Misses and black smoke

Tiny
JANET SHUE
  • MEMBER
  • 1993 PONTIAC GRAND AM
  • 3.1L
  • V6
  • FWD
  • AUTOMATIC
  • 1,250,000 MILES
When attempting to drive, car starts missing real bad and blows black smoke was told prob a sensor. Something about the fuel being too rich, but there are so many sensors how do I know which one? As you see the car is old and I cannot afford anything else. I cannot afford to play a guessing game with sensors either.
Sunday, May 21st, 2017 AT 7:50 AM

11 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Scan for codes A and B on diagnostic link below left side of steering column. then check fuel pressure with a gauge auto parts rent it. See link on where to connect. should be 41-47 psi it may be a regulator for fuel. get back to us with codes I do not think it is a sensor.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Sunday, May 21st, 2017 AT 10:47 AM
Tiny
JANET SHUE
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  • 9 POSTS
It came up code 13, which is a 02 sensor. Correct? But it doesn't say which one, there is more than one isn't there?
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Tuesday, May 23rd, 2017 AT 6:44 PM
Tiny
JANET SHUE
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  • 9 POSTS
Oops it also came up with code 31 and 13
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Tuesday, May 23rd, 2017 AT 6:57 PM
Tiny
JANET SHUE
  • MEMBER
  • 9 POSTS
And can you tell me exactly where these sensors are located please
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Tuesday, May 23rd, 2017 AT 7:00 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
The older models may only have one and it will be in front of converter. Code 31 is a park /neutral switch which could be a bad switch or a short. It's located under shift lever on transmission
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Wednesday, May 24th, 2017 AT 6:35 AM
Tiny
JANET SHUE
  • MEMBER
  • 9 POSTS
Was NOT the fuel regulator, we replaced it, the psi was 35 and still is. Where is the air/fuel sensor located, that's probably it cause its over $ 200, just my luck, we haven't replaced the 2 sensors that showed the code 31 and 13 yet. Don't know where to go from here
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Monday, May 29th, 2017 AT 1:47 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
In my first reply I stated what the fuel pressure should be if not at minimum you have a bad fuel pump. code 13 is O2 sensor item b in pic and other is neutral switch item N4 in pic those are what your two codes are saying is wrong with car as well as you have a bad fuel pump. pump pressure should be checked with key on only.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Monday, May 29th, 2017 AT 3:08 PM
Tiny
JANET SHUE
  • MEMBER
  • 9 POSTS
Doesn't the black smoke mean the fuel is too rich? How can it be too rich if the fuel pump is bad?
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Monday, May 29th, 2017 AT 3:44 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
First your very first question was a misfire and black smoke. Because of the misfire which is low fuel pressure is one of the causes can cause black smoke and the O2 sensor reads the mixture which if bad the computer can't read it so it richens the mix up automatically so the car will run. However with low fuel pressure it gets all messed up because it doesn't have the right amount of pressure going into the injectors so it goes overboard. Your fuel mileage has to be bad right now. Also if there are any vacuum hoses broken/cracked/ or off will cause the same problem.
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Monday, May 29th, 2017 AT 3:55 PM
Tiny
JANET SHUE
  • MEMBER
  • 9 POSTS
Well after replacing the fuel regulator and filter and throttle pos sensor, no black smoke but car is missing bad and a loss of power, thinking about having it put on a scope, what does a scope tell you, and what wont a scope tell you and will it tell you EXACTLY where the problem is
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Tuesday, May 30th, 2017 AT 2:26 PM
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
You really need to scan for codes scoping doesn't do a lot unless there is a real problem it will show which cylinder is firing an d some other tests that are way to lengthy to explain. Why don'tyou do a compression test an d get back with the readings. But if a 20% variance there is something wrong with that cylinder.
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Tuesday, May 30th, 2017 AT 3:26 PM

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