The 98.5 A4Q 2.8 with 111k miles idles kind of rough even after throttle body service from an independent I no longer patronize and after several bottles of fuel injector cleaner (applied at various times over the past 2 years). Aside from replacing the fuel injector(s) at considerable expense, what else can I try to smooth out the idle? The car runs great.
One Subaru person suggested CRC Mass Airfow Sensor cleaner; is this something I should try on the Audi?
Have you changed plugs, wires, fuel filter?
Vacuum leaks?
CEL showing errors?
If you don't know that the MAF is causing codes it is better to not mess with it.
Pull engine error codes and start from there.
There are no error codes. The car had a complete tuneup at 90k miles by the dealer. This situation has developed slowly over time; the car was checked for the vacuum recall back in January 2005, no problems then. It was just in to the independent who did a 4-wheel alignment and replaced a tie rod end, and they found nothing.
Speaking of tie rod ends, shouldn't those last more than 2 years?
A lot can happen to the vacuum system since January 2005 and given that the problem developed over a period of time I would suggest that you have the system checked out by more than a visual exam. Pressure test the system. Also some shops have a system that tests for leaks with smoke.
Still plugs, wires, fuel and air filters should be changed as well.
On older cars around the mid 1900s the following could be done without having to use diagnostics. Be careful not to damage things during the process. The Idle control valve may need a clean. Look at all of the electrical wiring for loose or broken wires and connections. Disconnect and reconnect electrical connections. Clean all the earth connections. Disconnect the relays and reconnect them. Look at the rubber hoses to the inlet manifold and the fuel pipes. It can be one or more of the many sensors that is not functioning properly, a connection, wire or the ECU etc. Most of the sensors can be checked with a multimeter.
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