Help With Exhaust Issue.

Mineral4.6

Member
Mar 17, 2015
76
14
18
01 GT
Long tube BBK headers
Full length CAI

A few months after purchasing this car it gradually started to lose power. Started stumbling and misfiring before 3k and then would go away once WOT. At idle would run horrible rough, and poped and stutterers. When accelerating car would jerk and miss.

Ran codes and came out with a bad MASS air flow. So I replaced the sensor and replaced all plugs. And tightend up my collectors found they were leaking. Car ran amazing, better then before. Then about a week later check engine light came back on, codes thrown where exhaust O2 codes. Then a day later it is now running even worse then when I replaced the mass air sensor.

Can bad O2 cause it to run this rough? Or is it more likely my mass air sensor harness?
 
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System efficiency below threshold bank 2.

must be another exhaust leak I missed. I'll check the back in when I do fuel filter this weekend

And O2 sensor bank 1 sensor 2.

Going to swap bank 2 sensor 2 for bank 1 sensor 2 and see if anything changes this weekend.
 
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Do you have a tune to turn off the rear o2 sensors? Long tubes will mess with them (if not cats) also you need a tune for the placement of the front (sensor 1) sensors as they are in a different location and will need to be adjust accordingly.

p0430 talks about the cats which I'm betting you either don't have or they are not functioning correctly if you do.
 
I have not tuned the car, purchased the car with all the parts already on it. Car ran great for a few months.

Yes the car has cats, my idea was to try swapping sensor 2 from bank two to sensor 2 bank 1 too see if the issue changes, the bank one sensors are the only two that send info to computer to control fuel ratio correct? I understand if that sensor is indeed bad and it being in the bank two would not pass admission. Would a clogged cat OR failed O2 sensor cause these issues (rough idle at 750RPM, back firing at idle and hesitation while accelerating, feels like it is miss firing in all gears under 3000RPM)

Was really irritating to replace MASS air sensor and plugs only for these problems to come back less then a week later.

I'm also considering a (or multiple) coil pack having an intermittent fail?

Check engine light is on, and every so often it flashes, this is indicating miss fire correct?

I have not taken apart the IAC to be cleaned yet, nor have I tested the TPS. I am considering new coil packs but would rather spend the money on what will actually solve the problem. Car is at 130k so no doubt the original coils wouldn't hurt to be replaced but if they are working fine for now I'd rather not replace them. Is there a way to test them? Ohm reading? I've pulled a few at idle and the motor was all ready so rough I couldn't see or hear a change, same with unplugging mass air sensor.
 
The P0430 code lists as either a failed cat, or a failed O2 sensor before the cat, or an exhaust leak. I've actually had this code before fixing an exhaust leak at the collecter on the drivers side, and to my knowledge the code was never cleared. Is it possible that this code is still in the system after the fact? I've already addressed the exhaust leak before the cat.

Car runs extremely better when cold. Has less hesitation and jerkyness when cold. But when car warms up it starts to back fire. I've also has the car die at start up multiple times and while driving.
 
What would the issue be from going back to front? They are the same part number. The harness may be a different length but if it reaches wouldn't it work? I don't have a code reader yet, but I guess I could go bug the autoparts guy to hook it up again.