My '91 Cavalier GSI 4X4 has an annoying habit of illuminating the engine management warning light at between 60-70mph. When this happens you can feel the engine tighten.
As I accelerate to motorway speeds the warning light will come on and stay on. If increase to 80mph and switch off the engine for a couple of seconds, the light will stay off and the engine cleans up. However if I drop to 70 or below quite often it happens again. The hotter the weather the more often this happens. I'm quite sure this must be a sensor problem.
Can anyone suggest what is could be?
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Please dont tell me that you switch the engine off while you are doing 80?
Your abs and pas go off too.
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I can't think it would be the same, but just in case.
Ages ago I kept getting similar behvaiour with my Dodge. I couldn't work out what was causing it, there seemed to be no consistency and although I could play around switching it on and off and get rid of it, it came back at another time.
Also, there was a reluctance on the engine to perform when the light was on, I guess the computer backs off for some reason. At the time I was living in Chile, so def. it was hot weather.
Someone here made a throw away comment about petrol making a difference. I almost always used the same gas station. I changed gas station and it never happened again.
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Mark,
if the Dodge is '96 or later it's probably fitted with OBD II engine diagnostics.
When the 'Service Engine' light comes on, the ECU can revert to closed loop mode. It ignores the readings from oxygen sensors etc. and uses a fixed mapping in internal EEPROM to try and minimise emmissions.
The effect on performance is usually quite noticeable.
Kevin...
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Take it to a Vauxhall dealer and get the fault code(s) read. This will probably identify which sensor / wiring is faulty.
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Cheaper than taking it to the dealers, buy a fault code reader from halfords, they are only about £15-£20 with plugs for ford, vauxhall and some other makes. Another suggestion, it may be the temperature sender or lambda sensor, these are two sensors that get hot and would be most likely to be affected at high speed/engine temperature. If they fail the ECU drops into backup mode and puts fixed values in to substitute. You may be able to create the fault by disconnecting each one in turn.
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You don't have much option other than getting the codes read to pinpoint the area in which the fault lies. My hunch is that it is probably Airflow sensor or (more likely) Crank sensor.
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Aside from the fact that I understood little of what you said, the bits that I did understand sound likely.
Strange that mucky petrol should cause it though. I use the same garage for the 4 Runner and it never has a problem.
I do occasionally think about filling up there to see if the problem comes back, but it seems like tempting fate.
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