Pre-cats: The Official MR2-ROC Information Thread

[Anonymous]

There are after market manifolds which will replace the oem manifold, but if you are asking if its possible to replace the pre cats with other pre cats the answer is no.

[Anonymous]

Hi,  Sorry if this ends up in the wrong place but I'm new to these 'puter things!
I have had an MRs jap import for a few years. It's a toy for me so I only do maybe a thousand miles a year in it. It's done 55k and has always been a little thirsty on the oil front. Going up the A34 on thursday all was fine, cruising bout 75ish when I noticed a slight lack of power then a huge amount of blue smoke from the exhaust. Luckily there was a layby not far and limped it in. I am fully aware of the precat thing and suspected this could be it but... the AA recoverd it home and on close inspection the coolant level has risen about 2 inches in the expansion tank, low oil but still just on the dipstick. No horrible noises at all and on testing the compression I got an even 13 bar from all cyls. The plugs are very black and oily but when you start the car there is no pressure from the dipstick tube, which is telling me that the sump isn't under pressure (which it surely would be if the main cat had collapsed). I can't believe that the oil rings on the pistons have all failed together instantly??!! I am now miffed and don't want to lash out on a new engine until I am sure it is terminal. Basically, the engine sounds and runs fine exept for the smoke sreen of blue smoke coming from the exhaust. Any thoughts? Cheers tootall

[mrzwei]

Blue smoke + oiled plugs = oil getting into the combustion chambers. Only two ways for this to happen (assuming non turbo) , either past the piston rings or down the valve guides; The history of the 1ZZ suggests the former. According to a US MRs chart the compression pressure should be 184 psi (+/- 15) which would seem to be about right in bar however, the presence of oil in the combustion chamber will tend to form a seal on the rings and can distort the compression reading. (The test to distinguish between worn valve guides and worn rings is to do a standard compression test and then pour some oil into the combustion chamber via the plug hole and test again. If there is no change then it is probably guides, if the compression increases then it is probably rings / bore). I would test the compression again with the engine unused for a while and really cold.
Another possibility is a blown head gasket but you would normally only get an issue with one cylinder.

[Anonymous]

There are after market manifolds which will replace the oem manifold, but if you are asking if its possible to replace the pre cats with other pre cats the answer is no.

Not quite true,there are some U.S. made units but then if you don't live in California why would you.

[Anonymous]

Cheers for that. I have just had the exhaust system off and to my amazement the precats are still in place and undamaged!! The main cat seems to be OK (basically it's not blocked and intact). I have fitted a new catless manifold. Drained the oil and nothing nasty looking at all. Refilled and started her up. Still smoking blue with a bit of white. Engine sounds fine apart from a very slight misfire. Like you say, if the head gasket was suspect it would surely point to one cylinder. Anyway, I am going to pull the head next weekend and see whats going on as I have now run out of ideas. On the bright side, if it turns out to be terminal I may well look at getting a 190 celica engine to drop in . I am sure there is a firm in Andover somewhere that has done a few already. Anyone has more ideas on the smoke I would appreciate any input.

[Anonymous]

There are after market manifolds which will replace the oem manifold, but if you are asking if its possible to replace the pre cats with other pre cats the answer is no.

Not quite true,there are some U.S. made units but then if you don't live in California why would you.

To pe pedantic, that is a replacement manifold and pre cats, not replacement pre cats, so my answer was correct, the pre cats cannot be replaced.

[mrzwei]

The blue smoke is definately oil and the white smoke is steam which really does suggest head gasket but if you are pulling the head anyway then I guess you will find out. Good luck.
Not many posts on head gasket failure here and the recorded miles are pretty low for these sorts of problems.

[Anonymous]

Cheers mrzwei,
With a lack of horrid noises, precats being intact, very good even compression, no foriegn bodies in the oil , the fact it happened instantly and the coolant level has risen a fair bit as well, it does really point at head gasket. I just can't understand how the oil has got from one pot to the other? Unless it's possible that it has travelled via the exhaust manifold somehow? The head is coming off anyway, hope something will be obvious on removal. Thanks for your thoughts.

[Anonymous]

Thanks to everyone who gave suggestions.  Head removed and no glaringly obvious faults. The valves all look fine, must be coming up through the pistons. Bummer.  Have sourced an engine from a wreck, 04 plate with 43k on it. Been through a hedge backwards cat c right off. had to part with 1100 sovs for it but only breaker who would guarantee mileage and age and give 6 months warranty. Being delivered on wednesday. Fun weekend for sure. Have got a decat manifold from the states to go straight on. MOT in a couple of weeks so gonna wait and see how she does on emmisions before I splash out on a new cat.  Been hell watching everyman and his dog tootling round with their tops down all weekend and my poor baby all sick and stranded in the drive!!  Hopefully more clio bating to be done once new lump installed. Again thanks to everyone for their help and hope to see you on  the road shortly.   Tootall.

[Anonymous]

If your pre cats went, replace the main cat or it will kill the new engine.

[Wabbitkilla]

If your pre cats went, replace the main cat or it will kill the new engine.

+1 for definite ... no joking here, we've seen it before many times.

[Anonymous]

Thanks for that.
I won't wait then!!  After doing 1100 on a replacement block and head, another couple of hundred on a main cat gotta be worth doing.  The amount of oil that must of passed through it, I am sure hasn't done it any good. Hopefully be back on the road in a couple of weeks. Will strip the old block when it's out and see exactly what went wrong.  Cheers again.

