Stuttering/Misfire

[RadRacer]

I believe it's a misfire; the car stutters under hard acceleration. If I give it over 25% throttle it begins to buck and is worst when the motor's cold. Below that, the car runs great and I can wind it up to the rev limiter no problem. Plugs were just changed, hoping to fix this; wires are 20K mile old, and coils haven't been replaced in the 2 yrs I've owned it. I can usually drive it with no problems as long as I control my throttle usage. Any ideas? PCV valve is new, oil changed not too long ago (~2K till next change), plugs are brand new NGK TR55s, wires are Xact Fit (Advance Auto brand) and fairly new (20K or so), coils however are old, injectors were put in 10K ago and they're from a LS1 with 10K on them. No codes are being thrown, which doesn't help at all. Any other ideas? When I replaced my plugs it went away for that day, but then came back, making me think it's wires, but I have checked at night and don't see any arching....

[poncho1961]

Re: Stuttering/Misfire

A little confused. You state that over 25% is when it happens but that you can hit the rev limiter with no problems. Are you talking a gradual climb up to that point as opposed to mashing the throttle and bouncing off the rev limiter? Just when its cold? Possibly a cracked vac hose? I've had similar problems with other makes and without codes and traced it back to the EGR. Anyone know if the EGR functions in closed loop or does it wait until operating temps climb?

[RadRacer]

Re: Stuttering/Misfire

If I keep the throttle under 25% it's fine; I can hold it just under the point it begins to buck and it'll hit the limiter no problem. But, if I go past that spot it begins to stutter pretty bad. If I gradually push into it it won't do it nearly as bad, but it still stutters. Also, noticed a burnt like smell after I made it do it a lot today....Leading me more and more towards wires. Hoping to pick up a set tomorrow.

[tkoforpresident]

Re: Stuttering/Misfire

coil pack or icm.

i believe coil packs when bad can still work under certain rpms but not in the higher ones.

do the old test, buy a new coil, swap em out one at a time, see if it fixes the prob.

[mattyacks]

Re: Stuttering/Misfire

plugs................

[cam98aro]

Re: Stuttering/Misfire

wires are Xact Fit (Advance Auto brand)

im willing to bet this is the problem

[RadRacer]

Re: Stuttering/Misfire

plugs................

.....plugs are brand new NGK TR55s....

coil pack or icm.

i believe coil packs when bad can still work under certain rpms but not in the higher ones.

do the old test, buy a new coil, swap em out one at a time, see if it fixes the prob.

That's what I'm planning on doing if wire's don't fix it. I do have a spare ICM from my last motor now that I think about it, but no idea of it's condition and if it works or not.

wires are Xact Fit (Advance Auto brand)

im willing to bet this is the problem

Me too; luckily, there's a lifetime warranty on them. I'm going to stop by today after work and see if I can get another set.

[ssms5411]

Re: Stuttering/Misfire

If your not throwing any codes, I would look into the injectors , might have one that isn't working as well as the others.

[RadRacer]

Re: Stuttering/Misfire

If your not throwing any codes, I would look into the injectors , might have one that isn't working as well as the others.

the injectors are like new basically; they came off a buddy's LS1 with 10K or so on them. I've ran injector cleaner in the car and it doesn't seem to help. I think I'm not throwing a code because I have the multiple misfire code tuned out, since my cam sets it. I even had my uncle try and use his Solus scanner to log the misfires, but he says it won't even let him do that since I tuned that code out.


Ordered a set of wires; they'll be here tomorrow. Worst comes to worst I'll have new wires on the car, since it's not costing me anything. If that doesn't fix it, I'll look into injectors and coils :(, but I hope that doesn't happen.

[96firebird311]

Re: Stuttering/Misfire

I had a coil go bad on me. Not uncommon. Obviously make sure a plug wire didn't wiggle it's way loose or something stupid too.

[RadRacer]

Re: Stuttering/Misfire

I had a coil go bad on me. Not uncommon. Obviously make sure a plug wire didn't wiggle it's way loose or something stupid too.

Plugs are fine. Brand new and in good. Still thinking it's a wire; it ran great the first day I did the plugs. Thinking one wire has a bad end or something and eventually wiggled loose again, giving me the misfire again.

[tkoforpresident]

Re: Stuttering/Misfire

i had crappy wires before and it made the car run fine down low but if you gave it any kind of gas it would stutter and spurt.

add wires to my list of goodies to check.

[RadRacer]

Re: Stuttering/Misfire

i had crappy wires before and it made the car run fine down low but if you gave it any kind of gas it would stutter and spurt.

add wires to my list of goodies to check.

That's exactly how it's running. Wires are being changed out tonight :)

[cam98aro]

Re: Stuttering/Misfire

That's exactly how it's running. Wires are being changed out tonight :)

dont be cheap, get good wires

[tkoforpresident]

Re: Stuttering/Misfire

get some taylors, summit can get them to you in 1-2 days.