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P0172 95 4.3 vortec running rich need help

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P0172 95 4.3 vortec running rich need help

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Old September 10th, 2018, 9:26 PM
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Default P0172 95 4.3 vortec running rich need help

Have done everything possible to solve this problem. I am simply baffled and I'm a certified Diesel mechanic. The P0172 code keeps coming back.

checked fuel pressures - good

checked fuel regulator - no leaks functions well

removed upper plenum - found no leaks, while i was in there i also checked poppets for leaks, CFI spider for leaks- its a new unit and all o-rings are good and sealing. Also replaced the main fuel hoses with CFI replacement. no fuel leaks anywhere in or out of plenum. Also tried swapping CFI injector with known good injector just in-case the new injector was bad.

checked and repaired all vacuum leaks.
isolated plenum from all vacuum sources (except brake booster for safety reasons - but verified booster is sound and sealed)

checked map sensor - tests all good

checked TPS - tests good no dead spots

checked O2 senors - all good - replaced upstream sensor to be sure.

Pulled and checked spark plugs - all are dry and not fuel fouled - dry light brown coloring - verified gap

replaced rotor and cap and wires.

also replaced plenum gaskets

The catalytic converter is now failing due to engine running rich for too long but was not the cause of running rich condition.

Last edited by 970joe; September 10th, 2018 at 9:50 PM.
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Old September 11th, 2018, 12:46 AM
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Originally Posted by 970joe View Post
Have done everything possible to solve this problem. I am simply baffled and I'm a certified Diesel mechanic. The P0172 code keeps coming back.

checked fuel pressures - good

checked fuel regulator - no leaks functions well

removed upper plenum - found no leaks, while i was in there i also checked poppets for leaks, CFI spider for leaks- its a new unit and all o-rings are good and sealing. Also replaced the main fuel hoses with CFI replacement. no fuel leaks anywhere in or out of plenum. Also tried swapping CFI injector with known good injector just in-case the new injector was bad.

checked and repaired all vacuum leaks.
isolated plenum from all vacuum sources (except brake booster for safety reasons - but verified booster is sound and sealed)

checked map sensor - tests all good

checked TPS - tests good no dead spots

checked O2 senors - all good - replaced upstream sensor to be sure.

Pulled and checked spark plugs - all are dry and not fuel fouled - dry light brown coloring - verified gap

replaced rotor and cap and wires.

also replaced plenum gaskets

The catalytic converter is now failing due to engine running rich for too long but was not the cause of running rich condition.
Do you have access to a professional OBD II scanner to check fuel trim and ignition issues?
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Old September 11th, 2018, 2:01 PM
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Is the engine temp ok?195,cooler will run rich
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Old September 11th, 2018, 2:22 PM
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The 95 is a 2 upfront o2 sensor?swap them,side to side, just thinking other 02 is not up to par
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Old September 11th, 2018, 8:51 PM
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Yes I have a scanner and both fuel trims are in the negative. This specific truck has an OEM Y-tube exhaust pre cat and only utilizes 1 pre / 1 post cat sensor. Yes the engine temp is above *195 F.
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Old September 11th, 2018, 8:53 PM
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These are the last freeze frames from when the code has shown up. P0172.
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Old September 11th, 2018, 9:12 PM
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Yikes,where's the timing at?
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Old September 11th, 2018, 9:19 PM
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And ft's at idle,still low?
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Old September 11th, 2018, 10:13 PM
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-21.5 cylinder #1 but the engine in my truck doesn’t have an adjustable distributor. Tried that route already. It goes in. Locks in place and doesn’t have any timing marks in the front of the enigine. It uses pulse width timing.
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Old September 11th, 2018, 10:17 PM
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Yes still low at idle. My next steps are to buy bosh 02 sensors and replace both. Also to check the operation of my EGR. What I have noticed is the long term fuel trim when driving at cruising speed goes to -18 and stays there. It does fluctuate when accelerating and deceleration but stays constant when cruising.
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