Thread: Misfire under load, increase with engine warmth and run time

Update. There was nothing wrong with plug 3 and it never registered on OBD again after that.
Now it's running like complete **** on idle or otherwise, big rumbling noise and shaking hard with strong smell of gas at all times. I wanted to do compression test but once again a bank error against my favor and I need 3 tires. The running quality has severely degraded over the past month.

A pic and video uploaded today. Gas smell coming from the driver side somewhere but can't tell where. Equally strong smell from front to back of cross pipe and toward center of engine but not beyond.
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If the GTP is the same routing as the GT then check the steel fuel lines as they route up against the drivers side firewall. There is insulation there and the lines are clipped in right against it which leads to rust. Also brake lines in that area. I've replaced 2 brake lines due to this design.

I'd carry a fire extinguisher in the car at this point. That sounds like a fire just waiting to happen.

Alright fellas, time for an update. Sorry I was real busy with some other **** for the most part but did do a lot of work on it.
1. Scotty it was squealing because the water pump gasket was broken and I was losing water.
2. Fordman the fuel lines are still good, I checked them again.
3. After a 3 day water pump ordeal in which the bottom left bolt suddenly didn't reach, I added 2 washers and it finally sealed.
4. The alternator red line stud/ bolt broke during the ordeal so I had to get a junkyard alternator which works better.
5. At night while wrapping up that ordeal, I noticed a spark coming off line 3 to the front header, only visible in dark.
6. While moving the wire it snapped, so I replaced it and it's fine now. I thought and hoped that would fix everything. No.
7. After all that **** it was still misfiring, I did a compression test. Everything was fine.
8. Broke the Tbar to vacuum harness during ordeal, redid that **** end to end. Not perfect and will need redone again.
9. That didn't fix it either, but misfire seems to happen almost entirely on boost call, acts exactly like a boost vacuum leak.
10. We're basically exactly back where I started, misfire under load, gets worse with engine heat.
11. Bonus: included new picture of Tbar workaround and video from interior of what it sounds like. Link below.
12. Double bonus: Now offering $20 to the first person that can accurately tell me what the problem is. Thanks.
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I guarantee I'm not the problem. I'm not an X man or avenger and have no supernatural ability to make the car misfire. I've tried everything on this forum and others. The fact that you can't help me is simply am insult to your ego since you think you know everything. Otherwise you'd be collecting an easy 20 just for writing a few helpful sentences. Instead you choose to write insulting sentences to pacify your fragile ego.

Originally Posted by Wakingcrow

Having a hard time with this one. Cold, runs fine for a few minutes, plenty of power. Warm, misfires while accelerating at any speed. Hot, misfires increasingly. After a few hours it's running on one or two pistons. Runs fine after cool off.
Recently, I replaced vacuum hoses and fuel filter. Swapped the 2 map sensors to see if it did anything different. Didn't.
Code says 300 random engine misfire. Autozone printout said ASE technicians would recommend reprogram PCM. I don't have a tuner. Does anyone know what would be most likely or what to test first?
Thanks.

Check the wiring under the throttle body. Common issue.

I forgot to mention, when I work the gears manually and accelerate using lower gears, I can usually avoid any misfires, up to a certain point when boost engages then it misfires as seen in the video. Anyone with knowledge knows that sparks and spark wires don't care if it's under load or not. It's only misfiring under load/boost. Ironic that someone that calls himself Bill Boost has no idea what the problem is that only occurs under boost engagement, isn't it. That's the way it is with people with fragile egos.
I've pulled the throttle out a couple times and didn't see anything irregular around it, but I'll check that wiring once it gets above 40.
Bandook which injector O-ring is it? There's 6 injectors. If you're right I'll send you 20 clams.
Thanks all, except Bill.

Originally Posted by mguzzo

I'm still going back to my post in September for a clogged cat.

I will return to my response that there is no cat present so that's impossible. Straight pipe down only. Which is not likely the problem because it worked fine in that configuration for 5 years before all this ****.

I should also add that idiots like you that don't hide behind their ****ing keyboard, but insult me in person, get punched in the nuts, kicked in the face, and end up in the hospital, you stupid ****. Keep it up ding dong.

Originally Posted by bandook

Which o-ring? That's for you to figure out, ding dong. When you bought your premium membership here what did you expect from the members?

BTW, bashing a dude that has more knowledge of these cars than you or I will obtain in two lifetimes is a real good way to get zero help in the future. Smooth move, ding dong.

Bill, unfortunately, you're a complete asshole. If any of you had been able to tell me what the ****ing problem was, it would be fixed by now. Because I can do all the work necessary, and proved beyond a reasonable doubt that it's not a compression problem. So the problem is something easy and very fixable but I'm not a master diagnostic, and very obviously you are not either Bill. You are a master insulter because of your ego problems. So basically you can all just **** off instead of insulting me, because obviously you haven't helped at all.