JemP

Today I changed the transmission fluid in my 99 RX300. Quite an easy job, drained, took the pan off, cleaned the pan and the magnets, replaced the filter, pan back on and filled up with 5 litres of T-IV fluid (same as came out). the old fluid looked alright, but with 130,000 miles on the clock I thought a bit of preventative medicine would be a good thing.
Got everything back together, idled the engine, ran the shifter through the cycle a few times holding in each gear for a couple of seconds, and went out for a test drive.
As soon as I put my foot down a bit hard, i.e. away from traffic lights, the car bucks and judders, like going over potholes. This is usually in 2nd gear, i can ease off and go into 3rd, but foot down and the bucking returns. All i did was change the fluid, what could have happened?
Also the CEL is now on, but my ELM OBD2 cant read the ECU!

hypervish

Welcome to Club Lexus!

It may just be a coincidence. Take it to AutoZone and have the codes read for free, and then post them here.

JemP

I'm in the UK so I don't have that option

mizak82

heard that was normal sometimes for a break in, after flushing the trans..

many cars have a a back door way to read the CEL's.. usually involves turning your key in a sequence and pressing the gas pedal a certain amount of times.. makes the CEL blink in code.. least that was the case in my last two vehicles..

perhaps the mods would know if the lexus does that too..

carguy07

I know a lot of guys will dislodge a hose from the air cleaner box that will trip the CEL on. I don't remember drivability issues associated with this though. I doubt it has anything to do with the transmission unless it is grossly overfilled.

JemP

I am wondering if this is just coincidence as well. Transmission wasn't grossly overfilled before the drain and fill, and the same amount went back in as came out, so there should be no change there. The only thing I touched in the engine bay was the dipstick to refill, so not sure how anything could have been dislodged. Really annoying that the OBD2 device that I use on all my other cars just doesn't read the ECU on this one!

carguy07

Sorry, when I saw the word filter in your post, I decided that you did the air filter too. Yea, I think it's a coincidence. Maybe just pull the battery cable to reset and see what happens.

kalali

Is it possible to mount the filter incorrectly? I've done numerous drain and fills but never done a filter change on my '03.

Lexmex

I'd recheck the tranny level. I've know that happen to friends after they did a tranny overhaul and sometimes they needed to add a bit more fluid as they would also feel similar thing you are experiencing. It's unfortunate you can't read the code, because this would be one of the most important situations to see what it says.

JemP

OK an update, I sat in the RX today, trying to connect to the ECU with a different device. I pressed down on the throttle when I moved in the drivers seat, and noticed that I couldnt rev over around 2800 rpm, and that it bounced on and off this limit! So when I was accelerating yesterday, I'd be losing revs, and on kick down too. This would have led to the tranny jerking, so makes me think its not a tranny issue. Still cant read that CEL, and disconnecting the battery hasnt made it disappear. I am going to see if I can connect to my cabled device, and if that fails I'll get it to a local garage to read the code.
Anyone give me any clues on this rev limiting?

Lexmex

If it is not the tranny, it could be any of a number of sensors causing issues. I am pretty positive that getting that code will lead to the particular sensor in question. There are some sensors in the tranny that could be at issue, but again, let's see what the code is.

JemP

Yes, the fact is that this rev limiting was happening in P, and showed the same characteristics as when driving under load with the accelerator pedal down hard. Anyone else had issues with OBD2 not communicating with the ECU? I've never had that before on any car i've used it on, very frustrating!

carguy07

I know that on some cars a blown fuse will kill the OBD2 port. Worth a shot.

I think it can actually be the ECM fuse. The car will still run and the ECM will work on the power that retains memory.

JemP

Well i will look at this next weekend, got a week away with work now. I drove around yesterday, no problem through the gears under 3,000 ish revs, and all gears selecting smoothly. Rev over 3,000 and its a bucking bronco!

salimshah

Kill the OD to eliminate the if it is engaging and disengaging.

Salim