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08-06-2011
I'll be deleting my Cat in my '04 GTP, Is there anything I should look out for in this process? Do I need to Fake a sensor here? All 02 sensor simulators i found were for up to the 02 models. Any help or pointing in the right direction would be great. Thanks.
08-06-2011
it may run a "CAT diagnostic" where the PCM will command fuel trims super pig rich and then expect to see a corresponding change in rear O2 readings to see if the cat is there. If it does not see this it will continue to run the test continuously until it does...and if you don't have a cat...you guessed it...your car is basically stuck locked running pig rich. A custom tune can eliminate this from happening. Does your state do a plug in emissions check to read the status of various tests prior to renewing your registration? that may be another issue even with the custom tune as the tune only masks it and keeps the MIL from turning on due to the failed cat check.
08-06-2011
Thanks for the heads up. MN does NOT run emissions, so that's fine. I'm expecting the thrown code. Where is the best place to get the tune done/learn how to do the tune to turn off the diagnostic? Is it a guarantee the diagnostic will continually loop?
08-06-2011
some cars it will and others won't. best bet is to get a canned PCM tune from a reputable vendor or a custom tune so that the diagnostic can be disabled. it's not a matter of a code or a light but you need to fool the diagnostic into not running or disable the cat check entirely.
08-06-2011
3800performance.com it is then. I'll see if my mileage varies greatly before ordering the new PCM.
08-06-2011
PS - Thanks for all your help!
08-06-2011
there are a couple threads either here or on 3800pro.com regarding this issue. you will need to mention to your tuner that you have a catless 04 and will need the cat diagnostic test dealt with.
do not remove the cat UNTIL you have this tune ready to go with it. runnign the cyliders too rich can foul plugs, the O2 sensor, or in a worse case can wash the cylinders down with fuel. it certainly will result in lower economy should this test decide to run and lock rich.
08-06-2011
Well, There was a slight **** up on my part. Not realizing the car had a resonator, and due to the location of the CAT. It wasn't until the car was in the air I realized what I thought was the CAT, was actually the resonator. I've never been under the car before and the CAT was much smaller then I've ever seen a CAT to be quite honest.
The Resonator had a pinhole exhaust leak causing a horrible sound. We cut it out, replaced it with a straight pipe, and the problem is solved.
I apologize for the mix up on parts.
For anybody searching - The exhaust pip is 2.25 OD from CAT to resonator, and 2" ID IMMEDIATELY following the resonator (IE Before the bends) We cut the exhaust support free of the the weld with a cutoff wheel, and re welded it to the straight pipe. This was less than $40 worth of pipe/fittings/clamps.
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