Re: Its Not Starting, Backfiring and Spitting Rust everywhere!!
Just read your post today..
If you want some info on engine problems have a look at John Whalley's website under Q&A.
Incidentally, the best thing I can suggest is to have your car plugged into an Alfa Examiner to check that all sensors are working. As the Examiner does not have a Q4 to select from the drop down menu it usually defaults to a Fiat Coupe Turbo 16V. The Examiner will automatically diagnose you an error with the EEPROM (intermittent) and may or may not (depending on the year of your car) also diagnose an error with the Knock sensor (intermittent).
DO NOT WORRY about these faults as the EEPROM one is simply the result of putting in the Fiat model to read your ECU. The two ECU's are virtually the same however the EEPROM chips are different hence the error. If your car is the first version of the Q4 (EEPROM No. 101.03) it should not detect the Knock sensor. If it is (EEPROM No. 101.04) it will detect the knock sensor error. Don't worry about it as this is a glitch in the Examiner / ECU interface software; there is nothing wrong with it and it is a pretty bullet-proof sensor anyway!
What you need to look out for are readings for engine temperature sensor, air intake temperature sensor, manifold absolute pressure sensor and throttle potentiometer angle as these are the buggers that usually tend to cause serious problems with the running of the engine.
The two temp sensors should always read positive values at all times. I recommend plugging in the Examiner when the engine is stone cold, turn the bugger on and then check that the values rise uniformly. If you get big negative values to start off with e.g. -50 deg C the sensors are buggered. The engine temp is the worst of the lot as it is known to be quite fragile and will bugger up your fuelling. It will con the ECU into thinking that it is extremely cold and therefore get it to inject too much fuel into the engine to warm it up!
The throttle potentiometer instead needs to be spot on 0 deg angle. If it is not it will need resetting but make sure that the butterfly is fully shut by ensuring you have plenty of play (2mm) on the throttle cable. If the potentiometer is off 0 deg, the car will idle quite roughly.
Finally, clean out the throttle body, idle screw (on top of the body) and intake manifold with carb cleaner. Also, take out the idle speed solenoid valve and give it a good clean (focus on cleaning the piston and the small holes in it). When disassembling it you must remember to count the no of turns it will take you to remove the 4mm bolt as this will set the preload on the spring. Also, note the way in which it is all assembled paying particular attention to the springs (these are different in stiffness) and also in which way the piston goes in. You've been warned!!!
To adjust idle speed follow this procedure:
Warm up engine to 90 deg C of water
Listen out for the fan to cut in and then out
Disconnect the electrical connection to the idle speed solenoid valve
Adjust idle screw to set engine speed to 850rpm
Reconnect the solenoid valve
Rev the engine a few times and check rpm when fan is out
Repeat procedure as necessary
Hope this helps,
Thanks to Evo Eng, John Whalley, Walkers Garage and Stephan from Squadra Tuning for their invaluable help over the year.