Contour Enthusiasts Group Archives Forums General Troubleshooting revs hang at 1500 at idle

OK
The car has just started doing this after a clean 50K. While driving around, the engine's warmed up, I put in the clutch and the revs will seek out 1500 rpms, hang there for one...two...three seconds and then fall down to a stable idle. Every time I stop it will do this, if the revs are lower than 1500 when the clutch goes in it will jump up to 1500 and hang there for few seconds...and vice versa. Strange??

I should mention I've done the TH fix, have no CEL triggered, recently optimized TB and installed Diablo Chip but reset computer after both.

Any suggestions?

It does this WITH the DiabloSport Chip ???
You may have to write to DiabloSport and ask them...

Have you tried removing the chip ?
Did you do the Throttle Hang fix ?

I'm not sure that I can blame it on the chip...I'm not exactly sure that it started when I installed the chip. I know it began AROUND the time that I was tearing the TB on and off and installing the chip. But I can't pinpoint the origin to either of them specifically.

Throttle Hang fix is done. I guess I should troubleshoot it...pull the chip and see what happens.

Anyone else have any thoughts?

If you changed the Throttle body, you will have to redo the Throttle Hang fix.

Why is that?

Removing the TB has no effect on the hoses (I forget exactly which hose the TH fix deals with, it was so long ago). The plug is still in that hose, so the same amount of air has been getting through. Right?

OR are you saying that I should let the computer re-learn the TH fix?

I didn't swap TB's, I just played around with a 65mm but ended up optimizing the stocker and putting it back on.

Also the issue does feel somewhat different from the orginal 'throttle hang' that the SVT's originally exhibit.

Just trying to understand you fully Pete

ok here goes a long one. i blew up my svt engine but used my buddies reg 2.5L engine until i can save up some money to get a new one. i used some parts of my svt engine like the accordian tube, new water pump, and a few other things. when we got it together it idles at 2000 rpms. what exactly is the throttle hang fix or do u guys think it is something else. thanks

When you change or optimize your throttle body, you IMPROVE the airflow.
This changes the way the IAC reacts to the Throttle Body,
because of the new Airflow values.

At Idle, it should not make a difference, but then, we are talking FORDs here...

I would get a new plug and just make a smaller hold in it and try it out.

the Throttle Hang fix cannot be responsible for an idle that far off, nor would it be a proper solution. I am just learning about idle control myself so I cannot say too much with certainty, but the TH fix is designed to remedy a very minor throttle hang that happens when you let off the gas in the mid-rpm range, it should not have any bearing on your idle.

Have you reset the computer completely? Make sure you do, b/c as I understand it the computer is reposnsible for controlling the idle. Also make sure it is not a mechanical issue....like a tight throttle cable....make sure the plate inside the throttle body is closing completely (you can hear it when it does). Hope it helps

and thanks for hi-jacking my thread....jk

thanks Pete

I would be more comfortable with that if my idle were constantly high but I'll give it a shot.

Cathode: You may want to check your optimized TB and make sure that there in no leakage around the butterfly. If the edges of the butterfly or the diamater of the bore where the butterfly closes change, you'll get extra air seeping past the closed throttle plate and a higher idle. Another source may be that the throttle shaft is binding and not closing all the way. Cleaning the shaft or adding a throttle return spring may do the trick for you. Might want to double check for other hose leaks/cracks while you're at it.