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this forum has been very helpful almost have my car running tip top, I will be replacing my clutch cylinder soon, curious if this could also be the culprit behind my erratic idle when going into neutral. (MT) I go to slow down, remove the car from gear and the rpm usually bounces up to about 3k, also does this in between shifting. I've now replaced my iacv, and my tps... No such luck, when I unplug the iacv the car runs and operates as normal...
 

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If you unplug the IAC and it acts normal, then your problem is not the clutch master cylinder which has no relationship to idle.

Do you still have the old IAC? If so, I'd recommend cleaning it, and re-installing it. It was probably merely dirty. Also clean the throttle body and throttle plate. The best thing to use is simply a rag and elbow grease. You can put a dab of carb cleaner on the rag, but I would not spray it inside the TB. I worry about chemical reactions between the chemicals in the cleaner and the TB. No issues have been reported, but since it can be wiped out with a simple cloth, I typically choose the simplest method.

Clean the IAC with carb cleaner, and be sure to use a Q-tip to move the plunger and clean the outside of the plunger. Allow to dry.

You might also want to clean your MAF while you're at it using spray MAF cleaner.

Once you've done all of this, remove the negative battery terminal for 5 mins or so, and then put it back on. This will reset your fuel settings. Start the engine, and do not touch the accel. Allow it to idle for 5 mins after the idle settles down to about 1k rpm. If the idle never settles down, then you have a mechanical problem somewhere. During the 5 min period, you will notice slight fluctuations in the idle, that is normal. The ECU is testing for the optimal settings, when it is finished, the idle will drop down to 7-800 which is where it should be normally. If you touch the accelerator during the test, the test will reset and start over again.

You might be able to get away with trying just the A/F reset procedure as described above- assuming that the IAC you just replaced is good. I always try cleaning the original IAC first. More than half the time that solves the problems. If the seal around the outside of the plunger is damaged, then the IAC is no good, so don't bother cleaning it. If cleaning doesn't make it seat completely sealing off the two chambers from each other, then it's probably not good either.
 

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I have done all of the above except cleaning the maf. There has to be some other explanation. I drove the car for 300 miles yesterday with it unplugged & it did just fine.
 

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I have a 2001 zx3 and have been noticing a really odd power fluxuation. if I am idling at night I noitce it more then day because of the head lights. it will idle and then all power dims stays that way, power goes normal for a brief moment and then back to dim again. when its normal it doesn't last long but I figured I'd ask and see if anyone has any ideas of what it might be and how to fix it. Thanks
 

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I would go to autozone and get your alternator tested, they do it for free, my surging issue is more motor related than electrical and I'm beginning to pull my hair out, I'm tired of part slapping....
 

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Weird. Your IACV shouldn't be doing anything at all when you're switching gears. The fact that unplugging it makes it run normally suggests that your new one is faulty.

Try whynotthinkwhynot's suggestion of cleaning and reinstalling the old one, or if you don't have it anymore, take the new one back where you bought it and try to get it replaced.
 

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I have a 2001 zx3 and have been noticing a really odd power fluxuation. if I am idling at night I noitce it more then day because of the head lights. it will idle and then all power dims stays that way, power goes normal for a brief moment and then back to dim again. when its normal it doesn't last long but I figured I'd ask and see if anyone has any ideas of what it might be and how to fix it. Thanks
Electrical issue. Had a similar prob in our 04, it ate 2 batteries and an alternator, but I think one of the real culprits was actually the ground cable. Check your battery and connections and the condition of the cable. Mine was corroded up inside the insulation. Voltage regulator was what went bad on the alternator, BTW.
 

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Discussion Starter #8
Funny, every iacv I received from autozone looked different, one didn't even fit right, I replaced it yesterday with a different one, seems to be performing better, still wants to hang around 2k in neutral until I come to a complete stop.
 
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