82 replies to this topic

[Robbie693]

Thanks FS. Had another go and managed to get a reading, the resistance tracks smoothly with no dropouts so TPS appears ok.

 

Re-checked the valve clearances - all ok.

 

So what's next? Lambda? Stepper motor?

[genpop]

You could check if the heater for the lambda probe is working. If lambda is not working,then ecu stays in limp mode that means lambda is not working and rpm is slightly higher.Disconnect lambda probe and measure at the socket.(Ignition on).If you have a laptop you could buy a cable for connecting to the ecu.At rmrsoft there is a data logger and analysing software for spi.Google for mems gauge and mems analyser.Attached is the diagram for the measureing.And of course there are other faults possible.E.g. if the thermostat opens to early and the coolant doesn`t reach 88°C ,the ecu still stays in limp mode.If the coolant thermometer ( in manifold) does not work exactly same problem.

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[Robbie693]

Ok thanks, I'll try voltage testing the lambda.

 

I'm assuming that if the Tstat opens too early I would see this on the gauge as a below normal running temp condition at this time of year?

[genpop]

"I'm assuming that if the Tstat opens too early I would see this on the gauge as a below normal running temp condition at this time of year?"

 

I fear "NO", you need test equipment. The difference between 87 and 89 is that minimal that you don`t see that at the gauge.Test equipment like mems gauge ,mems diag, mems rosco, mems-scan,acr,testbook and so on , show the temperatur signal what the ecu receives. If this signal is below 88 , ecu will not switch to closed loop.Even when all other parameters are in their range.

 

"Ok thanks, I'll try voltage testing the lambda."

 Not the lambda, the circuit for the heater supply. There`s a heater spiral inside the lambda probe. If the lambda doesn`t have a certain temperature it will not start working.

[Robbie693]

Ah I see. Ok thanks.

 

May be worth replacing the T Stat anyway as it's fairly old, I may have bunged it it up a bit when I was flushing the cooling system too.

[Robbie693]

Replaced the thermostat, the one in it, which has even there for about 10 years, was a 74 deg. How is been running fine up until now is anyone’s guess... Anyway, I replaced with an 88deg but it hasn’t made a difference.

So I checked for voltage at the lambda plug but got nothing. Checked continuity on the blue/red wire from the plug to the relay socket - ok. As is the black wire to earth. I have power coming in to the relay but nothing going out to the lambda plug as far as I can tell with my limited sparky talents. I tried the relay in the aux fan socket to test it and it works ok

I feel like I’m onto something but i’m not sure what!

[Robbie693]

Now looking at the wiring diagrams... Haynes 12 -41 shows the ECU circuits. Looks like the brown wire from the lambda plug goes to a fuseable link (item 32). I recall years ago I had problem with a short which melted the fuseable link in one of the alternator wires. Could this be the same fuseable link or are there others?

[genpop]

Sorry, I can`t find a fuse what is in charge for the lambda relais.I will attach both parts of the diagram. Now after you have tested the relay you should check if there is current between 86 and 85 at the relay.(blue). If not, i would have checked the ecu, even ecu`s cross the river.

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[Robbie693]

Ok Thanks, I'l check the pins you suggest.

 

I've attached the diagram from Haynes, the fusable link is at the bottom, item 32, brown wire

 

[genpop]

This is a very old and universal diagram. Mine is for year 1994 onwards.

[Robbie693]

Yes it now appears so! - Some of my wire colours don't match up to my diagram, the alternator and starter for example..

 

No luck with the fusible link - the one I was concerned about is in the starter motor line so not relevant,

 

So I checked the current between 86 and 85 at the relay and only got 0.2V... This was with the relay in place and checking the current on the pins at the bottom of the socket

[genpop]

I fear your ecu is defect!

Isn`t there a mini club in Birmingham that you could compare with a known good ecu?

[Robbie693]

I've found a place that can do a diagnostic. If it needs a rebuild then I guess it's off to ATP as they are nearby to me.

 

If I have it rebuilt is it just a case of refitting and starting it up?

[genpop]

I've found a place that can do a diagnostic. If it needs a rebuild then I guess it's off to ATP as they are nearby to me.

 

You need a place where they check and repair ecus!

 

If I have it rebuilt is it just a case of refitting and starting it up?

 

If nothing else is damaged, yes.

[Robbie693]

Hmm, does that mean a standard Rover diagnostic wouldn't show an ECU problem?