Misfire/stumble at idle, low MPG's.

Gamikatsu · Post by **Gamikatsu** » Tue Mar 19, 2013 1:50 pm

Well, here was my issue, as the title suggests...

my 02 LS1 hawk had a bad stumble at idle, the RPM's don't move, but you can see the oil pressure go up and down with the stumble. Gas MPG's were aweful (10 in town, 16 on hwy). power was aweful... it felt like a v6. here is what i did in the order i did it...

Fuel filter.. old one was very light, did not feel as if it had any resistance: no change

spark plugs and wires Duralast wires, NGK TR5IX Iridium plugs: much better fuel economy, and power, near perfect however still stumbling at idle

air filter (K&N) was cleaned: no change

MAF cleaned: no change

i had the fuel injectors pulled, and ultrasonicly cleaned, backflushed, and filters replaced: helped power and MPG's, but still stumbling at idle

at this point... i had just about given up... then the fuel pump died... its in teh shop now getting repaired, i will let you know how it goes!!!

96AZHAWK · Post by **96AZHAWK** » Tue Mar 19, 2013 2:12 pm

When it was running rough and you were on the gas, did it happen to shift abnormally hard?

Gamikatsu · Post by **Gamikatsu** » Tue Mar 19, 2013 2:30 pm

Nope. Can't say that it did. Shifted fine really. The dealership said 99% of my problems were relating to my low low fuel pressure.

TTOP350 · Post by **TTOP350** » Tue Mar 19, 2013 7:57 pm

A weak pump will cause all kinds of problems. A fuel psi gauge is a great cheap tool thats nice to have.

BLACK-HAWK · Post by **BLACK-HAWK** » Tue Mar 19, 2013 8:00 pm

It's free to pull the valve covers off to check the valve train

Gamikatsu · Post by **Gamikatsu** » Wed Mar 20, 2013 4:05 pm

Well... back with new fuel pump. Running like a scalded dog. Service manager asked me what I did to the engine. He swore it was faster than most of the vettes he had for sale... and faster than the 07 Yvette ls3 he owned. However... something isnt right and it grinds real loud under hard acceleration from the rear. I think the exhaust might be hitting something. It has a new poly trans mount so I don't think its that.

96AZHAWK · Post by **96AZHAWK** » Thu Mar 21, 2013 2:56 pm

Does "scalded dog" mean it is running good now?

Gamikatsu · Post by **Gamikatsu** » Thu Mar 21, 2013 2:59 pm

Yes. She's running great. No don't think its faster than a vette like they claimed but she is running real good. The exhaust is banging then underside... j got it wedged right now... I need to try and get it rotated a bit to where its hanging evenly.

96AZHAWK · Post by **96AZHAWK** » Thu Mar 21, 2013 3:01 pm

Glad to hear it is running well. Have fun with it.

Misfire/stumble at idle, low MPG's.

Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.

Re: Misfire/stumble at idle, low MPG's.