Cold Start Issues & Lambda Light ECT Issues ’91 940 B200FT

[StrongSpearWorks]

Originally Posted by Laird Scooby

Just had a look on FAE and it seems they don't differentiate between the engine management and gauge temperature sensors. .

Typical. Well I'll swap it again when I get home (as long as I can get it started again and see what happens.

[Laird Scooby]

Originally Posted by StrongSpearWorks

Typical. Well I'll swap it again when I get home (as long as I can get it started again and see what happens.

Just re-read your original description. What colour is the smoke you're getting when cold? I'm wondering if there's a completely different fault. Also when were the plugs last changed and what gap did you set them to?

[StrongSpearWorks]

Originally Posted by Laird Scooby

Just re-read your original description. What colour is the smoke you're getting when cold? I'm wondering if there's a completely different fault. Also when were the plugs last changed and what gap did you set them to?

This is an extension of another thread - you were heavily involved in that too about it smoking white (with a bit of blue) after a hot start.

Until I swapped this sensor, I'd not had any starting issues at all... bit of a lumpy idle, but never any trouble starting.

The faults codes read that there was a missing signal from the EZK side of the ECT - hence the new sensor, after setting about it with a multi meter.

No idea when the plugs were last changed. I've only owned the car for a couple of months.

[Laird Scooby]

Originally Posted by StrongSpearWorks

This is an extension of another thread - you were heavily involved in that too about it smoking white (with a bit of blue) after a hot start.

Until I swapped this sensor, I'd not had any starting issues at all... bit of a lumpy idle, but never any trouble starting.

The faults codes read that there was a missing signal from the EZK side of the ECT - hence the new sensor, after setting about it with a multi meter.

No idea when the plugs were last changed. I've only owned the car for a couple of months.

Is that the one where the suggestion was made to inspect and clean your intercooler internally?

What i would suggest now is refit the original sensor and reset the ECU. Take it for a drive and see what happens.
Have you cleaned out the PCV system since you've had the car? Also do you have a compression tester?

[TonyS9]

If there is a particularily pronounced cloud of blue smoke on start up you may have worn/damaged inlet valve seals. The little rubbers on inlet valve stems. Normally B200's are pretty valve guide wear resistant, but the rubber can go off.
Possibly the turbo is worn.

I doubt you can damage the ECUs with the wrong sensor.

Dave, on consulting my pin out reference for the EZK, you are partially correct in that it does use the temerature signal, I had made a wrong assumption there, but its not used when the engine is cold, its for when its "above" normal apparently.

[StrongSpearWorks]

Originally Posted by Laird Scooby

Is that the one where the suggestion was made to inspect and clean your intercooler internally?

What i would suggest now is refit the original sensor and reset the ECU. Take it for a drive and see what happens.
Have you cleaned out the PCV system since you've had the car? Also do you have a compression tester?

Yes, I flushed the inter cooler with degreaser, the PCV system is the first thing I changed when I got the vehicle.

It’s currently running the old sensor again after the new one made the symptoms worse... which makes me think there’s a bad ground or a broken wire in the break out cable from the loom.

So the order of events were;

Original sensor threw codes, on the EZK side but not ecu. No starting issues.
Replacement sensor threw codes on both ecu and ezk, including hard starting, lambda light on, rough running until warm.
Replaced the original sensor. Hard start, lambda light and rough running remain.

[StrongSpearWorks]

Originally Posted by TonyS9

If there is a particularily pronounced cloud of blue smoke on start up you may have worn/damaged inlet valve seals. The little rubbers on inlet valve stems. Normally B200's are pretty valve guide wear resistant, but the rubber can go off.
Possibly the turbo is worn.

This is an odd one. The smoke only occurs on a hot start, and not instantly... it comes about 1/4 mile down the road... clouds of smoke which then clears and is fine for the rest of journey.

