LT FUEL TRIM HELP! Mine is at +10.9 at idle whats yours?

Hi All,

I need some help figuring out why my long term fuel trim is at +10.9 at idle or whenever I let off the gas?

Is this normal?

I changed both the o2/afr sensors the maf sensor, I even tried a new throttle body.

I do not have a CEL.

Im pretty bummed at the moment...

Q

 

Friday help please bump!

 

Mine runs about 14-15. Mine is also supercharged but I think 14-15 is normal for N/A trucks also. How does it run? Is it bogging down or anything?

 

I have seen a lot of 1st gen 3.4 engine run in the +10 to +15 range on LTFT. Not what I consider ideal, but it is not uncommon. The number being positive means it is adding fuel, so it thinks the engine is lean. Check ALL vacuum lines and see if one is loose, or perhaps cracked/damaged.

 

Thanks guys.

The performance has gone down so I am trying to figure it out, the weird thing is if I disconnect the battery and reconnect it drives great for a bit but then bogs down after the ECU goes out of learning mode

I have tried a new MAF/Spark Plugs(IK22 and a duel ground 2 step cooler plug)/ 02/AFR sensors/Different Throttle Body/Disabled/Enabled the URD 7th/Rebuilt the supercharger.

I took it to the best Toyota Mechanic shop in my area after all of the above and they can't figure it out either.

They checked for vacuum leaks as well.

Q

 

Weird thing is it only happens at idle or when the gas pedal is not depressed.

 

I had a problem with mine running real fat after I installed the s/c. I disconnected the fuel pressure regulator from the blower and hooked it back up like it was stock and it ran fine. The instructions told me to hook the fpr to the blower but was causing it to get too much fuel. But it was only a problem at wide open throttle. Is your 7th injector wired up correctly? I know you said that you disabled it but there are a couple wires that had to be cut in two and if you got a couple of those mixed up then it might cause problems even with it disabled.

 

Nothing weird at all. Idle fuel trim and driving fuel trim are two totally different things.

 

Not ideal but fine if runs good and no cel. Likely just in the tune somewhere or small vac leak can cause this. Probably not enough to worry about. What are the stft's?

 

Interesting...

My local Toyota mechanics were all worried about the long term fuel trim being above +10.

The driving fuel trim is good.

My thought is a partially clogged cat, the only thing is it hasn't thrown a code so I'm shooting in the dark.

Flat roads it drives good, hit the hills (0ft to 2300ft) and it bogs down, not so bad on the 6% grade but the 14% grade you can feel.

It feels like the truck is fighting itself, engine seems to be working fine but it feels heavy/boggy/fat.

Q

 

I thought it might be a vacuum leak but I checked spraying TB cleaner on all the hose connections, I also had the mechanics look for a vacuum leak, they used a propane gun and found nothing...

Q

 

Thanks.

I checked the URD wiring guide twice before I soldered them and once after.

I checked again yesterday and all the wires are done per the URD instructions.

I would agree it could be a install error but the truck ran great for a while and then started to bog down, also if I restart the ECU and then drive the truck it runs good and then after about 65 miles the performance tapers off.

I am thinking the Cats are the issue or perhaps the stock tune is too rich(doubtful).
Q

 

I had that when my front catwas just begining to be plugged up. But i have the 2.7l

after that it was power loss it would hesitate like it was running out of gas then go

It reminded me of riding a motorcycle and needing to turn the petcock on or reserve.

It wasn't until until it melted out the bottom of my vacuum modulator that I figured it out. While driviving it with my front cat drilled out I got 25 mpg as opposed to at best 15. Thanks CARB and CHEKlifornia. Thank god I was under the 8yr 80,000. Because a new cat was like 2500. and no aftermarkets were available unless you drove to nevada

 

See, if the fuel trim is good when not idling, then that is of course NOT the problem. I would be looking at things like the MAF sensor, the oxygen sensors, possibly knock sensor, weak fuel pump or dirty fuel filter (actually a weak fuel pump or dirt filter would explain higher fuel trim numbers), and the catalytic converters.

 

Thanks Bama.

I replaced almost all those parts recently to try and stop the issue, the fuel pump is a Walbro 255.

I haven't checked the knock sensor, maybe I will try that.

Any ideas on how to check the cats myself, pull them off and see how it runs?

 

Anyone know how to check the catalytic converters without a sniffer?

I hit the rear cat with a soft bow and it is quiet, I hit the front and there is a bit of vibration noise.

Can I just remove them and see if they run better?