[Mk2] [Turbo] re: Think my ECU has gone, repair or replace ?

[Total Recall]

Hi, it`s 93 MK2 Rev 2 Turbo.

My MR2 will sometimes start up and sometimes not. When it won`t run the CEL light doesn`t come on when I turn the ignition on.

Sometimes the light comes on faintly or even flickers (not flashes) and when this happens it will start up but only keep running using throttle and sounds pretty rough. When it flickers I can`t even get it to go into diagnostic mode.

The odd time the light comes on as normal and the engine idles fine and sounds smooth - and I can check codes etc. as normal - but usually after a couple of minutes running (or even just with the ignition on) the CEL light starts to flicker, with relays frantically clicking in the engine bay and it eventually shuts off again.

I`ve checked loads of stuff, tried bypassing various relays to eliminate whether its them, checking voltage and continuity at the various ECU wires - and I`m 90% sure its my ECU itself.

I can`t say 100% but looking at the MR2 manual diagrams for the diagnostic circuit I can`t see anything else in the circuit that I haven`t checked that could cause the CEL light/diagnostic mode to be affected.

I took the cover off the ECU and looked under the circuit board and found what looks like what other ppl have seen on theirs - but I thought I would check here first to see if this looks likely - though looking at the pic I`m fairly sure if it isn`t a problem already, it will be soon!



The ECU is labelled 89661 17380.

Would it be best to get my current ECU repaired - or does it look too bad and need replacing? If so, any leads on where to get one?

Cheers for reading!
Dom.

[MartinF]

That definitely needs fixing.

It's a bit hard to tell if it's repairable until somebody starts to clean up the tracks.

[Peter Gidden]

That definitely needs fixing.

[Total Recall]

Lol.

Cheers guys, yeah better get it sorted - possibly a bit too late for preventative maintenance!

The only bit of hope for it is that it`s only borderline not working - somewhow it does sometimes work ok for a min or two, so maybe theres a chance it won`t be as bad as it looks once cleaned up.

Thanks again,



Dom.

[markstevieandmads]

Get that repaired as if u buy another it may need doing anyway.

There is a few threads on here Iincluding mine about this. If it's beyond repair then buy another and get the common caps replaced before they go again.

I'm using my repaired one now but have a spare just in case which needs them doing before it happens.

[Total Recall]

Hi, yeah looking at ur thread, mine seems pretty bad.

I have got another one coming just in case - though as you say no guarantees it won`t happen on that one too, so will replace the capacitors anyway.

Cheers,
Dom.

[Dame]

If it's just those tracks that have gone I'd say it's definitely repairable (I've repaired many retro computers with similar damage).

What you need to do is see if each track leads to a solder point it could be anything from a component leg to those little solder pads. As long as you can find a way to hook an appropriately sized wire to each end without bypassing any inline components - if there is a component in the way then solder your wire to that first then if necessary take it on from there. If you have no soldering experience I'd strongly recommend that you pass it on to someone who does.

If you do have a go yourself, study the board very closely since an incorrect connection could cause all sorts of bizarre issues, worse - if it's an incorrectly placed power line, it could fry components.

[Total Recall]

Hi, just an update.

First thanks for the info - I will get my old one repaired. If the tracks were a bit further appart I would have a go myself doing it with wires if neccessary but I have a few friends who are way better at that stuff than me, so will ask them to have a go, though I c what u mean about finding component solder points making it a bit easier.

Now I`ve got the other ECU - and surprisingly it hasn`t hasn`t fixed my problem.....

At least the ECU light now comes on every time the ignition is on and I can check for codes every time and jumper e1 + te1 to get the timing etc.

So far it`s not setting any codes though.

I have spark and the plugs are getting wet, so it`s got fuel - compression is 155-165, but it still hardly ever gets going properly - except the odd occasion when it`s perfect.

I had a look at a few youtube vids of MR2`s barely running and tbh I would have said mine sounds exactly like when the timing is out - but I don`t know what could cause the timing to be out one minuite and perfect the next, as the odd time that it runs fine, I have checked the timing and it`s spot on (e1 and te1 connected).

Could the igniter cause a problem like this - I thought they either worked or didn`t work at all giving no spark - but can it mess with the timing randomly sort of half failing?

It`s just like sum1 flicks a switch and it goes into scooby firing mode!

Replacing the ECU has still been worth it as there was obviously a problem with the diagnostics on the old one - and I have replaced the coil as the old one had a few cracks in it. Also I`ve ohmed the HT leads so don`t see any point in buying new ones as the readings all make sense for their length.

