3 years of random misfire
Oct 2, 2016 | 10:14 AM
#11
Thread Starter
Teching In
Joined: Oct 2016
Posts: 16
Likes: 0
key on engine off command pump on with a scan tool... Pressure should be between 345-690kpa (50-100psi) after pump is turned off it should stabilize between 500-599kpa(72-87psi) (if more than specified, replace fpcm, if less check for restricted fuel feed pipes or poor harness connections, if the test normal replace fuel pump)
Swapped fuel tank with friends truck and still the same , other truck runs completely fine with 300 kpa pressure .
Both trucks have same pressure reading but mine have the misfire .
Oct 2, 2016 | 01:51 PM
#18
FormerVendor
Joined: Oct 2015
Posts: 57
Likes: 0
From: Denver
re: misfire
i'm afraid that you have an issue somewhere in your engine wiring harness. back in the day, a friend of mine was a Saturn mechanic and they had 5-10 cars parked at the big central repair shop that had wiring harness issues. GM usually just wound up buying them from the owners.
Oct 2, 2016 | 01:51 PM
#19
Swapped engine, ecm, coils, wires, plugs, injectors, going to assume new intake gaskets when engine was replaced, no cats to be clogged, its starting to sound like a harness issue of some sort.... Could be a broken wire at the crank sensor, an issue with injector circuits or coild circuits or anything in between.... Have you by chance checked the map sensor and maf/baro sensor against what they are actually reading? Going to assume youve checked for vaccum leaks including the brake booster....