How to stop rough idle
 

My Audi A4 B5 has rough idle, I recently changed the MAF and temperature coolant sensor. It still has the rough idle between 700 and 1000 revs and I don't know what to do next. A couple of tines it has stalled and switched off.

Please help

You'll have to pull codes with a code reader. Your local autoparts store will have one to borrow.

That'll give you a start. It could be a lot of things but that's where to go first.

Hello
Thank you for your response let me start with that.

Kind Regards,

You might also try and reset your throttle. I don't know what year your car is (please create a signature with year, model, engine, transmission, and drivetrain like mine below - it'll help a lot with questions like this). Basically, disconnect your battery for an hour, then reconnect it. Turn the key to position 2 (full electrical power, but not cranking) for 30 seconds, then turn it off. Wait five minutes and repeat. Wait five more minutes and repeat a final time. If you do this with the hood open, while the key is on you'll hear a high pitch whine from the throttle. If your car is 99.5 or newer, you're hearing the throttle aligning itself. If it's a 99.0 or older, it's the TPS being zeroed out. Realigning the throttle often helps with a bad idle, and if your battery has been disconnected, it's a must.

wow, speak of the devil....I thought you must have sold all your fun stuff and were driving around in a mini-van by now. Oh, Odysessy, never mind.

lol what's up man? Nice seeing some of the old guard still around on here. Yeah I have the Odyssey but I still have the A4 and 540 also. Kids are getting older and into far more activities so my wrench time pretty much comes down to maintenance and repairs these days.

I'm with devil man, I clean your throttle body out. My 2.4 V6 was idling rough and the rpm would fluctuate wildly when I'd put the car in drive or reverse and jerk the car while moving slowly with the brake applied. At its last service, I had the dealer check it out for me and it turned out my throttlebody was caked with carbon and the tiniest amount can cause it to not settle in its seat properly and make it flap back and forth causing a rough idle. If not that, it could be a faulty injector - I've had that too on a previous Audi - one was leaky and after replacing all 6 injectors, the issue went away.

On the throttle body procedure I assume it wouldn't hurt to do a throttle alignment on a vehicle that sat for a few months and ended up with a stone cold battery? I'm working on getting my 2003 back on the road after sitting all summer basically. (Cheaper to drive my truck with premium gas considerably higher than regular.) Anyway, I got it started recently and this weekend I started it to a very rough idle. Took about 5 minutes before it would idle without my foot on the gas to keep the revs up.

Your truck gets 15 mpg and your audi gets 27mpg. I'm not sure you are saving money driving the truck, to save 50 cents per gallon reg vs high test.