Very High Idle Problem

Discussion in 'SN95 V6 Mustang Tech' started by Gr0und_Fault, Oct 19, 2006.

  1. Did you try a new TPS?
  2. No, I did not try a new TPS, not yet at least. From reading the forums, it seems to me that my idle tps voltage(.776 volts) is fine. Since I'm gettting a good voltage reading at idle from my TPS, doesn't that rule out the TPS being the cause of my high idle?
  3. Idle Speed Control
  4. You mean the idle air control valve?
    I got a new one from autozone and it didn't change a thing. I read on a different thread on this forum that a guy was having similar problems as I and got one from autozone that was crap. Then he got a ford motorsports one and that solved his problem. How can I get ahold of a ford motorsports IAC? Do I have to goto the dealer for that?
  5. *bump* for help. I still have the car sitting in my backyard with the high idle problem.
  6. How do I check the engine vacuum pressure? Is there a specific test point to do so?
  7. Just tried using some motor oil to try and find a vacuum leak. Some ended up dripping down to the exhaust manifold and since it was extremely hot with my engine reving at aprox. 3k rpm, a small flash fire happened. I thought that motor oil wasn't supposed to cause flash fires. I don't really want that to happen again so I think it may be time to take it into the shop.
  8. Ok..obviously I forgot to read over this post again.Ignore my response about the TPS in the other thread you posted.

    Your TPS is not faulty.A reading between 0.5 & 1.0 volts at idle is normal and wont cause idle issues.

    DO NOT USE motor oil or any kind of lubricant for that matter as a vacuum leak detector.Use starting fluid or even CRC Electrical Contact Cleaner or their MAF cleaner.Something with Methanol/Ethanol properties as the primary agent.And it also evaporates almost instantly so no worries about smoking up the neighborhood or lightin crap on fire.

    With an idle that high it would have to be a very large vacuum leak.Possible sources would be...the large vacuum line connected at the very back of the upper intake plenum.But even that hose unplugged from the intake doesn't cause my own car to run anywhere's near that high.I highly suggest you at least borrow a vacuum gauge and check the Hg level.20 or higher is normal.Lower than that and there is either a leak or some engine internals are worn.Does it smoke out the exhaust? If it does,what color/type?

    Check the bolts on the upper intake plenum.Have you ever removed them? Are any bolts missing?Could be an internal leak on the intake.

    You can also try what another member (don't remember user name) suggested in your other post.Unplug the TPS while the engine is running and see if anything shanges.I highly doubt this would do anything.What I had been thinking was even if the TPS signal (output) voltage was at 5 Volts (WOT sensor position),and the PCM responded by dumping more fuel through the injectors,the engine would not run that fast due to the fact that the throttle plate is in the closed position and only a very small flow of air is getting to the cylinders.It wouldn:t have the airflow needed to burn all that fuel and the PCM would recognize the low aireflow thus it would readjust injector pulse widths.It would then throw a CE light.and speaking of CE lights....I hate to have to look back at that other post,have you connected a scan tool to the car yet and checked for codes ?
  9. I wouldn't get electrical parts like that from AutoZone. Also, their EGR valves are questionable. I've put a few AutoZone EGR valves into a couple cars, and they didn't work properly.

    As far as the problem goes, I wonder if you could have a fuel injector stuck open and the car adjusts to high rpm to keep it from fouling out the cylinder. I would think if it were a vacuum leak, it would idle high, drop to where the car will almost die then shoot up again.

    It's a very peculiar problem, and I've seen some other folks with the same problem who don't ever find a solution -- or atleast they never post it if they do.
  10. Oh....and don't buy parts from Autozone.Their parts seem quite poorly made compared to Advanced (Discount Auto Parts).I never liked Autozone.Their parts are mostly some odd generic company who does half-ass rebuilds.If you can,go to Napa or Advanced Auto parts.Parts from FoMoCo are expensive and dealerships charge 1/3 to 1/2 more than they get it for from Ford.I know this because I just happen to have been working at a Ford Dealership in the shop for allmost a year and a half and counting.No more big employee discounts....

