Hello, I have a VERY frustrating problem [:@]that I am wondering if anyone can offer advise with. My 98 V6 Camaro has a very pronounced misfire that occurs only in certain RPM ranges...and only under load. While not under load (sitting still reving the engine) the engine is smooth through all RPMs. The engine is NOT throwing any codes...I have had it checked several times while debugging the problem. The first hard miss occurs at about 2300 RPM and it continues missing until about 2550. It is so bad that the whole car jerks and lurches while under load in this range. The tach jumps wildly in this range also. The same thing occurs at about 4000 RPM. The rest of theRPM ranges the engine is relatively smooth. It is bad enough inthese ranges that it won't hold cruise control if I set the cruise in the bad range. The following is what I have done...which has had NOeffect:1) Replaced Plugs and Wires, 2) Replaced Coils (all three), 3) Replaced Ignition Control Module, 4) Replaced Crank position sensor, 5) Replaced Cam position sensor, 6) Replaced Engine computer, 7) Disconnected Tach at the Ignition Control Module (for testing...then reconnected it), 8) Disconnected speedometerat the tranny (for testing...then reconnected it), 9) Disconnected spark knock sensors (for testing...then reconnected them). I generally like to work on my own stuff. This has been going on for months now while I try to debug it...and I am getting nowhere...so I may be relegated to the dealer's shop soon if I can't figure something out. I really believe that the problem is ignition related (since it is RPM relative). If anyone has any advise, please let me know. Thanks, Alan.

 

Looks like you went through the electrical stuff. Check the EGR valve it may not be working properly and opening at the wrong time. Unplug the wire from the MAF sensor & see how the engine runs. Check the MAP sensor especially if the engine does not run with the MAF unplugged. Also, possible but not likely, check the fuel pressure & pressure regulator.

 

Thanks. I'll try the EGR, MAF/MAP this weekend. I don't think it can be fuel because it is so predictable and repeatable. It occurs at exactly 2300 every time while under load...and disappears as soon as the RPM goes over 2550. I forgot to mention that I alsohave new coils.

 

I tried the MAP, MAF and EGR. I also tried the Throttle Position Sensor.As expected, the car didn't run right with these disconnected...but none of them affected the problem in any way. The car is now at the dealer [&o][][:'(][:@]. They have had it for 2 days and so far haven't located the source of the problem.

 

On my 98 V6, mine sputters while sitting at about 3500-4000 RPMs, but it doesen't sound like your problem you described...
On mine, it sounds more like the rev limiter...but is it really that low?

 

Mine has now been at the Chevy dealer for 2 days and they haven't found the source of the problem. I doubt that it's the Rev Limiter on your car .... unless it's malfunctioning. "Sputtering" sounds more like a fuel related problem ... maybe MAP or MAF.

 

I had the same problem it was the seals on my injector