Troubleshooting negative LTFT Bank 1

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Porter84
Posts: 2
Joined: 05 Apr 2021, 12:27
Location: St George, UT
Vehicle Information: 47 Willie's 5.0l swap

Troubleshooting negative LTFT Bank 1

Unread post by Porter84 »

I have a 2005 Ram with the 5.7. I wanted to add some headers and exhaust, do some datalogging and try to optimize it for my driving/hauling and just use it to learn with.

I wanted to sort out any existing issues in stock trim before adding anything.
I got this truck a few weeks ago with a bad miss and repaired a cross threaded sparkplug on Cyl 1 (bank 1) and replaced all the plugs.
I checked fuel pressure even though it's isolated to one side, I figured a pressure issue could compound the problem. It's over 55psi. I'll have to reference the service manual, but that isn't drastically off base. I noticed it leaking down durring that test, so I pulled all the injectors and found the 2 nearest the inlet were not spraying well and had a very slow drip under pressure.

Cleaned them all up in the ultrasonic cleaner and ordered some screens. Flushed the fuel system and installed a new strainer/filter in the tank.
Swapped the first O2 sensor from right/left. Bank 1(negative trim side) had some slight signs of carbon while bank 2 (zero trims or slightly -) was white.
Checked all my coil packs and plug color, not fouled but definitely running lean. Tips on reading plugs better than I do is appreciated.
Reset the PCM with a battery disconnect.
Monitored fuel trims and didn't see any improvement change.
I can't hear any exhaust leaks.
Spraying the intake on that side with ether makes no change in RPM, though I would think if that was the problem that it would trim the opposite direction, but It wasn't too involved to check it anyway.
I can't find any exhaust leaks.
If the previous owner drove it alot with this misfire is it possible he fouled the cat? I'm thinking of how to test for this, maybe getting it up to temp and taking an infared temp gun to the cats? I should see a difference from left to right if it's fouled?
Could a bad Cat cause the system to pull fuel?
Possibly something to do with a downstream O2 and the emissions system trying to maintain a specific catalyitic efficiency, Either with a bad cat or a bad O2/temp signal? I'm not sure if it actually measures temp at the O2 sensor or inferres it based on the comparison between the upstream and downstream sensor...

I'm not sure where to go next aside pulling the exhaust, but the cat is at least one bend in from either end without cutting pipe, so that's not my favorite choice for checking cat flow.
decipha
Posts: 1401
Joined: 15 Feb 2021, 12:23
Location: New Orleans, LA
Vehicle Information: 10x Supercoupes
Lincoln LS 5spd
Ls1 t56 ss camaro
Whippled Harley Truck
gmc 2500hd classic
gt40p explorer
Marauder
Chrysler 300 AWD hemi
3.5 Explorer

Re: Troubleshooting negative LTFT Bank 1

Unread post by decipha »

what plugs did you go with? Plugs are critical and can cause intermittent stalling on the hemi's which is unrelated to your issues.

Does it have the MDS ? When those act up they can cause the similar problems.

Plugs after 10k miles should look new unless you got something funky going on with the engine.

Fouled cats can do some funky stuff. Temp is inferred from difference of spark and mbt and how long its retarded.

How far apart are the fuel trims? How does the truck run and what do the trims look like when under a load?
Porter84
Posts: 2
Joined: 05 Apr 2021, 12:27
Location: St George, UT
Vehicle Information: 47 Willie's 5.0l swap

Re: Troubleshooting negative LTFT Bank 1

Unread post by Porter84 »

Used a platinum plug from AutoZone (I know, but hopefully not too bad)
No MDS.
Right bank #2 stays near zero and Max 2-3% negative.
Left Bank is fairly consistent around -17%. These number are from driving to/from work about 4 miles. I can log it again with my MPVI2 and get a better idea what the injectors and cleaning the TB might have done, but nothing at all in the garage.
I can go for a longer drive and get some decent grades to load the motor a little.
decipha
Posts: 1401
Joined: 15 Feb 2021, 12:23
Location: New Orleans, LA
Vehicle Information: 10x Supercoupes
Lincoln LS 5spd
Ls1 t56 ss camaro
Whippled Harley Truck
gmc 2500hd classic
gt40p explorer
Marauder
Chrysler 300 AWD hemi
3.5 Explorer

Re: Troubleshooting negative LTFT Bank 1

Unread post by decipha »

I wouldnt be concerned with that so long as it runs like it should.
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