Hi i hope some one out there can help me. I have a 4.3 manuel chevrolet s10. i am having problems with my truck. I keep experiencing a missfire when under light throttle load. I can be cruising down the road and go to pick up speed again and around 2-3000 rpm i get a missfire and load pops and bangs out the exhaust. if i push harder on the throttle it will clear and will be ok and drive alright. It just seems to happen when i am on light throttle. If any one has any ideas i will be greatfull

Thanks

 

Have you already pulled all the plugs and wires, inspected for cracks or obvious signs of wear?

 

First off, what year is it??? 4.3L Has been around a long time.

I had one with a broken Cap do something similar because it would not latch down tight. When we put a tiny c clamp on it, it went away....

And another one with a crank sensor Issue... GM has a TSB about that one.
Basically the o ring that keeps the sensor spaced away from the crank wears out from the heat. If it does not maintain the correct distance specified it causes a miss fire. I believe the distance was 1 Mil

 

its a 2000 model. thanks for the ideas, its hard to get parts for it as i live in the uk

 

I had the same problems with my 93 Grand Am. It had a 3.3L V6 with about 80k miles. It ended up being the ignition coil pack. The damn thing kept going out every 5 or 6k miles or so. I never got to the bottom of it though. I sold it when I graduated college and I bought my 2001 Zr2 Blazer.

If it is not the coil pack, check to see if it is not the fuel injectors. Sometimes they go bad and stop sending fuel to its respective cylinder.

Good Luck

 

i had the same problem with my 03 and it was the cap and rotor there is a gm bulletin about the vent on the cap and it causes build up on the inside of the cap

 

Only the 2.2L S10's came with a distributor-less ignition, although the 2nd generation S10's came with a distributor hybrid that electronically times the ignition through the PCM. Anyways. As everyone else said check your distributor cap, they like to build up excessive carbon. If you do decide to replace it (which you probably should anyways, they aren't that expensive), VERY CAREFULLY tighten down the Torx screws that hold it onto the distributor. They can crack very easily and you would most likely have to replace the entire distributor. Has your truck thrown any trouble codes, or has the Service Engine Soon light come on?

If that doesn't solve the problem, you may have a bad injector poppet valve. There are two ways to solve this, hopefully you have number one. You can take it to a dealership or local shop and they can run high pressured nitrogen (not oxygen, O2 is more flamable than N) and push the poppets and blow all the gunk out. The second is to replace the injector spider, and that can be a pain. Hopefully it doesn't come to that.