HELP! 2006 Toyota tundra very high fuel trims

Just to make sure it isn't the fuel pressure regulator, hook up the fuel pressure gauge. At idle, disconnect the vacuum hose. Fuel pressure should go up. Recconect and it should go down again.

 

Ok, I'll have to go rent the one from O'Reilly's. That's how I checked it before. I'll update as soon as I'm able to get the gauge.

 

I see your latest comment about finally checking the exhaust. How dod you check and all did you check….from rear sensors forward ?

Also you mentioned way back when that the ECU is the right one for your truck. Is that the original as far as you know or another from newer to you engine ?

 

I first did a smoke test and pressurized the exhaust to see if i could see anything leaking around either manifold. Then I took both manifold heat shields off and started the truck and felt around for anything. Also looked for soot stain that could guide me to the leak and found nothing. And the ECU seems to be the original from 2006. The last things I have not replaced in this entire mess of diagonistics is the ECU and fuel pump. So it could be a failing ECU but I kinda doubt it but then again I'm out of luck at this point so it could be. Is there any "testing" that could be done to it or is it just replace it?

 

Can the gauge be taped to the windshield?

Check pressure under load (driving). If it's dropping as your ltft rises, it usually means a bad pump. Pressure may be ok at idle but failing pumps sometimes won't provide enough volume.

 

I feel stupid for not checking it under load. I just checked while at idle since I was by myself. What’s funny about that is my fuel trims stayed great at idle but a couple miles down the road doing 50mph and that’s when I noticed they got bad. I’m definitely going to look into that.

 

I'm back now. Fuel pressure stayed constant 40psi under load. But no change since nothing has been done of course. However I had started to notice that I was hearing a ticking on bank 1. And I only heard it on acceleration. I decided to take like 3 hours to take everything apart on bank 1 to look at the exhaust manifold. I did a different style leak check on it with a vacuum cleaner (on blower mode not suction) and put soapy bubbles all over the exhaust. I am going to try to attach the video of what I found. It's a leak for sure. Would a leak like this cause a long term fuel trim to be 44.5? I would really like to know everyone's input.

 

You have a 2006, so you will have an Air/Fuel ratio sensor rather than an O2 sensor before the cat. Exhaust leaks absolutely can make the A/F sensor misinterpret the mix and report lean. Do you have a scan tool that can read A/F sensor data? IIRC, for a Toyota, you should see a steady around 3.3V for a 'good' reading. If it was an O2 sensor, you would see a wave going up and down between about .1 and .9v.

Also, for an A/F sensor, a low voltage means rich (opposite of O2 sensor), a high voltage means lean. Again, IIRC.

Also, sometimes there is more than one issue, and the 'lean-ness' can be cumaltive.

 

Yep, I used my scanner and get 3.4 volts on both banks. It’s leaking on the cylinder closest to the front of the truck.

 

Having trouble getting a video to upload since it’s coming from an iPhone mov. file

 

www.imgur.com

Post the video on there, tell it to include audio. Give us a link to the page it takes you to after upload, the forum will auto-link it.

Exhaust leak would result in upstream a/f sensor getting a less-accurate read, and potentially dumping more fuel. But I'd expect it to be pretty serious to affect fuel trims in the manner you're describing.

 

https://imgur.com/a/nYFnZO9

 

Really need the A/F voltages at different loads. Remember also that the A/F sensor readings will get closer to that they would like to see once extra fuel is added. Ideally you want to see what they are reading at the point your fuel trims change. Maybe drive with a buddy looking at the live data? Or see what happens with some WOT while stationary. That looks like quite an exhaust leak.

 

I can definitely mess with it with wide open throttle where it sits, I got a good amount of stuff taken apart so I’m not able to drive it atm but I’ll check that and put it on here.

 

Does it need to be up to temp before I can trust the reading?

 

All readings should be done at temp. The sensors need to be at something like 700 degrees to operate, but they have heaters. But the ECU is going to likely run a little rich until it reaches closed loop anyway.

 

That looks like a pretty substantial leak rigtht there. Am I correct that it's cracked where the cylinder 1 exhaust tube meets the flange? Or is it leaking at the manifold gasket mating surfaces and where the exhaust tube meets the flange?

 

I believe it to be leaking at the gasket and pushing around, I started the truck up briefly while it was cold and tried to get my hand near it to see if I could feel it, and I couldn’t feel it exactly around the actual front side flange of the header so it’s probably not cracked but again the gasket.

 

https://imgur.com/a/7E2cjVE. Here is that a/f reading at operating temp I beileve

 

Well, that is what I would expect to see with an exhaust leak at the manifold. Apparently those can suck air in. Something to do with the exhaust flow is actually a series of pulses and you can get lower pressure waves. Not a mechanic though.
It's the sheer size of the LTFT that's interesting though. But you def need to deal with that leak. Did you use new gaskets? I ask because the old ones may have 'formed' to the old engine exhaust surface.

 

I didn’t not, really wishing I did though. I have the fel-pro gasket ordered up and I’m going to check the manifold for warping or unevenness. I have the old exhaust manifold from my old engine so if the one I have on is bad, I do have a spare.