Ford Mustang Forum banner

Tuning issue getting short term fuel trims to agree

1K views 3 replies 3 participants last post by  lwarrior1016 
#1 ·
I'm getting my mustang tuned, and the tuner pointed out that I've got a constant 15-20 point difference between the banks 1 and 2 (bank 1 being the higher of the two) that doesn't go away with RPM. I've been trying to fix it for a hot minute now and I'm about all out of ideas.


For starters, here's everything I've done engine-wise:


  • Procharger
  • Comp Cams stage 4 cam (XE274H) with new beehive (beehave?) springs
  • BBK 78mm throttle body
  • Edelbrock intake
  • BBK shorty headers
  • MSD coil packs
  • MSD 2-step (which shouldn't affect anything)
  • 05+ slot style MAF
  • EGR removed
  • Wide-band (on bank 2)

And to list what I've already tried with no success:


  • Spark plugs
  • Fuel injectors (completely different ones)
  • Exhaust leak (pulled off and put new gaskets on headers + sealed with RTV and sealed downpipe connections)
  • Vacuum leaks (make a smoke tester, it broke in about 5 minutes. Did the old starter fluid trick and found nothing. Ordered a smoke tester, its on the way)
  • coil packs (all the old plugs looked fine)
  • Cams (exactly in sync from when I installed them last year. Note on that further down)
  • O2 sensors, swapped bank to bank
  • Compression test, all within 10 PSI. Only curious thing is that 3 of 4 cylinders on bank 2 were about 10 PSI higher than bank 1 (~150 vs ~140) and one on bank 2 was at ~140

And the note on the cams, my tuner thinks that's what the issue is, but I just got done checking them and they're both where they should be. Both cams are always the same distance away from the marked link on the timing chains. All the lobes look fine and I've checked filters every oil change since I did the cams. Plus, I looked at an old datalog when I had it tuned N/A last year with the cams on and the banks both agreed with each other. It's also ran just fine for the past year, and was driven on a roadtrip with the procharger supplied tune with no issues (even made full throttle pulls).

I put on the solid motor mounts I had laying around when I did the headers, and when I test drove it to see how it was I thought I could feel a cylinder not firing right (but its not throwing a code). During the test drive I held the engine with no load at a couple different RPMs and thought I could hear almost a gurgle or a falter coming from the exhaust, it was RPM dependent.

I checked the fuel pressure sensor and notice I had accidentally hooked it up to an old EGR line that didn't see vacuum and fixed that, which seemed to have made a new problem? On fire up the wideband pegs at full lean and then settles down to normal. Speaking of fuel stuff, I'm using the edelbrock fuel rails with the system plumbed with a T fitting on the passenger side to the driver side and the fuel sensor in the middle.

My working theories right now are a fueling issue because of how I made the fuel lines, cam sensors going bad, or fuel pressure sensor going bad.

Open to any and all suggestions (including lighting it on fire lol)
 
See less See more
#3 ·
ddubbrown



Even with no issues in the past, and older datalogs where the banks are ok? He suggested it could be sensors or alignment, so I've got a new camshaft pos sensor on the way. I've checked over and over everything and I can't find anything mechanically wrong, which is why I'm leaning towards sensors.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top