cruising speed misfire

[builderpaul]

I have had a lot of vehicles but never one with this problem. Just wondering if anyone else has experienced this with any type of engine.

Don't stop reading just cause I tell you it is a 94 Chev tracker with the 16 valve multi port injection engine.

It will misfire when under light throttle, light load. Can't hold any speed be it 30 mph or 50 mph on a flat road without a rhythmical misfire. Like one cylinder is missing.

The engine starts without hardly a crank. Idles smooth as silk. Accelerates without hesitation, nice and smooth. Only when trying to hold a steady speed does it miss.

I have replaced plugs, wires, cap, rotor because it sounds like an ignition miss. This did nothing.

I have sea foamed and ran techtron though the tank. Still nothing.

Any ideas???

 

Thanks.

[bamedic]

Had the same problem on an 2000 malibu. Turns out that after a tune-up, one of the new plug wires was bad. After it was replaced, no problems.

[ChevyTech007]

It does sound like a secondary ignition miss. If you used aftermarket stuff, that could be your problem. Wires are the best place to start.

[MustGoFaster]

my brothers jeep had nearly the identical problem. his had higher miles 173k, which is why we started to think injectors. however, before coming to that decision, we replaced fuel pump, cap + rotor wires, plugs, did a seafoam clean, replaced coil, crank sensor, dist, gear and sensor and other stuff I can't remember now. always under light load the thing acted all the world like a bad ground or a coil. never threw a code either.

 

Turned out that the injectors were becoming partially plugged. apparently there's a tiny screen on them, which got just plugged enough that under light load that injector couldn't flow enough gas, but at idle ot WOT, the duty cycle was large enough or small enough that the filter worked OK enough. Sent the injectors in to be reconditioned. the paperwork confirmed our suspicion that one or more injectors was failing. (low flow level) put the cleaned ones back in, and it works perfectly now.