skip that comes and goes

**dow inc.** · 10-25-2009, 08:14 PM

I have been trying to find a skip that comes and goes. my car has 56,000 on it. the car has full exhaust short tube headers, true ram air kit, hypertech power programmer & comp cams push rods. other than that it's a stock LS1 with a 6 speed. it would start to skip after a hard run and idle like crap it sounded like it had bad plugs. the SES light came on and it was a multiple misfire on #3&7. so I got new ac delco plugs and put them in. (#8 sux) the car was running good for awhile and I let it sit for about 6 months. one night I decided to take it out and it did fine for awhile and it started skipping after a good hard run but stoped after a few min. and it was good to go but as i was driving home and it started to break down. I got home and checked the header temp. and it was # 3&7 missing I was thinking bad wires. I ordered some MSD wires and stopped and new NGK plugs. why i had it tore down i took #2&4 coils and put on # 3&7 just to see if it was the coils. I pulled the valve covers to check the push rods and springs, it all looked good. I did a leak down test on #3&7 and both are good. I put it all back together and it did good for a bit, but the skip is back! It sounds like it is fouling the plugs but im not sure. the coils have a good hot spark. the wires are all on tight. the fuel psi is good. I checked for vac. leaks, none that i can find. now after a hard run it flutters at idle and after i idle it up it clears out just like a bad plug. I have tryed to check the header temp. but it is still to hot to find what one it is. plus about the time i start checking It clears up. the SES light is not on yet but im sure it will be soon. It sounds like it is #3 skipping but Im not sure. could it be the injector sticking open? if anyone knows what is wrong with it please help. Thanks Im tired of guessing.

**35th-ANV-SS** · 10-25-2009, 08:28 PM

Originally Posted by dow inc.

I have been trying to find a skip that comes and goes. my car has 56,000 on it. the car has full exhaust short tube headers, true ram air kit, hypertech power programmer & comp cams push rods. other than that it's a stock LS1 with a 6 speed. it would start to skip after a hard run and idle like crap it sounded like it had bad plugs. the SES light came on and it was a multiple misfire on #3&7. so I got new ac delco plugs and put them in. (#8 sux) the car was running good for awhile and I let it sit for about 6 months. one night I decided to take it out and it did fine for awhile and it started skipping after a good hard run but stoped after a few min. and it was good to go but as i was driving home and it started to break down. I got home and checked the header temp. and it was # 3&7 missing I was thinking bad wires. I ordered some MSD wires and stopped and new NGK plugs. why i had it tore down i took #2&4 coils and put on # 3&7 just to see if it was the coils. I pulled the valve covers to check the push rods and springs, it all looked good. I did a leak down test on #3&7 and both are good. I put it all back together and it did good for a bit, but the skip is back! It sounds like it is fouling the plugs but im not sure. the coils have a good hot spark. the wires are all on tight. the fuel psi is good. I checked for vac. leaks, none that i can find. now after a hard run it flutters at idle and after i idle it up it clears out just like a bad plug. I have tryed to check the header temp. but it is still to hot to find what one it is. plus about the time i start checking It clears up. the SES light is not on yet but im sure it will be soon. It sounds like it is #3 skipping but Im not sure. could it be the injector sticking open? if anyone knows what is wrong with it please help. Thanks Im tired of guessing.

A bad or dirty MAF could cause your PCM to make the car run rich/lean, which would could cause a cylinder misfire.

Fuel injectors - Have you checked fuel pressure?

Oxygen sensors.

**dow inc.** · 10-25-2009, 08:44 PM

fuel psi is good

**dow inc.** · 10-25-2009, 08:51 PM

if it is bad injectors I think my car has 28lb. stock could i go to a 30 or 34lb. with out having to flash my ecm.

**0rion** · 10-25-2009, 10:24 PM

Originally Posted by dow inc.

if it is bad injectors I think my car has 28lb. stock could i go to a 30 or 34lb. with out having to flash my ecm.

no you would have to tune for them.

**Cutlass** · 10-26-2009, 05:49 PM

If you suspect a possible bad injector, then swap them side to side and see if the miss follows the injector over. Maybe try the same with the front O2 sensors.

**dow inc.** · 10-26-2009, 08:10 PM

I have moved the coil packs and injectors and o2 sensors same problem, it will skip for a few min. and clear up. im going to take the hypertech power programmer down load off and see if that is it. has anyone else had the same thing happen to them?

**smartinz26** · 10-26-2009, 09:18 PM

i had a small skip and my maf was dirty.. took it apart and carefully cleaned it has been perfect since. no more random ses light either.

**dow inc.** · 11-08-2009, 07:14 PM

found my problem!!! the plugs are fouling out because I have blow by. I did a leak down test again when the motor was cold I have 100% leak down on 123567 and 30% on 4 & 8. (I did take all the rocker arms off) I put some oil in the cylinders and it held psi. I did a compression test an all were about 140 to 145 psi. looks like I get to build my 383 after all.

**Cutlass** · 11-09-2009, 03:52 AM

interesting. 100% leakdown past the rings is weird. I wonder if they are carboned up and getting stuck in the ring grooves, maybe??
Either way, have fun with the 383 build!!