Rough idle-> these are the codes I got...

Back2Mustangs

New Member
Sep 2, 2004
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P0153 Upstream Heated Oxygen Sensor circuit Slow Response - Bank No. 2
P0420 Catalyst System Efficiency below Limit - Bank No 1
P0430 Catalyst System Efficiency below Limit - Bank No 2

Car has an o/r x-pipe w/o MIL's so I expected this, but none of this helps me figure out why the car sounds like its missing and idling rough :nonono:

I already replaced the alternator, coils, plugs and wires. I think I'm just going to replace the front O2's, get the MIL illiminators, replace the IAC, EGR, TPS and MAF... I don't have time to chase this stupid problem. If none of that fixes it then I'll check the timing, and if thats all good then I'll just replace the whole d@mn longblock.
 
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Back2Mustangs said:
P0153 Upstream Heated Oxygen Sensor circuit Slow Response - Bank No. 2
P0420 Catalyst System Efficiency below Limit - Bank No 1
P0430 Catalyst System Efficiency below Limit - Bank No 2

Car has an o/r x-pipe w/o MIL's so I expected this, but none of this helps me figure out why the car sounds like its missing and idling rough :nonono:

I already replaced the alternator, coils, plugs and wires. I think I'm just going to replace the front O2's, get the MIL illiminators, replace the IAC, EGR, TPS and MAF... I don't have time to chase this stupid problem. If none of that fixes it then I'll check the timing, and if thats all good then I'll just replace the whole d@mn longblock.

WOAH time too stop throwing parts at it. ok for one it needs a bank 2 upstream sensor.

but that is probally not your idling problem. i would look for a vac leak. check all the vac hoses.. then spray carb cleaner around the base of the intake. if you hit a spot where the idle changes ( smooths out) then i would check that spot. keep in mind most vac leaks are at hoses. take your time. listen for hissing check hoses and spray carb clean.

report back here for more help when needed.