Stalls in traffic and oxygen sensor light is always on

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PAULT
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Hi. Recently acquired 1987 VW Cabriolet (210,000 miles, 1.8 L, 5-speed manual) which experiences stalling when in stop-and-go traffic after 5-15 minutes. Does not happen at highway speeds or light city traffic. It loses revs then stalls or it surges followed by pretty wild revs fluctuation then stalls. Will re-start but stalls again. After waiting about 15 minutes the car will function normally as long as I do not again encounter stop and go conditions. Same thing happened once upon sharp braking. Have replaced distributor. One injector was loose-ish - replaced donut o-ring. Others seem tight. Oxygen sensor light is permanently lit. Car does not overheat. Your help on this specific set of symptoms very much appreciated. have searched site but not found exact match, only come away with a long, long list of possible causes. Thank you.

Feb 20, 2007 at 11:04 PM
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KIN CHAN
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Does this problem happen all the time or only after the engine warms up? if that happens after it warm up your O2 sensor malfunction might play a role. Because O2 sensor don't have a role before the thermostat open on OBD1. let me know and i'll follow up..
Feb 21, 2007 at 9:22 PM
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PAULT
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Kin, thanks fot your reply regarding the stalling VW Cabriolet. Can only say that when the stalling has happened the car has been thoroughly warmed up, which takes only a few minutes and a couple of miles. Critical thing it seems to me is that it only happens when in stop-and-go traffic for more than 5 minutes. The kind of traffic where you go 2-3 car lengths lengths then stop and wait, and again and again. 5 minutes of that and it will start to stall no matter if I just left the parking lot or have been driving all day. Thanks, Paul.
Feb 22, 2007 at 10:25 PM
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ASEMASTER6371
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Good evening,

This model had a fuel distributor that controls the idle and high speed operation.

This unit tends to carbon up over time and needs to be cleaned and adjusted. You will need a shop with an old timer like me that can perform this procedure.

It is not hard or expensive to do this service.

Roy
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Mar 25, 2020 at 5:17 PM