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[Anssi]

Hi all and congratulations for the new forum. Better and accessible, imho.

After a long break (nearly 2 years) I am seriously trying to get my toy (1990 QV with CAT and ABS) back on the road. Tere are still a few issues to solve before trying MOT (Actually vuosikatsastus, since I live in Finland. Same thing anyway). Hope you can give your input on this:

The engine has repeatedly failed MOT test due to too high CO2 in over 2000 rpm measurement. The engine runs ok, but consumes only 5,5 litres of gasoline per 100 kilometers. The real problems start when the weather gets below zero degrees (most of the year here). In near-zero temperatures the engine starts to have difficulty starting at all, and when it does, it does not run well. The idle is non-existent and even with the gas pedal it is difficult to keep the motor running. In subzero-temperatures the engine doesn't start at all.
The other abnormal symptom is, when trying to keep the revs over 2000 rpm in exhaust test, the engine drops the revs occationally below 2000. It happens as if the gas pedal suddenly stops to effect. The revs drop back to 1000 or so (the idle speed) and right back to over 2000 when i press the pedal to correct the revs. Annoying.

The air flow meter is good. The problem is not in there. Lambda and CAT are also ok.
If someone could give me a good quess, I would greatly appreciate.
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[amir]

Hi,

Coul be the engines Temp sensor, or the cable that connects it. This cable tends to break. Have you read out the ECU error code, if there is any?

AFM can be OK, but out of calibration (how can you tell anyway that it is OK?)
It is quite easy to calibrate it. If you want to know how to do it, send a mail...

good luck

amir

[Anssi]

We tested the AFM by measuring it with a multimeter and comparing the results with ML 4.1 Jetronic diagnostic manual. Air temp sensor gave the readings exactly in line with the manual. Same thing with the carbon bridge.
Yet to be checked are the wiring connections from afm to ecu.
The engine temp sensor is also on the list of measurements to come, but I doubt that it is the cause, since engine temperature is correctly displayed by the temperature meter wich gets its signal from temp sensor as well, I think.
When I manage to get the engine running again, I will take it to a garage where they can measure exhaust gases and calibrate afm at the same time.
By the way, what conclusions should I make with my idle speed actuator? The idle is steady enough, but when I disconnect the actuator when engine running, the rews do not rise as described in diagnostic manual. Instead the engine dies the same way it would if I disconnect the battery terminals or ecu. Immediately, that is.
What is wrong with the actuator? Should I replace it?

[Admin]

Hi

Think the temp gauge and the ecu get there signals from seperate sensors.

I would try cleaning out the idle control unit with carb cleaner first. They are not cheap

All the best

Keith