Thread: Random Misfire and P0171

I am having the same problem with my 2004 Gtp Comp G. Po300 comes up when boosting at high rpms, works fine under regular accelerarion. Plugs and wires were changed just a bit ago. Po300 code turned on at the track and then 2 days later it went away. Let me know if you find a solution. Ima check it out soon

Originally Posted by Mbueno19

Hello everyone, I need a little help with a random misfire and what you guys think it might be.

Okay, I have already changed the plugs to NGK Iridium gapped at .060, new plug wires, new fuel filter, new air filter and I am pretty sure I have fixed all the vacuum leaks it had. I have a problem with the engine setting off a P0300 code which is for a random misfire. It only misfires though when it is on boost. When it is off boost it runs good. I checked the fuel pressure and it seemed good if i remember correctly it was around 55PSI. I put some injector cleaner thinking it was a clogged injector but that still didn't help at all.

Also I'm thinking that maybe the P0171 would set off the random misfire? I hear a ticking noise in the engine bay that flutters or gets louder when you give it gas, so I am guessing the lean condition is happening from that exhaust leak.

The car is completely stock, so is it being gapped at .060 bad? That was how it came out of the box. And also, what could cause the misfire only under boost, if off boost it runs good? I fixed almost everything but now this misfire is just getting too me....

Well it turns out the misfire is coming from cylinder number 6. I just received that OBD2 bluetooth scanner and it is reading the misfire and still P0171 even with the crack sealed up. This tool is awesome, just wondering what to put under the boost under vehicle profile. I'm 3700ft above sea level so I'm not to sure what to put.

Did you figure out what was the cause of the lean code and cylinder 6 misfire? Got exact problem can't figure it out...

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