Anyone got any advice re. erratic idle speed on the 355 (UK) ? Mine generally starts out OK at around 1100 rpm but, especially when warm, can climb up to 2k for instance when coming to a halt at lights etc. When this happens, I quick blip of the throttle usually sets it back down to where it should be. It was a hot day out yesterday and this was happening all the time so it certainly seems that the temperature could be a factor. Sometimes it will also do this when cold - start the car, sits at 1000 rpm ish then climbs to 2k with no input from the driver. The other way to get the rpm down is to engage a gear, let the clutch out a bit so the engine rpm drops and then it sometimes will stay low. Because of the cold start symptom, I am not convinced that it is anything to do with a sticky cable or linkage (otherwise why from cold would it climb with no throttle input and no opportunity for the cable to get stuck ?). I am thinking about the idle control valve - I have had the connector off and reseated it and I can see inside the end and the little rotor thing turns ok but quite what this little box does and how it works I can't seem to find out to give me any indication on what might be the problem. Any clues anyone ? Thanks Arron.
I would still check the throttle tower for signs of sticking, it sounds like its a random fault rather than one with a pattern, and although normally the tower sticking issue is normaly tempreture related, it isn't always the case. Check for air leaks, exhaust bypass vacuum pipes, secondary air connections etc....oh, and check the floor mat isn't jamming up the throttle
I think you are on the right path with the idle control valve. If you search inside the 348/355 Forum, there is a recent post by 355Bob about this valve causing erratic idle speeds and poor part-throttle driveability. He cleaned the inside of his liberally with carb cleaner and that seemed to have solved the problem. I suggest that you remove the valve (5.2 cars have 1 valve underneath the Y-pipe, 2.7 cars have 2 valves) and look closely inside the air passage, then clean it as mentioned above. I have this on my to-do list for my car too. -Greg
Also, along with a dirty/fouled ICV, it could also be defective. Other things that could influence this is the coolant temperature sensor for the Motronic, which is located by the oil filter. If this is defective, and sends a signal of "cold" coolant, that could raise the idle speed, but probably not to 2000 rpm. Also, an unmetered air leak in the ICV hose routing could also cause a faster idle speed. Check that the ICV is properly fitting into the rubber mounting hose connection. I would suspect air leak or floor mat as the first things to check.
Many thanks for your input so far. First of all, I have checked the floor mats and it's definitely not them. Secondly, I can pretty much rule out throttle linkage as referring back to my last service in March 2012, I note the indy checked the cable and greased all the appropriate points etc. and was happy that it was in working order. I have now discovered another factor. The problem is influenced by whether the a/c is on or off. With it off, no problems at all, with it on the problem persists. This is to the point where, if you are sat at lights with the a/c on and the car idling fast at say 1750-2000 rpm, switch the a/c off and the rpm drops to normal, turn it back on and it climbs again - you can just sit there switching the a/c on and off and watching the idle speed climb and drop again. I have had the idle valve out (the bit on the 5.2 car that sits just behind the Y split in the air intake pipes ?) and noted that it looks pretty clean, the rotor spins although it feels like it is in a magnetic field if you follow me ? Is that correct or should it just spin very freely ? It looks pretty clean inside but I have not taken it apart yet as all the screws are sealed up. I have also checked - to the best of my ability - that there are no air leaks in any of the vacuum pipes. Any more advice now considering the a/c interation would be greatly appreciated. Thanks Arron.
Idle is supposed to go up if the A/C is switched on, to prevent engine stalling when the compressor comes on....but not that much. Possibly a problem with the Motronic? Would be interesting to swap a known good Motronic with your existing one.
Golly...... next to impossible to diagnose this with so little info, as there is a wide variety of things that could cause your symptoms. Other than performing a thorough once-over visual inspection of everything to make sure nothing looks obviously damaged, disconnected, loose, or otherwise physically out-of-whack ---- you really need to hook up an OBDII reader and check for DTC's stored to point you in a direction. Otherwise, you are pretty much wandering around in the dark without a flashlight .
http://www.ferrarichat.com/forum/showthread.php?t=378059&highlight=spark+plug Start at post #14. He is having a similar problem, perhaps you can exchange ideas?
I had this same issue. Replaced both of the fuel pressure regulators with the Bosch version for about 30 dollars each and it fixed the problem. I figure it was one of them. There are a few threads about those on here and how to test them. But the symptoms sound identical.
