MR2 Owners Club

Hi all. After several years of not owning an MR2, I'm wanting to return to the fold. I've previously had a couple of MK1s and a MK2 Turbo, but am now contemplating a MK3. I've seen and test driven a few and think I may now have found "the one", a 2005 Red edition, but have a couple of reservations about it and would appreciate some advice.

The car drove well and looks good, but the check engine light is on. I didn't have an OCBD reader with me, but the seller said that the garage who had just serviced it said it needed new "emissions chip" at around £50, and that the fault was that the "fuel burn sensor" was giving wrong values; the car has just passed an MOT too and the advisories do not mention either a fuel/emissions problem or an engine warning light.

Does this sound like a MAF issue or something else and, either way, should I be worried? If it really is a £50 ish job then it wouldn't put me off and I'd just haggle accordingly.

The MOT advisories do mention front discs and pads being worn, but I assume these could be replaced relatively cheaply; there was no sense of warp or binding on the test drive. Service history and previous MOT history are both good and I felt confident that seller was honest and being straight with me, so I'm keen to do a deal but would like to feel more confident that the above problems aren't going to bite me in the bumper.

All advice appreciated and it's good to see Jimi is still here - he helped me greatly with my MK1 when I was Edinburgh based many years ago.

Sounds like an o2 sensor is knackered from what you say but I’d confirm that with a code reader before parting with any money

Buy Denso sensors tho it’s cheaper in the long run

Thanks for the speedy reply Vinny. Not sure I can find my code reader but I guess I can ask to get the info from the servicing garage. If it is just an O2 sensor, is it a DIY job for a reasonably clumsy oaf?

Update: spoke to the garage who couldn't recall exact fault code number but said it was a heater circuit sensor for the O2, used when engine started from cold. Looking at the fault codes leads me towards a P0135 or similar. Anyone know how easy/costly to fix? The garage owner did echo what I've read on here about using a decent part, not a cheap one.

There are 3 sensors. You need to find out which one to change so I would get one of these and download the torque app to get the code.




You will need a 22mm spanner or O2 sensor socket tool and the lower one seems to be the hardest to get out but no harm done if you cant shift it and have to get a garage to do it.
https://www.sparkplugs.co.uk/amfinder/? ... nt-7790338

Welcome back Pat how's tricks

Tricks are a little tricky it would seem as I've made the "buy in haste repent at leisure" mistake and bought a car that I now know has THREE fault codes, PO135, PO141 and PO155. I've also joined the MR2 Roadster owners club, so have found some useful info there about O2 stuff too, including where to buy replacement sensors without needing a mortgage. What I'm wondering is whether I should be a cheapskate and just replace the upper two sensors in the hope that the fault code on the lower one will then also disappear? Or, given this news, should I be looking at replacing the manifold with a stainless de-catted one instead? **sigh**

Unlucky to have a Heater Circuit Malfunction on all 3.
The correct Denso replacements cost £51.71 each from Sparkplugs UK.

I presume you have seen this link I posted on the other thread.
https://www.mr2oc.co.uk/forum/42/158309.html

Your call whether to go for an aftermarket manifold.
Bear in mind the likely need to declare the mod to your insurer.

Hi Tony. Yes, unlucky indeed. Thanks for nudging re the other threads, which I've read. Think I'll probably play it safe and order all three sensors from sparkplugs and fit the pre ones first, test it, see if the third one's necessary too, and fit it if it is. If it isn't, I'll have a spare for the next time... My soldering is reasonable, but I think I may be lazy and go with the non-generic, just in case the existing plugs are getting brittle too.

As for aftermarket exhaust, I'm going to trawl through the various receipts that cam with the car and see if there's any mention of pre-cats having been removed already. If not, is there anyone on here that offers such removal for a fee/pints?

Quite possible that all three lambdas have gone (maybe not at the same time but not dealt with as one by one they went :( ) as they are quite "delicate" Also, if this is the car that had a recent MOT, the owner obviously reset the light to get it through the MOT as it is now an MOT fail :( The general concensus of opinion in Roadster circles is to use OEM Denso for replacement lambdas.

If you choose to bash out the precats, please use loads of PPE, otherwise get a new precatless manifold.

Ah well, having saved a fair bit on another remote key and fob today, I've taken the plunge and ordered 2x DOX-0204, 1x DOX-0206 and a 22mm lamda tool from SparkPlugs, and a large can of PlusGas. Will report back once I've fitted (or failed to fit) them. Cheers for all of the advice above.

OK, DOX sensors received. PlusGas applied. I'm no 7-stone weakling - in fact I look like might have eaten a couple of them - but squeeze as I might I can't find the right spot to release the cables of the existing sensors from their female counterpart. I'm resisting the brute force approach as I'm stuck in the middle of nowhere if I break a connector. Can anyone give me a hint/diagram please?

Panic over - I've done the two pre-cat ones after finally managing to undo the connectors, but I may never play the piano again! I found that despite how little the plastic sneck was that held them together, it helped to slide a small terminal screwdriver in to give a little more separation. It also helped, with the one nearest the battery, to unclip it from the small conical-cross mounting clip first, as that gave a vital couple of centimetres more clearance for my hams, and it was then possible to push the connector up against that same mounting plate to gain more pressure on the release. The lower one can be done another day...

Did you take a look in at your pre cats through the sensor hole ?