I have a 1997 Z71 with the L31 engine and it has a misfire so i changed all the plugs to the E3 plugs. I changed the fuel filter and drained and re filled the gas and ran alot of Lucas fuel system cleaner through it and i still have the misfire, so i bought a OBDII reader and it is telling me that i have a cycl 7 misfire. i pulled the plug wire off and the truck ran the same so i put a plug on it and touched it to the head and it sparked just fine. Does anyone have any ideas as to what it might be?

 

did the plug you pulled out look different than the others? i'd run a compression check. it could be a leaky poppet valve from injector, burnt/cracked/bent valve, bent pushrod, bad lifter. again, run a compression test on all cylinders, just make sure the throttle body is wide open.

 

I have not had good experience with the E3 plugs. I have had brand new ones be faulty. I might suggest trying a new plug or switching to NGKs

 

But thats only my experience, yours may be different. I always try to adhere to the KISS method when it comes to tracking a misfire.

 

We had a #8 misfire and did all they suggested. Didn't fix problem. We finally put a 1/2 can of seafoam into the brake booster line and let set for 15 min. then took it out and drove it pretty aggressive. Did the job for us. Put remainder in the fuel tank and away we went.

May have just been a freak deal but it sure fixed our problem.

Hope this helps.

Dad

 

I had a cylinder 5 misfire. and the day michael jackson died, i did the spark plugs. then after that, the cap, rotor, wires, coil were replaced. still it developed a misfire. so... did a static compression check, turns out i have wonderful compression. from the factory the compression is 150, i got 110000 miles, and my compression is 150 across the board. at 99000 miles when i decided to run a better oil pump, i still had the honing and cross hatch on my cylinder walls. yeah... anyhoo, running compression was 25 psi low, so something was not closing all the way. well, turns out my lifter took a dump. its had a tick on cylinder 5 for a while, so i knew it was bound to go... and today i just swapped the old ones out, and put new pushrods and rocker arms with the roller tip in. now i just have to put everything back together and hope it starts lol. but yea... do a compression test, and running compression test. general rule of running check, your compression should be half of that cylinders static compression. so mines 150, should be 75. good luck.