Random misfire and LTFT negative.

[LouisiAnimal]

I’m having this issue that I can’t seem to figure out. I get a code sometimes for Random misfire on startup and sometimes I get a code for misfire on 1. I can feel a miss about 1800 rpm only when I’m not heavy in the gas. Can hear an occasional mos in the exhaust when idling. LTFT gets between -15 and -20 STFT stays around 0. Tuner said my injectors might be stuck in open. Got em cleaned, Cleaned injectors, new coil pack and plugs, evap purge valve seems to be working, but hadn’t changed it. I moved the injectors to different cylinder after cleaning, and also moved coils around to see if the mis followed. It didn’t. I changed upstream o2 on that bank. Idk where to go from here. IMRC locked out.
17 gt w/18 ported mani, catless headers, full exhaust, t56 swap.

Sponsored

 

[JFBullitt]

Only things I can think of that are left are a vacuum leak or something internal. Maybe a compression or leakdown test is in order.

 

[GregO]

I can feel a miss about 1800 rpm only when I’m not heavy in the gas.

What Cold Air Intake are you using.
Just a WAG, verify the MAF transfer functions.

 

[LouisiAnimal]

Only things I can think of that are left are a vacuum leak or something internal. Maybe a compression or leakdown test is in order.

I thought vacuum leak would cause it to run lean? just in case I searched around for a leak. Sprayed carb cleaner around the manifold etc nothing to be found. I do hear a random tick from the throttle body at idle. I hear that’s normal though.

 

[LouisiAnimal]

What Cold Air Intake are you using.
Just a WAG, verify the MAF transfer functions.

Sorry forgot to list that. JLT intake. I cleaned the MAF and made sure it was in there the right way.

 

[GregO]

Sorry forgot to list that. JLT intake. I cleaned the MAF and made sure it was in there the right way.

That’s good but transfer functions could be skewed a bit.
Who’s the tuner ?

 

[LouisiAnimal]

That’s good but transfer functions could be skewed a bit.
Who’s the tuner ?

Lund. Last datalog I sent the recommended I clean the injectors cause o was running rich and they may have been sticking open.

 

[GregO]

Lund. Last datalog I sent the recommended I clean the injectors cause o was running rich and they may have been sticking open.

Right, I seen that in your first post.
Wengerd
Ortiz

 

[LouisiAnimal]

Still fighting this issue. Ford dealer says there's un metered air after MAF. Wouldn't that create a lean instead of rich? Also p0300 p0308 p0316 He's changing the MAF, and wan't to put the stock intake tube on it. I'm tuned for the JLT, and have an 18 mani on it. I can't flash to stock, and I'm not sure it'll run right with the JLT tune on a stock Intake tube.

 

[Robottrainer]

If you can't

I’m having this issue that I can’t seem to figure out. I get a code sometimes for Random misfire on startup and sometimes I get a code for misfire on 1. I can feel a miss about 1800 rpm only when I’m not heavy in the gas. Can hear an occasional mos in the exhaust when idling. LTFT gets between -15 and -20 STFT stays around 0. Tuner said my injectors might be stuck in open. Got em cleaned, Cleaned injectors, new coil pack and plugs, evap purge valve seems to be working, but hadn’t changed it. I moved the injectors to different cylinder after cleaning, and also moved coils around to see if the mis followed. It didn’t. I changed upstream o2 on that bank. Idk where to go from here. IMRC locked out.
17 gt w/18 ported mani, catless headers, full exhaust, t56 swap.

If you can't find anything wrong, try reloading the tune. It happened to me on a 2013 Shelby

Sponsored