F355 M5;2 idle speed high after deceleration.

Mine did the same but with no difference if AC is on or off. I noticed that the gas peddle was not smooth. So a bit of WD40 on the linkage all around did the trick.

 

Well, I'm not intimately familiar with how this is set up on an F355 but many obd2 cars have a pressure sensor on the high side a/c line that is read by the ecu to calculate torque loss by the a/c compressor.

If it was reading wrong/abnormally high the ecu may add too much idle airflow to compensate.

Again, not sure if the F355 works this way, just an idea.

 

Mine does the same thing! 1997 5.2

After letting off the gas, it hangs up at 1500 RPM then drops to 1050. Only when the AC is on....always wondered about this!!!!!!!

 

I would think this is normal.. ive had other cars that do the same thing.. the ecu adjusts the idle to compensate while the AC is on.. thus why the AC drains power/ throttle response when on..

try being at idle, with AC off... then turn on AC.. you will likely see the rpm lift up abit and then settle back down..

unfortunately.. the AC is not functional on my 355.. so I have not experienced this yet during my short ownership thus far.. I already bought a new compressor for repair in the spring.

youre not seeing the rpm hang when the ac is off.. only when its on.. so more then likely this is normal behaviour..

and would make sense when slowing down..
cruising at 3k rpm.. then come to a stop.. the ECU probably hangs the idle at 1500rpm for a few moments as youve seen to accomodate for the AC being on...and then drops back to normal idle..

I also have a Vortech SuperCharged 350Z, the SC is belt driven directly on the crank.. thus the SC like an AC compressor acts like a drag on the crank..and can hang up the idle briefly under deceleration..

 

Bunched up floor mat?

 

Tony

This is most certainly not normal.

Ferrari's are not supercharged nor are they Datsuns or whatever a 350Z is.

Revs should fall back to 1050 quickly and smoothly whether AC is on or off.

My M2.7 falls back to 1050 always.
There's a component that has failed somewhere.

 

it's a Nissan 350z. and know ferraris aren't supercharged lol I own a 355.

the AC on my 355 is not functional at the moment so I don't know if this is normal behavior
therefore in regards to the 355 likely you are correct this is not normal with AC on

but most other cars I've owned, when engaging the AC caused the rpms to perk up abit and then settle back down.

 

Agree. What mine does very specifically:

After pushing in the clutch and letting off of the gas, it seems like the rpms do fall perfectly back to a normal 1050, but there is a slight pause on the way down.....sort of like vroooooom-oomoooooom, if that makes any sense, as opposed to perfectly smooth dropping of RPM's without the surge/hangup issue. It always falls back to normal RPM's with the AC on OR off, its just that when the AC IS ON, there is a slight hangup on the way down.

The first time I heard it, I broke out in a cold sweat and said "OH GOD what the hell is that?"

Anyone else have any more input?

Sure....i see a short change in the RPMS as soon as I hit the AC button, but things seem to return to normal right away.

My issue seems to be specific to falling RPMS only. No acceleration or idle issues.

It simply hangs up for about one second or less on the way down.

The fact that I only get AC out of the defrost vents also makes this problem annoying at best. When it's 90 degrees out and I have the AC on, I feel like I am in the desert, cooking like a Hot-pocket.

 

Ready...

Your car is not at optimum.
Should be no rev hangup with ac on.
Your ventilator adjustment motor is whacked.
Air should be vented to wherever you want it vented.

These cars are simple but they use many small parts to make a bigger part...after 20 years things fail....they are precision instruments...not like Datsuns or toyotas, etc.....
When everything is at optimum they are in the top 10 of greatest sports cars ever made, ever (355).... The trick is getting it all working at optimum all the time!

 

Thanks for posting the solution

 

Can you elaborate, I have the same problem were the idle sometimes stays at around 1200 RPM after decelerating, but I never turn on my AC, so I'm not sure if it's related to AC compressor.

 

Yes

Good on you for posting the solution

 

Hey,
Im having the same problem, could you type the part number of the o-ring please?