I`m not sure what`s the next most logical thing in line to check though.

I`ve had plenty of ideas from old forum posts but so far nothing seems to have solved the problem.

Any other ideas ?

Cheers!
Dom.

[Peter Gidden]

Check cam timing. Then you'll know it hasn't jumped a tooth through a weak tensioner. If cam timing is correct, assumimg you haven't messed with it, distributor timing must be correct. If all OK you know the engine mechanicals can be eliminated.

You don't want wet plugs. The spark is designed to ignite a fuel vapour, not a puddle. Remove plugs, stick them in a blow torch flame and refit.

Then if you have spark and fuel it'll either fire or not. If not come back.

[Total Recall]

Hi thanks for the reply.

Yes I checked cam timing first thing. This was a few days ago - but since then it has run properly and badly. Just to check I`m doing it right - the crank pulley at zero and the marks on the cams (with the S and little dimple) pointing at the indentations on the back plate. I will check again 2moz tho as it`s only a 10-15 min job to make sure nothings changed.

I haven`t moved the dissy and the odd time it has run with the latest ECU I`ve checked and the timing is about 8 degrees.

I did clean up the plugs and dry them off - and this usually gives it a bit more of a hint of firing - the longer you keep the starter going, the faster and more it starts to fire - but it doesn`t make it run smotth even if eventually gets going. If it`s going to start and run properly it starts the second you crank without delay and runs perfect right from the off.

It appears to have spark, fuel and compression, so surely it should fire every time?

I checked for spark with a sparkplug tester at the plug - but I will take a plug out 2moz and check the spark visually to make sure it`s a good one.

Thanks again,
Dom.

[markstevieandmads]

Stupid question - is there an aftermarket immobiliser on there? Reason being is its strange it fires fine sometimes and others not. Sounds electrical...
Has the new ecu been checked for same problem?
I know u said u get cel but I would still check.

[bobhatton]

If the plugs are old try a new set as it sounds like the engine is getting flooded, lots of fuel but weak spark will do that.

[Total Recall]

Lol you won`t believe it - I looked at them this morning and thought - I`ll put some stock plugs in - (there were grade 8 NGK iridiums in it) - and it started and ran fine.

Not building up my hopes yet as it has started before and then not the next day or even later in the day - but I have tried again tonight and it`s started up smooth as anything. Proper test will be in the morning.

I`m wondering if there is some cold start problem with it though - as surely it should still start with the grade 8 plugs? Could the injectors not be spraying properly making the plugs foul more easily ?

I had cleaned them all up nice - but they were wet and fouled each time I took them out after trying to start it. I was putting it down to something causing them to foul (which it still may be) rather than the plugs themselves being the problem.

As for the immobiliser - not a daft question as I really hope it is something obvious that I have missed - but in this case it doesn`t even have an alarm or remote locking!

I checked inside this latest ECU and there are no leaking capacitors - so far - but as soon as I get my old one sorted and confirmed working, I`ll replace the ones in these.

Thanks everyone for the ideas - I will deifnitely post back whether it has been sorted or not but I`m going to make sure it`s ok for a few days b4 I decide it`s fixed.

It`s still wierd that the original ECU failing was coinciding with it not running yet the new working ECU didn`t solve the running problem but new plugs may have....

Cheers
Dom.

[markstevieandmads]

When my ecu failed in the same way, I also found out that my CEL bulb was missing and my air flow meter was faulty so in a way its helped me sort other problems too.

[Dame]

Great news if you've sorted it. If you haven't one other thing to consider is the wiring loom. I had similar problems to you a few years ago and it turned out that a broken loom was responsible - robbing the sensors from being able to send correct signals some of the time but not always. Anyway maybe something to check.

[Total Recall]

Well the car is still running fine so I think (well hope) it is sorted!

Definitely seemed to be a combination of problems - a dodgy ECU and the plugs which it didn`t like.

Yes, really helps having the cel bulb working - otherwise every slight probem ur wondering if the diagnostics would have given u an easy fix.

I had a wiring problem causing similar problems in my old REV1 turbo - think it was 1 of the wires going to/from the dissy (the connector at the back), took ages to find - just by wiggling wires as a last resort in the end as it was completely random. I thought this might have been the same, so was the first place I looked - but they were all fine. So just shows u can have similar problems with different causes.

Thanks everyone,



Dom.