Idle is making me crazy

mike94sc

Registered User
I've searched a ton and found a lot of info on this subject. This board has a wealth of info. You guys are awesome. It seems that the IAC valve is the big hitter with idle problems. I have already replaced the IAC, TPS, and the ETS with no success. Actually, I put my old IAC back on since the new one didn't fix the problem. I even tried resetting the computer by disconnecting the battery. When I coast to a stop (i have a 5 speed) the idle seems to stick at 1500, then about 1100, and finally to the resting idle about 900. Sometimes is never drops from 1500. Has anyone had this problem? Other than the iac, tps, ets, I don't know whats left. I even got a code reader and its not throwing any codes.

Thanks,

Mike
 
I always thought that the idle would be lower and ruff if there was a vacuum leak. How do I go about finding a leak? Is there any one particular hose that could be causing this?

Thanks,

Mike
 
Normally you're right. I have heard all kinds of problems with the computer though. I have had a lot of surging problems because of vacuum leaks. I think the computer tries to compensate and it just causes all kinds of strange stuff to happen. I would just grab a can of carb cleaner and spray it all over the engine compartment, near the hoses, and see if idle changes. Just one more thing to check.
 
Do you have larger injectors, MAF,cam or any other mods? A vacuum leak can cause high or low idle i have had both problems.
 
mine was like that

crank sensor ..sorta ...it was really the harmonic balancer ...floating around on the crank shaft ..after the bolt broke..due to having no O/D ..which took out the motor mounts ..and that took out the harmonic balancer .. buzzing it @ 4000 rpm + on the highway for months ....dave
 
its a vacume leak

here is how I test
first i went to home depot and got some end caps for drains,


they have clamps on them ,

put them on exhoust, then took hose from pcv and clamped a air chuck into it and added air ,

then sprayed soapy water at all joints and couplings,
also all vacume lines make soapy water rich in soap it will bubble.

or just shove potatos onto exh and plug that way dont use alot of air just 15-20 lbs you dont want to pop a vac line under dash.
 
do u think it could be egr related?
maybe its sticking open a little bit
just a thought since u ruled out many other possibilities
g/l
 
i added a bigger throttle body and had this type of problem . i thought the throttle wasnt going closed far enough but it was ok . i just unhooked battery again to reset then it took about 3 days to learn everything and to idle right again
 
Thanks for all the ideas. Brianas, I was going to post a reply and ask if this could be EGR related. Someone I work with mentioned that it could be my EGR. Could problems with the EGR cause the idle to be randomly high? Would it be the egr sensor or the egr itself? I haven't searched if there is a way to test either one. I'm sure there is a way. This just maybe a project to figure out in the spring. It's getting rather cold now and almost time to put the SC away for the winter.
 
If the EGR valve is leaking at idle the engine will stall. No matter what EGR would lower idle or kill the motor.
 
it could be egr , but a vac leak will do the same the computer gets a message from oxy sensors and other sensors saying

lean condition so it richens the mix then iac trys to lower
idle, and it goes on and on .

I know from my inverted a vac leak will make it idle fast 1500-2000
then shut off comming to stop,
then idle rough, sort of lopy

so remove egr pipe plug with something thumb? and have someone fire engine if it stops running like do doo then its egr
if it stays same look for leak mine was on underside of intake in lifter valley some are not easy to find
 
I have the SAME FRICKING problem! I have done all the things you are doing/done. I have a friend that is a Ford driveability tech, (I worked at Ford for a few years) and he is bringing over his Ford NGS scan tool, and we are going to get this damn thing. I even replaced my PCV. I was reading the re-seal procedure a couple of months ago...(who would have thought to do that?) and they list a propane test.....leak propane out into all the I/C joints, intake manifold, etc...and read the o2 switching...looking for a rich code. So, I will do this also, and will post my findings. Are you getting crappy mileage?
Mike
 
Checked car out with an NGS, and found IAC working its balls off trying to compensate for the fact that the throttle plate set screw had wiggled down, on the pass side of the TB, and was now making the car idle at 1500....and after a while the computer was able to get it to at least try to lower its speed.....so adjusted that, re-lock-tited the screw, re-set the PCM, and the car is running like it never has since I got it. Thanks for your time and input......
Mike
My car was doing the exact same thing! I always look for the hardest thing first.......I am trying to get smarter after all these years....... :)
 
mine just yesterday had this again , it was seals around fuel injectors not only vac loss but 3-5 lbs boost blown out two bad seals . a sort of whistleing sound was heard .
 
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