Lean issues, any ideas?

[suprakid24]

Not sure if it's really AEM related or something else, but we have been debugging this for a while and decided to see if anyone else can help us find the answer.

The problem is the car will start leaning out when trying to accelerate after driving for a while. This is with regular driving too, any amount of throttle will instantly read lean on the wideband. The car will hit a few readings of fuel and manage to accelerate but still acts groggy and sluggish. On a cold start (and at random times it seems like) it will run and pull strong. I know this is not very specific, but we aren't sure what to look for. We've already replaced the TPS and AIT sensors with new ones and have been looking all over trying to find any sensors that look like they need replacing.

We've also had the car professionally tuned and tried changing the computer with the same results. Any ideas? We believe it may be in the fuel system somewhere.

 

[peste noire]

what kind of pump do you have??

 

[thevork]

A cracked hose, only showing when warm? checked for leaks already ?

 

[Radial]

you should try and temporarily tape a fuel pressure gauge on your windshield (connected to your fuel rail/pressure line of course) and take it for a long spin.
Observe fuel pressure when lean-conditions occur... if fuelpressure actually IS low, replace pump and FPR....and try a new fuel filter just in case.

If pressure is correct, your wideband or AEM must be bad somewhere.

It's not very uncommon that worn fuel-pumps loose pressure when they get hot.

 

[suprakid24]

1 in tank walbro and 1 external tsunami, fuel lines are braided. As an exapmle, we can drive the car 5 minutes somewhere and do 4 or 5 pulls on it fine - Drive back and once we try to go from a stop sign it starts acting up.

 

[suprakid24]

Radial - we tried setting the tsunami to come on at a low rpm to rule out any low fuel pressure issues, but that didn't help. I guess we should really watch the actual pressure while this is happening to try and rule out the fuel system or electronics

 

[Turbo Habanero]

Definitely sounds like a overheating fuel pump

 

[suprakid24]

If one was overheating the other should still be working unless both are overheating

 

[suprahero]

What's up Craig, aka Suprahero slayer?
My Stinger has fuel added when you give it gas going down the road. (acceleration enrichment) It's a percentage. I'm sure the AEM has the same thing. Have you checked to make sure it isn't something with the tune like that? Maybe it's even in the fuel trim for when the water temperature gets above a certain degree. If you had it professionally tuned then this isn't likely the culprit, but it won't take you a minute to check it out.

It's more than likely a fuel pump problem. Is there a constant 12 volts to the pumps? One time on the dyno I was having problems with fuel pressure and for some reason my fuel pumps were getting irregular voltage. We fixed that and ended up with a constant 12 volts. Again, I'm sure you've got this covered, but thought I'd mention it.

 

[suprakid24]

Hey Jay, it' been a while. Good thing you didn't go to tx2k this year! lol You would have beat us for sure and got your revenge because we were having clutch issues.

As far as the tune goes, Justin @ boost logic did it so I don't think there was anything missed. Also when we look at the logs all the air temps and engine temps look fine so we don't think it's falling into any holes in the map. We also tried hooking the fuel pump straight to a battery and it was doing the same thing.

We just got back from a drive, took about 20 minutes but eventually it started acting up. We pulled over to read the fuel pressure regulator and it was reading 52 at idle and going up when revving so the pressure is there - at the same time the wideband was pegged lean. We brought it back to the house and left it running trying to look for something and after a while it cleared up without changing anything (removed the gas cap, but we don't think that did anything).. drove around the block a few times and the symptoms came back.

 

[suprahero]

Does the AEM have fuel trims for when the air temperature and / or water temperature reach a certain degree? It seems like it could be something like that since it only does it when it reaches a certain temperature and then returns to normal after cooling down. Maybe someone accidentally typed in a negative number at say 195 degrees making it pull fuel. Then when the thermostat opens causing it to go back to 185 or whatever it runs fine again.
It seems you've eliminated the fuel pump, and the volts going to it. It's either a tune issue or somehow there's more air getting into the head than is being accounted for. Wish we could be of more help.

 

[Radial]

So fuel pressure checked out OK, no holes in map...
Try a different wideband.... thats my advice!!

 

[suprakid24]

A few updates - replaced the in tank fuel pump and the same thing is still happening. Started after about 30 minutes of driving/pulls and the temperature was the same as when it was working correctly (around 190). Turning off O2 feedback doesn't clear it up either