Intermittent engine light

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DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Intermittent engine light

Post by DaveWS »

Hi all. For about 6 months now the engine check light in the dash has been on / off intermittently and I've no idea as to the cause.

It's never on during the very first few seconds of engine running, and after that it's on roughly 75% of the time and starts to turn off if the engine gets really warm (but not always).

Because it's never on until the engine runs, jumping the pins on the diagnostic port yields no error codes (I assume this can only be done with the engine off?).

Any ideas? Thanks
oVerboost
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Re: Intermittent engine light

Post by oVerboost »

Could be lambda related?
SonicSW20
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Re: Intermittent engine light

Post by SonicSW20 »

So to confirm, when you put it in diagnostic mode the engine light just flashes at you at a regular interval, indicating no codes stored?

How is the car running otherwise?
DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Re: Intermittent engine light

Post by DaveWS »

SonicSW20 wrote:So to confirm, when you put it in diagnostic mode the engine light just flashes at you at a regular interval, indicating no codes stored?

How is the car running otherwise?


Yep exactly. Car seems to be running fine!
tsango
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Location: Birmingham

Re: Intermittent engine light

Post by tsango »

I have the exact same issue. Orange engine light comes on when car starts to warm up.
Baldurbus
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Location: Valhalla

Re: Intermittent engine light

Post by Baldurbus »

Check ECU for leaking capacitors. I had same problem until I replaced them.

Thanks
Draven
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Re: Intermittent engine light

Post by Draven »

Baldurbus wrote:Check ECU for leaking capacitors. I had same problem until I replaced them.

Thanks


^^ i had the same problem but my car was bucking and coughing too. new ECU fixed the problem.
Baldurbus
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Re: Intermittent engine light

Post by Baldurbus »

Draven wrote:
Baldurbus wrote:Check ECU for leaking capacitors. I had same problem until I replaced them.

Thanks


^^ i had the same problem but my car was bucking and coughing too. new ECU fixed the problem.


Do you still have a old ECU?

Thanks
Draven
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Re: Intermittent engine light

Post by Draven »

Baldurbus wrote:
Draven wrote:
Baldurbus wrote:Check ECU for leaking capacitors. I had same problem until I replaced them.

Thanks


^^ i had the same problem but my car was bucking and coughing too. new ECU fixed the problem.


Do you still have a old ECU?

Thanks


That was many years ago, car gone with all parts.
DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Re: Intermittent engine light

Post by DaveWS »

Hi guys, unfortunately this is still happening :cry:

Something I've discovered today though, is it's related to the pump relay. Basically if I start the engine, after idling for 10-20 seconds, just as the engine is almost fully settled, the engine check light will turn on, and at exactly the same time, the fuel pump relay switches (I can feel it click).

Any ideas? :-k
platmatt8
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Re: Intermittent engine light

Post by platmatt8 »

Having the same issue,

Turn ignition on, dash lights up, fuel pump can be heard running, start engine ECU light stays on.

Car seems to drive fine, but have been reluctant to take it out.

It did go out after a 15min drive to work but can back on for the journey home.

Funnily enough I can get the ecu light to flash when using the paper clip diagnostic tool.
DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Re: Intermittent engine light

Post by DaveWS »

Yeah if I do the paperclip test it just flashes normally :(
SonicSW20
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Joined: Mon Nov 29, 2010 7:54 pm

Re: Intermittent engine light

Post by SonicSW20 »

What happens if you let it idle in diag mode? I am not sure exactly how the code reading works on an MR2, but perhaps it'll flash something at you if the fault occurs while in this state?
DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Re: Intermittent engine light

Post by DaveWS »

I tried that, basically the engine light flashes constantly at first, and then the light turns solid (matching it turning on when not in diag mode). It doesn't throw up a code :(

Weirdly if I remove the paperclip with it running and reinsert it again, the engine rpm picks up for a few seconds then bogs right down to 600rpm or so. :-k I guess the diag mode is only for when the engine is off because it seems to mess with the fuel mix or something.
DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Re: Intermittent engine light

Post by DaveWS »

Are there any non-critical relays I could swap out with the fuel one to see if that makes any difference?
DaveWS
Posts: 34
Joined: Sat Oct 01, 2016 7:09 pm
Location: Leicester

Re: Intermittent engine light

Post by DaveWS »

I've replaced the o2 sensor, still no luck: https://youtu.be/bB7t4IqJtp0
More: https://www.youtube.com/watch?v=EPV8AyRSgxQ
SonicSW20
Posts: 3681
Joined: Mon Nov 29, 2010 7:54 pm

Re: Intermittent engine light

Post by SonicSW20 »

DaveWS wrote:I tried that, basically the engine light flashes constantly at first, and then the light turns solid (matching it turning on when not in diag mode). It doesn't throw up a code :(

Weirdly if I remove the paperclip with it running and reinsert it again, the engine rpm picks up for a few seconds then bogs right down to 600rpm or so. :-k I guess the diag mode is only for when the engine is off because it seems to mess with the fuel mix or something.


Diag mode is used to set ignition timing, it puts the timing into static mode so a drop in RPM is normal.

Clutching at straws really... Have you removed the ECU and taken the cover off to inspect the board? They're at that age where capacitors fail which can cause all sorts of odd issues.
platmatt8
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Re: Intermittent engine light

Post by platmatt8 »

DaveWS wrote:Yeah if I do the paperclip test it just flashes normally :(


If I do the paper clip in the port the Light stays lit and doesn't flash at all.

I'm thinking ECU fault.

Might throw a video on YouTube for comparison.
platmatt8
Posts: 2113
Joined: Sun Sep 10, 2006 8:41 pm
Location: Blackburn (Home of the mighty Rovers)

Re: Intermittent engine light

Post by platmatt8 »

Draven wrote:
Baldurbus wrote:Check ECU for leaking capacitors. I had same problem until I replaced them.

Thanks


^^ i had the same problem but my car was bucking and coughing too. new ECU fixed the problem.


Was the coughing and bucking present at any particular instance.

Mine coughs and bucks in 4th or 5th under slight load
platmatt8
Posts: 2113
Joined: Sun Sep 10, 2006 8:41 pm
Location: Blackburn (Home of the mighty Rovers)

Re: Intermittent engine light

Post by platmatt8 »

Just pulled the ECU and found a leaking capacitor C512 it's a 10mf 50v.
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