Idle Speed Control

Dave, try cleaning and treating with Stabilant 22 the connectors to the following: Idle control motor, air temp sensor, and the MAF sensor. If you would like to try another idle control motor, I have a known (used) good one.

Josh O. told me once that the air temp sensor and MAF sensor connectors are the first things they clean and check when this sympton comes up.

Dave

 

Could the problem be a faulty "A/C compressor is on" signal to the ECU? Which is to say, is your A/C on when this problem occurs during the radiator fan-on cycle?

 

Do you get the same 400 rpm drop when the fan kicks on if the A/C is OFF?

Anyway, I'd think that the top 3 things to cause this sort of problem would be as you've identified, i.e. a faulty idle speed controller...or the system isn't handling current draw...or the air intake is being impacted by the fan kick on (which you have solved by installing the Gothshields).

I suppose an easy "air intake" test would be to open up the the air filters and engine cover bonnet to see if you still get the RPM drop...surely that would rule out the air intake/rad fan angle.

 

Good stuff to check there ND !

I have read even the 360's have something similar. This could be a host of things as a few things happen when the AC compressor turns on.......... as ND said the idle control valve feeds air to each runner through a manifold buit-into the bottom part of the intake housing (where our velocity stacks are) to compensate for the compressor load. I also believe when the AC is on the LH fan should be on full time...anyone?? Then all the fans/blowers are drawing current as well......

Sometimes I get a low/rough idle when I shut off the car and start it after about five minutes. It then stabilizes within a minute. One possible contributor to the rough start could be, the air inside our ten foot long intake tract has heated and the engine is inducting that until the temps in the tract homogenize. Or it could just be the idle control valve having a moment....

As for aero's issue....I think what ND said will help locate the culprit(s). I will check into it more this afternoon......

 

Easy to test your theory on heated air in the intake tract by opening up the air filters/MAF to direct outside air.

 

Well it was not every time... and the since I have driven the car more frequently.... most if not all of these quirks are now gone . It has done it once out of about every thirty hot starts..... so maybe it is just a sticking idle control valve.......... I believe a large portion of these issues are caused from inactivity..... because my car runs/idles very well (knock on wood) since the increased activity and not a single code for well over a year now. This is no accident, as I have been massaging the car with this goal in mind since I have owned it !

 

Would be nice if someone had an SD2 or SD3 as I would assume it would give read outs to all the various sensors, so you could compare the read outs between when it is running correctly and when it is not. It would certainly narrow down the search. Either one of the sensors is intermittment in operation, or it is getting a funky temperature or input of some sort.

 

Cool !!!

Does your LH fan run full-time with the AC on, or does it cycle?

I am pretty sure my LH fan runs full time during AC operation.

 

If the RPM drop is more pronounced with the A/C on, could the problem be related to the current surge through the radiator fan when it first clicks on?

If so, would this be a failing battery/alternator issue...or perhaps just point to needing 40 amps worth of NTC thermistor surge "protection" in the wires going to the radiator fan?

 

Shouldn't the LH fan go on and stay on in lockstep the AC switch??

 

Doesn't that fan cycle on when the coolant temp is over 190 and then turn off once the coolant temp is down around 150?

 

Yeah, when the AC is off it starts at 190 and back off at 170...

Now here is what I was alluding to earlier about 360s having this "idle" issue.... but this time its a 430.......

From the 360/430 section:

http://www.ferrarichat.com/forum/showthread.php?t=165802

 

Interesting, as that is all occuring at start up. This is the exact problem I have experienced for the past couple years with my 1997 355 spider. My problem is intermittent. It used to happen both hot or cold start, it would initially idle around 750 rpm. Shut off and restart, and it would idle normally, around 1400 cold, or 1000 rpm hot. I replaced the following (in this order), the idle control motor, throttle position potentiometer, then the water temperature sensor. All seemingly to little or no effect. Although, right after replacing the TPS, I had no recurrance of starting idle issues for two months...but then it returned. I recently had the car at Ferrari of Seattle, and they thought they found the problem in a bad pin in the Amp connector to the idle control motor, but the sympton returned, so that was not it. One change since I started the parts replacement sequence, the problem is only occuring upon cold start, it does not happen with warm or hot start, ever.

When it does cold start and idle at 750 rpm, if I leave it...it will slowly creep up to the correct idle speed after 20 to 30 seconds. But it doesn't sound right, and vibrates a bit, so I always shut down and restart. Once in a while it requires two or three tries.

 

Perhaps you both should plug a voltmeter into your cig lighter outlets to rule in/out large voltage fluctuations while your idle is erratic.


I can say that Motronic systems (M2.5 and up) cue off of fuel maps that are hit with an extremely rich adjustment based upon the detected battery/alternator voltage (i.e. a low voltage means keep the injectors open longer to deliver the "same" amount of fuel).


I'd also wonder if spraying starter fluid or brake fluid at the base of your intake plenum (are you feeling lucky, well, are you?!) might detect an intake gasket leak (rpms would change if there is a leak and if you don't catch yourself on fire in the process).

 

Duct tape a 2 inch cardboard extension to the fin dividing the fan inlet from the air cleaner inlet and see if it changes.

Dave

 

Duct tape and cardboard ??? Is this how these things are fixed ?? Just kidding Dave I know what you are trying to accomplish !!

What do you think is causing the same thing on the 360/430 as they have their air intakes on the top of the rear fenders ??

 

I just figured if it was something that could be tried in 3 mins or less....

I have yet to see it on either of the later models.

Dave

 

I hope you mean brake cleaner, not brake fluid. Brake fluid is not usually in an aerosol form, and sprayed on a painted surface will eat it.

 

Yeah... one of the two symtoms being discussed for the 355 is a "cold start" rough idle almost identical to the one the 360/430 guys are having. Check out this thread from that section:

http://www.ferrarichat.com/forum/sho...d.php?t=165802

What do you think ?

You are right ! I do think he meant brake "cleaner" fluid.... !!

 

Hey, that could start a new fad: the eaten-up engine-paint look!

 

Goth,
Can you repost the link? It is not working.

Thanks.