High Idle...Again

[sandman0023]

I've had a high idle problem for a while. I'll be sitting at a stop sign or light and the engine will rev up and stick. I'll be pushing around 2500-3000 rpms. While I'm shifting, same thing. I replaced the throttle body and EGR plate and it still did it.

Yesterday I went to Kragen and ran it on the code machine. It came up with 2 codes: 33 and 4. I looked up 33 and it said it was the EGR Valve. I replaced that today and it was fine for a few test drives. Then it came back. Not as bad as before but it is still there. I'm going to replace the vacuum line to the EGR Valve tommorow and see if that does the trick. Anyone have another idea? Also, what is code 4?

 

[DMAN302]

do the idle set from the corral tech area, then after (or before) spend some serious time looking for hidden cracked or broken vac lines..I hooked over the engine bay probably 20x's before I found the bad one in the passenger fender...TADA surge and hanigng idle gone like magic. Just a tip, hope all goes well.

 

[HISSIN50]

i'm with Dman - check for vac leaks. the lines under the upper (in the front) are notorious for leaking/cracking.

often the EGR and sensor interface is off. the new valve should have corrected this, but i might check the EGR seat to sensor interface to be sure.

not sure there is such a thing as a code 4. the codes are double digit for us, triple for SN pushrod motors, i think.

good luck.

 

[DoubleAgentMan]

You have some great advice....Most of the time these idle problems seem to almost always end up being vac leak related...but here is something else if you haven't tried it already, and it's free....can't beat that right?

Ten pins

And if I'm not mistaken (usually wrong though.. ),I think the "4" you got might have just been the ingine ID bleeps you get when running the codes..I want to remember that 4 is for a V8 and 2 is for a 4cyl....I could be way off on that though...

Hope some of this stuff helps you out man...

 

[Idwitheld-1`]

That's quite a jump. Would be a big vacuum line... HISSIN is right. Look closely at the vacuum tree lines under the upper plenum, very prone to heat rot. Also, check the PCV line. I left this out once and started the car and it idled at 2500 rpm's like yours.

 

[dastang2]

while it is running spray starting fluid over all of the vacuum lines and ports, if the motor revs, look in that area for leaks

 

[BlueThunder1988]

I fought that same problem--the mysterious jump in idle to 2,800 or so at at stop in traffic--along with a high/hanging idle that would be fixed (at least somewhat) by cycling the ignition off/back on. I replaced the TPS and tada! Problem fixed! Finally fun to drive the 5.0 again! A few others have reported this same issue fixed with a TPS swap so do check into it.

 

[sandman0023]

I just replaced the throttle body and control module on the front of the TB (can't think what it is called) I switched out the EGR valve and sensor yesterday. It was fine for a while then started up again. The TPS is on the bottom of the TB, correct? If so, the new TB has one. I'm going to do what Corral said and then start looking for vacuum today.
Thanks

 

[sandman0023]

Well, I did just what the tech article at Corral said and drove it for a little while and it seems fine. I'll drive it to and from work tomorrow and let you guys know.

 

[lit_mike_2001]

efi sucks

 

[89MustangGX]

If you still run into trouble -- I agree with all of the above. I'll second the 10-pin connectors being cleaned out, as well as the IAB being helpful.

 

[sandman0023]

Well, that didn't work. Starting to search for vacuum lines. Is there more than one way to do this?