Does anyone remember the old Wankel powered snowmobiles? How they kinda went BRIIP BRIIP BRIPP when they were idling or running at low throttle.
Well,, when a 4.3 sounds like that it's NOT a good thing.
Here's the symptoms. Engine starts fine and runs well cold. As it warms up it picks up that Wankel sound and gradually develops a skip that can be quite pronounced. Until it gets really bad it is only apparent at very low throttle settings. A couple times it has gotten to skipping so bad it can barely accelerate.
Let's say you're climbing a hill, plenty of power and running smooth. Hit the top and back off the throttle and the skip starts. Start downhill and it gets worse as the engine starts holding the truck back.
Or traveling on a level road at just above the speed for the 3-4 shift. Just a slight stumble occasionally until the shift, then, as soon as OD engages it starts to stumble. Feed in a little throttle and get it back into 3 and it smooths out.
When it's not skipping and you nail the throttle it pulls fine and maintains power right to the transmission shift points. From that I tend to discredit the fule filter as a problem, if it is flowing enough to reach high RPM it should be flowing enough to carry cruise throttle at 40 mph.
So far, more in the idea of routine maint. rather than diagnosis, it has gotten new plugs, wires, cap and rotor. Still stumbling.
Last week we had a no start after tinkering with and finally replacing the starter. (This was after the ignition work had been done). We finally hooked up a new coil and it lit right off. At that point we assumed we had flooded it by repeatedly cycling the fule pump with the engine not cranking.
Once it had started we swapped the wires back onto the old coil and it took off fine, but my helper did mention it looked like a pretty yellow spark off the old coil. I'm wondering if it's worth throwing a coil at it at this point.
If I'm right here, when the computer sees a low load, part throttle condition it advances the timing. As throttle is opened the computer pulls off timing to avoid spark knock at high loads. It that is the case, could a weak coil not be putting out enough voltage to light the fire under a low throttle, high advance condition?
Well,, when a 4.3 sounds like that it's NOT a good thing.
Here's the symptoms. Engine starts fine and runs well cold. As it warms up it picks up that Wankel sound and gradually develops a skip that can be quite pronounced. Until it gets really bad it is only apparent at very low throttle settings. A couple times it has gotten to skipping so bad it can barely accelerate.
Let's say you're climbing a hill, plenty of power and running smooth. Hit the top and back off the throttle and the skip starts. Start downhill and it gets worse as the engine starts holding the truck back.
Or traveling on a level road at just above the speed for the 3-4 shift. Just a slight stumble occasionally until the shift, then, as soon as OD engages it starts to stumble. Feed in a little throttle and get it back into 3 and it smooths out.
When it's not skipping and you nail the throttle it pulls fine and maintains power right to the transmission shift points. From that I tend to discredit the fule filter as a problem, if it is flowing enough to reach high RPM it should be flowing enough to carry cruise throttle at 40 mph.
So far, more in the idea of routine maint. rather than diagnosis, it has gotten new plugs, wires, cap and rotor. Still stumbling.
Last week we had a no start after tinkering with and finally replacing the starter. (This was after the ignition work had been done). We finally hooked up a new coil and it lit right off. At that point we assumed we had flooded it by repeatedly cycling the fule pump with the engine not cranking.
Once it had started we swapped the wires back onto the old coil and it took off fine, but my helper did mention it looked like a pretty yellow spark off the old coil. I'm wondering if it's worth throwing a coil at it at this point.
If I'm right here, when the computer sees a low load, part throttle condition it advances the timing. As throttle is opened the computer pulls off timing to avoid spark knock at high loads. It that is the case, could a weak coil not be putting out enough voltage to light the fire under a low throttle, high advance condition?