PDA

View Full Version : Searched, didn't find...black smoke only under full throttle


StuckonTheDock
June 29th, 2012, 14:08
I searched and found references to a possible o2 sensor issue, but mine only runs rich under full throttle when the tranny kicks down into passing gear (automatic obviously). Other than that, the exhaust does not even smell rich, let alone blow black smoke.

Suggestions?

Thanks,
Stuck

GrimmJeeper
June 29th, 2012, 14:36
could be a bad injector dumping fuel at WOT

StuckonTheDock
June 29th, 2012, 15:23
could be a bad injector dumping fuel at WOT

I am trying to think of a way to test this. I know that injectors are just solenoid valves with their timing/duration controlled mainly by the ECU. I just can't think of how it could dump fuel at WOT but not at a lower throttle setting.

How would one test for this situation?

Thanks!

old_man
June 29th, 2012, 15:29
Black/Blue smoke at full throttle can be rings.

I would start with a plug reading, followed by a compression test.

As far as injectors, I wouldn't do anything until I had run a can of BG44K through the fuel.

StuckonTheDock
June 29th, 2012, 15:32
Black/Blue smoke at full throttle can be rings.

I would start with a plug reading, followed by a compression test.

As far as injectors, I wouldn't do anything until I had run a can of BG44K through the fuel.

Does NAPA carry BG44K? I will pull the plugs, I have no compression tester, I'll ask around and see if I can locate one to borrow...

GrimmJeeper
June 29th, 2012, 15:33
I am trying to think of a way to test this. I know that injectors are just solenoid valves with their timing/duration controlled mainly by the ECU. I just can't think of how it could dump fuel at WOT but not at a lower throttle setting.

How would one test for this situation?

Thanks!

not sure how you could test it but yes the injector is just an on/off valve. what varies is the fuel pressure, at WOT (on the 95 and earlier models anyway) when the throttle body is wide open the fuel pressure regulator loses vacuum and opens up the full pressure to the fuel rail.

old_man
June 29th, 2012, 17:43
Does NAPA carry BG44K? I will pull the plugs, I have no compression tester, I'll ask around and see if I can locate one to borrow...Normally NAPA carries it. Autozone has a compression tester in their loaner program. Post up the pix of the plugs. Keep them in order.

GrimmJeeper
June 29th, 2012, 18:26
Post up the pix of the plugs. Keep them in order.

yes. close up of the electrodes in focus is best ;) doesn't matter much what the rest of the plug looks like the only relevant part is whats in the combustion chamber.

old_man
June 29th, 2012, 18:41
yes. close up of the electrodes in focus is best ;) doesn't matter much what the rest of the plug looks like the only relevant part is whats in the combustion chamber.
Good to see another old school troubleshooter. I don't know why they don't teach reading the plugs. It tells you more about an engine than most computers can.

GrimmJeeper
June 29th, 2012, 19:00
Good to see another old school troubleshooter. I don't know why they don't teach reading the plugs. It tells you more about an engine than most computers can.

that was actually one of the first thing my pop taught me about cars, and I am grateful for it. he told me reading the plugs is the fingerprint of your engine. pretty good analogy IMO, definitely becoming a lost art.