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Matt, Engineer
Category: VW
Satisfied Customers: 21995
Experience:  Mechanical Engineer with 20 years experience in the auto industry, 8 yrs in formula 1 engine testing
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I have a1986 cabrioet that was away out on timing reset

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i have a1986 cabrioet that was away out on timing reset timing repalcin timing belt car runs beautifully but will not idle under 1500 rpms it backfired badly when out of time will this affect the idle function?
JA: How many miles are on the timing belt? Have you ever had to change it before?
Customer: no ,the car has 199000 kms on it
JA: What is the model/year of your VW?
Customer: 1986
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: yes ihave tried readjusting timing and have thoroughly inspected idle linkage
JA: Anything else you want the mechanic to know before I connect you?
Customer: car runs fin has lots of power but will stall at lower rpms


if its no longer idling since replacing the belt I'd 1st check that the ignition timing is correct with a timing light as it should be 16 degrees at 750rpm

I'd also suggest checking for airleaks after the carb

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas /propane or brake cleaner around each joint in turn. If the engine rev's up you've found your leak.
Now you might think that spraying lighter gas around a hot engine isn’t wise, however the flash /ignition point of gas is about 400°C so you need a naked flame or spark to set it off and I’ve used this method for many years without incident.
Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

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