running way too rich

[oohyeah4]

 

Sorry this is a long one....here goes, vehicle : 1990 blazer s10 4.3 tbi, problem: running way too rich gas mileage down from 16 mpg to barely 10 mpg. miles on vehicle, almost 200K , things iv'e changed: plugs a/c delco, cap & rotor ,plug wires, all sensors IE: throttle position, temp,map,spark sensor,idle sensor,new injectors,rebuilt fuel regulator, car runs pretty good except a good miss on the highway, if you floor it alot of carbon exits exaust pipe. could the computer be bad? dont know what else to do..... suggestions welcome, at witts end! Rob

[Bent Wrench]

Sorry this is a long one....here goes, vehicle : 1990 blazer s10 4.3 tbi, problem: running way too rich gas mileage down from 16 mpg to barely 10 mpg. miles on vehicle, almost 200K , things iv'e changed: plugs a/c delco, cap & rotor ,plug wires, all sensors IE: throttle position, temp,map,spark sensor,idle sensor,new injectors,rebuilt fuel regulator, car runs pretty good except a good miss on the highway, if you floor it alot of carbon exits exaust pipe. could the computer be bad? dont know what else to do..... suggestions welcome, at witts end!   Rob

 

<{POST_SNAPBACK}>

 

 

[Butch 02 Denali]

Bent Wrench, you forgot your message!

 

oohyeah4

 

How about the 02 sensors?

Have you had it scanned for codes?

There are 2 water temp sensors in many of the trucks in these years. One of them controls the cold enrichment and acts like a choke, adding extra fuel as it warms up. It could be stuck in rich mode. The one you want is usually on the passanger side, down under the exhaust manifold. Quite often the wire corrodes on these and that turns out to be the problem. They can be checked with an ohm meter without removing it. Check it cold, then check it hot, if it doesn't change, it's bad.

[oohyeah4]

Butch, I changed both temp sensors maybe the wire could be broken at some point, will check though, the only sensor I havent changed is the 02 sensor. this thing is running so rich, if you give it gas hard a few times it leaves real black spots on the ground carbon of course. gonna try changing o2.....

[Haulin' 8.1]

Check the alternator for excessive A/C voltage. Test between the output terminal and the case. Anything over .450 will cause problems. If it's high the diodes are shot.

 

Vernon

[whitesnake01]

Vaccuum leak?

[05W/T]

I had a similar problem with my 89 K1500 4.3 tbi, while idling it would backfire and blow carbon all over any car parked within 6' of the tailpipe. My mileage dropped from 17 to 11. After tying many of the things you did, I took it to the dealership and was charged $60 diag. fee. What they did was unplug the various sensors and emissions components until the engine ran correctly. They also plugged vaccum and air injection hoses. It turned out to be something wrong with the air injection pump. Since this year was available without an AIR pump, I just bought a new belt and mileage returned to normal.

 

Brian

 

2005 GMC 1500 W/T 4.3

1989 Chevy 1500 4.3