2001 Cadillac Deville codea P0171 P0174

Tiny
BILL LANGFORD
  • MEMBER
  • 2001 CADILLAC DEVILLE
  • V8
  • FWD
  • AUTOMATIC
  • 64,000 MILES
I have 2 codes a p0171 and a p0174 I have a rough idle but runs well under acceleration. When I unplug the MAF sensor the idle holds steady but higher than normal. Should I clean or replace the MAF sensor or is something else wrong
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Saturday, January 3rd, 2009 AT 8:42 AM

7 Replies

Tiny
BRIAN 1
  • EXPERT
What are the long and short term fuel trims? There are alot of things that could cause these codes.O2 sensor, exhaust leak, vacuum leak, plugged air filter, bad mass air flow sensor, plugged exhaust, restriced injectors. Post back with more info, and will advise from there.
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Saturday, January 3rd, 2009 AT 10:37 AM
Tiny
BILL LANGFORD
  • MEMBER
Don't know the fuel trims. I was using a code reader from Advanced auto parts. The rest of the story is that the cars idle had stuck high on me after doing the WOT tsb where you put the car in 2nd run it wide open from 40moh to 70mph to blow it our. After performing this procedure the idle stuck high and woukd not kick down, I unplugged the MAF and the idle dropped. I pluged it back in drove it and the service engine soon light come on and it idles rough and jumps from 575 to 650 rpms with the MAF plugged in. If I unplug the MAF then the idle comes up to arounf 800rpm and the car seems to run better. Does cleaning the MAF or throttle body have any affect on this problem?
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Saturday, January 3rd, 2009 AT 11:04 AM
Tiny
BRIAN 1
  • EXPERT
It might, try cleaning it and see what happens. If it does not work could have other problems, post back if this works/doesn't work and will advise from there.
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Saturday, January 3rd, 2009 AT 11:12 AM
Tiny
BILL LANGFORD
  • MEMBER
Have you had experience cleaning MAF sensors alot of the stuff ive found on the internet says it dosnt wprk or dont bother? Any tips or tricks on cleaning these and have you seen this problem before? The codes are from the o2 sensors running lean both banks correct? It dosnt seems possible that both one bad and that the only problem I have is a low and rough idle. By the way thanks for the help.
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Saturday, January 3rd, 2009 AT 11:18 AM
Tiny
BRIAN 1
  • EXPERT
Just remove the mass air, then I clean it with dragon fire or top shot, which is made for mass air sensors. You can pick this up at your local parts store. Yes I have had experence with these codes.I need to know the long and short term fuel trims because this will help me diagnose it, fuel trims monitor and add/subtract fuel depending on engine load and driving habits it trys to get the best fuel balance and economy. These codes are very hard to diagnose. Do the above first and post back with what you find and will advise.
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Saturday, January 3rd, 2009 AT 1:21 PM
Tiny
BILL LANGFORD
  • MEMBER
Well I bought the mass air flow sensor cleaner cleaned the sensor and throttle body and damn was that throttle body carboned up bad got done drove it blew it out cleaned the codes drove it about 20 miles and the light came back on. The idle is better and holds at about 675 rpms when hot and in gear but I still feel a miss at idle under acceleration it runs great. Will the MAF cause a miss/rough idle? Should I replace it? It might be time to give up and let a real tech work on it.
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Saturday, January 3rd, 2009 AT 4:19 PM
Tiny
BRIAN 1
  • EXPERT
I wouldn't just throw a part on it, mass air sensors are expensive. Rescan it and see if it's the same code. No a bad mass air sensor will not cause it to missfire, I think you have other problems, post back if you still want me to help you.
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Saturday, January 3rd, 2009 AT 6:50 PM

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