cat converter

[jfirios]

I just went to DMC Cali to get my car re smoged. I failed the smog, seems that I have burnt out two cat converters that were just over a year old. Had the whole stage one installed about a year and half ago. According to all their tests, the car is running lean yet it backfires a lot which suggests that it is running rich. Anyone have any ideas what might be causing me to burn through two new cats in just over a year?

[NightFlyer]

What do your spark plugs look like?

[Delorean Industries]

I just went to DMC Cali to get my car re smoged. I failed the smog, seems that I have burnt out two cat converters that were just over a year old. Had the whole stage one installed about a year and half ago. According to all their tests, the car is running lean yet it backfires a lot which suggests that it is running rich. Anyone have any ideas what might be causing me to burn through two new cats in just over a year?

Your fuel mixture is incorrect. I would advise having the mixture checked and warranty converters installed for smog testing.

[jfirios]

could it be a problem with the computer for the fuel mix or is that something that needs to be adjusted manually?

[Rich]

Anyone have any ideas what might be causing me to burn through two new cats in just over a year?

Yes, an O2 sensor that's not getting the right signal to the Lambda control unit. Did DMC Calif. rule that out yet? They don't last forever.

[Chris 16409]

This happened to one of my friends as well! His Stage 1 catalytic converters were fried after only about 2 years!. Since DMC-CA did the installation he made them replace the cats under warranty. They should have set it up correctly in the first place! I would demand a warranty replacement! I need to get a SMOG check as well. Luckily, I have a SPEC I exhaust from DPI. Did I forget to mention it has a lifetime warranty?

[Rich]

I just went to DMC Cali to get my car re smoged. I failed the smog, seems that I have burnt out two cat converters that were just over a year old. Had the whole stage one installed about a year and half ago. According to all their tests, the car is running lean yet it backfires a lot which suggests that it is running rich. Anyone have any ideas what might be causing me to burn through two new cats in just over a year?

The following applies to any 3-way cat, not just on D's.

You say that the cat burned out. That's due to overheating which occurs when the cat sees too high a concentration of unburned hydrocarbons at a high flow rate over time. The two likely causes for that are a rich mixture and an internal oil leak (rings or valves).

You're sure the O2 sensor and the Lambda unit are OK? The car should not be running lean like they say it is - although that's OK for the cat - and it should not be running rich under any conditions except full throttle. The Lambda system keeps the mixture pretty close to spec., like within 1%. I assume you don't run wide-open-throttle most of the time (excess enrichment occurs, but is tolerable up to a point).

[Ron]

What did they do/use to determine it was running lean?

Exactly what did they say?

[David T]

What did they do/use to determine it was running lean?

Exactly what did they say?

I have heard that they run the Stage II's on the rich side so they will run a little smoother. The cams have more overlap than the stock ones and that causes a lower engine manifold vacuum and a lumpier idle. One way to make it smoother is to run a little richer but that shouldn't burn cats. Maybe the plunger in the mixture unit is sticking or the CPR is out of calibration. A misfiring cylinder can also pass more hydrocarbons into the cat, that WILL burn it up. A Lambda stuck in open loop can also burn cats. That can happen if the O2 senor is bad or the WOT switch or wiring is bad. Same for the temp sensor. If you are going to a "D" shop they should know all of this. Something is not making sense here. You cannot run "Lean" and burn cats up. I have seen Deloreans running rich and those cats and the muffler can glow BRIGHT red! You KNOW something is wrong! And they stink.
David Teitelbaum

[Ron]

Yeah I'm with ya....but I'm wondering if they used an analyzer, simply read the dwell, or ?? And what they say caused it to be lean. Did they fix that part...you know, the skinny ;-)

Sounded like the O2 sensor to me, not knowing anything else....way to little info to guess tho.