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1991 Chevrolet Lumina weird OBD code

Tiny
MIKE LUCKEY
  • MEMBER
  • 1991 CHEVROLET LUMINA
  • 3.1L
  • V6
  • FWD
  • AUTOMATIC
  • 160,000 MILES
91 lumina 3.1. Car misses and hesitates, tune up not that old, recent new injectors, cleaned iac, egr. The car also idles wierd when cold, high uneven idle and will die a couple times. When its warm, this goes away, but the car still misses and hesitates. I got a trouble code 44, and 45. Both lean exhaust and rich exhaust. How can I get both codes? I have also checked for vac leaks, and did a redneck smoke test. SEEMS to be no vac leaks. Also. The engine cooling fans don/t come on at all. The only time they come on is when I do the paper clip in the obd1 terminals. Any help would be appreciated! Thanks. Mike.
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Thursday, September 25th, 2014 AT 4:27 PM

4 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,192 POSTS
I agree. That makes no sense. Are these the only codes you got? Also, after thinking about this, I am questioning the coolant temp sensor. It could cause the fans not to work and by telling the computer a wrong temp, cause the system to over compensate the fuel mixture. Basically, if it thinks it is very cold, the mixture would be rich. On the other hand, if it thinks it is warm, it will lean the mixture.

Your thoughts?
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Thursday, September 25th, 2014 AT 6:19 PM
Tiny
MIKE LUCKEY
  • MEMBER
  • 38 POSTS
Yes, these are the only codes. I did consider the cts, but would that really cause the idle problems when cold, and also the missing and hesitation? Someone suggested a bad ground on the pcm, but that would even be worse problems wouldn't it? Thanks so much for the reply!
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Friday, September 26th, 2014 AT 3:04 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,192 POSTS
About a month ago, I had a chevy van in my shop. It had a bad idle, missed, and ran really bad one minute and perfect the next. Using a scanner, I found the CTS to be sending a signal telling the computer it was -40 degrees one second and then it would go back to normal. As a result, one second the computer would dump fuel thinking it was cold, and then try to change to a warm reading. This vehicle did not have both codes you have, but it did say it was a rich mixture. The funny thing is no code was set for the CTS because as far as the computer was concerned, it was receiving a signal. Thus, it was working. Even though the signal was incorrect. So with that said, see if you can get your hands on a real time scanner for OBD1. The I would suggest running the vehicle to see what is actually happening.
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Friday, September 26th, 2014 AT 8:00 PM
Tiny
MIKE LUCKEY
  • MEMBER
  • 38 POSTS
Wow, sounds like exactly the same thing! OBD1 is so funky anyway. When we were having injector problems with the car it threw no codes whatsoever. Really frustrating. I would love to be able to scan the car myself, but no way to do it. I will take it to a mech. That I know of and see if he can help with the scan. Thanks so much. When I first noticed the cooling fan prob, a local auto parts store guy told me it was highly unlikely that the cts would be causing this, so I have been looking hi and low. Also, I will get back to yall afterwards and let you know the scoop. Thanks again. Mike.
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Friday, September 26th, 2014 AT 10:32 PM

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