[Laird Scooby]

Originally Posted by TonyS9

If there is a particularily pronounced cloud of blue smoke on start up you may have worn/damaged inlet valve seals. The little rubbers on inlet valve stems. Normally B200's are pretty valve guide wear resistant, but the rubber can go off.
Possibly the turbo is worn.

I doubt you can damage the ECUs with the wrong sensor.

Dave, on consulting my pin out reference for the EZK, you are partially correct in that it does use the temerature signal, I had made a wrong assumption there, but its not used when the engine is cold, its for when its "above" normal apparently.

It seems we've both found two different sources of information Tony, if i could find the one i had again then i'd link to it but to me it makes more sense that it uses the temp signal to advance the timing when cold and retard when hot - whether it does that by automatically starting the advance at a higher point and then retarding once up to temperature or selecting the advance from a table and referring that to the actual temperature is another matter.

Same end result though, the timing is retarded once up to temperature.

Originally Posted by StrongSpearWorks

Yes, I flushed the inter cooler with degreaser, the PCV system is the first thing I changed when I got the vehicle.

It’s currently running the old sensor again after the new one made the symptoms worse... which makes me think there’s a bad ground or a broken wire in the break out cable from the loom.

So the order of events were;

Original sensor threw codes, on the EZK side but not ecu. No starting issues.
Replacement sensor threw codes on both ecu and ezk, including hard starting, lambda light on, rough running until warm.
Replaced the original sensor. Hard start, lambda light and rough running remain.

All of this is pointing towards broken wiring to the sensor. For example, when my engine is cold, the oil pressure warning light doesn't work - if i wiggle the wiring it comes on.
Once the engine is warm though, the oil pressure warning light works every time.

Perhaps you need to check the wiring back from your sensor, longer and more involved but it's a possibility.

[StrongSpearWorks]

Originally Posted by Laird Scooby

All of this is pointing towards broken wiring to the sensor. For example, when my engine is cold, the oil pressure warning light doesn't work - if i wiggle the wiring it comes on.
Once the engine is warm though, the oil pressure warning light works every time.

Perhaps you need to check the wiring back from your sensor, longer and more involved but it's a possibility.

Reading this: https://www.volvoclub.org.uk/faq/Eng...ingECTFailures it says to take the plastic cover off the ECU to access the rear of the pins, to test voltage to the sensor.
How on earth does this come off?

[Laird Scooby]

Originally Posted by StrongSpearWorks

Reading this: https://www.volvoclub.org.uk/faq/Eng...ingECTFailures it says to take the plastic cover off the ECU to access the rear of the pins, to test voltage to the sensor.
How on earth does this come off?

First, disconnect the battery. Remove the drivers kick-panel trim and under-dash trim panel and locate the LH-Jetronic (on the side of the kick panel) and EZK ECUs, remove them from their clips and you will have a pair of ECUs dangling on their wiring, a bit like this :




Press the metal retaining tang down towards the ECU body :




Then lift from the cable end of the plug, noting the hook on the end that locates under a bar on the ECU :




Remove the screw securing the halves of the plug together :




Turn the plug over to find the rubber seal :




Lever it up carefully using a small screwdriver :




Pull the seal out carefully :




With the seal removed :




...... you can now ease the actual plug out of its housing :




............ to gain access to the connectors to enable back-probing :



Rebuilding, you "Haynes it" but ensure the seal sits squarely and ease it in with something wide, flat and blunt or the length (not the tip!) of the screwdriver blade. Note that the first remaking of the plug to ECU will be extra tight as it recompresses the seal.

With the plug disassembled as above, the plug can be refitted to the ECU to enable live testing or use a multimeter on resistance ranges to check continuity from the ECU plug to the component (CTS/ECT) and check resistances across the two wires feeding the sensor.

Just FYI, that's an ABS ECU which lives almost directly above the LH-Jetronic ECU, however the plugs are very similar so this guide should give you a good idea of what's needed.