I've been fighting with this misfire with Grumpy for a while. Usually misfire codes are due to dirty injectors/sticky poppets. I've done Seafoam twice and the GM Fuel System Treatment Plus, also twice, to no avail. Since the injector/poppet is usually the cause, I decided to swap the injector for cylinder 2 with another cylinder. This in theory should move the misfire to another cylinder, if the injector is indeed the problem. Having completed the swap between cylinder 2 and 4, Grumpy still sets code for cylinder 2.
Here's a list of causes for P0302 errors that I found on the net and if I've done something about it:
* Faulty spark plug or wire - New installed
* Faulty ignition coil - Temporarily swapped in Green's coil
* Faulty oxygen sensor(s) - Swapped sensors between banks
* Faulty fuel injector - Moved injector to different cylinder
* Burned exhaust valve
* Faulty catalytic converter(s) - Exhaust does not smell like rotten eggs
* Running out of fuel - Fuel pressure is good
* Poor compression - Wife hasn't reported smelling burnt oil after following the van.
* Defective computer
I've also borrowed Green's cap and rotor (5k miles of use), code still set.
Now here's the weird thing that I noticed. If I clear the code and don't let it idle, the code will not set. Any ideas what's happening with partial throttle that would prevent it from setting?
Aaron
1999 Astro (Green the Daily Driver) - 2WD, 4.3L, 3.23, 200k+ miles, FE2 steering
1997 Astro (Grumpy the $250 Rally Van) - AWD, 4.3L, 3.42,
330k+ miles on the orig eng and trans, $30 eBay fuel pump