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Old 09-09-2012, 05:00 PM   #1
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new exhaust and poor running (idle adaptation faults)

so my '01 S w/ 95k miles just got a full Maxspeed Motorsports exhaust installed, with the 4 200 cell cats.

after i picked up the car it ran fine for the drive to work, but would barely idle when i got in the parking lot. idle swinging up and down +- 300 RPM, sounds very loud, exhaust tips black with soot.

drove it back to the shop and CEL came on. got to the shop and they checked the faults, and came up with Fuel Trim Adaptation faults.

so basically the engine can't adapt the fuel trims and it's running FULL rich (black tips).

they've tried moving the post-cat O2's around (exhaust has 4 O2 bungs on each side), but this should be front O2 related. i replaced the front O2 sensors with aftermarket ones about a year ago, so the shop is going to try factory O2s (another $500 ) on monday.

if anyone has any ideas... ?
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Old 09-10-2012, 11:16 AM   #2
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I have 01 box and the two O2 sensors per side are attached to the header before the front cat and right after the cat. nothing is connected to the secondary cat.

I read somewhere that all the heater elements are powered by the same electrical tap, and if one of the O2 sensor heater is shorted, it will affect all four sensors.
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Old 09-10-2012, 06:36 PM   #3
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shop installed new pre-cat (B1S1, B2S1) O2 sensors. 2 extented test drives and sitting in their lot idling for 2 hours, runs fine. i get it back and drive it 20 minutes to work, idles like crap again.

if was heater related, it would give heater faults. and after the engine and exhaust is warmed up, the O2 heaters are out of the picture.

but all we're getting is fuel trim faults.
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Old 09-10-2012, 06:47 PM   #4
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Quote:
Originally Posted by Dave928 View Post
so my '01 S w/ 95k miles just got a full Maxspeed Motorsports exhaust installed, with the 4 200 cell cats.

after i picked up the car it ran fine for the drive to work, but would barely idle when i got in the parking lot. idle swinging up and down +- 300 RPM, sounds very loud, exhaust tips black with soot.

drove it back to the shop and CEL came on. got to the shop and they checked the faults, and came up with Fuel Trim Adaptation faults.

so basically the engine can't adapt the fuel trims and it's running FULL rich (black tips).

they've tried moving the post-cat O2's around (exhaust has 4 O2 bungs on each side), but this should be front O2 related. i replaced the front O2 sensors with aftermarket ones about a year ago, so the shop is going to try factory O2s (another $500 ) on monday.

if anyone has any ideas... ?
Just so I understand you correctly, you're running both 200 cell pre-cats and 200 cell secondary cats ?
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Old 09-10-2012, 07:26 PM   #5
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Quote:
Originally Posted by Dave928 View Post
shop installed new pre-cat (B1S1, B2S1) O2 sensors. 2 extented test drives and sitting in their lot idling for 2 hours, runs fine. i get it back and drive it 20 minutes to work, idles like crap again.

if was heater related, it would give heater faults. and after the engine and exhaust is warmed up, the O2 heaters are out of the picture.

but all we're getting is fuel trim faults.
isn't idling the car for long periods of time really bad?
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Old 09-10-2012, 08:28 PM   #6
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Quote:
Originally Posted by Johnny Danger View Post
Just so I understand you correctly, you're running both 200 cell pre-cats and 200 cell secondary cats ?
yes. here's the link...

Porsche Boxster 986 NHP Performance Exhaust 2.7L/3.2L

Quote:
Originally Posted by ohhh my View Post
isn't idling the car for long periods of time really bad?
as long as the water pump and cooling fans are working, isn't going to hurt anything.

-----

was brainstorming with a friend earlier, it sounds like an exhaust leak at the manifold gaskets. when at idle it would draw air in, making the S1 O2 sensor think the engine is running lean, so the ECU adds fuel, making it run rich. then at cruise, the exhaust blows out thru the leak, not affecting idle fuel trims. EXCEPT, it's both sides.

so either there's a header leak on BOTH sides (seems unlikely) or the problem is upstream of the engine... ECU, MAF, or throttle body. the question is why one of those would crap out from just changing the exhaust...
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Old 09-11-2012, 03:15 AM   #7
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well after driving it home, there were 11 DTCs.

P1125 LTFT Add. Air B2 too rich
P1126 LTFT Add. Air B2 too lean
Fuel Sys 1 Closed Loop
Fuel Sys 2 Closed Loop
Calc. Load 26%
ECT 183deg F
STFT B1 25%
LTFT B1 28.9%
STFT B2 25%
LTFT B2 28.1%
RPM 2840
Speed 72mph

P1128 LTFT Mult. Air B1 too lean
P1130 LTFT Mult. Air B2 too lean

P1132 O2 S1 B1&B2 control signal too high
P1133 O2 S1 B1&B2 control signal too low

and DTCs for multiple misfires.

those fuel trim numbers are at max enrichment.

so after a lot of reading, i'm thinking the MAF crapped out. cleaned it and reset the codes. will find out in the morning (not starting it at 3am).
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Old 09-18-2012, 03:46 AM   #8
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You can usually self check the MAF by completely disconnecting it. The engine should still run as the lambda probe will trim the fuelling to suit the emissions. The primary lambda probes are wideband and designed to control fuelling to ensure the engine doesn't run lean or rich. The secondary lambdas are not control they monitor for emissions. Assuming the lambdas were not switched round ,one possibility is that maybe you have a manifold leak on the block that is flexing when the engine is hot. I assume all the gaskets were replaced and the manifold (header) bolts torqued from the inside outwards ( ie the bolts at the ends of the headers are tightened last).

The only other case of rough running i've heard of is when the cross tee on the inlet manifold has become loose, this allows more air after the MAF to enter the engine causing a lean mixture. you could also check the hose clips on the inlet manifolds on the cross tees.
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Old 09-18-2012, 08:26 PM   #9
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just got the car back from the shop today.

disconnecting the MAF did make it run fine but it still ran poorly with a new MAF. reinstalled orginal.

shop thought both aftermarket S1 O2 sensors could be at fault so replaced those. no change. reinstalled originals.

vacuum and smoke checked the intake/vac lines. there are no leaks, so no false air.

checked fuel pump pressure and volume, both are good.

next to last thing the shop did was to reinstall my original exhaust system (bad cat and all), car now runs almost normal.

the only thing they found after this is that the bank 1 cam timing deviation is out of spec. bank 1 is -6.5, bank 2 is -5.5. so the only thing the shop can figure is it needs the cam adjuster pads replaced ($$$$$) and that the better breathing new exhaust was amplifying the condition.

any other guesses? we're fresh out.
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