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Short Term Fuel Trims

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So I had an '08 truck in this week with P0284 and P2002 in memory and the MIL on. The tailpipe was crusted with soot. The owner complaining that the MIL comes on, there is a loss of power and the truck smokes badly. (black)

 

It got a new DPF.

 

The truck was road tested several times without incident. I performed all of the required tests for the cylinder contribution DTC including TSB# 08-16-7 to LOAD test the injectors. Relative compression, fuel pressure, cylinder balance... all fine.

 

Short term fuel trim on #8 is +12.

 

I was always told by the Hot-Line that anything over + - 10 is a red flag. They dismissed it. Declined approval for an injector - which I feel in my gut has an intermittent issue above and beyond the fuel trim.

 

This is all well documented on the RO and on the Prior Approval form. I don't want to hear it if this thing comes back with a bent rod or a washed down cylinder on #8..

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Had exact thing happen before. Was at 13 just a few trim levels from popping the cel. Got declined and sent vehicle out with just dpf. 4 months later its back with bad knocking noise. Cylinder 8 was dead. Hotline wanted oil change recipts along with oil level etc... long story short tore down engine 8 was washed out. Got the long block. That's what they get for turning down the injection because it wasn't missing

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I can only suggest swapping injector positions as a diagnostic step... OTOH, with a printout indicating tepidline is basically washing their hands of the concern, you should be able to squelch any future claims of "ineffective repair".

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