04 cobra high fuel trims problems

[Donny24]

Hey guys running into a weird problem . Running ported blower 60lb ford injectors Diablo sport mafie kennybell boost a pump had the car dyno tuned . On start up my LT and ST fuel trims are high st bouncy around from 0.0 to 0.10 and LT from 0.5 to 0.25 AF is 14.7 at idle . After driving the car for alittle the fuel trims are better at idle st are 0.3 and LT are around 0.0 to 0.10 AF 14.7 . Did a smoke test I have no vac leak and engine vac at idle is 19 psi . Trying to find out why my fuel trims are out of Whack and some time there spot on

 

[03Steve]

Pressure test the exhaust system for leaks.

 

[Donny24]

Ok thanks I'll start there

 

[Donny24]

Found a small leak on pass side put a new gasket with copper rtv . Going to let it sit over night . Hope it fixes it

 

[Donny24]

I fixed all the leaks and looks like my fuel trims are still high . Anywhere els I should look or try thanks

 

[gt347mustang]

Have you discussed this with your tuner?

 

[Donny24]

Yeah he said it was weird problem to go off my AF numbers .But my AF has always been fine he was running out of ideas . Driving the car the fuel trims are good . It's only after the car sits for a little the stay high but after a short drive there in range . I didn't know if I was over looking something .

 

[gt347mustang]

Is there driveability issues, or are you just looking for problems?

 

[Donny24]

Car drives fine driving around AF 14.7 and in boost AF 11.8 -11.9 is spot on . Just trying to fig out why sometimes my fuel trims are high and sometimes there not bugs me .

 

[gt347mustang]

Car drives fine driving around AF 14.7 and in boost AF 11.8 -11.9 is spot on . Just trying to fig out why sometimes my fuel trims are high and sometimes there not bugs me .

Your fuel trims move around to maintain stoic. Sounds like they're doing exactly what they're supposed to do.

As long as trims don't max out and you run into driveability problems I wouldn't worry about it.

 

[Donny24]

ok thanks guys I'll stop looking at the fuel trims and go of my AF it's going to drive me nuts

 

[jackwabbit703]

Don't bother with fuel trims. I had my car dyno tuned and it is suppose to be near 14.7 little up or down when idling. Under boost, is spot on like yours. You have to remember 14.7 lamda is 1.00% on fuel trim calculator. I believe your car is running fine. If you were running too rich or too lean, it would have thrown a DTC code by now.

 

[Donny24]

Just a update now I am getting a p0175 bank 2 rich poping up now . Some times the fuel trims are fine and sometimes at idle I saw the st start climbing up from 10 all the way up in the 30% range then I rev the car and they come down some , the LT trim are good sometimes and other times they get to -18 -25 . Driving the car there always fine ST and LT0 .2 -0.5 . And at WOT 11.7 AF Only new stuff I added was a ported blower 60lb and mafie and a boosts pump and got the car dyno tuned beforehand the car ran great . I did a smoke test no leaks engine vaccum is 20 steady and I put new 02 in . Anyone have a idea where I should start looking ? Running out of ideas

 

[Bdubbs]

Do you get any smoke out of tail pipes on a cold start up?

 

[Donny24]

No smoke at idle . AF at idle is still 14.7-15 car has 28k for miles . It all started after the new tune and blower swap . On the dyno car made good power 510hp and 510 tq

 

[Bdubbs]

With the P0175 code I'd start with some simple stuff. Clean Maf sensor with actual maf cleaner of course. Maybe a faulty o2 sensor. Check coils and plugs. It could also be a fuel injector. Reason I asked about smoke on a cold start up is because I once had a leaky injector. It would stay open and drop fuel in the cylinder. Once I started the car up it would smoke for 1-2 seconds.

 

[Donny24]

I gotcha yeah it's weird how there fine sometimes and other times there high . But driving there car there fine it's only at idle and AF stays at 14.7 while there high I cleaned my maf I put in new plugs and ome out my coils there all good pretty shure I have no Exhaust leaks I can't hear anything . I got new ford 02s . If I hook up my Sct tuner and check the fuel pressure , turn the key on and see 39-40 fuel pressure and check for leak down to see if it holds for a few hours would rule out a leaking injectors?? ... Or is my maf going bad or the mafie cars starting to drive me nuts

 

[cj428mach]

I gotcha yeah it's weird how there fine sometimes and other times there high . But driving there car there fine it's only at idle and AF stays at 14.7 while there high I cleaned my maf I put in new plugs and ome out my coils there all good pretty shure I have no Exhaust leaks I can't hear anything . I got new ford 02s . If I hook up my Sct tuner and check the fuel pressure , turn the key on and see 39-40 fuel pressure and check for leak down to see if it holds for a few hours would rule out a leaking injectors?? ... Or is my maf going bad or the mafie cars starting to drive me nuts

If it was something like the maf or mafia both banks should be effected not just one.

 

[Donny24]

See sometimes the LT after revving the engine it's almost like the default to -25 like a switch both banks when it comes back down to idle , and ST are around 5-7 . But then other times there like -10 and -18 LT

 

[decipha]

do you have an x pipe?