Just had Crawford hi-flow cats installed on my '04 5AT sedan, and am getting the 'service engine soon' (aka CEL) light and it feels like the car has been way de-tuned (VERY sluggish from ~2000-3000 rpm, and sluggish above that too). I suspect the timing is being dialed back by the ECU for whatever reason, but that's just a guess. AFAIK, these cats are supposed to be OK on 2004's....

Spoke to Doug @ Crawford briefly - he's great - and he mentioned there was one customer with an '04 that was leaning out for a couple of days until the ECU adjusted. I'm resetting the ECU overnight (via battery terminal disconnect).

Anyways - if anyone has had similar issues, or can verify they *haven't* had issues on an '04 G with these cats, or has suggestions....all info appreciated. Thanks

 

Even after the reset you'll probably have to put on 50-100 miles so that the ECU can adapt to the additional airflow.

 

jelly, thanks for the reply. do you have the Crawford cats? fyi the CEL does not come on until I go WOT, but once it does, it sticks.

 

I have the Kinetix cats, which are very similar. I've never had a problem in the 6 months that they've been on the car. I'm not quite sure what the problem might be.

How many miles do you have you driven after the cat install?

 

I just had the cats put on yesterday. CEL showed up first time I got on the throttle. Then drove ~140 miles with the CEL on, disconnected the battery overnight (which cleared the CEL), drove it for ~10 miles this morning without going over 1/2 throttle...and after going full throttle the CEL was thrown again.

Do you have an '03? I'm wondering if the '04 change to ULEV (and different ECU software) could be related to this.

 

Maybe you damaged an O2 senser while you were reinstalling it. I understand that they can be very sensitive.

 

You should be able to reset the ECU (and CEL) by:


Z/G35 ECU Reset #1

1) Turn ignition on, wait 3 seconds
2) Push fully and release the gas pedal 5 times within 5 seconds
3) Wait 7 secs, fully push gas pedal and hold for 10 seconds until the CES light starts to blink
4) Release gas pedal (you are in diagnostic test mode 2)
5) Press and hold gas pedal for more than 10 seconds. Release pedal.

 

You just need to get a scan. Maybe its something totaly different. I have Crawford cats and when I installed them two days later my check engine light came on but it was one of the spark plugs, it had oil on it. Go figure!

 

fyi this appears to be resolved. I had a fitment issue on the left-hand cat where the heat shield was contacting the bottom of the car. once this fitment issue was resolved, no more problems - the car runs great, and no more check engine light. my guess is that the contacting/vibration was somehow throwing a code (maybe knock sensor, I dunno) and causing the timing to be severely dialed back...but this is no more than a guess.