Black Smoke...

Hi my 91 s-10 w/ the 4.3 v6 w/ 190k miles is pouring out black smoke at higher rpms and when you give it more than 1/4 throttle... i have replaced the thermostat, 02 sensor, plugs, plug wires, dist cap/rotor, have tried fuel injector cleaner and still spits out black smoke. i've talked w/ some people and they have suggested the MAP sensor, but i'm not familiar w/ that. does it have a throtle position sensor? or are the injectors worn out? i'm clueless at this point and am throwing it up to some different people that may have experienced this problem, any help would be appreciated, thx.

I don't have a clue what is wrong, but I will say this, black smoke means all the fuel is not getting burned.

check the throttle sensor

I don't have a clue what is wrong, but I will say this, black smoke means all the fuel is not getting burned.


ya and the gas mileage is so horrible... which is why i'm pissed cause i live in that thing **sigh** and gas prices are so high **sigh**... i'm going to replace the throttle pos sensor see if that helps, i found out it does have one... which i had no clue... i thought only 94+ had them for some reason. will post an update, thx for the replys :)

now r u entirely sure that u didn't pay atention at the pumps and put in some diesel? cuz that'll def. do it.

Hi my 91 s-10 w/ the 4.3 v6 w/ 190k miles is pouring out black smoke at higher rpms and when you give it more than 1/4 throttle... i have replaced the thermostat, 02 sensor, plugs, plug wires, dist cap/rotor, have tried fuel injector cleaner and still spits out black smoke. i've talked w/ some people and they have suggested the MAP sensor, but i'm not familiar w/ that. does it have a throtle position sensor? or are the injectors worn out? i'm clueless at this point and am throwing it up to some different people that may have experienced this problem, any help would be appreciated, thx.
You have a '91 4.3 which is TBI. I find it hard to believe that the O2 didn't set a rich code. However, since you have shotgunned it this far you may consider the injectors in the Throttle Body. The nozzles may have widened after 190K miles. A lot of fuel has passed through them.

I assume that you don't have a scanner to view the data stream. You may be staying in open loop operation.

Also have him check the map sensor

installed the throttle position sensor and it sort of worked, it doesnt spit black smoke near as bad, less hesitation as well. black smoke only coming out mainly at higher rpms 4000+ which i'm beginning to think theres nothing i can do unless i replace the injectors and is nothing more than 'normal' for a high-mileaged 4.3 that gets 'driven hard' alot.

when you say that it should have set a rich code, are you saying the serv. engine light should have came on? cause i have never seen the light come on, and it does work, it comes on at initial startup. how would i go about checking to see if its staying in 'open loop operation'? can the local parts house help me figure this out?

With a '93 TBI he doesn't have a MAP sensor.

I ment '91.

installed the throttle position sensor and it sort of worked, it doesnt spit black smoke near as bad, less hesitation as well. black smoke only coming out mainly at higher rpms 4000+ which i'm beginning to think theres nothing i can do unless i replace the injectors and is nothing more than 'normal' for a high-mileaged 4.3 that gets 'driven hard' alot.

when you say that it should have set a rich code, are you saying the serv. engine light should have came on? cause i have never seen the light come on, and it does work, it comes on at initial startup. how would i go about checking to see if its staying in 'open loop operation'? can the local parts house help me figure this out?That is what I am saying. If you have black smoke coming out, the O2 sensor (s) should have read a rich condition and triggered a code. I would suspect, since there are no codes, you are staying in open loop operation. Closed loop operation is where the computor adjusts the engine, in open loop, you are running on default cold which will give you a richer condition. You will need a scanner that can read the data stream OR if you want to shotgun for a few bucks, try swapping out the ECT sender.

Here's something for you to ponder. How does a cold engine start without a choke? A choke provides a richer condition to start a cold engine. Your engine does not have a choke so the computor, on cold start, creates a richer condition by increasing the dwell time on the injectors. The result is the same. If the ECT is not telling the computor the temperature of the engine, it thinks it is cold and will create a richer condition.....Black smoke and no code.

ok so i shotgunned it again, replaced the ECT... still getting rich, black smoke. i was also reading in the manual that if it is running rich like it is at normal operating temperature, as you said, the O2 sensor would have detected a problem and triggered the light. i'm still getting no light. i think i'm going to stop shotgunning it and take it to the dealer where they can read the data from its computer, it might be something stupid like a wire being grounded out from one of the sensors, that stuff happens all the time.

On a side note... about 3 months ago, before it ever started doing this stuff, i decided to put in a 160 deg thermostat cause i put one in my other car (its a 1985 chev) and my friend w/ a 98 silverado 5.7 ltr also put in a 160 deg thermostat... yea i NOW know this is a bad bad thing. and me putting in the 160 deg thermostat has triggered this... so mabye i just really screwed it up O.o **sigh**. so knowing about the 160 deg themostat, any new suggestions before i haul it to the dealership?

on another nother side note, the timing was adjusted by a friend of mine who said it was advanced to far, i know nothing about timing so i let him do whatever he did, i can't remember if this is before or after i put in the 160 deg thermostat, but he did mess with the timing... if there are no error codes from the ECM, could it be just bad timing? or am i not even in the right parking lot... any additional help would be greatly appreciated :)


it has a 195 deg thermostat now too btw...

John

Get it timed again, this could easily cause your problem. Make sure the shop does not time it by ear or to some "believed to be better" setting (I know some here feel 4 btdc is good). By adjusting the timing to anything before zero, the factory setting, you are putting unneeded strain on the pistons and cylinders. No question give it a try before taking it to the Stealership.

If you have an AutoZone parts store near you, they can download any malfunction codes for you and they typically provide the service free. I would try this before dragging your ride into the local Chevy dealer who will charge you dearly for any diagnostics.

I think Mikado14 is in the ballpark with his assessment: an engine running that rich would have to set a code (probably multiple ones) unless the computer "thinks" it's doing the right thing based on its inputs (which in this case are faulty). Garbage in, garbage out.

.... and the idea that you might have topped off with #2 diesel is not as far fetched as one woud think, especially if it is sold right alongside gasoline as opposed to being a seperate pump.

Mike

Man, guys, anyone thing his timing is way retarded?

Hurky, go get your tming check with a timing gun with the beige and broen timing wire disconnected from the computer under your glove box.

`91, S-10, Certainly Does Have A Throtle Sensor.make Sure The Egr Valve Isn`t Stuck Partialy Open.