running rich, 3/4 plugs carbon fouled
 

My 1993 240SX won't pass the emissions test. I replaced the spark plugs, and #1 was fine but the other three were sooty black. I though maybe the O2 sensor needed to be replaced again. (Last year's emissions test looked identical, and after replacing the O2 sensor it passed). The sensor is also covered in black soot. A voltmeter reading shows the O2 sensor is working properly, but also shows that the car runs rich in idle. I figure the real problem is the rich mixture, and that 3 fouled plugs and 1 normal plug is a clue. What is the problem? Has anyone had something similar?

Yy manual says that means you are running rich or having weak ignition. Says to make sure the plug has the right heat range, check for clogged air filter or fuel system or engine management system. Also check for ignition problems.
Sooo, clean your mafs, throttle body, injectors, fuel filter, etc.
Ever try seafoam? worked well for my car.

As well, there is stuff you can buy at the auto store to help your car pass emissions.

Dr.

Thanks
 

Right now I'm running Guaranteed to Pass through on this tank of gas. My puzzle is why plug #1 was clean and the other three were fouled. I thought maybe the fuel injector(s) on the first cylinder is/are plugged, and the computer is trying to compensate causing the other three to be too rich. Anyone got any ideas?

Lots of carbon deposit in your engine possibly? Try running some seafoam threw there and it should clean most of it out.

brilliant idea hyjnx, wish I had said that

lol.

Dr.

sarcastic doc? lol

yeah, lol. I was like seafoam is a good idea, great suggestion bud, then I was like. . wait a minute, I told him that too!

Dr.

....lol:dunno:

here:

Doc's post:now ur post (two posts later): ;)

we are just hijacking the thread...doesnt this always happen lol

soooooooo, would that make us the "Pirates of the Message Board"?:dunno: lol

:laugh: Arrrrrrr! lol...pirates and whores? haha

great, you're both a bunch of loose pirates.

Think his questions has been answered, anything else ?

Dr.

lets wait till he responds...

a bit to rich for my taste
 

Yeah, I've got the cleanup down. Even if I clear up all the deposits, it's still running rich. WHY? Again, I think the best clue without any trouble codes is that there was one plug that wasn't fouled. Anybody had a problem like this?