Mechman

I own the later model of a 2002 audi a4 quattro 1.8T with about 150000km and no manual. When I bought the car last year, the malfunction indicator light would turn on from time to time. Now it turns on every time I start the car, and it feels like I have lost power compared to 8 months ago. I brought it in and was told I had a minor oil leak at valve cover and chain tensioner area, and coolant leak at back of the cylinder head. Also, I had the following codes: P0411 Secondary air injection system Incorrect flow; they said it could be a vacuum hose. P1479 Bake vacuum system Mechanical malfunction; they said a check valve may be leaking, but I don’t know where to look. P0571 Cruise/ Brake Switch (A) Circuit Malfunction Sporadic; they said it’s a brake light switch. I’m a student and mechanically inclined so naturally I want to save as much money as possible by doing what I can by myself. I repaired the coolant leak myself and while I was at it, I took off the egr vacuum valve because I read it could be damaged if the metal pipe carrying exhaust gas to it was rusted inside. I tested it by using my mouth to create a vacuum at the small port while a friend softly blew where the rusted pipe was. It seemed that the valve worked as it should but I still cleaned it with some throttle body cleaner, and replaces the vacuum hose. When I replaced the coolant flange, the temperature sesor was a slight brownish colour with no vissble damage . I then had an oil change place flush my coolant system, and I noticed that the coolant reservoir had some sort of buildup in it. The leak seems to have stopped although one time the coolant temp and level symbol showed up with the word sensor writen beside it. At times the ESP light will turn on and at other times the ABS light turns on. On a few occasions while driving, the car will suddenly lose its power and it dies down to an idle before finally picking back up again. It’s not raining when it happens and it seems as though it is the computer deciding to restrict it and then picking back up again. I have read this can mean the mass airflow sensor needs to be replaced, but I would like to take it off to see if there is any visible blockage or damage, and have yet to do so. I was wondering as well if the O2 sensor could cause such problems.
The following may or may not be related.
• The sunroof works sporadically
• The front right headlight shimmers constantly and the head light symbol comes on in the dash
• Heater is warm at best on any set temperature or strength, although it used to work fine.
• When in tiptronic mode and I shift up to second and apply power, it will hesitate around 3000 rpm. It is as if the CVT does a slight shift part way through the gear, as if there is a 2A and 2B. It does not feel like the engine hesitates, it feels more like the transmission.

awcjacobs

I may have a few suggestions, may not be fixes, but ideas that could lead to solve some problems.

On my A6, when the brake light switched failed, my ESP and my ABS light came on and my car went into 'limp mode' In limp mode, I had no power at the low RPMs and really had to push the gas pedal to go anywhere. When you get the same warnings appear, check if your brake lights come on when you depress the pedal. Try not to drive it with no brake light as it is risky. I replaced my brake light switch myself. The part from Audi was under $30.00 and instructions came with the part. Maybe take you 10 min to repair . So that could be your ESP, ABS and power issues.

For your heat issues, your heater core might be plugged. As you said you noticed some build up in the coolant tank, so that gunk is everywhere in your system. A flush from the local oil change shop may not clear the heater core as most flushes only flush the rad, not the entire coolant system. You will need to remove the coolant lines to the heater core and flush it with clean water. I have done this also (not on the Audi) and the crud coming out was amazing. Gone from cold air to nice hot air in about an hour.

Your front headlight flickering and the 'burnt bulb light appears' is most likely the bulb is burning out. Is it HID? You can do it yourself, but could be costly as the bulbs are not cheap.

Hope this helps with some of your problems

Mechman

Thanks For your input, i will try replacing the brake light switch tomorrow and let you know how it goes. Also, I realize I made a mistake. It is not the coolant temperature sensor symbol that shows up at times. It is the engine oil level symbol and it says the word sensor beside it. Any ideas?
Cheers

awcjacobs

Most likely is an oil sensor malfunctioning. I am not familiar with the A4 engines so I cannot give anymore details, might have to have someone look at for you.

audigemini

Hi

I am curious how you made out?

I also have an Oil Sensor light coming on and I have limited heat.

I am wondering if the 2 are connected somehow??

i.e sludge

I am considering getting a flush for the Rad and Heater Core

thanks