i have been having idle problems with my car since i got it. The problem is only when the car is in gear. I have and OBD1 and an OBD2 pcm and they both do it. The car idles high when you first start it up and as long as it is in neutral or park it idles normal. Once it gets warm and you are driving it will idle down really low when you are stopping or at a red light. Once the car starts idle'ing low you can hear a tapping sound from the motor. Could this possibly be a misadjusted rocker arm. Also any ideas on what is causing the low idle. I have already changed the tps and tried using the adjustment screw on the throttle and it still has the low idle in gear problem. thanks in advance for any ideas.

 

From What it sounds like is a vacume leak. The ticking at low rpm could be the rockers but there only one way to find out. Do you have any kind of scanning program?.

 

i have sprayed the whole engine looking for vaccum leaks and cant find any. I have a scanning program but i have Vista installed on my laptop right now doing some testing and i can get any of the software to run correctly on it.

 

I finally discovered wher this was coming from. the belt tensioner bearings were going out. it sounded just like and internal problem. It would tap with the lope of the motor and go away when you would pres teh gas enough to smooth out the motor.

if you have a tapping while idling this would be a good thing to check. The screwdriver stethisope method seems to work.

 

Same problem happened to the drive belt tensionser for the supercharger on my Grand Prix. I put an automotive stetoscope and traced it down that way as well. Pretty easy fix, I was afraid at first that a bearing in the supercharger was going bad.

 

I didnt know what was going on because i had just purchased the car. I started noticing it after i installed the hot cam and just assumed it was something i didnt adjust right. I had pulled the valve covers 2X and nada. It was a big load off my shoulders. I sprayed it for the first time that weekend. All is good now.

 

Man, mine idles rough just like that and i cant figure out what it is, mine does it just like you explained but without the tapping noise. I bought the car a year ago and its done it from day one. I put a new MSD cap and rotor button, MSD plug wires and all new spark plugs in it(because when i bought it, it still had 2 original plugs still in it, i guess they didnt think it was important to change them too), but new injectors, cleaned the TB, looked for a vacuum leak and now i am pretty much out of ideas. Please help me too.

 

My low idle seems to be ok now, i think it was the terrible tapping sound that was driving me crazy. im idling between 600 and 1100 depending on the temp and how long the car has been running. I was expecting a little bit rougher of an idle than normal with the hot cam installed. Car just sounds like a beast now.

 

My car only idles around 300-400 rpms when it idling rough, can you adjust the idling on a LT1 car?

 

the idle can be adjusted in the pcm calibration. You can use lt1 edit or any of the other pcm programs. It can also be adjusted by slotting the tps switch and turning it a little. You will have to use a multimeter and see what the numbers should be at. There is a little set screw in the intake behind the throttle but i didnt have any luck with that. I could idle it up there but as soon as the car wa in gear it seemed to isle back down. Im guessing that the pcm and tps tuned that out.

 

I guess turning up the idle would be more hiding the problem than fixing it anyways. thanks for the help