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DTC trouble

J

jrichardson

Veteran CEG'er
Joined
Feb 8, 2011
Messages
562
Location
Hillsboro, MO
I have been chasing this for a while now, I have a 99 SVT with codes p0171 p0174 set. I also have p1131 and p1151 pending and floating between those two. I have spend an hour now looking for solutions to this problem and the only solutions I see I have tries already. I have replaced UIM/LIM gaskets, replaced the MAF sensor with one from the junkyard(I know that this sensor could have failed aswell but we pulled it from a car with about 100,000 on the odo) and we have replaced lower O2 sensors(this was to eliminate codes for them though). If anyone has any other suggestions I would be very grateful.
 
Could be EGR clog, fuel injector issue, upstream o2 sensors (most likely the oxygen sensors are causing the lean issue).

First, check for ANY, and I mean ANY vacuum leak, anywhere, from the PVC system to valve cover and any hoses to the EGR system and related nearby equipment.

I want to know the numbers at idle, the LTFT numbers.
 
I wont have time to get in and check the LTFT but I spent a good hour checking for leaks though a combination of ether with the engine running(sprayed around any connection) and smoking the engine at work with the smoke machine. I'm betting on the o2 sensors aswell just not looking to dump a $100+ until i'm sure.
 
If there are no intake leaks then its time to replace the upstream O2 sensors. THe P1131 and P1151 are normally indications that the O2 sensors are going bad. Also if range on a full tank of gas has dropped 50 or miles to the tank then its also an indication of a dying O2 sensor.

P1131 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1
P1151 - Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 2
P0171 - System too Lean (Bank 1)
P0174 - System too Lean (Bank 2)
 
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