Mechanics Fixing My Car Perplexed: Can't Fix The Automatic Transmi

[Helgso]

So the other day I sent my Lexus RX300 2000 petrol AT model to very respected mechanics. I did not send it to Toyota due to they are far too expensive. The persons working on the car previously worked for Toyota and should have the knowledge to fix the car.

I sent the car because the automatic transmission failed. They repaired the transmission, rather than replacing it to spare some cost (I asked for it). Next, they noticed when testing the car that it did not shift into second gear but went straight from first to third gear. They tried fixing the problem by replacing the ECU (the car's computer). Even after reprogamming the new computer, the problem still persisted.

They said:

When the car is cold, the car almost always shifts directly to third gear from the first.

When it is hot, the problem is milder and the car less often shifts from the first gear to the third.

Does anyone have a clue what else could be checked?

So far the following has been done to the car:

The automatic transmission has been rebuilt,

the ECU has been replaced with a second hand one and reprogrammed,

the oxygen, acceleration and one other sensor/detector have all been replaced,

all the glow plugs have been replaced,

the exhaust manifold system has been rebuilt.

[Geoffers]

Not sure if its related but on my IS250 auto I was having some odd gear changes and revs would just drop randomly. It was the MAF sensor.

[steve2006]

When you say the tranmission was rebuilt I assume this included the shift solenoids and possibly the valve body and they have used Toyota Type IV transmission fluid?

Have a search on google for Lexus RX300 Transmission, apparently transmission issues are a major problem on this model and it also mentions about a Planetary gear update to titanium.

[ihpj]

So...on a petrol vehicle the glow plugs were replaced?

...and you wonder why this 'mechanic' cannot fix your vehicle?

[ColinBarber]

I'm concerned that things are just being replaced, essentially as guesses to fix the problem.

Oxygen sensors would have no effect on transmission shifting.

The ECU on that model is essentially unprogrammable so I'm not sure what they think they have achieved.

Possibly a problem with the transmission speed sensors which may need cleaning/replacing.

*** Make sure Toyota T-IV fluid has been used *** if not make sure all of the incorrect fluid has been fully removed (not just a pan drain) and fill with T-IV.

[ColinBarber]

I would also add that auto transmission skills in the UK are lacking - mainly due to the lack of exposure.

[DanD]

Glow plugs? Really? To my knowledge you find glow plugs on diesel engines only

[Helgso]

No, sorry. Not glow plugs but of course spark plugs

[Duncan Roberts]

This saga regrettably confirms that not going to a dealership can be more expensive and ineffective in finding a cure.

Spark plugs or glow plugs are highly unlikely to affect the transmission for starters so it suggests that however "respected" (by whom?) these folk are they do not know what they are doing!