Wondering if anyone else has similar experience.

I have a Downey cold air intake and Downey headers on my truck. They are both CARB certified. But every time I smog my truck I fail and have to replace the catalytic converter.

I just had it done at the local Gold Shield station and he told me the Downey equipment was overheating the cat and ruining it. I'm thinking of having flanges put in around the cat so I can keep a new one for smogging and leave an old one in the rest of the time.

Anyone else have a similar setup and problems? This is on a 91 3.0 4x4.

 

Sounds like the way to go if you plan on keeping the headers on . no sense in buying one every time you smog.

 

Did the technician say why he thought the Downey gear was roasting your cats?
To lean?

 

Lean is the only reason I know of that makes really hot exhaust, but he didn't say why the Downey gear was overheating it, only that it was. But yeah, lean is my guess. Otherwise though, he said the truck runs perfect.

 

The Flanged temp cat replacement might help you get through the sniffer laws. But if you are running that lean your prolly cooking your pistons.
It's been a long time since I thumbed through a Downey catalog but wasn't there something about turning some gears in the VAFM to richen the fuel mixture up.

 

maybe, but not in CA instructions. CARB forbids aftermarket companies from recommending any engine management changes.

Doesn't the O2 sensor prevent running lean so long as it is functioning properly?

 

CARB does not 'forbid' adjustments. Matter-of-factly, if it can be adjusted, the non-"Test Only" stations can perform adjustments and repairs. They just have to submit tests between significant adjustments and repairs.

Now, out of curiousity, what part of the test is failing?
Considering you only have to test every other year (unless you change ownership), and the new strict guidelines basically requiring OEM quality for converters just came in to use last year... If you're having to change your converter every other year you get a test, you're getting bad converters or you've got something else major going on.
So... what part of the test is failing?

 

http://arb.ca.gov/msprog/aftermkt/de...eo/D-165-9.pdf

Paragraph 4 prohibits the instructions from recommending tuning different than factory.

I failed on all 3 gases at 15 mph. Same thing happened last time I had to smog. My cat was only about 18 months old and under warranty because they legally have to be warrantied for 5 years, but they hosed me by saying the exhaust ran too hot and fried the cat. Could've been BS, no way I could prove otherwise.

 

maybe get higher octane fuel for the test?

 

All that EOD says is that Downey Motor Sports cannot recommend changes to the system from factory settings. That means the headers are bolt on and should not affect engine operation at all. It does not mean that over time, engine operation, wear, etc. won't require operational adjustments or repairs to the system such as throttle position sensor, etc. However, those generally shouldn't require readjustment anyways.

Who's converter are you using? magnaflow, maremont? The 70 dollar ones we used to be able to get at autozone are crap and you've been lucky if they last more than a year.

Do you have the numbers from the test? All 5? NOx, HC, CO, CO2, O2.

 

I have DT headers on my truck, and I purposely put flanges on my hi flow cat due to the reason I didn't think i'd pass smog. simple swap in for emissions, and swap it back out when I pass

 

I put the full Downey kit on my '89 V6 Runner, which included a Magnaflow cat. I have not had a problem with smog. It seems you might have another issue going on, or, really cheap cats. I wonder if the new, more expensive cats will last longer, or if going back to the stock cat would be an option?

 

expensive as in how much? mine was 68 dollars... and its the "newer" model.