Have following problem on my 355 ( 5.2 motronic ): isolated the idle power is 1400 instead of 950 round per minute. sometime the fault accure after about 15 minutes started driving. then a bit later the idle power is normel again. it changes without any rule. it seems that in these times the engine gets to much fuel. does the engine has a seperate cold start injection valve or a sensor for that valve which is mayby broken and gives isolated wrong signals?? following works i already performed: 1. new bosch idle air valve 2. gas pedal removed, cleaned and fit with oil 3. new throttle cable. thank you markus
I would start looking for an air leak after the mass air flow sensor. Any unmetered air after the MAF will cause a high idle speed. Check all the various connections are tight and leak free. Also check that the idle control valve is properly plugged into the rubber socket it fits into. My car once had a very high idle and and found the ICV had come loose.
but if there should be a leak the engine should have all the time the high idle !!! but sometimes it happens sometime not !! is there a sensor for the idle controll valve which may failed sometimes ??? thanks
I only have a general understanding of the 5.2 Motronic system...I am NOT an expert. The ICV is controlled by the Motronic and receives input from both the coolant temperature sensor, as well as the throttle position sensor. (there may be others) You may wish to check the operation of these two other sensors, as well as the Motronic wire harness ground...which is located at the right rear of the passenger side valve head. Understand also, that an air leak can be intermittent, and not always present.
hallo, thank you for the info. the Motronic wire harness ground...which is located at the right rear of the passenger side valve head. sorry to ask again but i don´t know where this area is !! ( passenger side valve head ) is it inside of the passerger cabin , codriver side? is it possible to attach a picture. there are two temp. sensor at the engine ( pos.40 price 12 dollars and beside the oilfilter pos.39 für 120 dollar ) i think the one for 12 dollar you mean ?? and the throttle sensor pos.17 is at the rear end of the suction manifold ? regards markus ( from germany ) Image Unavailable, Please Login Image Unavailable, Please Login
#40 in the second picture is the Motronic coolant temp sensor. The ground is not in the two pictures provided.
I had a high idle problem when I first received the car and it was due to out of whack throttle plates. Competizione (a loca shop) re-tuned them and it was fixed. Good luck.
can you explane please where the the Motronic wire harness ground is located. is it at the codriver side , inside the car ?? what do you mean with "valve head" ?? thanks markus (from germany )
The Motronic wiring harness ground point is a ring mount bolted to the right side engine valve head, on the back side, facing to the rear of the car. It is located on the right side of the engine, where three Bosch connectors all meet, on a bracket. If you find this bracket, then look very near this spot, but on the engine....and you will see a black wire, with a ring mount, bolted to the valve head. Sorry, I cannot provide a picture, I am traveling this week and not near my car.
hi, do you mean the pos. 20 on the picture ?? but this is the wireing ground from the electrical control station of the relais at the passenger food rest :-(( lg markus Image Unavailable, Please Login
I am speaking of the ground point in the engine compartment, on the engine itself, and specific to the Motronic ground harness. I am sorry I cannot provide a picture, and I am sure language difficulties are contributing to the misunderstanding.
ok, look at the picture . is it located near by the pos. number 23 ?? where one of the eight srews fix the valve cover ?? markus Image Unavailable, Please Login
These are the grounds on the RH head of a 2.7 car so may be similar on a 5.2 Image Unavailable, Please Login
ok, thank you very much. i will search for it. kepp you informed when i found the problem of not normal idle run. regards markus
when its doing the high idle thing, is it always the same rpm? when it is at high idle does turning on the a/c load the engine back down? when its doing the high idle thing have you out of the car and tried manually pushing on the linkage near the throttle body on both sides and see if the idle lowers.
yes it has all the time the same high idle (about 1300 rpm) bushed already all inlets rupper during running. mayby it is the throttle potentiometer ??!!
Not sure about the TPS on these cars the ones that I have had problems with on other cars there have been "dead" spots in positions across the range of the sweep. looked like the connection opened up. Not sure if the ones on these cars is just a switch. I'll have to look at that one day.
