1990 Chevy Lumina At a loss - fuel mix too rich -

Tiny
TERESAPUGH
  • MEMBER
  • 1990 CHEVROLET LUMINA
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 104,560 MILES
I have a 1990 2 door Lumina Euro - Bought the car a couple months ago - ran sweet for the first month then the ECM died - we replaced it as well as a faulty crank shaft position sensor and a worn alternator belt - car starts now but its burning a very fuel rich mixture - to the tune of about 3 - 5 miles to the gallon! Hooked it up to a sensor and got the code for a faulty MAP sensor - went to the parts store picked one up and installed it, and the car won't turn over at all. Replaced the new MAP sensor with my original one and the car starts but with the fuel ratio issue and super rough idle - its also blowing a LOT of carbon out of the exhaust - took the MAP sensor back to the parts store and got a new one in case it was faulty but had the same issue - engine won't even turn over with the new MAP sensor in. Any ideas what to do next?
Tuesday, June 17th, 2008 AT 10:14 AM

10 Replies

Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
You might have to check the wires from the MAP right to the ECM. Must be a short someplace, what code did you get?
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Tuesday, June 17th, 2008 AT 12:38 PM
Tiny
TERESAPUGH
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  • 4 POSTS
The code I'm getting is 45 - rich exhaust - will check the wires as you suggest. Thanks :)
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Tuesday, June 17th, 2008 AT 12:45 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
You said you got a code for the MAP that should be a 31, 45 is 02 sensors reading rich. Which they should do if this much fuel is burning, my suggestion is to look for a stuck injector or two. Unplug any that arent clicking. Or use a noid light, it should flash, not stay on solid.
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Tuesday, June 17th, 2008 AT 1:00 PM
Tiny
TERESAPUGH
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  • 4 POSTS
We used a noid light - every thing looks fine - got a code for MAP Sensor before we tried to change it, now the only code coming up is the rich exhaust code. Someone suggested maybe a faulty temperature sensor but we haven't got that far yet - were looking to get it back on the computer this afternoon and verify the codes and maybe try to locate the temp. Sensors - according to the book there are two. Thanks again for your help :) this thing is making me nutty, lol.
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Tuesday, June 17th, 2008 AT 1:14 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Check the power and ground to the ECM, it sounds like it's stuck in limp mode, or open loop. ECT(temp sensor) can be checked with an ohm meter, should be about 50,000 ohms cold and drop to 177 ohms full warm.
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Tuesday, June 17th, 2008 AT 5:51 PM
Tiny
TBDK87
  • MEMBER
  • 11 POSTS
I had a similar problem on an 87 grand am. Didnt burn that much gas though. Turned out to be a faulty o2 sensor. Try that as well. If the o2 sensor faults it will tell the engine to use more gas then reuired and make engine run rough. It will also still recognize a rich problem.
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Tuesday, June 17th, 2008 AT 10:01 PM
Tiny
DNAPRORACING
  • MEMBER
  • 120 POSTS
I went thru a similar issue, black smoke thru exhaust. New map/o2/fuel filter and pump, and injection service done. Fuel pressure was fine. Turned out to be the computer telling my injectors to stay open too long.
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Tuesday, June 17th, 2008 AT 10:22 PM
Tiny
MERLIN2021
  • MECHANIC
  • 17,250 POSTS
Yeah. That's the ECM I mentioned above.
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Wednesday, June 18th, 2008 AT 2:59 AM
Tiny
DNAPRORACING
  • MEMBER
  • 120 POSTS
I got it replaced for $227. Runs like a champ now. Had me worried for a while after replacing the entire fuel system and the issue remained.
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Wednesday, June 18th, 2008 AT 7:09 AM
Tiny
TERESAPUGH
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  • 4 POSTS
Thanks guys, for your time and insight. I'm going to take your advice and check the areas you suggested and go from there. Should have a good idea of wether we're on the right track or not by Monday and I'll be sure to let you know. Thanks again for your help, it's greatly appreciated - I'm definitely out of my depth as a home mechanic, lol.

:)
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Thursday, June 19th, 2008 AT 7:41 AM

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