Hi All, was trying to adjust my idle on the 348 (it's not terribly off (~1200 instead of the normal 950+-100)) but will not pass smog like this). I've got the Motronic 2.7, and saw a couple of threads on here. I tried to just "micky mouse" it by turning the idle adjustment screws equal amounts on each side, but no success, the idle will not budge, it stays high. Question: has anyone had problems with their idle adjustment regulators (i understand they can be taken apart and cleaned). Any ideas how one could troubleshoot the idle adjustment regulators (#142342) to check whether they are bad? Once again, the idle is not too far off, but even screwing the air bypass screws all the way in will get me the exact same idle (after battery disconnect+relearn) so i think it must be the computer idle adjustment right?
The idle regulators are 142432, not 142342, in case anyone gets confused on that. Did you check for vacuum leaks and mechanical problems before you tried adjusting the screws? Is it possible that your throttle cable is adjusted too tight (no slack at the bellcrank) or someone cranked on the linkage synchro controls? Check the stops at the bottom of the throttle position sensors and see if the linkage is obviously wrong. If the linkage doesn't touch the stops, then chances are that's your problem, and it would be relatively easy to fix. You could also have a vacuum leak somewhere, maybe the rubber intake tubes aren't seated properly, or their clamps are loose. Maybe the hoses to the idle stabilizers have cracks in them. Maybe the vacuum hose fittings at the vapor canister solenoids have snapped off.
I would unplug the idle air adjustment regulators (because it's so easy to try). If she idles high with them unplugged, then something is stuck wide open letting in air, right?!
IIRC idle is not adjustable because it is a function in the motronic. If idle is off you got an air leak. try the propane trick to locate it. Also maf sensor to 282 ohms iirc too is required for proper function. I forget which terminals. Check for complete throttle closing and check linkage to each throttle body. I have seen wiring trap and impede closure.
thanks guys, good tips so far! the throttle cable is slack so thats not it. i was suspecting vacuum leak myself, will inspect that a bit closer tomorrow and report back..
quick update: -checked the linkage to the throttle bodies, looking good, there is no gap or obstruction, the butterflies are all the way closed at idle -checked for vacuum leaks with starter fluid, no leaks seen as far as i can tell. -checked the MAF ohmage, appears correct, both sides are ~380 ohms, was adjusted some time back by Tillack (i think) -opened up the electrical idle adjustment motors. they both seemed fine, but i cleaned them anyways. I visually checked them and connected the cable while they were off the engine (but engine not running), and they are fully closed with power on. no success!! what is happening is that the car starts up fine, idles at ~1050 for a while which is good, then as it gets warm and fans are kicking in, it moves the idle up to 1200. anything else you guys can think off? I did notice that the engine starts hunting the idle so maybe one of the O2 sensors is bad? I read out the ECU codes and i only get 1121 which is fine with turned off engine. help!!!
Do you think it is remotely possible that the ECU burned chips are bad? I still have the other 2 you burned here somewhere. I also have another set of ecus to try somewhere. Did you use electical contact cleaner to clean out the TPS and MAF connectors? Did you softboot the ecus by disconnecting battery? A/C will kick up your idle but the car should run clean at all rpms because it is closed loop. The only time it is open loop and on a program map is at wot I think. How about the smog air rails?
I really don't think the ECUs are bad, they've been in the car for so long now, and besides it is running fine and even the idle is not too far off. You'd think if the bits start rotting there would be all kinds of hellish effects! I have been reading a bit more about other people on the web having problems with high idle on Motronic cars (bmws, saabs etc.) it appears quite often it is either the idle adjustment motors or the MAF/O2 data feed. This seems logical: if the computer brain is not broken, it must always be right. so therefore, if the idle is wrong it can only be because a) the brain got wrong data as input or b) the instructions of the brain were not carried out correctly (output). a possibly marginal O2 sensor and/or marginal MAF might be to blame. I visually checked the idle motors and they shut closed completely when the ignition key is turned on. i conclude that the output side must be good. Therefore perhaps the input from O2 or MAF must be slightly off, leading to the slightly higher idle. what do you think?