    Not to cut off the subject................................................
  11. let me help with the basics..
    i told you in the last thread to disconnect the tps with the car running tell me exactly what happened with idle the same with the maf
    after you have plugged in the tps. what exactly happens..
    make sure you have you air ducting tight and secure if not the maf will
    try to recalculate the lower amount of air traveling through the air filter, because there is more air volume being uncalculated somewhere else..
  12. I have a vacuum gauge, I just had to get batteries for it. I checked the vacuum at the vacuum tree on the drivers side. I got aprox. 21 in Hg of vacuum right there. Is there other spots that I should check my vacuum at? I replaced pretty much every vacuum hose. The vacuum going into the back of the upper intake is kind of hard to get to. Hard to tell if there is a leak comming from back there. I can reach my hand back there and unplug/plug it(and it seems to be pretty secure) in but I can't tell if it leaks any vacuum from there while the engine is running. I have never removed the upper intake. I checked the bolts and they all seemed to be on pretty tight. I didn't check the torque on them, but they are on there pretty tight. I have not disconnected the TPS with the engine running yet, but I have disconnected it and then started the car up. When I do that, the car still idles at 2.5k - 3k rpm. Same with the MAF, I have disconnected it and then started the car, but not while the car has been running yet. When I disconnect the MAF and then start the car, the idle fluxuates between 3k rpm and 0 rpm. Basically it's wanting to stall out, then it bounces back up to 3k rpm. I will try to disconnect them with the car running later on today and post results. I did check the codes a while back and had a camshaft position sensor fault. That was just before the winter and I cleared the code then to see if it would come back up again. I have since drove the car around a bit and dropped it off at a friends house and the code has never came back up since.
  13. Oh yeah, just to add. I have checked pretty much everything on the "Surging Idle Checklist" except for checking the grounds and voltage on the O2 sensors. I have never touched the idle stop screw, but since I have owned the car it has been backed all the way out. If I tighten the screw so it makes contact, it will raise the idle even higher. I must have missed this before, but I just went over the checklist again, and found this:

    "The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. Any car that has a 3G alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects. "

    I am actually having an issue with 2 of my gauges. I believe the oil pressure and engine temp gauges. So this ground can effect idle and the gauges? I just don't know exactly where this is at, I tried to look for it, but could not find on my vehicle. Anyone have a photo of where this ground wire/strap is?
  14. I believe I read on here somewhere that if you take off the IAC and cover the air ports on the intake so no air gets in/out that your car should idle fine. Is that true? I took off my IAC, blocked the two air ports off using duct tape. Started the car and it doesn't even want to start. I thought that the car should be able to start/run just with the amount of air that it recieves through the hole in the butterfly valve and that the IAC just adds more air as you add more throttle. I did this just to re-verify that my IAC is still working properly.
  15. I just disconnected the TPS while the car was running and had no change in idle speed. I connected the TPS back up and disconnected the MAF and the car stalled out. I just got off of the phone with my friends dad and he mentioned that since I did have a error code for the camshaft position sensor that I should look into changing that. Would that sensor have an effect on my idle speed?
  16. you either got a bad maf or iac..
    does your scanner read data? can you get it to read rpm?
    which scanner are you using?
  17. replace the iac first, get one from napa.. if it doesnt work.. it can be returned as long as your gentle with the box and dont mar it up or get it greasy..
  18. The OBDII scanner that I was using was a rental from Murrays auto. It was an Actron scanner. No, it doesn't have an option to read RPM. My RPM on my dash reads fine though. Alright. So I already replaced the IAC with one from Autozone. I guess I will try to replace it with one from NAPA and see if that works. I should be able to do that today. I will post the results later on today after I do that.
  19. Just went to Napa and bought a new IAC for $120. Apparently the one that I bought from Autozone was a piece of crap because I put the new one from Napa on my Mustang and the high idle(3krpm) dissapeared! It now idles beautifully at 600 rpm. Now, is it supposed to be at 600 rpm or a little higher? The idle set screw is backed out all the way, so I'm assuming the idle was initially set a little higher than 600rpm? Just a thought that crossed my mind. Thank you everyone for all of your responses and time taken to help me solve this problem!
  20. the reason i told you to disconnect the m.a.f. is to see if it would run,,and it
    should have even with it unplugged..when it didnt i knew the m.a.f. could not compensate for a vaccum leak.. which you had because the iac was wide open.
    glad i could help..