Engine stumbling at 3000 RPM

jonprt · May 10

I have a 2005 Lexus RX 330 that is driving me nuts. Recently it would not start. I checked out the starter and replaced it. Everything seemed fine, then it threw code P102 and stumbled at 3000 rpm. This led down a rabbit hole. The MAF is fine. I swapped it with the same one from my Highlander, no change. I purchased a MAF from Toyota to make sure it was the specific part. No change. I replaced the wire connector with a new one. Checked and rechecked the vacuum lines and replaced the intake and plenum gaskets. There is no sign of a leak.

My CRP123 shows the MAF reading at 0.040 gps when it should be around 4.0. I had a company flash an ECM from the vin and replaced it, thinking that was the problem. Nothing has changed the lack of power at 3000 rpm.

It has to be something interfering with the electrical signal getting to the ECM, but I can’t find the problem. Has anyone experienced this happening?

Is there a limp mode to explain this?

McBrian · May 12

Is that the only code it is showing? Anything in Pending?

jonprt · May 13

Yes, that is it. I've been through the list of possible fixes. The only explanation has something to do with the airflow being registered so low, which is probably causing the ECM to run it lean.

That still doesn't explain why, no matter what I do, it won't rev over 3000 rpms.

McBrian · May 13

Interesting challenge.

Mine had a "similar" problem but there was a definitive code for the throttle body not operating correctly. Same description of results though.

I also did a short ram intake (just for simplicity of access going forward find my Weapon R thread for visual) when I replaced the TB and was warned by the install company multiple times to make sure the MAF was installed facing the right direction. No assumption, but double check to make sure the airflow is being metered correctly(?) A reach, but worth a check.

Vacuum lines on mine were also a mess and causing some weird behaviour with no codes. How's all the rubber on all of those useless check valves?

jonprt · May 14

Good news. I found the problem. It is nothing like it would seem.

I found a you tube video that described an RX330 that wouldn't rev over 1800 rpms. He replaced the blown ECTS fuse and everything works. Mine didn't even appear blown, but after replacing it, we are back to full function.

Apparently, that fuse doesn't disable the gas pedal. It does disrupt it's function and put it into limp mode. The MAF flow is now normal, and no more codes.