[tequilla]

My second engine went wrong...third engine is on the way   s8) s8)  

http://www.youtube.com/v/140JpPfIhww

[spuggy]

thanks for a good thread guys
i followed these instructions and de catted my pre cats last weekend.....no signs of wear on my 2001, 67000 miler but i just wanted to be on the safe side  s:D s:D  
turned out to be quite an easy task in the end...i even managed to keep all my knuckles intact  s:bounce: :bounce: s:bounce:  
so a BIG THANK YOU to all who have commented/advised....your help was really useful  s:bowdown: :bowdown: s:bowdown:

[Anonymous]

Just like to say a big thanks to everyone for their help when my engine went bang... I have know fitted a low mileage 2006 engine from a celica!! Had to swop the engine mounts, injectors, inlet manifold and the oil dipstick over but otherwise a straight swop. Now running with a jdm racing manifold (no precats) new underfloor cat and TTE exhaust. Sounds glorious but not offensive. Zipped through it's MOT last week and now I remember why I bought the car in the first place!
It seems that I had worn oil rings (2000 engine) and just hadn't noticed really. The head gasket went and pressurised the bottom end pushing even more oil into the block. The precats were actually still intact so I guess I was a victim of the naff early piston design thing?
Can also recommend Hills salvage of Lancashire. They weren't the cheapest but were the only quality yard I could find who not only guarantee the mileage and age of the donor car but gave a full written guarantee as well.
Anyway, if you see a black MRs with full factory bodykit and TTE pipes with a smiley dude behind the wheel this summer, that will be me!
Thanks again.

[furkh]

HI ALL!

Can anyone tell me of a garage in the huddersfield/west yorkshire area that will remove my pre-cats?

or anyone know of where to buy adetted manifold/downpipe?

I've had my engine swapped successfully, but i need to now go one step further and remove the cats...

Many Thanks

[Anonymous]

Did you look Here.

Replacement headers can be bought from che on spyderchat,  m http://spyderchat.com/forums/showthread ... -48-States m

[Anonymous]

Just spotted these on Ebay. Anyone any experience of these? Seem cheap enough.....

 m http://cgi.ebay.co.uk/Toyota-MR2-Roadst ... 5d29dc1878 m

[Wabbitkilla]

No experience with them, but they are missing the lower bracing which prevents tubular manifolds from cracking.

[Anonymous]

 s:D s:D  OK good call, I'll disregard it then. Cheers

[weddallenko]

Hi Guys,

I've just signed up to this club after looking up advice in the forums, thought I may be able to contribute something (maybe!)

Well, I bought an MR-S back in October 2010, a 1999 W reg. Only had 55,000 on the clock and it has been fantastic.
Up until recently I checked the oil say once a month, but a few weeks ago I noticed it was very low, no changes in performance or engine sounds - also no oil warning light lighting up. No exhaust smoke and no oil leaks on the drive way....

I paid a trip to my local Toyota dealer and spoke to a very knowledgeable mechanic there, he explained that the 1ZZ engines can be "real oil burners" and gave me the impression it may be ok. He explained that Toyota had extended the warranty on these engines, providing it had full service history.... and "only lost" 1 litre of oil per 1000 miles...
So I dug out the service books and went back the same day....
Unfortunately, he had found out the extended warranty only applied to cars less than 7 years old (bugger) and if the car had full Toyota service history (bugger).

Having read about Pre-cat failure and the damage caused, I am bricking it....
I have yet to take out the O2 sensors and have a look but am I too late? Where do I go from here?
Any advice no matter how brutal would be greatly appreciated,

Thanks in advance guys.

[markiii]

check precats, remove, change oil and hope

main cat may be toast depending on the state of the precats

[scipio]

...have been following this thread with interest ....bought mine last year Oct....2002 model, 44K km's (in 8 years!?), thought it was a Toyota -  you can't go wrong! A Yaris (do you have them in the UK..? smallest of the Toyota range) with the same k's would cost me the same...for my wife (of course!). Started reading...joined the club...heard about the pre-cat thing...was told about oil usage on purchase...didn't care, I just loved what I saw...bought her anyway!

Over the weekend, slowing down to 60km/h (from 140) I noticed she was running on 3 cylinders, CEL came on, I thought it was a faulty plug.

She had been using almost a liter of oil every 550k's - that's a hell of a lot...performance was still good (although I did not have a yardstick to measure from) and I felt that if the engine goes, so be it, I had a policy covering any mechanical failure.
Well, this weekend was that time.
A piece of pre-cat lodged itself in one of the valves and broke a small edge off the valve....allowing the exhaust to breathe freely and cause the cylinder to fail.

She's at a reputable Toyota dealer (voted best in the country a couple of times) and I spoke to the mechanic personally....told him what I read...he handed me the outlet manifold and there it was....cracked pre-cat on both sides....checked the play on the pistons in the block...Paul (the mechanic) said that there was excessive play....hence the oil usage.
I have put in a claim for new valves, new rings and bearings....I hope the claim goes through!
They have to include the new outlet manifold and pre-cat in the quote but have given it ( the manifold) to me and I proceeded to clean it out this afternoon...screwdriver and mallet...no problem.
Started reading intensively about 02 sensors - Paul reckoned that the pre-cat sensors would communicate it's info...the post-cat sensors would do the same and the computer would still spit out the right amount of fuel. Reading all the posts, including the official vote, it seems as if no mod is needed on the sensors...IS THIS CORRECT?...IS PAUL CORRECT?!   s:bowdown: :bowdown: s:bowdown:  
thanks for your time...

[scipio]

can anyone tell me if I need to replace my main-cat or can I clean it with compressed air....also, what is the story with the 3 O2 sensors....have been reading a lot on the forum but there seems to be differing views....can anyone help?
My '2's engine is in a million pieces as I type this...  s:flame: :flame: s:flame:

[Anonymous]

I would replace the cat, why take the chance on fubaring a new engine?