Ok, my 1992 Blazer 4.3L Z code seems to run rich. Today I got the correct air filter housing with the hose and hot gas tube for the exhaust manifold, I also replaced a vacuum line that was rotted, the line ran from the ball canister thing? on the passenger inner fender to a check valve and then from there to the firewall and a sensor in the front of the intake manifold. Now if I trun the vents on they work, which is good but odd to me b/c I didn't see how that fixed the vents. I also replaced the air filter. It runs a little better, but barely noticable. What else should I look into to lean out the A/F mixture?

 

Your vents are vacuum controlled and the "ball canister" is the vacuum reservoir for the HVAC system.

Concerning your rich fuel mixture... Do you have an exhaust leak ahead of the O2 sensor? Do you suspect that the O2 sensor is original or at least quite old? If so, you may want to replace that along with a full tune up if you haven't done so already.

 

unplug the 02 sensors and see if that makes any difference. If not, your not going into closed loop mode, the puter isnt adjusting your a/f ratio according to your 02 sensor readings. Itll run with the 02 unplugged, however itll suck gas like mad.

Also clean your MAF sensor, do you have a K&N filter, if so, get rid of it, the oil messes up the MAF sensor.

Verify your dont have any false air, air that doesnt go past the MAF sensor before it ends up in the engine.

Aslo verify you fixed all the vacuum lines, lack of proper vacuum will cuase various performance issues. and you alrready said you had a vacuum problem. Look for the vacuum port on the backside of the intake manifold by the distribuator, more of a feeeling thing, extremely hard to see by eye.

 

Tim... 92 = no MAF!

 

Hey guys, I changed the tstat this morning and once it warms up it seens to lean out a lil bit, also the tailpipe doesnt move very much at all now.

 

Could the absence of a cat and possibly a bad o2 sensor cause a rich mixture?

 

Absence of a cat, not likely. Bad O2 sensor, yes.

 

so I drove it to work the other day, it ran great, no problems, until I left work. When I started it to leave it backfired right as it started, then it was fine until I let off the gas on the highway when it had a few more but smaller backfires through the exhaust, it does have a bad ground that I attempted to temporarily fix that had come undone shortly before the backfires on the highway (I know it comes undone when the turn signals stop working and the headlights dim/flicker and when I wrap it around the bolt hole I used to temp. fix it it works they all work fine again). The timing doesn't seem to be off, but I could be wrong, my dad thinks it could be the bad ground, which is from the battery to the body by the headlight, or a lean fuel mixture. any ideas?