I've got an update to this issue: after replacing the O2 sensors with new ones (Amazon.com had them for 60$ each!!) the idle settled at the correct level of ~1050rpm, and the car passed smog without a hitch. Ferrari DIY worker pride restored, $$$$ saved... Whats interesting about this is that the car did not throw any codes. I guess they were still just barely within specs but nevertheless made the idle rev ~100 rpm too high... go figure. Wonder how many hours the Ferrari techs would have billed to figure that one out?
Hello, I am new owner of 94 348 Berlinetta. Car is good overall but there are things that needs to be put together. (I have repaired starter motor, change fuel sender, spark plugs and spark wires so far) I am gonna change timing belt and stuff later this year but now I need to solve ignition and revs. I have higher idle (arround 1100 rpm). But when I pull back the pedal a little bit more by hand idle sits on arround 900 but not still. (Cable is new by last owner) I did check throttle linkage and it is clear that on the left TB linkage does not touch the stop on the bottom of TB when relased. Right side is OK, cable seems ok. Now I am not sure how to adjust. Maybe check length of both left and right linkage? Or it looks like there is some screw to synch those linkages but I am not sure. I would be very thankful for help.
Yo don't need to alter the length of the linkages. First, check whether the butterfly stops at the bottoms of the TBs still have the original factory seal: Image Unavailable, Please Login Image Unavailable, Please Login If it looks like the stops have been altered (seals broken), you should check/adjust the gap as shown on the sketch at the right above. To geometrically synchronise the TBs (both butterflies hitting their stops at the same time), disconnect the throttle cable and turn the screw #4, shown on the drawing below, until you achieve that both butterflies "click" at the same time when you rapidly release the bell crank (to which the throttle cable connects) from somewhat open throttles. Image Unavailable, Please Login
You were right, seals on stops are gone. I will adjust throttle bodies and clean idle control valves too. I will let you know how it works. Thank you.
The next adjustment check is the TPS-s (Throttle Body Pots). To make it easy, you should make a "special tool" like this: Image Unavailable, Please Login Then, with the tool inserted, throttles at idle stops and the ignition "on", measure the voltage between pins 1 & 3 on the LH TPS and between pins 2 & 3 on the RH TPS. This voltage should be somewhere between 400 and 600 mV. At the same time, the difference LH to RH should not exceed 80 mV. If your difference is greater than 80 mV, some adjustment can be made by loosening the two screws that hold the TPS and rotating it in the appropriate direction. The holes allow only small adjustment so, if you still cannot achieve the specified voltages or the voltage difference, you should be able to rotate the TPS-s more if you enlarge (file) somewhat the TPS holes at the sides as required to rotate the TPS more in the desired direction. The sketch below shows measurements on my 348 after I "fine tuned" the TPS positions. I managed to achieve zero difference LH to RH but this is not necessary. NOTE: It is not possible to perform setting of the TPS-s by measuring their resistances as they are calibrated to produce specific voltage for the given TPS rotational position and not to have any particular resistance. Image Unavailable, Please Login Finally, remove the throttle bypass screws (pic below). First, loosen the locking nut and count the number of turns to fully screw-in the bypass screw (keep the count just for record). Then, remove the bypass screws and clean any gum/carbon. Inspect and clean the bypass orifices too. After cleaning, install the bypass screws at 1.5 or 2.0 turns out from fully closed and lock their nuts. NOTE: Moving the bypass screws further in or out will not alter the idle speed because the idle speed is controlled by the ECU-s via the Idle Control Valves (ICV-s). The position of the bypass screw basically brings the ICV's operational span within range. Too small or too large bypass opening may render the ICV unable to properly control the idle speed. Image Unavailable, Please Login
Somebody fidled with car in the past but not in the correct way. I hope the ICV are in good condition and the car will run after correct TB adjustment... Thank you for massive info. I will be in the garage in four weeks working on this. I am gonna change gearbox, engine oil and correct ride high. If you have any advice to ride high i would be thankful, but its a different topic. ( I have both service manuals) Thank you very much
The original Bosch ICVs, 0 280 140 505, are now very hard to find but, if you need to replace them, you can see some good alternatives at Spareto (search using the mentioned Bosch number). You may also be able to find them locally as they are (were) used by a few other cars. There are also many equivalent brands (including Polish Maxgear): Image Unavailable, Please Login
