Service Engine Light in on
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Joined: Sep 2008
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Service Engine Light in on
Pretty new at the truck repair stuff, but want to start doing it myself....
My truck has been idling pretty bad lately. It goes from about 800 down to 500 and back up when parked or at a light. The past few days it just idles around 500 rpm.
I got the truck checked out and it threw codes P0171 and P0174. The suggestions on the print out say that the MAF sensor could be the problem when both banks are shown on code printout. I was goinig to clean it by following the instructions in one of threads on this web site but was not able to get the whole thing off. Once I got the rubber boot off I could not figure out how to release the sensor from the line. So I sprayed the crap out of the wires while still attached. Waited until it dried and reassembled the air filter, however, no change to the Check Engine light.
The other suggestions say that if both codes are coming up it could be the O2 sensors (Bank 2 Sensor 1).
Anyone else had a problem like this or know what else I can try before changing the sensors?
2004 Heritage, 4.2L, V6 with about 130,000 miles
My truck has been idling pretty bad lately. It goes from about 800 down to 500 and back up when parked or at a light. The past few days it just idles around 500 rpm.
I got the truck checked out and it threw codes P0171 and P0174. The suggestions on the print out say that the MAF sensor could be the problem when both banks are shown on code printout. I was goinig to clean it by following the instructions in one of threads on this web site but was not able to get the whole thing off. Once I got the rubber boot off I could not figure out how to release the sensor from the line. So I sprayed the crap out of the wires while still attached. Waited until it dried and reassembled the air filter, however, no change to the Check Engine light.
The other suggestions say that if both codes are coming up it could be the O2 sensors (Bank 2 Sensor 1).
Anyone else had a problem like this or know what else I can try before changing the sensors?
2004 Heritage, 4.2L, V6 with about 130,000 miles
Elder User
Joined: Jan 2008
Posts: 589
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From: Stockton Ca.
Odds are you have a vacuum leak that is affecting both banks, if it was a V8 I'd say check the PCV line and boots but I don't know about the V6s.
Time to buy a can of starting fluid and spray it here and there until you find the problem.
Good luck
Time to buy a can of starting fluid and spray it here and there until you find the problem.
Good luck
Postmaster
Joined: Oct 2009
Posts: 3,432
Likes: 7
To the original poster, you have a vacuum leak. You need to find the leak and fix it. The leak can be in any of the vacuum lines, the canister purge solenoid, any of the vacuum motors, the brake booster, the upper intake plenum or the lower intake plenum. Lean codes can also be caused by low fuel pressure.
Neither the MAF nor the O2 sensors are likely to cause the codes, though they could be involved. Countless people on this forum have replaced O2 sensors and cleaned the MAF trying to fix lean codes with little or no success. Don't get me wrong, O2 sensors are still maintenance items and if they are over 80,000 miles they should be replaced. But their failure does not result in lean codes.
Postmaster
Joined: Nov 2006
Posts: 4,517
Likes: 3
From: SE Wyoming
Agreed if you want to find the leak easier you can start the engine then use some tb cleaner or starting fluid spray it around the vacuum lines and when you find the leak the engine will rev. On the V8's the elbow at the back of the TB is usually the culprit.
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