I bought this truck recently and it has failed emissions badly on CO and mildly on HC. It runs great but it's got some tubing plugged around the TBI, the factory air cleaner was replaced with an open element type, so there's no intake tube between the computer and TBI , no air pump (did it have one?).

The truck came with old spark plugs in a box that were BLACK, it appears to have new ones. I should probably get a manual for it.

Any ideas?

 

it could be a bad cat causing high CO and HC but it is probably cheaper to change the air filter and oxygen sensor first if they have not been replaced. they trucks tend to like the NTK brand o2 sensors. also make sure there is no vacuum leaks

 

I found a vacuum leak and had replaced the cat before I ran it through inspection. I changed the oil, pcv, air filter, and ran a gallon of camp fuel through it. If it fails again maybe I'll replace the 02 sensor like you said. Would it throw a code for bad 02 sensor?

Thanks for the reply.

 

I have tried to get this truck to pass emissions 5 times, and I'm running out of ideas.

I think it had an air pump on it, but it's gone. Should I put one back on? I always thought it only helped the cat get hot when warming up and it didn't do anything once the engine was hot.

Any other thoughts?

Thanks.

 

if the air injection is upstream of the cat...it works as you noted. if the air injection is into the cat...its function is to oxidize co and hc.

 

Look at your cat, If it has port for an air tube then it had a air pump. I had a 90 and it didn't have one. Did you check for any codes? If it has any post them.

http://www.allpar.com/fix/80s-codes.html

 

I had a header-back exhaust put on with new 3" cat without a tube. I think this had an air pump at one time because I see a metal tube running through the frame to the cat area, so it may have had a tubed cat. Would be nice to see a stock one for reference.

I would like to swap in a 440 in the future.

 

its either running rich or a missing air pump. Post the emission
test printout with all 5 gas results.
if its running to rich, the co and hc will be high, the 02, co2 and nox low.

 

I finally registered it in a county that doesn't require an emissions test. That gives me a year to figure this out.

It is running rich (due to high CO, HC ok) and it is missing the air pump, underhood decal shows one. It had a diverter valve that feeds the air to either exhaust manifold or cat, depending on whether the engine is warm or not. I have headers. I heard newer cars had an electric air pump so am looking into going that route and plumbing it into the headpipe right before the cat.

If that doesn't work maybe I'll put a diesel in it, even though I'm not much of a diesel fan, they have good power and mpg.

 

cadillac ran a electric air pump. Since its caddy, it won't be cheap. When the punps wore out, the vehicle sounded like a jet turbine.


do not use old divertor or check valves...if the check valve fails, the hot exhaust gas take out the air pump.