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Floyd2u 08-04-2021 03:39 PM

Short Term and Long Term Fuel Trim readings
My LTFT going up hills was 11 at the same time my STFT was -3 or 4 is that something to worry about?

MrMark52 08-04-2021 04:35 PM

I’ve found Jon @ Brazel’s, a sponsor on this site, to be very helpful when trying to troubleshoot LTFT and STFT numbers.

From what I remember of everything I read and he and I discussed, I’m thinking your OK as the numbers are additive - and anything below 10 is good.

But for grins, let me make some suggestions -

If you have a K&N filter, be very careful in how you lubricate it - ANY excess oil that slips past the filter will contaminate the MAF and pretty much ruin it.

Clean your MAF with MAF cleaner or rubbing alcohol ONLY.

I had previously replaced my plugs (41-101’s) and plug wires (Magnums) from Brazel’s before I started conversation with Jon. Against others advice, I did not regap the plugs from .060 to .045.

My coach is an ‘02. The 8.1l used a fuel rail mounted regulator/dampener through I think ‘04. One test for the regulator/dampener is to pull the vacuum line and check for raw fuel. It should be dry (mine squirted gas at me - so replaced).

Borrow a fuel pressure test kit from a local auto store and follow the fuel procedure test procedure for the engine. I don’t recall the numbers exactly, but I believe it’s supposed to be 55 - 68 pounds with the engine running, and drop to no more than 48#’s after 3 minutes.
Fortunately the PO of our coach had recently had the fuel tank and pump replaced - only thing I don’t know is what quality of pump was installed.

In the end on our coach - I replaced the MAF after having sent “live data” numbers to Jon for assessment.

Best deal I could find on a new Delphi MAF or regulator/dampener was from Amazon, and as noted above, plugs and wires from Brazel’s.

Due to recent family issues, we’ve not been able to get the coach out on the road since doing all of the above - but with each “fix”, I noted increased pep in this old girl with 37k miles on her.

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