4.3 Running Rich

[Justins_S10]

My 4.3 liter tbi engine is running very rich. When I first start the truck it blows black smoke for about 2 seconds then stops. Also when accelerating it will blow black, more noticeable in reverse. I put in new plugs, distrubuter, rotor, ignition coil, and still no luck. I had a new cat put on 2 days ago and it overheated, and plugged the muffler. The exhaust odor is so bad that one day i let the truck idle in the carport which is behind the house, and the gas fumes got so bad in the house that we had to get out.

The motor also started knocking when this problem started and is not as loud as a rod knock, and can only be heard if you are parked next to a curb, or if you put your head by the wheelwell.

[jackfast]

I read theis in CHP i beleive had the same type of problem on a tbi camaro they said it may be a vent line or return line on the fuel pump. after years of driving they can become plugged hope this helps

[Melonhead]

Think your on the right track, FUEL PRESSURE. http://www.s10v8.com/images/smilies/icon_biggrin.gif

[rayL]

what year?? the vortec 4.3s werer bad about the fuel lines inside the plenum leaking and/or the fuel pressure regulator inside the plenum leaking.

[chris1972]

check coolit temp sending unit..the one that has 2 wire on it yellow and black...if it reads wrong will make it run rich..and if your coolit is low will do the same ...thinks it still in warm up ...check see it if the motor get hot enough usely 190 to 210...check if tps is working too also check for leaky o-rings in the injectors

[Justins_S10]

The truck is a 91 Ext Cab TBI. The engine will run rich cold or hot and blows black smoke when first started or accelerating. I forgot to note when i turn right or left and accelerate it seems to lose slight power but returns to normal after driving straight for 5ft. I'll try cleaning the injectors by hand as i have tbi and they are easy to get out and see if that helps. If there is anything else that i should check let me know, the 4th is my day off of work so i have the whole day to waste until the fireworks of course.

[Melonhead]

Justin, do you have the means to aquire a pressure gauge and fittings to check fuel pressure? If you do, diconnect the line at the throttle body and hook up the pressure gauge. Turn the key to on and not start the truck. Observe the pressure. If it's too high, the regulator is out. Reconnect as normal. If it's good, disconnect the return at the tank. Hook up something to catch the fuel. Turn the key again and look if any is returning to the tank. That will verify all the lines are clear. If you get nothing out the return, start the truck and have someone watch the return line. If you still have no fuel or very little, the return is clogged. The clogged line will increase fuel pressure making the engine run pig rich. Hope this helps. http://www.s10v8.com/images/smilies/icon_biggrin.gif

[Justins_S10]

ok i will try the fuel pressure test as cleaning the injectors didn't help. Would this fuel pressure problem make the engine feel sluggish accelerating around corners, like for example, i will turn right and for about 20ft after i turn i won't get full power from the engine till the speed reaches around 35mph.

[ZR1BLAZER]

sure it would feel sluggish. its getting drownded by fuel.