1999 Volkswagen Golf Hi Runs Fine S Cold Once Engine Warms Maybe 2 3

1999 VOLKSWAGEN GOLF
103,000 MILES
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JAMESMFLINT
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Hi,
My golf runs fine when it's cold, but once the engine warms up (maybe 2 - 3 miles) the engine starts skipping, and acceleration becomes very poor, and almost like it's struggling to get fuel. At low revs the engine often stalls, and is very difficult to start again - the engine turns over, but just won't start. Also, if running at say 60 mph, suddenly it will lose revs for a split second and really jerk around. All very odd, as it runs perfectly when the engine is cold. All of the above problems only happen when the engine has warmed up.
My local garage has replaced the fuel pump, but it made no difference so am reluctant to take it back there - they clearly don't know what to do.

Help!
Nov 1, 2012 at 8:43 AM
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HMAC300
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scan for codes first then check engin e to battery ground and battery to body. this would be tough to diagnose by computer.
Nov 1, 2012 at 1:53 PM
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JAMESMFLINT
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Sorry - a bit of a novice here.. what do you mean "Scan for codes"?
Nov 1, 2012 at 2:09 PM
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HMAC300
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you have to have a scanner to hook up to your computer to see what codes if any are popping up.auto parts stores do this. this cold be a wiring or a sensor that is not making good connection as well,
Nov 1, 2012 at 4:35 PM
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JAMESMFLINT
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Ah ok. Any reason something like this would only happen with a warm engine?
Nov 1, 2012 at 4:45 PM
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HMAC300
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yes on a cold engine you arerunning openloop and on a warm engine you are running closed loop. in other words the computer takes control of car once it reachs above 100degrees F engine temp
Nov 1, 2012 at 5:12 PM
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JAMESMFLINT
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All fixed now. Turned out the crank shaft sensor needed replacing. All changed, and fixed, and running perfectly again.
Nov 8, 2012 at 2:47 PM
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