Here's my situation. About a week ago the cel light lit up and the vehicle started idling rough, but it still operated fine when going down the road. So I took it to a local mechanic to read the codes. Readout discovered two codes,
DTC P0171
system too lean
(bank 1)
DTC P0174
system too lean
(bank 2)
The guy said both sides are lean, so the problem must be somewhere in the middle. He recommended cleaning throttle plate as a start. Which I did, and while in the process I went ahead and changed the throttle positioning sensor (which was probably not needed). After I did that I started it with no idling improvements, but here is my first question.
Question #1 - Should I have disconnected the battery after cleaning and new throttle sensor? If so, should I go ahead and do that before I continue?
So I was busy the next few days with no chance of getting it back to him. I still ran it with the same problem at idle. I finally got it back to him to find out now that I have four codes reading, and he wasn't going to be able to get to it until next week. He also said the the engine would Idle fine for a period then it would start idling rough and jump back and forth like the engine computer was cutting in and out.
DTC P1131
Insuff. Switching
Control Valve
Sensor/Lean
DTC P1151
H02S Bank 2 Sen 1
Insuff. Switching
Lean Mean
DTC P0171
System Too Lean
(Bank 1)
DTC P0174
System Too Lean
(Bank 2)
I have read some similar threads and sounds like I need to check PCV hose connection, clean the MAF sensor, and look for air leaks. I also read about an Automatic Idle Control Valve, but I am not for sure what/where that is and I also wondered if that is the same thing as the throttle position sensor from the description of it in the thread.
I know I have a lot questions, but any advice would be greatly appreciated. Thanks
It is running lean. Check the PCV hose elbows. They are known to crack and suck air, especially the on at the rear of the intake manifold. Next, try cleaning the MAF. If dirty, it will not properly measure the airflow across it and cause a lean condition. Just spray the two small filiments with brake parts cleaner. Do not touch them.
check the small hose on top of your head cover(passanger side) on the pcv,that one goes to your(carb looking thing)is like a 3 way hose,many times that is broken and absorbing air and that will give you all those codes,hope this helps
Last edited by therrera60; 07-06-2007 at 07:07 PM.
Reason: editing one word
The back elbow was cracked and the others were soft and collapsed. Changed them and it is running with no problems and no cel light. I went ahead and changed the PCV valve while I was at it, around $15.00 to fix it.
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