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Car Forum / Ford / Ford Mustang / February 2008Solve The Idle Problem From Hell -- Win a Prize!
Patient: 1993 Cobra/125,000 miles -- stock except: shorty headers, advanced timing, 73mm C&L mass-air meter and an A9L processor. This combo ran solid for a number of years and the symptoms suddenly -- no mods or changes were made -- just appeared. The symptoms have gone on now for about 1 1/2 years. The frequency of the symptoms has slowly increased from maybe once a week to almost every day. But despite the symptoms, the car performs well without any popping, missing, stalling, gassy smells, or smoking. ----- Symptoms: Reved-up idle. Sometimes. Some days, the car will run fine all day long, or for a couple days. Other days, the reved-up idle will continue to happen. Idle speed varies, but generally sticks -- doesn't roll -- somewhere between 1600-2200 rpms. Never goes above 2200. Generally, I get the reved-up idle a few minutes -- 3-4 minutes -- after a cold start AND after I dip into the throttle a little bit. But frequently I get the reved-up idle when/after the motor is fully warmed up. Miles and miles of driving -- 20-30 -- even at highway speeds, often, won't alter the reved-up idle. Running the car hard, even really hard, doesn't change the idle (if anything, it often makes it go higher up in the 1600-2200 range). Normally, running the car hard will trigger the reved-up idle. ----- Complications: Shutting the car off and restarting _always_ fixes the idle, at least for a while. No codes have _ever_ popped up in the computer. Sometimes the idle will just fix itself while driving. And a few times _while reved up_ I've had it just fall to the normal idle speed and stay there. And a few times, after falling to a normal idle, I've had it return to the reved-up idle -- like someone is controlling it by remote. A scan tool was run once while the idle was reved up and, for some unknown reason, the reved-up idle didn't return for nearly 4 months. Also, a few minutes _after_ the [scan] tool was _unplugged_, the idle dropped to normal and then a few minutes later it reved back up. Coincidence? My mechanic, and he's extremely good, was at a loss, but thought the processor might have some issues. (Note: My mechanic drive my car home that night and the car ran PERFECT for him. It's about a 40-mile loop for him to drive to and from work.) ----- Recent developments: A few weeks ago, I noticed on two occasions, a missing while driving/ cruising at highway speeds. The missing has since gone away. Also, after a cold start leaving work one day, a few weeks ago, the idle went below the normal idle speed and the car acted like it was going to stall. After a few minutes of driving the problem went away and hasn't returned since. ----- Treatments used so far, in this sequence: 1) Fuel filter 2) New TPS 3) New Air-Idle Control valve 4) New Mass-Air sensor (the actual sensor unit in the mass-air meter) 5) New A9L Processor Each treatment was used independently, but nothing has helped/worked. ----- Besides a gun, does anyone know of a cure? Patrick > Patient: > [quoted text clipped - 87 lines] > > Besides a gun, does anyone know of a cure? Have you looked at the BAP/MAP sensors? They allow engine control adjustments based on the weather (i.e. barometric pressure etc.). Have you ever changed the O2 sensors? They may be feeding periodic errors to the ECU. Other things that come to mind are vacuum leaks at various places (although I don't think this is it) like the throttle body/ERG spacer. My money is on a sensor going bad very slowly/intermittently. I'm surprised a code hasn't been tripped though. >> Patient: >> [quoted text clipped - 95 lines] > spacer. My money is on a sensor going bad very slowly/intermittently. > I'm surprised a code hasn't been tripped though. I'll go with a vacuum leak. Maybe a split in one that doesn't bleed all the time, thus the inconsistency and absence of codes. >>> Patient: >>> [quoted text clipped - 102 lines] > I'll go with a vacuum leak. Maybe a split in one that doesn't bleed all > the time, thus the inconsistency and absence of codes. This is typical with a car that is 15+ years old. There are so many components that just wear out and are hard to identify when they do. The Fox cars have just enough electronics with poor diagnostics to make them a pain for us old school mechanics. > >> NoOptio...