Engine hunting revs

[Samuel_and_his_Golf]

Hi all, my name is Samuel and I’m new to the forum, i have a 2002 VW Golf SE 1.6SR, I’ve owned this car since June and it’s been a joy to have. The only thing I noticed was that when the Air Con is off and you’ve been driving for a while and u stop it’s begins to rev between 1190-1250 rpm. I’ve spoken to multiple people and they’ve given me different problems it might be, so I decided to join this and see if any of you guys/girls could help me diagnose the issue I might be having.


Samuel


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[JustCruisn]

A diagnostic scan is the first place to start.
Usually this hunting is caused by a vacuum leak. The vac lines will have become quite brittle over the years and crack or break easily.
Leaks are likely at junctions.
The brakes work from the vacuum system so while you are stopped with foot on brake the vacuum will drop the revs will up to compensate and the cycle goes around.
When AC is on the engine runs at a slightly higher rev so the vacuum is adequate.
If it was a GTI I could tell you exactly where to check for leaks, my GTI got about 3 over the years but sorry not sure on the SR model.

[Samuel_and_his_Golf]

Hi there, yep I have done a diagnostic scan on the car and I believe that was one of the codes that came up, though I was using a lite version of the software so I’m upgrading to Windows 10 and checking again. But when I saw the code I checked my engine and there were pipes that had cracks and weren’t together, so I did some DIY and got duct tape and went to Supercheap and get some new pipes to replace some of them. But I think there’s more to be repaired because it still does it. The only good thing is that my uncle knows Guy Harding who might have some parts but he mainly tunes.


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[JustCruisn]

I was able to repair the rigid vac lines, by running some heater hose over the pipe. The pipe would crack at the junctions, the heater hose was a tight fit.
Heater Hose - 19mm (3/4) x 1.5M | Supercheap Auto


For softer sections silicone tape worked well.
SOS Silicone Tape - Black, 25mm x 3m | Supercheap Auto

Speaking of Guy Harding, it was when I bought a Diverter Valve from him years ago that we found a hole in the vac line, his solution was to put some wider silicone hose over the top of it.

[Samuel_and_his_Golf]

I was able to repair the rigid vac lines, by running some heater hose over the pipe. The pipe would crack at the junctions, the heater hose was a tight fit.
Heater Hose - 19mm (3/4) x 1.5M | Supercheap Auto


For softer sections silicone tape worked well.
SOS Silicone Tape - Black, 25mm x 3m | Supercheap Auto

Speaking of Guy Harding, it was when I bought a Diverter Valve from him years ago that we found a hole in the vac line, his solution was to put some wider silicone hose over the top of it.

Well we did get them and put them on so I don’t think it’s a leak anymore, maybe a dirty throttle body?


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