guys someone explain to me why my car is running rich, but i dont have any error codes, it's a 1986 lg4 with ccc q-jet, the car drives perfectly no bogs no codes, but if i go behind it my eyes water and you can smell the richness, i need to go through emissions and i'm afraid it'll fail cause of this, if it's running rich how come the o2 sensor doesnt tell the ecm this? it's a regular o2 sensor, i have coated headman shorty headers on it, with the o2 bung just below the driverside collector in the y-pipe, myself i can smell the exhaust fumes on when i get out of the car, someone help me out

 

An oxygen sensor generates a potential (voltage) across the zirconia element in the presence of a given level of oxygen at high temperatures. As the oxygen level increases, the signal decreases.

An oxygen sensor that is weakening or failing tends to generate a progressively lower potential, which is interpreted by the ECM as a lean condition. If your sensor were failing, the ECM would be led to believe that the exhaust oxygen content was acceptable, even though it is in reality very rich.

That cover it?

 

yes, i understand, i just installed a heated o2 sensor and new spark plugs, i hope that fixes it, will keep you updated.

 

this is bull doodoo, i went and bought an 80 dollar heated delco o2 sensor, and this damn car still burns rich, i back it up after a drive to the garage door and my eyes burn, no ECM codes or nothing, how can that be?

 

There probably won't be any stored codes until the system reaches closed loop mode and there are inadequate O² crosscounts. If you're just starting and running it briefly, and trying to tune it cold, you may indeed be running it very rich.

 

vader, i drive the car all day and it's still rich, i'm baffled

 

When you set up the E4ME, what was the duty cycle (dwell reading) of the MC solenoid?

What is the TPS voltage at idle?

 

i didnt check the dwell, i'll have to get a meter, tps voltage at idle was .47

 

vader i determined this tonight, when i try to start the car after sitting all night it takes a long time to start, when started vacuum is 14", after i took it for a spin vacuum was 16" @ idle and the dwell was varying between 30-34 at idle, what does this mean?

 

ok i ripped the carb off, it looks like the primary fuel wells are leaking, there has not been no sealent just looks like aluminum crap, what kind of epoxy should i use to seal these up?

 

ConAp makes a good two-part that is fuel and heat resistant. Dev-Con makes a wide variety of epoxies. Just remember that the surfaces will reach at least 300°F and are exposed to hexane, ethanol, petroleum distillates, octane, and anything else you might find in fuel. Any epoxy rated for that kind of duty should work well.

BTW - You found the problem before I could reply. Good analysis. I'm guessing the fuel well repair will solve all your problems.

 

vader i got it back and running, it seems to not "stink" as much while driving and using the 4bbl, i brought it back home and the dwell reads 20 on the 6 cyl scale and really doesnt move much, shouldnt it be higher? i got a reading of 30 before the fuel well repair

 

You are correct. Adjustment of the idle mixture stops would be a good idea to get the MC solenoid duty cycle closer to 50% (30° dwell on a six-cylinder scale).

The good news is that it has changed, so the O² and ECM are detecting a change in exhaust gas oxygen. The elimination of leakage is probably the reason, so now the MC soleniod should be in better control of the mixture.

 

thanks vader!

 

vader found out after this the TPS was set to .15 volts at idle, i'm sure this had something to do with it, i adjusted the mixture screws and the idle air bleed and the tps and i'm now getting 30% dwell and it runs sooooo much better i love this site, thanks again!

 

No need to thank us. You did all the work.

Better than thanks, add your experience and aid the next time you see a thread like this. THAT'S what makes this a great place to surf.