Engine Sputtering

[Hairdo12]

Just recently when my engine is in any gear when the RPM's get at 3400 the engine looses power... seems like a misfire. You can hear a sputtering from the exhaust. If you hold the accelerator down while it is happening it will continually do it, if you release and allow tranny to upshift works fine there after (as long as it stays below 3400). Spark plugs are AC Delco rapid fire, wires are brand new, fuel pressure was tested and shows no pressure drops, and no check engine light comes on. Also no unusual smells, and no loss in gas milage (roughly 25-26mpg). An example when this happens in during a heavy acceleration, or at highway speeds when your curzing in 4th and you hit the gas to drop down into 3rd to make a pass. I am very stumped with this one, any one have any ideas?

thanks

[KickingZ]

It sounds like you have some bad gas or some water in your intake. Pick up a bottle of Sea Foam at a parts store and put that in your motor. I'd put half the can in your gas tank and the other half through a vacuum line. That should fix the problem but if it doesn't, you have a problem some where in your fuel system. Did you check the fuel pressure at all RPMs or just at idle? If it was an ignition problem, you would have a rougher than normal idle with rough low RPMs and it would smooth out as your RPMs increased.

 

Later, John