Before I say anything else, I must point out that I have 4 almost brand new CPS and NO codes.....
So about 6 weeks or so ago, I was hammering home in a very heavy rainstorm. I came off the M25 onto the A3 and there was a huge pool of water at the bottom of the sliproad. I accelerated hard as I came out of the 'puddle' and spun up the RHS rear wheel. Next thing I know the exhaust note has changed, a bit like when the CPS goes bad. It stayed like it for about 4 miles then slowly but streadily cleardd itself and everything went back to normal. I checked with the Peake and got nothing. I put it down to the exhaust having been immersed in cold water for a bit, or one of the O2s or temp sensors getting an odd reading from having a bath.
I thought no more about it until Wednesday, when I had a special M5 'moment' at the local Polish/Eastern European car wash... The guys were very excited by the M and as I was paying one of them said it would be a 'great honour' if I would 'give it some gas please' as I left. Well how could I say no! The thing is that having just been sitting in pools of soapy water, the rear wheels spun up like they were on ice. Luckily it didn't slew sideways so the DSC didn't trigger, and the wheels just kept on spinning and the next thing I know there are 2 HUGE clouds of white tyre smoke behind me..... and then it gripped. Awesome. I couldn't possibly have planned a better exit if I'd tried! BUT..... having spun the wheels, this strange exhaust note returned. It stayed for a bit then slowly wore off again like last time. For the next 20 miles or so there was a distinct hesitation if accelerating from 3 or 4k rpm. I stopped, turned her off and on again and everything was totally fine and has been since. Again - no codes.
Both times it happened after the car was around large amounts of water. I am not a big believer in coincidence, so I would guess something is getting wet and the heat of driving a few miles dries it up.
Could be CPS on one side, perhaps a wire is getting wet and CPS works intermittantly until dry? Not all CPS malfunctions throw a CEL/SES. Did you check for codes with a Peake or equivalent?
Regards,
Jerry
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'01 Black/caramel
Dinan Stage 3 suspension, SS jet coated headers, ESS SC kit, open brake ducts, Hamann front splitters, TEC cupholder, U.S.(Euro style) tilt/slide armrest, 6k HID fogs, 6k super white low beams, V1/Stealth1, dual head LI, 2.65 diff w/40% lockup/2x dynamic, compact spare, Euro trailer hitch, Mocal oil cooler, ACS type rear spoiler, Rogue custom SSK and tranny mounts, ST 355 BBK (fronts), BP sway bar brackets, Bluetooth retrofit
I'd agree, it's the CPS. Before one of my CPS' died, I would get these exact intermittent gravelly exhaust moments with torque loss that would go away without throwing an SES light or any codes. Finally after a month, it threw its first SES. Man... there are four of these damn sensors on this car!
I don't think a CPS symptom would go away just by switching the car off and restarting, I might be wrong, but this is what normally happens when the car goes into limp mode - at least this is the way I "cleared" the limp mode several times...
-BTW - I never found the cause, and haven't had it for more than a year now - knock on wood...
Cheers for the help all, but I must stress, as I did at the beginning of the thread, that I have NO CODES and all 4 NEW CPS! I guess a new one could go faulty, but I have had the Exhaust CPS go on me twice since I got this car over 4 years ago. I know the symptoms very well and the noise is not quite as deep or rich sounding and the car loses no power. I also always had codes before, even when it went bad for just 2 minutes when the fault first started. Another difference is this hesitation. That didn't happen with either of the 2 previous CPS failures.
I'm kind of with the water theory but I have had it washed a few times since and been in very very heavy rain since too.
The only truly common thing between the 2 incidents is the wheels spinning - I don't tend to do that very often.
i've noticed something somewhat similar, and i also have 4 new cps. its a change in the exhaust tone, almost sounds like a slight exhaust leak or gurgleing exhaust tone. i cant explain it and it only happens intermittently.
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