@aol.com wrote: > >>> Patient: [quoted text clipped - 103 lines] > > I'll go with a vacuum leak. Maybe a split in one that doesn't bleed all > > the time, thus the inconsistency and absence of codes. > This is typical with a car that is 15+ years old. There are so many > components that just wear out and are hard to identify when they do. > The Fox cars have just enough electronics with poor diagnostics to make > them a pain for us old school mechanics. Another option is putting back in the original 1993 computer, because that year computer spits out more codes than the older A9L. Patrick >>> Patient: >>> [quoted text clipped - 103 lines] > I'll go with a vacuum leak. Maybe a split in one that doesn't bleed all > the time, thus the inconsistency and absence of codes. VLeaks - check the little rubber elbow at the gas fume canister, front engine bay, lower, passenger side, they expand and get too loose, almost fall off, no replacement available, got to roll your own. Clean the injectors ? (long shot) replace distributor cap, (shorts on inside of cap) replace rotor too....... the O2 sensors get "lazy" after long time you could have a wiring problem, somewhere (like that helps!) Seems like something is intermittent in open loop. Let us know what you find, thanks -87 5.0 -93 5.0 8# KB > >> NoOptio...@aol.com wrote: > >>> Patient: [quoted text clipped - 108 lines] > engine bay, lower, passenger side, they expand and get too loose, almost > fall off, no replacement available, got to roll your own. I will look at that. Thanks! > Clean the injectors ? (long shot) I always use Top Tier gas. And often the car runs soooooo good/ smooth. > replace distributor cap, (shorts on inside of cap) replace rotor too....... I did that not too long ago. The idle problem remained. > the O2 sensors get "lazy" after long time The O2s are fairly new. > you could have a wiring problem, somewhere (like that helps!) > Seems like something is intermittent in open loop. > Let us know what you find, At times I can almost feel the problem through the gas pedal. Like click, and idle changes. Other times, it like someone is running it by remote control; the idle will just rev up and stay there, and sometimes it'll go back down. I think the car is haunted. Patrick > > NoOptio...@aol.com wrote: > >> Patient: [quoted text clipped - 101 lines] > > spacer. My money is on a sensor going bad very slowly/intermittently. > > I'm surprised a code hasn't been tripped though. > I'll go with a vacuum leak. Maybe a split in one that doesn't bleed all > the time, thus the inconsistency and absence of codes. I'm afraid at some point I may run out of things to try and just tear the whole top end off -- plenum, egr, t/b -- inspect everything and then put it all back together. Patrick >>> NoOptio...@aol.com wrote: >>>> Patient: [quoted text clipped - 78 lines] > the whole top end off -- plenum, egr, t/b -- inspect everything and > then put it all back together. Put a code reader in the car and carry it at all times. When the problem occurs connect it up and pull the codes. This might give you a clue. > NoOptio...@aol.com wrote: > > Patient: [quoted text clipped - 88 lines] > > > Besides a gun, does anyone know of a cure? > Have you looked at the BAP/MAP sensors? They allow engine control > adjustments based on the weather (i.e. barometric pressure etc.). I have not. > Have > you ever changed the O2 sensors? One was changed a few months ago. It tripped a code. But the new sensor didn't affect/change the idle problem at all. > They may be feeding periodic errors to > the ECU. Other things that come to mind are vacuum leaks at various > places (although I don't think this is it) like the throttle body/ERG > spacer. My money is on a sensor going bad very slowly/intermittently. > I'm surprised a code hasn't been tripped though. It is the weirdest thing. I just can't nail down when it does it. Some days the car runs flawless and others the idle keeps reving up. Patrick > Patient: > [quoted text clipped - 89 lines] > > Patrick Does the car have air condtioning? Does working that control have any effect on the hi idle speed? > NoOptio...@aol.com wrote: > > Patient: [quoted text clipped - 88 lines] > > > Besides a gun, does anyone know of a cure? > Does the car have air condtioning? Does working that control have any > effect on the hi idle speed? It does have A/C. But powering the A/C on or turning it off has no affect. I too, quite a while back, thought the A/C might affect the idle, but as with everything other hunch I've tried, nothing has worked. Patrick > Patient: > [quoted text clipped - 89 lines] > > Patrick Had a similar problem with my 2001 GT but with a twist. Every few months I'd start the car and the idle would stay at about 2500. After the car warmed up a bit, the idle rpm when back down to normal. It happed for about the tenth time and this time the idle didn't return to normal. Took the car to the dealer, and they replaces the idle control valve. All seemed well for a while. A month later, I started the car and the idle dumped. I had to keep it running with my foot. After the car warmed up, it started to idle normally. It did this a few times over a three month period. Then, it happened and the rpm idle didn't come back up. It just dumped every time and I had to keep it going with my foot. Took it back to the dealer and it turned out that the replacement idle control valve was bad too. Replaced it again, and