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wandering idle

LASER4G63T

Proven Member
92
0
Apr 4, 2005
Fort Worth, Texas
I looked around at idle surge threads, but mine isn't as described in most. My idle surges between 500-850 and sometimes at stoplights it hovers on 1000. Other times it is rock solid on 750...where i have it set. the stock boost gauge also moves with the rpms (nothing on the aftermarket). I looked at ICS threads and they all describe high (2K) rpm that i am not seeing.

Ok..so my UICP hisses a little if I put my ear to the joint at the TB elbow and it does not stop if i tighten the hose. I am sure its the hose, not the TB. Could this be the problem, or is it in more likely the ICS problem? Thanks in advance.:laser:
 

FORMONTOYA

DSM Wiseman
2,260
57
Oct 7, 2004
Houston, Texas
I had a similar issue when I put on a K&N FIPK on my car. I run a HAHN SMIC with original route piping.

What happened is that when the passenger side fan would come on it would push air into the upper IC pipe then be directed across the FIPK disrupting the flow across the MAS causing the idle to "hunt" a bit as you described, otherwise it idled fine. I have since replaced the FIPK with a standard cone type filter and no longer have any issue.

Might not be it, but something else to look at.
 

LASER4G63T

Proven Member
92
0
Apr 4, 2005
Fort Worth, Texas
I'm going to run a boost leak test today..and also I'm going to make a shield for the K&N so it's not effected by fan blow. I'll let you know.
 

LASER4G63T

Proven Member
92
0
Apr 4, 2005
Fort Worth, Texas
I did a test and nothing at the TB seemed to be leaking nor any of the lines. The IC was hissing bad though.
 

aovsi

Supporting Member
1,948
8
Sep 30, 2002
Chicago, Illinois
ISC?

I ran into this kid about a year ago in a parking lot with the same problem. We checked all hoses--everything was tight. I remembered reading that leaking ECU capacitors sometimes cause a similar problem (more or less). I mentioned it to the guy and he said he'll check it out.

Several months later I ran into this kid again and the guy wanted to give me $20. ROFL
He said he took the ECU out, looked at it and sure enough two of the capacitors were no good anymore. He said he borrowed a good ECU from a buddy and the car behaved properly with it. Had the capacitors replaced and car behaved properly with old ECU. He didn't offer any details, I was in a hurry and that was it.

Seems trivial, but something worth checking into. Not like it's going to cost you money to take a look at it.

Some informational reading: DmTaLoN's Idle Speed Control Test/Fix Page!
 

laserspeeddemon

Proven Member
6,718
40
Jul 26, 2002
Fredericksburg, Virginia
ISC?

I ran into this kid about a year ago in a parking lot with the same problem. We checked all hoses--everything was tight. I remembered reading that leaking ECU capacitors sometimes cause a similar problem (more or less). I mentioned it to the guy and he said he'll check it out.

Several months later I ran into this kid again and the guy wanted to give me $20. ROFL
He said he took the ECU out, looked at it and sure enough two of the capacitors were no good anymore. He said he borrowed a good ECU from a buddy and the car behaved properly with it. Had the capacitors replaced and car behaved properly with old ECU. He didn't offer any details, I was in a hurry and that was it.

Seems trivial, but something worth checking into. Not like it's going to cost you money to take a look at it.

Some informational reading: DmTaLoN's Idle Speed Control Test/Fix Page!
This why us senior members rock!

3 most likely causes are a bad ISC, bad ECU, or bad signal from the MAF (indicates it will crap out soon). The symptoms you describe suggest an electronic issue, but to be sure makes there are no obstructions in the TB and that the TB cable is not binding.
 

aovsi

Supporting Member
1,948
8
Sep 30, 2002
Chicago, Illinois
If you DO find the capacitors FUBAR, throw in a DIFFERENT GOOD ECU into your car and see what happens. Sometimes the leaking acid will cause damage that needs to be repaired beyond capacitor replacement and problem persists even after capacitor replacement.
 

LASER4G63T

Proven Member
92
0
Apr 4, 2005
Fort Worth, Texas
I replaced the capacitors a few years ago, before the board was to destructed. I'll look into the ISC thanks.
 

LASER4G63T

Proven Member
92
0
Apr 4, 2005
Fort Worth, Texas
Update:


I did another boost leak test and I found:

leak at dipstick (fixed)
UICP leak (small, fixed)
TPS (small, barely noticeable)

That's all I found. The idle still does the same thing, so I looked into the ISC as suggested. I checked resistance between posts and they were all 29-31 ohms. I then put 6V to posts 2/5 and 3/6...nothing happened. Is this it?
 
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