However I got lazy and didn't disconnect the battery. The stumble is still present, should I disconnect the battery and let it learn the strategy with the blocked EGR valve? Again I'm tossing Sh!t!

Thanks!

 

[punisher]

Blocked EGR valve isn't going to effect idle strategy, or any idle/off idle driveability concerns, unless it was malfunctioning to begin with.

 

[demarpaint]

Thanks, then it is safe to rule the EGR out again.

 

[mechanicx]

I think the only way this issue is going to be fixed is if the diagnostic process was started over followed to a T and might require factory service information and scanner. Everything has been checked but either something wasn't done as claimed by one of the mechanics who worked on it or maybe a part that was replaced is bad right out of the box.

I would start with the base idle being set by the book, ignition spuot disconnected and timing verified 10 degrees + or - 2, IAC unplug, .050" feeler gauge between the throttle adjustment screw, run engine till warm, set base idle to 650 rpm, Engine off wait 10 seconds plug ISC and ignition spout, do idle relearn etc. I'm probably paraphrasing the exact procedure and it varies by year and engine but I think that is the right one. From there I would want to check that TPS voltage was right with KOEO. You'd probably want to look at the ISC duty cycle and compare it to the expected value. And also that the TPS gives a smooth transition as the throttle is pressed. That would require a good scanner or voltmeter.

I know you already said you went through all this, but it seems like the problem would lie in the base idle/TPS or ISC. But like punisher said who knows the problem could be elsewhere and hard to find like in the ignition system and swapping parts trial by error might be the only way.

I was wondering do you still have that ISC spacer plate installed that I seem to remember you using? I doubt it is the source of the problem either way. I guess it's a matter of truely getting the fixed would require you or a comoetent mechanic to go through everything systematically from start to finish until the problem is solved. I just get the impression that a few mechanics worked on it and couldn't get it done, but who knows what they really did or didn't do?

 

[OVERKILL]

Originally Posted By: mechanicx
I think the only way this issue is going to be fixed is if the diagnostic process was started over followed to a T and might require factory service information and scanner. Everything has been checked but either something wasn't done as claimed by one of the mechanics who worked on it or maybe a part that was replaced is bad right out of the box.

I would start with the base idle being set by the book, ignition spuot disconnected and timing verified 10 degrees + or - 2, IAC unplug, .050" feeler gauge between the throttle adjustment screw, run engine till warm, set base idle to 650 rpm, Engine off wait 10 seconds plug ISC and ignition spout, do idle relearn etc. I'm probably paraphrasing the exact procedure and it varies by year and engine but I think that is the right one. From there I would want to check that TPS voltage was right with KOEO. You'd probably want to look at the ISC duty cycle and compare it to the expected value. And also that the TPS gives a smooth transition as the throttle is pressed. That would require a good scanner or voltmeter.

I know you already said you went through all this, but it seems like the problem would lie in the base idle/TPS or ISC. But like punisher said who knows the problem could be elsewhere and hard to find like in the ignition system and swapping parts trial by error might be the only way.

I was wondering do you still have that ISC spacer plate installed that I seem to remember you using? I doubt it is the source of the problem either way. I guess it's a matter of truely getting the fixed would require you or a comoetent mechanic to go through everything systematically from start to finish until the problem is solved. I just get the impression that a few mechanics worked on it and couldn't get it done, but who knows what they really did or didn't do?


Agreed. I think this is good process.

One other thing to try before doing all of this:

Pull the SPOUT. Set base to 14 degrees. Replace SPOUT. See if the added timing makes a difference. Used to be good for a few ponies on the EEC-IV 302, and would often help with the manners of non-stock engines.

 

[demarpaint]

still have the spacer plate installed, on or off made no difference.

OVERK1LL- Timing is set to factory spec. I can play around with it. You mentioned base to 14 degrees, is that BTDC? Its been a while.

Here's the lousy part of being a DIY'er taking a vehicle to a tech. Do you believe them or not? I put my faith in them and trust them but as mentioned I really have no clue what they did, if they did it right, or did it at all? I did a lot of the testing myself, only to have them confirm what I did was in fact correct, I hope! They did some other diagnostics, and years back Ford had it for the same problem, and was unsuccessful. I stab at it from time to time because it PIzes me off!

I guess I have to pony up the cash and look for another tech and start from scratch again. But have a feeling I'm headed nowhere fast and will be tossing good money to the wind again!


I can try a few more suggestions from here myself, like play with the timing, remove the spacer plate, again, check base idle, and then make a decision. At $100/hr labor, costs add up fast. I'm limited to a vacuum gauge, volt meter, timing light, tach, a primitive code reader, tons of hand tools, and a thick skull. I'm wondering if this is one of those issues that might never be resolved?

The last guy that had it was cool, he promised me that if he couldn't fix it I wouldn't have to pay. I felt bad and tossed him $100 for his efforts. He said he'd live with and wished the van was his. I might just go back to him and see if he wants to buy it! LOL

Again thanks!