that cleared up the problem. That has been the only problem I've had with my 2001 since I purchased it brand new. If the dealer cant find anything else and the problem continues, have a look again at the obvious things like the air idle valve. You could have gotten a "putz" replacement part like I did. Michael >> Patient: >> [quoted text clipped - 110 lines] > > Michael Have also solved similar problem by replacing idle air control valve ( intermittent fast idle speeds without setting any trouble codes); >>> Patient: >>> [quoted text clipped - 112 lines] > Have also solved similar problem by replacing idle air control valve ( > intermittent fast idle speeds without setting any trouble codes); Have seen the same in a Jeep, sticking idle air control valve... dirt/carbon buildup caused it to stick intermittently. Weird thing is, resetting the ECU always made it work ok for a short while. (disconnect battery cables). I guess the ECU re-read all sensors once and adjusted to the prevailing conditions (open valve) Jan > >> <NoOptio...@aol.com> wrote in message > >>news:b6afe3a0-370a-4323-a304-67b0495690e4@l32g2000hse.googlegroups.com... [quoted text clipped - 120 lines] > while. (disconnect battery cables). I guess the ECU re-read all sensors > once and adjusted to the prevailing conditions (open valve) Now four votes for an IAV. I think I'm going back to the Ford dealer. Patrick > > <NoOptio...@aol.com> wrote in message > >news:b6afe3a0-370a-4323-a304-67b0495690e4@l32g2000hse.googlegroups.com... [quoted text clipped - 110 lines] > > look again at the obvious things like the air idle valve. You could have > > gotten a "putz" replacement part like I did. > Have also solved similar problem by replacing idle air control valve ( > intermittent fast idle speeds without setting any trouble codes); Two votes for IAC valve... hmmm.... I may try that, again. Patrick > <NoOptio...@aol.com> wrote in message > [quoted text clipped - 107 lines] > again, and that cleared up the problem. That has been the only problem I've > had with my 2001 since I purchased it brand new. > If the dealer cant find anything else and the problem continues, have a look > again at the obvious things like the air idle valve. You could have gotten > a "putz" replacement part like I did. Michael, I might have to try another one because I'm out of ideas. Patrick >Patient: > [quoted text clipped - 89 lines] > >Patrick Even though you already replaced it, replace the IAV again, as one of the other poster mentioned. If you want to mess around before doing that you might also try readjusting the idle speed. I replaced the IAV on my 88 and it still had a lot of fluctuation until I adjusted it as follows... Engine off, back out the idle stop screw till it no longer even touches the lever. Then screw it in to the point where is just barely touches the lever and then give it an additional quarter turn. Then try driving the car and see if things improve. If that doesn't work, give it another quarter turn in and try again. If that doesn't work, buy a new IACV. >>Patient: >> [quoted text clipped - 102 lines] > give it another quarter turn in and try again. If that doesn't work, > buy a new IACV. If the idle stop screw was never touched in the first place, I'd stay away from it. Changing it might compound the problem, making diagnosis even more difficult. >>>Patient: >>> [quoted text clipped - 106 lines] > away from it. Changing it might compound the problem, making diagnosis > even more difficult. true. I would also clean (inside) just behind the throttle valve itself, I found a rim of carbon built up behind it from the manifold exhaust that is fed back into the intake, which was sticky. > >>>Patient: > [quoted text clipped - 112 lines] > rim of carbon built up behind it from the manifold exhaust that is fed back > into the intake, which was sticky. I already tried that. It didn't work. Patrick >>>Patient: >>> [quoted text clipped - 106 lines] >away from it. Changing it might compound the problem, making diagnosis >even more difficult. It's not rocket science. If that's a concern a person can always count the turns so they can put it back just exactly where it was. >>>>Patient: >>>> [quoted text clipped - 109 lines] > It's not rocket science. If that's a concern a person can always > count the turns so they can put it back just exactly where it was. Still, no reason at all to change it if it's never been touched. It's obviously not the problem. >>>>>Patient: >>>>> [quoted text clipped - 128 lines] >Still, no reason at all to change it if it's never been touched. It's >obviously not the problem. Well, the original parts of any sort were never "touched" so I guess there's no reason to replace or adjust anything to solve the problem, just call in someone with chicken bones to say a chant over it. >>>>>>Patient: >>>>>> [quoted text clipped - 133 lines] > to solve the problem, just call in someone with chicken bones