2002 Toyota Sienna - high fuel trims on acccel (SOLVED)

nikovdh

Hi Scotty.
I recently bought a used 2002 Toyota Sienna with 134k miles. I found out a day later that is smokes blue on cold morning starts (for about 5 seconds) - so it possibly has bad valve seals. It runs pretty well otherwise and doesn't smoke any other time. It also has a problem with high fuel trims during acceleration. During idle the fuel trims are pretty close to 0% -/+ 8%, but acceleration causes long term fuel trims to jump up to close to +25%. It doesn't seem like there's any fuel pump kind of problems, but I haven't done a fuel pressure test. MAF readings are good, no check engine lights, good engine temperature readings, IAT, etc. If I hold a steady speed 50mph+ on the highway for a bit, the +25ish fuel trims will randomly dip down towards +10-15ish for a bit, and then rise back up to +20-25 without any vehicle speed changes. Sometimes it will even go up to +30, but I haven't received a lean code yet since it hasn't hit 35+. The only other obvious issue besides the morning blue smoke is that the transmission is fairly worn and doesn't shift smoothly. The engine seems to rev or roar significantly louder when accelerating but the sound smooths out once speed is steady. My other 1MZ-FE engine (on my 99 Lexus ES300) is much quieter in this regard and doesn't have these high fuel trims. Should I worry, since the repair manual says this is within normal fuel trim limits? Should I suspect a fuel system related issue and investigate further? Can engine conditions such as bad valve seals cause high fuel trims like this?

Thanks for all your videos!

Comments (5)
No. 1-4
nikovdh
nikovdh

SOLVED: Even though the MAF readings seemed fairly normal at idle and racing at 2500 no load (readings shown in Pre-Check of Engine Diagnostics of the Toyota Repair Manual for the 2002 Sienna), this was apparently my problem. I took the MAF out of my 99 Lexus ES300 since the part is compatible and the long terms are now reading literally perfect readings when accelerating. If you're ever having this issue, and you're not having any symptoms of fuel related troubles, and your MAF readings seem decent otherwise, I would try finding a good compatible MAF from another vehicle. I'm not sure how you're supposed to really test these MAFs to pinpoint it without swapping in another, but I may read up about that now.

StarLighter
StarLighter

Have you tried replacing the fuel filter?

nikovdh
nikovdh

I also added Redline Fuel System Cleaner (apparently high PEA content) today with a fill up just in case it's dirty injectors. I will be driving it on the highway for awhile later tonight when traffic is slim and hoping it will help :O

nikovdh
nikovdh

My recent work on the van: oil change, change PCV valve/grommet (OEM Toyota), new air filter (OEM), transmission fluid drain/fill, MAF sensor cleaning, new battery