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Discussion Starter #1
Looks like a problem I had before, but exploring what you guys think because they are supposed to be fixed already.

Went somewhere, only stopped the engine for 5 minutes, then starting it again (still warm) it started to be really rough, with check engine light (found later code 54), rpm going up and down between 400 and 1200rpm almost stalling. Then after one minute was fine. Moved to the other work place a kilometer away.

Starting it again to go home, after 40minutes sitting there, it just doesn't start at all and same check engine light comes on. After many tries, does not want to start at all. Called for a towing, took 10 minutes to end the call, tried to start it again and it started, rough but started, and check engine light went away after a few seconds. Told them I didn't need assistance anymore and moved quickly out of there before it does it again.

On the way home (30km) the check engine light came once and I lost power, engine still running but as if I wasn't giving it any gas (which I was), no throttle, slowing down, but only for 2-3 seconds, after that it was fine again and was able to make it home just as usual, boosting correctly, everything as usual.

Those sympthoms remind me of the 2 main problems I had. ECU capacitors and fuel pump relay/resistor. Maybe I didn't do the capacitors correctly and they're done? Or it's other capacitors this time (I changed only 2)? Also when I had a capacitor problem the same 54 code came on. But for the fuel, at least the fuel pump was defenitely working (bypassed the relay) as I was hearing it when starting the car.

Tomorrow I'll look at the ECU maybe and try to see if something is wrong with it. Until then do you have any other ideas?

Another detail, changed the coolant temp sensor just a week ago, added more fluid, but noticed it had a tendency to overheat after, temp was going way higher than usual (only at idle for 10-15 minutes, if I am driving, it's at normal temp.) I guess I have bubbles in the system? Someone told me to try to drive it with air climate to warm and full blast, didn't do anything apparently, so I guess I need to burp it? Any advice? I'm saying it here because I have no clue if those two issues are related. Better have more infos than less!
 

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Definitely bleed the coolant properly. The gauge should never go above half way. Check how to do it with the clear tubes off the radiator and heater pipes up front. Buy the correct O ring for the radiator bleeder as it will leak when you try to do it back up as they are old. Happens every time when I have worked on multiple cars. Still sounds like the ECU isn't behaving, get it fixed and see if you have any issues afterwards.
 

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Discussion Starter #3
Definitely bleed the coolant properly. The gauge should never go above half way. Check how to do it with the clear tubes off the radiator and heater pipes up front. Buy the correct O ring for the radiator bleeder as it will leak when you try to do it back up as they are old. Happens every time when I have worked on multiple cars. Still sounds like the ECU isn't behaving, get it fixed and see if you have any issues afterwards.
Thank you I'll do that. And also tried to start it a few times right now, it worked perfectly as normal. did that before with capacitors too, started normally for many times then a few minutes after, it was completely dead. Symthoms are the same so, it sounds like that to me yeah, ECU
 

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Discussion Starter #5
I'd say, go find someone with a known good ECU to borrow and test but in your area with your ECU it might be very very hard to find that specific one.
It's just that "in my area" would be at least 200km away
 

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It's just that "in my area" would be at least 200km away
Where you hiding out? I'm in central Alberta. I don't have a gen3 ecu but I am pretty handy when it comes to wiring/electrical issues and am getting more and more adept at these cars and engine.

If yer close HMU and maybe I can see about giving ye a hand sometime. I'm probably a good week away from my '2 being drive-able (mostly waiting on parts) But once I have it happy, I'll be able to get to you (assuming yer close enough)
 

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Where you hiding out? I'm in central Alberta. I don't have a gen3 ecu but I am pretty handy when it comes to wiring/electrical issues and am getting more and more adept at these cars and engine.

If yer close HMU and maybe I can see about giving ye a hand sometime. I'm probably a good week away from my '2 being drive-able (mostly waiting on parts) But once I have it happy, I'll be able to get to you (assuming yer close enough)
Yeah well I'm in a rural area of Québec, so we're like over 4000 kilometers apart sadly

Also I'm thinking someday instead of buying an old ECU that will also break eventually because they are old to get a brand new ECU ready for tune, ATS sells a Link ECU for the MR2s with their own base map, what do you guys think of that?
 

