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Juan Crespo
Juan Crespo, ASE Certified Technician
Category: Audi
Satisfied Customers: 1513
Experience:  A.S.E. Master Technician, Advanced Level, Emissions - Asian, Domestic, & European
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Audi A4 Quattro: My 99 1.8 T runs great and then will run

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My '99 1.8 T runs great and then will run as if it had water in gas, it's that type of shuttering and if you bring it to idle it will be running as smooth as can be. I can run car to the redline cut off and shifting (automatic) is very responsive. But then it will shutter as if it was out of gas, then it stops and runs normal. doesn't matter what speed or RPM it does it on all ranges and at different running times. any ideal of what is going on?

Welcome!

I've known fuel pumps to do that on occasion. The first step would be to check fuel pressure; it should be 50 psi at idle and go up to 58 psi under acceleration. Residual pressure should be 36 psi after 10 minutes. If the fuel pump is faulty, be sure to replace the filter as well.

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Customer: replied 3 years ago.

Before I give you a bonus, you received an excellent from me already as I took the car out for a "drive", it all points to the fuel system, and as I tested it for how long it ran crappy before it cleared up, you can tell it was pressure. Good call, I hope! one hat did they do? One other thing I got the car used , they put in an Alpine, picked stations up fine. Had AC replaced and I get nothing now. I checked and antenna is connected. Antenna amp have a fuse or shorted out? What did they do?


 

The antenna amplifier is powered by the head unit through the big antenna wire. They are known to go bad. Here is a graphic depicting its location in the driver's side 'D' pillar:

 

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