LT1_ownr

Hey guys I just installed a set of LT headers and replaced the plugs but now I'm getting a pretty bad missfire. It's a P0300 code which means random misfire. The thing is, I installed brand new plugs with the header install. I used the NGK TR55 Platinum's. Is this too cold of a plug for a basically stock car? All I have done is the exhaust and K&N filter.

LT1_ownr

I didn't gap them because the box said not to cuz they were pregapped and had a sensitive electrode tip.

LT1_ownr

And all my wires I made sure were placed a good distance from the headers. Last night I had my brother look down on one wire that was close to the header to see if it was arcing off and it wasn't. And if it was, you would see that in the dark right?

LT1_ownr

Yeah I'm not sure when or if my opti has ever been replaced. I read about another guy having the same problems as me and it ended up just being a bad o2 sensor. And the funny thing is my driver side o2 sensor cracked and one wire was wanting to work it's way out and I've had to push it back in several times since I did my header install. But once I get that new o2 if it's still doing the same thing I'll check out the opti. But thanks for the advice. I'll let you know something prolly tomorrow.

94jetpilot

ran into same problem,yesterday...,i installed some bbk shorties, started to get random misfire, want to replace wires but could it be bad o2 sensor?? please let me know, thanks!

Hot94Z28

Mine did that shortly after my header install. I changed my opti. It worked good for awhile but I guess when my opti was going bad it took out my wires and I put new plugs in.

speed_demon24

iTrader: (6)

Unplug your 02's, reset the pcm, and see if it still does it.

94jetpilot

thanks i'll try it this, all helps believe me! thanks again.

94CamaroZ28SS

well i didnt do my headers a shop did them, but i had them install new plugs too. I got the car back and it idled fine but when i got on it about 2-3 grand the car sputtered and missed like hell. I thought it was the opti and so did the shop that did my headers. So i took the car home and went through and pulled every plug and come to find out they smashed two of the spark plug contacts to where there was no gap. so i bought regular plugs cause the ones i had them put in where the Bosh platnuim 4 and i heard those suck on a domestic. changed the plugs and the car ran great. CHeck the gap on them i think the stock gap is .050. when my opti went the car would miss and run rough at ible and back fire like a mother. did you put your car under a load when you looked for arcing of the wires? have someone put it in drive and hold the brake and check it again.

94CamaroZ28SS

Performance and Technical information on setting spark plug gaps.
Are plugs pre-gapped from the factory?

Yes and no. A spark plug part number might fit hundreds of engines, and although the factory will typically set gap to a pre-selected setting, this gap may not be the right one for your particular engine, and may not take into account modifications that you may have performed to the engine.

Insufficient spark plug gap can cause pre-ignition, detonation, even engine damage. Too much gap can result in a higher rate of misfires, noticeable loss of power, plug fouling, and poor economy.

When you raise compression or add forced induction (a turbo system, nitrous, or supercharger kit), you must lower the gap (reduce gap about .004" for every 50 hp you add on an V-8 engine, for a Harley-Davidson V-2 engine every 12.5 hp you add). However, when you add a high power ignition system (such as those offered by MSD, Crane, Nology,) you can open the gap back up about .002"-.005".

As an example, let's use a hypothetical `96 350 Chevrolet LT1 engine build-up. The standard gap is .050" for an un-modified LT1. We'll add 150hp Nitrous, so we must lower the gap about .012" to .038". We then decide to add that killer MSD 6A/Crane Hi-6 box and, using our guidelines as outlined above, we can now open the gap up .002"-.005" to about .040"- .043". By following this basic guideline should get you very close.

Further experimentation may be necessary, but by always starting with a larger gap than it thought necessary to reduce the risk of detonation, you should be safe.

koolaid_kid

iTrader: (21)

I would never install a plug without at least checking the gap. You never know what it is set at. It's a lot better than having to pull them out again to check or change.

blk97z28

iTrader: (3)

ngk
idirium!

FAD2BLK93

I just got some tr55"s today and they are gapped at .060 right out of the box. I will be gapping them to .050 before they go in.

ZFan88

iTrader: (4)

Just did headers and have a misfire? My bet is on a burnt wire..

Matts94Z28

iTrader: (6)

burnt wire!

96blackz28

iTrader: (3)

burnt wire or 02 sensors... my 02 sensors went out awhile after putting longtubes on.. tha twas because i ran open headers for like 3k miles, it ran so rich with a bad 02...

RaM AiR 97

iTrader: (1)

When i installed my headers first problem were O2s. i would check the gap on the plugs stay away from ac delco rapid fire. I installed them on my car and had random misfire until went back with NGK. Just recheck your wires at night use a water bottle spray to see more clearly if it is the wires

97Formy

I didn't realise that a bad o2 sensor would cause a misfire? I really don't see how it could. Been wrong before so I guess I could be wrong on this asumption also.

camarolvr69

would the car even run with a burnt wire??

ZFan88

iTrader: (4)

Yes, it'll misfire pretty bad and obviously be low on power. I had the same code. PO300.

O2s would set off a different code, as I have that right now as well lol