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The first thing I had to do when I got my SW20 was replace the ECU. The car started acting up just days after I bought it, despite two problem-free test drives with the seller and a smooth ride home. Very bizarre symptoms, a lot of the same ones as yours.. and they would come and go. My mechanic determined it was the map sensor, but changing it didn't do anything, which led him to believe it might be the computer itself. I actually checked if ATS had a direct replacement unit on hand (I live close to them), but they did not. I ended up buying a refurbished ECU from All Computer Resources, changed it myself (very easy job) and the problems cleared immediately. Still haven't had any issues even close to that since, except for when the car began stalling occasionally at idle while the AC was on. This went away after replacing the alternator with a rebuilt Denso unit, though.
 

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Discussion Starter #10
The first thing I had to do when I got my SW20 was replace the ECU. The car started acting up just days after I bought it, despite two problem-free test drives with the seller and a smooth ride home. Very bizarre symptoms, a lot of the same ones as yours.. and they would come and go. My mechanic determined it was the map sensor, but changing it didn't do anything, which led him to believe it might be the computer itself. I bought a refurbished ECU from All Computer Resources, changed it myself (very easy job) and the problems cleared immediately. Still haven't had any issues even close to that since, except for when the car began stalling occasionally at idle while the AC was on. This went away after replacing the alternator with a rebuilt Denso unit, though.
Yeah, I replaced 2 capacitors and the problem was solved immediately. But now the same thing, maybe the other capacitors? Anyway, the ECUs I found online for gen 3 were about 600 to 800$ US, and I could get a new one with base map for 1095$ and have it tune (so I would get some power/response gains with that too). It's a lot of money but I am considering it
 

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The only issue with getting an aftermarket ECU is tryna find someone to tune....
Make sure someone around knows the one you are putting in and can tune it.
The other factor is the actual tuning itself. It can add up.. the closest shop to me that offers it charges ~$350 as a minimum to get the car on the dyno and a basic tune with a pre/post tune sheet, then something like $100/hour if you want them to dig for a better tune.....

I've never had a stock ECU fail on me but can understand that it happens. If you aren't planning on pushing the power limits of the car, you may be better off getting another stock ECU to replace. The advantage of a NEW ECU would be that you know the guts of it haven't been "rotting" for 30 years. The disadvantage is the actual purchase price of the ECU is probably only about half of what it's gonna cost you to get it working.... some of them need different sensors than stock and also will require some wiring, which can be a little overwhelming for some people, then getting it tuned.... Adds up pretty quick.
 

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Update: I thought it might be due to humidity or something, because the problem happened only when humid/raining (it was very dry for 2 weeks and since it started to rain and have fog everyday it didn't like it. Also when starting it, white smoke at cold, then it was fine. No water on the engine either as I covered it.

But today the idle was higher than usual, even at warm, it would stay around 1200rpm, usually it would go down to 800. But it was driving fine, so I took it out, after around 40km, check engine light comes on, and I lose power. Like last time, but lasted more than 3 seconds, it kept doing it. The engine is boosting but doesn't want to go, looks like if I boost more it wants to slow down even faster. As if there was not enough fuel or something. Then I stopped on the side of the road, idle at 800, up, down, unstable, so I stop it. Doesn't want to start again, but as usual, I know I just need to wait for a bit until it starts... so I check for the ECU, the engine. All I could see is that some hose seems to be leaking on the valve cover, I have no idea what it is so I'll show a picture (from valve cover to the intake, so I don't get why it would be "leaking" but it does seem to shoot something oily around. I noticed because when recently torquing the spark plugs recently I cleaned the valve cover, I don't if it's related but I'd like to know what it is anyway, I'm here to learn.

Anyways, on the side of the road, I started the car a few times at intervals of 5 minutes. After 20 minutes it finally started, check engine light goes away after 2 seconds, runs fine, going home, no problem. Since a while also it does kind of misfire a little, I can tell at idle, so I am thinking maybe my distributor is done? Coil was replaced a month ago and I have an ignition control module on the way.
70861
 

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Starting simple, my mind immediately goes to an air bubble in the coolant.

I don't think it should be spitting that much oil. check level to make sure its not over filled.

Make sure the PCV valve is working properly.
 
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