Ok now RPM fluctuates

[Mighty Thor]

Well at first my RPM was surging to over 2000 and now it's fluctuating.

Fist I replaced the idler control motor and that didn't do the job. But I left it in there because the old one looks horrible. Then I replaced the TPS. I took it to the shop because I don't have a scanner and a way to tune it. I only paid for the labor.

The problem seems to be fixed. The RPM doesn't surges anymore and it stays at around 700 rpm at idle. But after driving it for 60 miles and going as fast as 90 mph (yes my 2.8 can do that) I notice that my RPM is flutuating at around 500-900. And you can hear the engine tune is doing that too.

Now this only happen when the engine has been driven for awhile and the Auto is at "D". But as soon as you put it back to "P" or "N" the RPM stablizes.

Now I'm out of ideas. The shop's scanner said I'm free of codes. Any idea guys?

[3.4 slow to go]

vacuum leak?

[NOS2006]

My 3.8 does that from time to time too. Usually when I'm low on coolant..

[Mighty Thor]

I checked the vacuums it's all fine. That's what I thought too. It only does that when it's really been used and hot. But when I drive around the corner it's OK.

Coolant sounds like something I should look into. I wonder if its the Thermostat.

Thanks guys

[3.4 slow to go]

did they check your icm when the shop had it?

[Mighty Thor]

I don't think that was mentioned. What's that anyway? Is it Idle Control Motor? Because that the one I changed and the shop adjusted.

[3.4 slow to go]

ignition control module. inside the distributor

[Dizturbed One]

If it's your 2.8 that's doing this I wouldn't be suprised if it was just a cap and rotor problem.

Happened to my 3.1

It would surge to 2000 out of nowhere sometimes, and every once in awhile would want to die when I came to a sudden stop.

Sometimes I would go a full 30 or 40 miles without a problem, then it would start jerking a little, and would want to die off the line

But if I put it in neutral, it would rev up just fine, like nothing was wrong with the motor... Besides the surging tach, it never seemed to act up unless it was under load.

My tach was jumping up and down really funny and acting really skittish from it too.

When I did a tuneup about a week later, I pulled the cap and rotor and it was BAD... I don't think the previous owners ever changed it just because of the semi difficulty of getting to it (it really isn't that hard though)

Every point in the cap had a 1/4 inch of white buildup, and the rotor was worn through the metal almost down to the plastic where the spring loaded point for the ignition coil touched it.

I thought my car was going to die for a week, but it turns out it was a 10 dollar problem... lol

[Mighty Thor]

Thanks alot guys. I haven't had the time work on it but I will this Sunday. I check for both ICM and Cap and Rotor.

[3.4 slow to go]

remember, icm cain be checked for free @ AZ, advance auto, etc. just don't forget the goop to put back underneath it.

[Rob Bell]

The probalem Dizturbed One described sounds very similar to an ICM problem I had, but mine was on a Cavalier. On mine, at idle the tach would flick down and then return to normal idle every few seconds, but the engine sounded normal. If I gave it a lot of gas (in gear under load, trying to accelerate) the engine would sputter and the tach would go totally nuts, jumping all over the place. It usually just did it when the engine was warm. A new ICm solved the problem.