to say a > chant over it. Time plays a factor in a lot of problems, e.g., sensors wearing out or getting dirty, vacuum hoses splitting, etc. Throttle stop screw isn't one of them. >>>>>> On Sun, 30 Dec 2007 14:19:45 -0800 (PST), NoOption5L@aol.com >wrote: [quoted text clipped - 156 lines] >getting dirty, vacuum hoses splitting, etc. Throttle stop screw isn't >one of them. And you know his has not backed out because???? Or that it was not improperly set at the factory because??? >>>>>>> On Sun, 30 Dec 2007 14:19:45 -0800 (PST), NoOption5L@aol.com >>wrote: [quoted text clipped - 158 lines] > > And you know his has not backed out because???? I doubt Patrick would've messed with it in the first place. And IIRC, those screws had a factory plastic seal (or something similar) around them to discourage tampering. > Or that it was not > improperly set at the factory because??? The car had been running fine until recently. >>>>>>>> On Sun, 30 Dec 2007 14:19:45 -0800 (PST), NoOption5L@aol.com >>>wrote: [quoted text clipped - 32 lines] >>>>>>>>> >>>>>>>>>Generally, I get the reved-up idle a few minutes -- 3-4 minutes I have to admit this is an interesting thread, The OP has been convinced he dare not touch that idle screw yet if I read it right, he's considering tearing the whole induction system off and putting it back on if nothing else works. I just hope he doesn't touch that idle screw in the process. > >>>>>>>> On Sun, 30 Dec 2007 14:19:45 -0800 (PST), NoOptio...@aol.com > >>>wrote: [quoted text clipped - 40 lines] > > - Show quoted text - +1 for the IAC. I've seen similar problems on each of three Fox - bodies, and each time the IAC solved my problem. I also gotten great results spending half an hour and half a spray can of carb cleaner on the existing IAC, although the last IAC (new) shouldn't have that problem. <snip> > ----- > [quoted text clipped - 16 lines] > > Patrick If you have run out of other options, try tracing down the ground wires for each sensor, but particularly the ECU and make sure that they are clean underneath to frame. Also look at any splices that are inline as a bad crimp can do most of what you describe. cheers, chuck... > <snip> > [quoted text clipped - 22 lines] > for each sensor, but particularly the ECU and make sure that they are > clean underneath to frame. I did this. All was well. > Also look at any splices that are inline as > a bad crimp can do most of what you describe. Nothing has ever been spliced on this car. Patrick NoOption5L@aol.com wrote in news:b37e3626-8b96-429d-a248- 80ad253407db@v4g2000hsf.googlegroups.com: >> <snip> >> [quoted text clipped - 31 lines] > > Patrick Hi Patrick, actually every connection is 1/2 of a splice as it involves crimping the terminal to the wire. If the connection is made by crimping over the insulation instead of on the bare wire it may work for a while or be intermittent (unfortunately, I've had this happen to me) and a pain in the butt to find and fix. Another remote possibility is a chaffed wire that makes contact when it passes through a bulkhead (firewall) or touches bare metal. I've seen them where the contact is made only when the vehicle is running or someone is in them. cheers, chuck... Sounds like a possible bad wire (shorted) going to the AIR IDLE solenoid. > Patient: > Symptoms: > [quoted text clipped - 19 lines] > Normally, running the car hard will trigger the reved-up idle. > ----- > Besides a gun, does anyone know of a cure? > > Patrick Hello Patrick - Ever fix this yet? Just a couple of questions - AIC and TPS - you buy them from Ford or Autozone etc.... TPS - when you installed it did you check the voltage? (Should be set to ~1.0 Volts) Like Michael Johnson suggested, a 15 y/o these are normal problems. My 1990 has a few idle issues when cold and I'm almost sure it's the IAC. And I don't drive it as a daily driver anymore (and come to think of it had better change the oil today - embarrassed how many months - not miles though - have passed since last change) And just throwing this out there since it's cheap enough...when was the last time you changed the PCV? (thinking along lines of vacuum relted issues ... One last thing....the linkage...springs etc to the throttle body...they still have their tension and have you checked is anything physically binds? TB not closing all the way cause it's got junk/ buildup in there? Jimmy >> Patient: > [quoted text clipped - 52 lines] > > Jimmy yup, old PCV can screw things up a lot, and it is not easy to replace. Forgot what problems it causes........ On the 93 I replaced all the vacuum hoses, some were hard brittle and cracked I had a problem with the throttle cable sticking some, but when I got a rebuilt put in we straitened out the cable. The idle seems too high, mine goes to 1000 and drops to 800 stays there. TPS? Sticky TB valve inside Air Bypass gunked up Let us know what you find. |
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