Carlos-RX300

My previous car was a Volvo V70 which had the turning circle of a supertanker, so my RX300 (cheeky plug: it's up for sale as I'm getting a company car soon) is a doddle to park by comparison!

The problems were definitely down to the wrong sensors. Fitted the correct ones yesterday and it's running like a dream now, silky smooth. Thanks for all your help chaps! The previous (new but wrong) sensors seem to be OK so they're going on Ebay next week - sparkplugs.co.uk basically said 'sorry but tough' so caveat emptor.

Spoke to a chap from World Car Parts who said it was the correct part but was happy to accept a return for refund after I explained the problems I'd had and Denso's response. The parts are now on order from Rock Auto so third time lucky maybe...

They've sent DOX-0261 sensors. :megaangry:

Interesting stuff - thanks Colin. Are there any online resources with this sort of information for UK RX300s? Most of what I've found has been for pre-03 models and mainly US ones, which have some pretty major differences.

Cheers, I'm a bit stuck too as I've also done a bit of searching and got similar results! Will update when the new sensors are in, hopefully early next week. Heh, fair point :-) The bizarre thing is that it's the same engine (Toyota 1MZFE) but it seems like the ECUs in pre and post 03 models are configured slightly differently. Toyota didn't think to change the physical fit of the sensor nor its electrical connector so it's as easy to fit the wrong part as the right one (I dare say plenty of other manufacturers do this too...). I've driven misfiring cars in the past and it doesn't feel like that, more like it's in a cycle of over and under fuelling but only in particular states of acceleration, which from a layman's perspective would tie in with problems in the fuel map.

Hi Jason, my answers in blue... - Does the problem happen when running on petrol also? Yes. - Have you checked your coils? No - is there an easy way of checking them? (Especially bank 1...) - Have you tried an ecu reset? Yes (only very slight improvement.) I suspect it's related to the A/F sensors as the problem only started when I changed them - the throttle response is much better but the kangarooing on acceleration can't be good for the engine and transmission, and spoils what's otherwise a very nice car to drive.

Yeah, to say there are quite a few RXs knocking around there doesn't seem to be much definite info out there. My old Volvo V70 was never this difficult to source spares for... The best way I can describe driving the car is it's 'not quite right' - when cruising or flooring it the car is fine but under moderate acceleration it feels like the throttle is being applied then released roughly twice a second. The parts are due Saturday so by Sunday or Monday I should know one way or the other!

Toyoparts lists the A/F sensor for Mk1s as 89467-48011 (which seems to cross reference to Denso 234-9009 and DOX-0243) and for Mk2s as 89467-48050. I've also been advised by Denso that the core of the sensor and the calibration of the signal differs between these parts. Although the sensors fitted to the car at the moment are apparently the wrong ones they haven't thrown a CEL, surprisingly.

I've got the (allegedly) correct parts on order from World Car Parts, at least I hope they are as it's costing me a fortune!

Update - a helpful chap at Denso UK has confirmed that DOX-0243 isn't compatible with 2004MY. The correct part, Toyota 89467-48050, is only available in the UK at the moment as a grey import (or cheap copy!). Sensible offers accepted for 2 x nearly new DOX-0243 with a couple of hundred miles on...

Bumping with a supplementary question! Is there any information online about the differences (if any) between 99-03 and 04-07 UK spec RX300s? I've found some info about US models but hardly any for UK ones so far. Looking at what few part references I can find it looks like I might have fitted A/F sensors for a 2003 model.

I probably should've mentioned that it's running on LPG! So around 14-15mpg equivalent, which still seems thirsty. (It has the same issues on petrol so it's not the LPG system at fault). I've replaced the MAF sensor with a second hand part today and that's helped quite a bit. The A/F sensors are Denso DOX-0243 from sparkplugs.co.uk. The plugs in bank 2 were changed 30,000 miles ago and look slightly sooty but otherwise OK (haven't even attempted bank 1!). Is there a guide anywhere for checking and adjusting the TPS?

Hi all, first post here. I bought an '04 RX300 a couple of months ago and have recently changed the A/F sensor on bank 2 to cure a P0430 code and an insatiable thirst (12 mpg average!). It seems to have been successful but the car is now kangarooing on moderate acceleration between 2000 and 3000 rpm. Bank 1 A/F sensor has been changed this week which has improved things slightly. I've tried to locate the IACV to clean it but my car's throttle body looks nothing like the pics I've found which seem to be US RX300s and have dual throttle bodies. My car has a single throttle valve. Idle speed is fairly steady and the car doesn't stall. Carb cleaner hasn't made much of a difference, neither has an Italian service. Any ideas welcomed!