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Engine runs fine when it is cold, but gets worse as it warms up

Tiny
BARBARA907
  • MEMBER
  • 1989 VOLKSWAGEN GOLF
  • 1.8L
  • 4 CYL
  • 2WD
  • MANUAL
  • 180,000 MILES
We have done a lot of work to this car, including new transmission, coil, sparks plugs/wires, clutch, new swivel gasket. Now it runs fine when cold, but gets worse as it warms up--hesitating and eventually it just quits running. We have checked the timing and also run it with the 02 censor unhooked/hooked back up, and it makes no difference. Any ideas? Thanks!
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Monday, October 19th, 2015 AT 12:57 PM

10 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
When warm and it stalls, does it start right back up?
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Monday, October 19th, 2015 AT 6:29 PM
Tiny
BARBARA907
  • MEMBER
  • 5 POSTS
Yes it starts fine. Today we checked the coolant temp sensor and the air temp sensor and they both seem okay too. Thanks!
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Monday, October 19th, 2015 AT 7:22 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Since it starts right back up, chances are it is a sensor. The problem is, which one? Do you have access to a real time scanner that you can view data while the vehicle runs?
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Tuesday, October 20th, 2015 AT 5:41 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
Rewind. I forgot it is an 89. The scanner won't help. When it stalls, is it like shutting the key or does it slowly die?
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Tuesday, October 20th, 2015 AT 5:42 PM
Tiny
BARBARA907
  • MEMBER
  • 5 POSTS
I would say slowly dies... It just kind of gets coughier and more spluttery and then quits.
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Tuesday, October 20th, 2015 AT 5:47 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
What you described sounds like a fuel related issue. Have you checked fuel pressure or replaced the filter?
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Tuesday, October 20th, 2015 AT 5:52 PM
Tiny
BARBARA907
  • MEMBER
  • 5 POSTS
It runs great until the temp needle starts to move to the middle of the range. At that point, it starts to idle rough and will stall, but doesn't diesel. We haven't checked the fuel pressure, but we did replace the filter. Using a Robert Bentley service manual, we tested the digifant two module/connectors. We didn't get the right values for the ICU. The airflow sensor had 1 test that was good and 1 that was bad. We didn't really understand the testing process for the O2 sensor. We have gone through all the vacuum lines and we didn't replace them, but they look okay.
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Tuesday, October 20th, 2015 AT 7:26 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
If you can allow the vehicle to idle in the driveway till it warms up and dies, put a fuel pressure gauge on it and confirm it doesn't drop off. If it checks okay, the next focus area is the crank sensor.

Let me know what you find.
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Thursday, October 22nd, 2015 AT 5:38 PM
Tiny
BARBARA907
  • MEMBER
  • 5 POSTS
We tested the fuel pressure. It was 35 PSI when the car started, but as the engine warmed up, the fuel pressure dropped to 20PSI and the car started to run bad. After the car died, the fuel pressure dropped to 18.
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Saturday, October 31st, 2015 AT 1:05 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,133 POSTS
If the fuel filter has never been replaced, try that first. It is cheaper. If that doesn't help, most likely, the pump itself it bad.

Let me know if you have questions.
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Sunday, November 8th, 2015 AT 4:51 PM

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