1995 Jetta III Bucks- Hesitates

Tiny
ANGLEMAN
  • MEMBER
  • 1995 VOLKSWAGEN
Hello. My daughter's 1995 VW Jetta III, 4 clynder, 5 speed manual with 120,000 miles has a hesitating problem. It bucks like a horse when giving gas, it hesitates. It simmers down when the engine is revved high. Had the spark plugs, wires, rotor, cap replaced with VW original parts. Also had the fuel and air filter replaced, all at a full service national garage - transmission shop. The mechanic drives it for 15 minutes and runs fine like a champ. Next morning she drives around and after 20-30 it bucks and hesitates again as it did before the repairs. It idles and starts fine. She lives in Phoenix, AZ. Can the heat have anything to do with it by some odd chance? Joe, Palm Coast, Florida
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Sunday, July 8th, 2007 AT 3:04 PM

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Tiny
BUDWARDO
  • MEMBER
I also have a 1995 VW, Mine is a golf III. It hesitates like that with heat. If I have the air conditioner on for a few minutes while it idles at rest it looses power for about 15 minutes, if I drive it and allow it to cool down. I am checking the coolant temperature sensor since this is a significant engine management component. If I am successful with this repair I will let you know.

Bud
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Thursday, August 2nd, 2007 AT 10:01 PM
Tiny
REDANDWHITE
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Have you checked for vacuum leaks? That's what this sounds like. The rubber intake boot is a common culprit. With the car idling, spray a light mist of starting fluid or carburetor cleaner around the fittings on the vacuum hoses. If the idle speed increases you have found your leak.

This causes performance problems because the computer tells the fuel injection how much gas to spray based on how much air the airflow meter says is coming in. If you have extra air coming in from a leak, it is not metered by the airflow meter. Why? Because the meter is located right after the airfilter, and your vacuum leaks occur further down the line. This causes you to have too much air for how much fuel is being pumped-aka running lean. It isn't as noticeable at high RPMs as there is more vacuum created, and a lot more fuel being pumped to the injectors.
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Monday, August 6th, 2007 AT 11:37 PM
Tiny
BUDWARDO
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Yes, I replaced the boot and have checked the connection. There was no leak there, however there is a bit of oil in it. I noticed an oil vent going to the boot that allows oil to go down near the mass sensor when the car is not running at a high idle or speed. Any ideas? I assume this oil is tricking the mass sensor.

Bud
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Thursday, August 16th, 2007 AT 7:31 AM

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