I have a 91 RS with the stock 305 tbi. It has about 115k on it and is fouling plugs. I replaced the old ones with Bosch p4's. About a week/200+- mi later I pulled one of the front plugs (the easiest one to get to) to see if the plug was ok. I found that it was fouled. Not horribly, just more than I would expect for that short period of time. The fouling is dark, bubbly, corrosion looking sediment. I thought that the valve seals may need replaced.

I recently had a new clutch installed and told the mechanic of my concern. When I picked the car up from the shop the mechanic said the the engine is in excellent condition and that it had been well maintained. He said that the car was running rich and I should have it dinoed and adjusted.

Obviously it is just a stock motor and I don't want to fork over the $$ to have it tested. Is there any way I can adjust it myself or maybe take it to a chevy mechanic for adjustment?

Also, it is a tbi and I thought that the mix was computer controlled. Any thoughts or suggestion would be great. I live in Denver so the air density is significantly less than at sea level. Hence the thought that the air fuel mix is off.

 

Id try a new fuel filter and oxygen sensor. They will cause lean/rich mixtures and arent to terribly expensive to replace.

 

That might be your problem right there. For some reason, platinum plugs do not seem to work well in cars like ours. I have seen way too many people complain about platinum plugs, especially on Thirdgen.org (I would suggest doing a search over there, but it's down at the moment).

I'd highly suggest taking out the platinum plugs and putting in some new AC Delco R45TS spark plugs (stock replacement), and then see what happens.

 

bosch sucks ballz. put some ac delcos back on it. didnt realize i had a clogged fuel filter and was getting an 18:1 air fuel ratio so i was runnin hella lean and my ac delcos didnt foul at all. replace your fuel filter if it hasnt been done in a while. and get rid of those bosch plugs.