Yep...mine does it on occassion. I can come to a slow down or a near stop and the rpm's bounce up and down. It cut off one time, but mostly just revs up and down. I have set the timing to factory 10* and it's had a tune up with oem plugs and wire and stuff. I put an ignition coil on it 2 years ago, but it was a stock replacement from Autozone for about 15 bucks I think. Maybe its going out on me. What has everyone found about this problem on your car and how'd ya fix it?

Ken

 

Usually, that's a sign of a vaccuum leak.

 

Sounds like you got another problem. When it's going bad it isn't accurate. You could be driving 40mph and it's showing your RPMs in the red. That's the way mine is... Not really worried about fixing it.

 

vacuum and bad battery and elec connections do it.

 

I'd try cleaning/adjusting, or just replacing your iac valve. I believe there is a write up in the tech articles area that may be helpful to you.

 

Does the engine sound like it's revving up & down or it is just the tach in the cluster? I ask because one of my friends has a 1991 V6 Camaro and I have a 1991 V8 Camaro. It's funny because whenever I have a car problem, he gets the same thing a week later & vice versa. We have two distinct problems with out clusters:

1.) Two or three of the lamps are not getting power (they are good, but are not illuminated). If I hit the dash hard, they'll sometimes pop on.

2.) At low speeds (<10 MPH), the speedometer bounces up & down instead of tracking the speed. Everything tracks >10 MPH.

The second problem looks like either a.) low speedomoter signal current or b.) dirty contacts (or both -- dirty contacts could cause current limiting).

 

Yeah..its not a gauge problem. The engine actually goes up and down while slowing or stopping. The battery has a good connection and I need to get a IAC housing gasket cause I want to clean the housing altogether. Might replace the IAC just to do it. I did the spray thingy one time to find vacuum leaks, but did'nt see any at the time or very small to notice it. I have put a negative cable on 3 or 4 months ago, but never got around to the positive lead. Wonder if it might be the tensioner pulley too. It's just irritating having the car run like this. Also, after I took off the smog pump a few months ago, I plugged up the vacuum line that went from the air pump to the fuel pressure regulator. Don't know if this has any bearing on it.

Ken

 

Could even be a partly sized compressor clutch. Try running the engine without any belts (but only for a few seconds unless you feel like trashing it).

 

My V6 2.8L does this as well, and I assumed something was leaking on the vacuum system, turned out to be the DIVERTER VALVE. Checked the MAP first though, pulled the hose and the surging stopped, but that is a FALSE CLUE, and buying a replacement MAP sensor may not cure this at all ! There is a module mounted on the back of the Air Pump, called the "Diverter Valve" by some books, or "Air Control Valve" by others (i think). A hard plastic line runs to this body from the TBI base, distributor side. If you have checked all of the other vacuum leads, then the "Diverter Valve" may have a ruptured diaphram. Pull at the TBI base, suck on the line -- hold a vacuum? If so, you are lucky, they are expensive and dealer only item (i think), and $$$. Keep shopping for a vacuum leak !

 

Err... I don't think any of that applied to the MPFI system..

 

Check your vacuum hoses. I had the same exact problem and replacing a hose or two was the solution.