Seems just about everything I try will only work temporarily for curing high idle (disconnecting computer, throttle body synch) Seems once the computer relearns what you did,it comes right back. I tried restricting the air flow thru the IAC motor and it caused my car to whistle so loudly I thought my engine was going to grenade (actually quite funny!) Nothing like whistling dixie at 110 decibles going down the highway..
A few days ago for shits and giggles I replaced my 02 sensors since they control SO much of your idle, air mixture, etc. My car was running a tad rich and the sound of the exhaust didn't sound *normal*. (Upstream O2's, I have simms on the rear, belanger headers)
I haven't had a high idle issue since a few days ago. It's actually doing just what it should. I"m thinking perhaps the Vipers computer is so touchy that a small amount of soot or gunk on the 02's still has them working and not throwing a code, but yet just enough to cause the engine to overcompensate throwing more air , etc causing a high idle....
I've had the erratic idle issue for 3 years and this is the 1st time I haven't had it in 3 days. I'll keep my fingers crossed.
Gerald
About 2 years ago I had the same problem and it was the throttle position sensor. The voltage at idle was only off about .05 volts but that was enough.
I haven't had the problem since.
Gerald
About 2 years ago I had the same problem and it was the throttle position sensor. The voltage at idle was only off about .05 volts but that was enough.
I haven't had the problem since.
take a look at my post on the O2 versus a/f. I logged the O2 voltage on my car after the idle went crazy. It is easy to pickup an erratic O2, but you have to log the two together with a scan tool. If you have a scan tool you can also engine brake and see if the the O2 voltage goes to zero, if it dosen't the O2 is out of range. The Bosch O2's are $60 and the oem NTK's are $82.
Basically as you drive in closed loop the voltage should range from .2 to 1.0, the closer to .5 the better. It appears that if the voltage excceds 1.0, but, goes no greater than 1.5, it sets a soft code. This is what it did on my 97, a different year PCM may react differently. I believe once it exceeds 1.5 volts a hard code will be set. The short verison is, the new O2 fixed my problem.
When the idle issue started, one exhaust manifold was running about 300 degrees cooler than the other. From the sound you could tell right away one bank was not right. On more item, a narrow O2 sensor will change characteristic under different temperatures/pressures, a SC or a turbo sure can't help the NB on our cars since it is so close to the engine.
I wouldn't be changing any 02s without a scanner reading or watching the voltage change. If you disconnect an 02 the mixture will go rich,low volts to computer. To drive the computer lean and shorten the injector pulse width you disconnect 02 and hold the connecter to the computer and then hold a Positive like the jumper terminal by the fuse box. That sends about 1 volt to computer ,rich run, and leans it out. Tells you if 02s do the same and if computer able to run the rich/lean. The most common reason for a high idle is a vacuum leak. PCV hose cracked, PCV valve stuck full open, vacuum hose off,intake leak, brake booster leaking. Any time unregulated air goes into an injected engine the 02s see lean and richen it up also increasing the idle so it won't die at idle from rich run. What was the whistle noise you heard?? a vacuum leak?
Last edited by snkbyt : August 30th, 2006 at 12:08 AM.
Reason: WTF 2 year oldpost
Linear Mode
