Volkswagen Mk2 GTI Idle Surges

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SARAH21
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[color=green:56ba5a61f7][/color:56ba5a61f7] :?

Mk2 gti 16v, has recently got a mind of its own and is over revving, and do not have a clue why this it just started about a week ago, once she has started up revv's to just over 1000 and goes up to 4000 and back down repetedly? Can any one help??
Dec 18, 2006 at 1:10 AM
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LOSONE
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I need the model year to determine what type of fuel injection you have. Let me know. Losone
Dec 18, 2006 at 1:32 AM
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SARAH21
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[color=green:04390eeba8][/color:04390eeba8] Yes it a H reg 1990-1991.
Dec 18, 2006 at 1:46 AM
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LOSONE
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The most probable cause of your idle problems is a vacuum leak in the rubber plenum that goes from the air cleaner to the fuel control head. Any vacuum leak will cause a problem. It could be you power barke booster.

Check your engine RPM and pump your brakes if the RPM varies more than 100 rpm it is the brake booster.

One umlikely cause would be trash in the area below the fuel head. There is a round flat plate that often gets trash if the mechanic isn't careful when he changes the air filter.

Good luck but it sounds like a VW mechanic should look at it.

Let me know losone
Dec 18, 2006 at 4:57 AM
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Suggested Repair

Check for a vacuum leak in the rubber plenum between the air cleaner and fuel control head, and test the brake booster by pumping the brakes while watching RPM. Also inspect the area under the fuel head for debris, and have a Volkswagen mechanic diagnose it if needed.

Conversation Summary

The owner of a 1990-1991 Volkswagen Mk2 GTI 16v reported that the engine recently began surging at idle, repeatedly rising from just over 1000 rpm to about 4000 rpm. The expert said a vacuum leak was the most likely cause, particularly in the rubber plenum or brake booster, and suggested checking whether RPM changes when the brakes are pumped. Debris beneath the fuel head was mentioned as a less likely cause, with a Volkswagen mechanic recommended if needed.

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