Misfire Help

[01KnightRiderGT]

I beg of y’all please help me with this problem. Ive tried everything.

It started about 8 months ago and slowly getting worse. My car misfires horribly but it only starts when I drive the car for around 45 minutes or so. But lately its been starting sooner like just after 15 or 20 minutes. When it misfires I can just turn off the car and let it sit for a few minutes and everything would be back to normal.

When it misfires it is also gradual. It would start after just 45 minutes of driving. It starts just like a little hiccup, then it just get worse to the point where the car wants to shutoff. When I try to accelerate the car tries to cut off. I also have a wideband o2, and when it misfires the A/F ratio goes to 10.xx meaning it’s really rich. So I’m assuming it has to be a spark issue not a fuel. But I may be wrong.

It does not throw any CEL for missfire. Do COP gradually go bad, or they a good and bad deal only.

Only code i have is p0455 which is Evap leak, and p0136 which is the rear o2 sensor.

Could it be my ECU or any other sensors

Plugs have 20k miles
I have MSD COP for around a year.

 

[x10shooter]

Sounds like a bad coil pack. They often start out as nothing and progressively get worse.

 

[joshjwc9]

Yeah, it also could simply be the insulation boot around the spring has split causing it to arc and create a misfire. I would pull them and check them visually by applying slight pressure in bending the boots checking for cracks.

Check your evap leak too, that could influence the misfire as well by getting to much fresh air into the fuel system.

 

[01KnightRiderGT]

Thaks for the help. The boots are good, no cracks at all