Theinen73

2004 Audi A4 cabriolet 1.8l, I've had this for almost 2 years put nearly 30k miles on it, but now it's gotten to a total of 104,000 miles. Randomly irregardless of weather or activity, it will take quite a while to start, it'll crank multiple times, at one point for over 2 minutes before turning over, immediately after this it will go into a rough idle that makes the car shake a noticeable bit, once driven for a little this stops and does not appear again until another rough start.

My friend tells me that this could be related to the fuel injector, fuel injector cleaner and and oil change followed by another 20 miles did not fix anything so i figured I'd try to find some help here.

old guy2

Probably your rear CTS (coolant temperature sensor). What happens is that it sends a faulty temperature signal to the ECM and consequently the fueling is off until the engine reaches the proper operating temperature.

Think of it this way: With an old school carburetor the choke activated when the temperature dropped in order to enrich the A/F ratio until the motor heated up. With modern engines it is all controlled electronically. The Rear CTS is an electronic version of the mechanical choke. Obviously this is a bit of a simplification but the concept is sound.

And some additional information before you ask: The rear CTS is a four pin sensor which means it is essentially two sensors housed in one sensor body. One signal goes to the temperature gauge in the dash display and the other signal goes to the ECM for fueling and coolant temperature control. So your temperature gauge can function normally and still have an issue with the fueling.

The rear CTS is inexpensive and not too difficult to replace. I believe that will solve your problem.

old guy2

Here ya go: