Suggestions about odd exhaust odor from my MX-3
 

Hey guys,

The MX is a '92 and in excellent shape, but it does sit for weeks at a time without being driven. When I do drive it, there is a horrible smell coming from the exhaust. It's not a rotten egg smell or anything and the cat's fairly new anyway. I can't seem to pin the smell on anything in particular or describe it very well... it's just a strong offensive odor. I get no smoke at all.

So, what kinds of things should I look for? I know I have a rear valve cover oil leak that's causing oil to get inside the spark plug holes. But I've had this before with no effects on exhaust smell. If it's just a problem with a dirty engine, are there are any good 'engine cleaners" you can recommend? I have used Redline products almost exclusively when it comes to fuel injector cleaner and such.

Also keep in mine that my engine is a swapped 2.5L, but almost everything is the same as it was on the little 1.8L V6. IOW, I didn't have to make major modifications to wiring harnesses, sensors, etc. The only thing I had to do was add a 3rd temp sensor. The car has run very well with the new engine for the most part, and this smell from the exhaust just started happening in recent months. I just want to make sure it's not the start of some serious engine problems.

Thanks for any tips!

Something crawled in the exhaust, built a nest, and died?

I can't think of anything else that might cause such an odor.

If you have access to a gas analyzer, see what the readings are at the tailpipe. You may have a rich condition. Another thing to look for is coolant loss. I you have a blown or leaking head gasket, coolant in the cat will also cause a strange odor as well.