heres a tricky one

[birdOFprey]

I had the exhaust redone on my car about a year and a half ago... since then i have had to replace the catalatic converters three times... thankfully there all under warrenty, but it is becoming annoying... i need to take it back in for the fourth time this weekend. I have already changed the MAF sensor, and i know its not running to rich for them cause the last two months ive been fighting with my programmer trying to get it to work cause it makes my car run too lean... could it possibly be the O2 sensors? i talked to slp and they said my O2 sensors might be bad, which is keeping my tune and MAF from coresponding... could this be whats burning out my cats too?... please help... and thankyou once agian... you guys have been nothing but help to me and i really appriciate it

[Injuneer]

When you say "ive been fighting with my programmer trying to get it to work cause it makes my car run too lean"...... under what conditions does it run lean - idle, part load, WOT? And, how did you determine it is running lean - wide-band, plug exam, etc?

And you are replacing both cats, simultaneously? What method are they using to determine that the cats are faulty?

Cats can be damaged be excessively rich exhaust. To get an excessively rich exhaust, the PCM has to see a "false" lean condition. That can be caused by leaks in the exhaust system before the pre-cat O2 sensors, misfires, leaking injector(s) or faulty O2 sensors (including the wires and/or the sensor). You can usually detect a false lean by running at a scan and looing at the long term fuel corrections. They will be unnecessarily elevated with a false lean. Have you had it scanned? Are you getting any codes?

Other things might screw up the A/F ratio, like the MAF or the fuel pressure, but the PCM is capable of compensating for a "true" lean or rich condition with the long term fuel correction.

Finally, things like a faulty MAP sensor, a faulty TPS sensor or a faulty coolant temp sensor can cause the engine to enrichen the fuel mixture, in response to what it thinks are things like heavy engine load, rapidly opening throttle blades, or cold engine. A scan would show up problems in these areas as well.

Do you ever run leaded fuel?

[Joe 1320]

One reason cars run a little rich from the factory is that the extra fuel at WOT "squelches" the hot catalyst to prevent overheating damage. Too lean a mixture and the catalyst is ruined. Too rich with reduced heat as in cruise mode causes the catalyst to become carbon fouled. So your tune has to good if you're going to drive it.

It could be the 02 sensors, it could be ignition problems, it could be fuel problems. You'll have to go step by step and find the cause so that you can stop treating the symptoms.

[birdOFprey]

yeah what i meant by fighting with the programmer was that, ill put the normal tune on the car, and about two weeks later, the SES light comes on and the programmer says both fuel banks are too lean... so then to see if it was just because the new MAF (slp ensured me it would work with the programmer) not corresponding with the program, i put the original MAF on and about too week later again my SES light came back on just this time it was for the cat in bank 2... i have had problems with the bank two cat since i baught the car about 2 years ago. It always happens like that though, where ill replace it and about a week later the SES light will come back on for bank 1... so now im to the point of just replacing both of them when one goes bad... but yeah i baught the car used so i dont think the spark plugs, wires of fuel system has been cleaned.... that should probably be where i start... thanks again guys

[birdOFprey]

yeah what i meant by fighting with the programmer was that, ill put the normal tune on the car, and about two weeks later, the SES light comes on and the programmer says both fuel banks are too lean... so then to see if it was just because the new MAF (slp ensured me it would work with the programmer) not corresponding with the program, i put the original MAF on and about too week later again my SES light came back on just this time it was for the cat in bank 2... i have had problems with the bank two cat since i baught the car about 2 years ago. It always happens like that though, where ill replace it and about a week later the SES light will come back on for bank 1... so now im to the point of just replacing both of them when one goes bad... but yeah i baught the car used so i dont think the spark plugs, wires of fuel system has been cleaned.... that should probably be where i start... thanks again guys

and sorry i missed your question injuneer, but no i never run leaded fuel... just 91 octane

[birdOFprey]

k i took my car to the dealer today so they could run a diagnostic on it (i took the diablo tune off the car)... they ran the check and said that this is one of the best LS1's they have seen... all the compressions were identical, rocker ratios excellent and everything.... not to mention the cats were awesome as were the O2 sensors.... has anyone every dealt with SLP? are they cool people? its definitley the programmer and the MAF not working together, after they told me it would... the only problem is that its been about 5 months of trying to get it to work so my 30 day garuntee is over... ..... anyone have any suggestions... thank you

[Injuneer]

Why not just contact SLP and ask about your problem. They are reputable, they've been around for years.

What kind of "diagnostic" tells you the rocker arm ratio? Why would they not all be the same?

[birdOFprey]

Why not just contact SLP and ask about your problem. They are reputable, they've been around for years.

What kind of "diagnostic" tells you the rocker arm ratio? Why would they not all be the same?

sorry they are all the same... i was just blabbing about everything the mechanic was telling me that was getting me nowhere sorry.... contacting SLP sounds like a good idea... thank you very much, all who have helped me... it was much appriciated