Replacement engine

[littlepolo]

The saga continues...

Disconnected ECU plug adjacent battery, cleaned with electrical cleaner and reseated. Battery was on charge overnight. Removed airbox to access throttle body, vacuum pipes, etc. Engine started first time and idled OK from cold. Coolant reservoir was down slightly but since the heater is now working (again) I took that as a good sign.

I had reset the codes and then looked at the fuel trims, short term was -25%, long-term was 0%. The short-term value seemed not to change.

Did a gas test with propane and there was no change in engine rpm when I sprayed around the vacuum pipes, inlet manifold, etc. The only hissing I could hear was from the throttle butterfly and when I sprayed a short burst of propane here the engine soon stalled. Coolant temp was up to 52C at that time. Attempted restart - engine fired first time and then stalled right away.

Not sure how to interpret the short term fuel trim but this seems not normal - the value was -25% from cold until the engine stalled. What could be the issue here?

[bvs]

Well done for getting this far LP
The short term fuel trim with a minus value I think means that the ecu thinks that the mixture is too rich ?
The simplest item to cause that might be the coolant temp sensor (CTS) or wiring/connections to the CTS.
Do you have a spare CTS to slave into the engine ? might be worth a try ?
I guess you maybe have too many fault codes to help diagnose ?

rgds baz

[littlepolo]

I found the fuel filler cap was loose so tightened it up. Engine fired first time as usual. STFT went to -50% and still no warning codes.

Engine ran for a minute or two before it stalled. Coolant indicated 22C at the time. If fires on key but will not run.

The ECT display on VCDS appears to correlate with ambient temp when cold, then warming up to around 90C (before). Now I cannot get it to run long enough to get up to temp. In fact, it seems to be getting worse (very high compensation for calculated overfuelling and running for shorter intervals before staling. There is no smell of excess fuel.

Will it run with the ECT sensor disconnected?

[littlepolo]

Some VCDS data:

Group 032 Bank 1 Lambda Control 0.0%, Bank 1 Voltage of Oxygen Sensor 2.310V
Bank 1 Lambda Control -50%, Bank 1 Voltage of Oxygen Sensor 0.446V
Engine Speed 1136 (idle), Coolant Temp 17C, Percentage Oxygen Sensor Control -48%, Oxygen Sensor Control ON
Group 033 Lambda (Add) Self Adaptation 0.0%, Lambda (Multi) Self Adaptation 0.0%

Just found a code:

P1554 Throttle Actuator (J338): Conditions for Basic Settings not Met (Intermittent)

With the engine off:

Coolant temp 18C
Intake Air Temp 7C
ABS Pressure 1012
Throttle Angle 8.3
Voltage 12.2
Load Status - Part Throttle
Bank 1 Lambda Control 0.0%
Bank 1 Voltage of Oxygen Sensor 6.225V (this seems high?)

[alexperkins]

I wonder if the pre cat lambda is working properly. That’ll cause underfuelling if it reads wrong

[littlepolo]

I'm leaning toward the pre-cat O2 sensor also.

Probably worth swapping it out. What brands are OK?

[alexperkins]

OEM, NGK, or Bosch. Needs to be the right one though. Not a cut and crimp job

[littlepolo]

Would this one do (It has the connector)?

febi bilstein 36892 Lambda Sensor

[alexperkins]

Absolutely. Febi are top quality

[littlepolo]

New O2 sensor on order. Can I unplug the existing one and run the engine without it for a day or two?

[alexperkins]

It’ll cause major running issues. I wouldn’t bother. Best to wait for the new one

[littlepolo]

I'll wait for the postman.

Just wondering why the ECU is not showing any fault codes when the fuel trims are so far out of range.

Also, from Googling about O2 sensor outputs it seems the voltage should vary between 0.4V (or thereabouts) and 0.9V or thereabouts. So how can the values of 2.310V and 6.225V be explained?

[bvs]

Fingers crossed for you that the O2 sensor does the job - it does seem strange that there are no error codes showing though ?
Can you keep the engine running with a little throttle or would it still cut out ?

[littlepolo]

I was able to keep the engine running before with some throttle but now I cannot. The condition seems to have worsened in that respect.

[littlepolo]

New O2 sensor arrived this morning - Febi Bilstein 36892. It has four connectors and the one fitted has six.

Does anyone have a part number for the correct sensor please?