Misfire! Help!

[SUBURBAN5]

Took it to a local shop, they warrantied the distributor. There was moisture in the distributor, so they replaced the whole assembly and went ahead and did spark plugs. Picked it up, still had a miss (not nearly as bad), and this time a P0300 and P0340 code. Dropped it off at the shop again yesterday

Well if it's still missing with all new parts I suspect fuel and head leak. Fingers crossed hopefully not

 

[Canon Lansdell]

Well if it's still missing with all new parts I suspect fuel and head leak. Fingers crossed hopefully not

Yeah hopefully not lol. It misses when you go from a stop if you're easy on the throttle and misses when you steadily go 50-65mph. Any time cruise is locked in it will miss. So it seems like it does it mainly just in low rpm? it'll pop from the exhaust when you let off the throttle sometimes.

 

[Canon Lansdell]

Picked the truck up yesterday. Happened to be the pins of the cam position sensor out of wack and pushed back into the plug. They replaced the plug and she runs like a top

 

[GoToGuy]

So is this a case of " a little knowledge is dangerous" ? Hmm .. A warrantied distributor, manufacturer unknown. And a loose cam position sensor plug. But now have all new fuel components, bty you did install new fuel filter with spider and fuel pump. A little correct troubleshooting, or immediate return to who last performed the service. A little hint when doing a cylinder compression check. When a cylinder is lacking in gross or total compression, perform a differential press check. Bringing the piston to TDC on compression ignition cycle. With 80 to 100 psi in through spark plug. Stay clear of belts and fan. With the cylinder pressurized at TDC you then may be able to narrow thecause of a weak cylinder. Air noise in intake- weak intake vavle. Air leak and or noise in crankcase listen at oil fill - rings. For the exhaust valve either gaining access to exhaust port or process of elimination. Coolant from cracked heads or cylinders sucked and burned in exhaust will kill the cat converter eventually. Exhaust gasses escaping into cooling water jacket will get bubbles in water with rad cap off. Test strips similar to PH paper or a liquid dye that identifies exhaust in coolant. It's not an over rich Holley 850 doublepump thats gonna clear up running hard to 90 plus. All you did was drive the ECM crazy trying keep up with demands it could not give. Oh well education isn't free.

 

[homeslice]

Canon, what about the coolant leak it appears you have ? In post 21 you say the coolant tank gets sucked dry.