1991 auto 1.6 high idle RPM, lumpy turning off then backfires

August 02, 2025, 06:34:14 PM

Hi all

I recently purchased a 1.6 auto mk2 Golf.

Driving home everything was well, but after doing ~1k miles in it I've got a slight issue.

When starting up it'll rev to 4k RPM, when put into drive it sits around 1,600 RPM.
When turning the engine off it'll run for about 10 seconds lumpily, and sometimes giving a final salute with a backfire, the backfire is pretty cool.

It's got a carburetor.

Any idea what would cause this, and how to go about diagnosing it?

Re: 1991 auto 1.6 high idle RPM, lumpy turning off then backfires

Reply #1 – August 06, 2025, 01:30:49 PM

First of all, does it have the original Pierburg 2E2 Carb? These get a lot of stick, but once you get your head round how it works its not that bad. There are various you tube videos that explain how it works and what you need to check. I recommend you view them first. In terms of what's wrong with it, it could be one of the following.
- The vacuum hoses at the back of the carb are split.
- The 3 point unit is not working properly (possibly because of the hoses or the diaphram inside has gone)
- The waxstat is faulty
- The linkage between the waxstat and the throttle arm needs adjusted
- The rubber mount is split

The fact that the engine runs on suggests to me the throttle arm is not going to the off position (controlled by the 3 point unit), so I'd check the hoses first.
https://www.youtube.com/watch?v=taTBdkrQouI