1990 VW Jetta idle problem

CB in central NY · Nov 3, 2011

Good morning.

I have a 1990 VW Jetta GL, Wolfsburg edition, had it since new. The car has about 167,000 miles and does not get driven much. A few weeks ago I was driving uphill when all of a sudden I lost acceleration. The engine started idling very roughly and would just about (but not quite) stall in Park or Drive. Depressing the gas pedal all the way to the floor did nothing. Once or twice I was able to get the RPM"s up but as soon as I shifted into Drive, they would lug back down.

I turned the engine off, got a bottle of dry gas and threw it in the tank. I then turned the engine back on. It instantly raced at top RPM and would not come back down until I depressed the gas pedal a few times. It then returned to normal idle and I was able to drive home with no problems.

The other day it happened again, same tank of gas, but this time I was able to get back home.

I recently changed the fuel filter.

Any thoughts or advice would be appreciated. Thanks in advance.

Allan in NE · Nov 3, 2011

I have absolutely no idea, but that really does sound like the effect of water in the fuel.

Allan

BCnT · Nov 3, 2011

sounds like a throttle position sensor if your car has electronic fuel injection.

Dell (WA) · Nov 3, 2011

CB........uh? Wolfsburg edition don't mean much to me (plastic stripes on side of car?) ...but... in certain atmospheric conditions, you can gitt ICE in yer induction system. When you turned the engine off to add "dry-gas", (which was a good thing to do) the latent heat of yer engine MELTED the internal ICE and vola' yer engine starts and races 'cuz yer floor throttle was wide open. You probably have a thermostat problem.

Ittza NOT yer fuel filter........icy Dell

Anonymous-0 · Nov 3, 2011

I don't remember if VW still used the fuel injection system with a movable vane airflow meter in 1990. But if it does, you might check to see that the vane will move very easily. In older VW's the airflow meter was under the air cleaner element.

What might cause the vane to stick? Oil sure could, but I like Dell's idea of icing. Was it really humid and cold? There should be a duct to bring in some exhaust heat when the system is cold, to prevent icing. Once the engine gets heated up, icing SHOULD disappear.

It has been a long time since I messed with VW's....if I remember right, Wolfsburg Edition meant the car had a bit fancier interior and usually air conditioning. Good luck with it!

CB in central NY · Nov 3, 2011

Thanks for the ideas.

The Wolfsburg edition meant that the VW was made in Germany, not Mexico.

It was probably not due to ice. The last time this happened, it was a warm Fall day.

I'll check about the oil idea.

mkirsch · Nov 3, 2011

It doesn't have to be cold for ice to form. The venturi effect of the air rushing into the engine intake can cause icing in the right conditions.

1990 VW Jetta idle problem

CB in central NY

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Allan in NE

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BCnT

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Dell (WA)

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Anonymous-0

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CB in central NY

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mkirsch

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