random misfire issues.

I have a random missfire issue that I can't track down my root cause. started with a misfire on cyclinder 4, pulled the plugs and the gap on cyclinder 4 was too small. Replaced all plugs, still have a slight misfire when accelerating from a stop in 1st gear at aprox 1500 rpm, but no code. also had a slight stumble at idle.

I noticed the the more gas from a stop the more noticable the mis. so i put the car in 2nd(sport shift) and put more load on the car and the car boogs horribly up to about 3k rpm, and throws a misfire code cyclinder 4. pulled plugs everything looks fine.

under had acceration in 1st I have gotten cyclinder misfire on 1,3, and 4, all seperate occasions weeks apart. I figured cyclinder 1, 4 mis was becasue of the coil pack. replaced both and issue is still there but no where near as bad. checked the resistance on the wires and the resistance was ok, no high resistance.

Im going to replace the plugs again because in thinking 1k miles on failing coil packs didnt do the plugs any good. Any thing else that im missing? I was thinking of doing the compression test, pull the valve cover and check the timing, and maybe seafoam the motor. All this has been getting progressivly worse until i replaced the coil packs.

Car is an 2003 p5 sportshift 142K miles.
I may upload a video of it if that will help.

slayne said:

I have a random missfire issue that I can't track down my root cause. started with a misfire on cyclinder 4, pulled the plugs and the gap on cyclinder 4 was too small. Replaced all plugs, still have a slight misfire when accelerating from a stop in 1st gear at aprox 1500 rpm, but no code. also had a slight stumble at idle.

I noticed the the more gas from a stop the more noticable the mis. so i put the car in 2nd(sport shift) and put more load on the car and the car boogs horribly up to about 3k rpm, and throws a misfire code cyclinder 4. pulled plugs everything looks fine.

under had acceration in 1st I have gotten cyclinder misfire on 1,3, and 4, all seperate occasions weeks apart. I figured cyclinder 1, 4 mis was becasue of the coil pack. replaced both and issue is still there but no where near as bad. checked the resistance on the wires and the resistance was ok, no high resistance.

Im going to replace the plugs again because in thinking 1k miles on failing coil packs didnt do the plugs any good. Any thing else that im missing? I was thinking of doing the compression test, pull the valve cover and check the timing, and maybe seafoam the motor. All this has been getting progressivly worse until i replaced the coil packs.

Car is an 2003 p5 sportshift 142K miles.
I may upload a video of it if that will help.

Click to expand...

nailed it....Also check and clean your egr valve. After replacing the plugs (they're at .044 right?) and cleaning the egr you should be good.

I would put on some new leads/wires too

Yeah all the plugs were gapped .044. A buddy mentioned using the msp plugs either the g power or v power, what are the benefits of the speed plugs? And the about the egr valve, buddy gave me a header that I need to put on and it has the egr tube blocked off and I have a air filter and fitting to go on the egr. Should I still clean the egr out even tho it will be using fresh air rather than exhaust, or will it still mess with the air/fuel ratio?

slayne said:

Yeah all the plugs were gapped .044. A buddy mentioned using the msp plugs either the g power or v power, what are the benefits of the speed plugs? And the about the egr valve, buddy gave me a header that I need to put on and it has the egr tube blocked off and I have a air filter and fitting to go on the egr. Should I still clean the egr out even tho it will be using fresh air rather than exhaust, or will it still mess with the air/fuel ratio?

Click to expand...

I've actually never heard of anyone doing that with the egr...Maybe someone who knows about what you want to do can have more input. I know you can get a block off plate etc. but you will have a CEL. The speed plugs and na plugs are basically the same....you can get better plugs or basic plugs for either model and just gap it accordingly..I would still clean your egr valve however. If it is gunked up and or stuck it can be a pain

Yeah, as far as plugs go i would just use normal ones

I would go ahead and repplace the wires with new ones. Started happening to me with about 40k old wires.

I replaced the plugs and the stumble is gone.

Glad you got that taken care of Scott! And as for the breather filter on the egr, Evan (lewis99124 or whatever lol sorry Evan ) was running it and said it worked fine. Seafoam the girl bro! Lol