Hi,

New here with many questions to come I suspect.

My son bought a 2001 Audi A4 1.8t (manual). We have little info on the history; it is clear the previous owner didn't put much effort onto the car. It is a bit of a project car; early days.

His problem...

Had the car for 2 weeks. When picked up, all seemed fine with a small power dip which we believe is when the turbos kick in and the dip is due to a small hose leak (according to the previous owner).

A week later, the car idles smoothly, but on acceleration, there is no power, then revs up irratically then down up etc around 1,000 rpm each way. If holding the throttle steady, this happens.
If gently pumping the throttle, the revs can be controlled slightly.
We can hold the revs reasonable smoothly once around 3 or 4,000 rpm.
If slightly take food off the throttle, the revs generally drop right down.

I cleaned the air filter and maf today. Not fixed!

Next thought is to look where there may be a hose leak in the place where the previous owner said.

Any suggestions welcome. I hope my explanation is clear enough.

 

There should not be a "power dip" due to the turbo, which should instead be a pretty quick increase in power. As bad as you say that car runs, there very likely are fault codes stored in the engine control unit (ECU) that will help your troubleshooting. Preferred is the VAG-COM or VCDS software by Ross-Tech, and their diagnostic cable. In a pinch, connect a generic OBDll code reader, perhaps for free at the auto parts store, and write down the fault code numbers.

If the engine idles OK, then a hose leak is less likely. All kind of things could cause a car to run as you describe, but they fall into two types of problems- either ignition, or fuel delivery. Inspecting your spark plugs and reporting if they look all the same, or some different, can be a clue also.