miss-fire at full throttle...any ideas?

[TDWPgtp]

welp, car just turned 100,000 yesterday and at 99999.4 i had a missfire. i had it scanned and reset. later that night, i went full throttle again, and it missfired again. i dont know anything about missfires, so if anyone could try to help shed some light on what might be wrong, thatd be great thankssssss

[grandprixgtx00]

posting the year of your car may help...i would assume its a GTP from your username. Also, were you able to pull any codes?

[Scrapper]

i'd say start with your coil pack and tps-throttle posiition sensor.

[TDWPgtp]

its a 97 gtp. and i wasnt told the DTC code, but im pretty sure he said cylinder 5. ill go up to autozone for a scan tho for sure and ill post back. do you guys think theres any risk drivin it right now?

[tblake]

When was the last full tune up done to include new plugs and wires, and if recently, what brand was used? Hairline cracks in the porcelin of new plugs can cause missfires in load conditions.

[TDWPgtp]

its P0305. cylinder 5 misfire.

the plugs were changed about a month ago or so, the wires were not. i used the stock AC Delco plugs. is there any ways to help diagnose the cause?

[doctorhrdware]

What I would do is take the wire from plug 6 and use for plug 5. Then take the wire from plug 5 and put it where plug 6 wire was. If the problem follows the wire the wire is bad. If not could be the coil pack or the fuel injector problem.

[BNaylor]

Originally Posted by doctorhrdware

What I would do is take the wire from plug 6 and use for plug 5. Then take the wire from plug 5 and put it where plug 6 wire was.

Why swap #5 and #6 ignition wires?

Easier just to deal with the front odd bank cylinders on this one since it is a P0305 DTC. I'd swap cylinder #3 and #5 wires.

Note: When you swap out ignition wires for troubleshooting a misfire condition you do the spark plug end and respective coil pack end.

To the OP regardless with 100K miles you should replace the ignition wires in their entirety. If stock or you want to stay stock use the AC Delco Premium Silicone 7mm wire set or you can spruce it up with Taylor Spiro Pro 8mm or even MSD brand wires.

[doctorhrdware]

Originally Posted by BNaylor

Why swap #5 and #6 ignition wires?

Easier just to deal with the front odd bank cylinders on this one since it is a P0305 DTC. I'd swap cylinder #3 and #5 wires.

Note: When you swap out ignition wires for troubleshooting a misfire condition you do the spark plug end and respective coil pack end.

To the OP regardless with 100K miles you should replace the ignition wires in their entirety. If stock or you want to stay stock use the AC Delco Premium Silicone 7mm wire set or you can spruce it up with Taylor Spiro Pro 8mm or even MSD brand wires.

BNaylor you got me, demerit points on me. That is what I had in my mind, but when you get old like me, you think one thing but do another . I am sory that I had a brain fart. I will try, not letting it happen again.

[grandprixgtx00]

100K is getting up there for wires. as suggested switch cylinder 3 and 5 wires if the misfire jumps to cylinder 3 which should give you a P0303, then you know its time for some wires.

[TDWPgtp]

well i appreciate all of your help, but upon inspecting the post on the cylinder 5 coil, i noticed some corrosion. i sanded it off and so far the SES light has turned off and i dont feel any hesitation or jerking at full throttle. and by the way, the wires are NOT the original, although i do not know how many miles are on them.

[grandprixgtx00]

glad you have located the problem. hopefully that works for you

[TDWPgtp]

thanks, ill be sure to post again if something else seems to go wrong. it always does...

[TDWPgtp]

well apparently it didnt fix the problem. the misfire isnt nearly as bad now, but its still present. the SES light turned off after i cleaned the post, but i had it scanned and its still pulling the code for a cylinder 5 misfire. the post on the coil seems to have corroded more over night... time for new wires?

[doctorhrdware]

I would move the coil pack for cylinder 5 and 2 to another position or replace the wires, and maybe the coil pack too. Maybe because the wires are old and causing cylinder 5 coil pack connection to corrode?