RDS928S

Yesterday was 70 degrees in NJ so I decided to start my turbo after 3 mos of storage & let it run/idle for a while.

Once warmed I started to rev the motor ( in park) & it cut out at 4,000 rpm.
Big flat spot or as if it was programmed to do it-no fuel etc?

Below that was fine. Sounded good with crisp throttle blips/revs up to 4k rpm.

Any ideas?

Thanks in advance.

Berra

The engine will never reach optimum temp when on idle, no matter how long you let it run! I would never rev it as high as 4000, maybe up to 2000 but that's it. It's up to each and one of us I guess but just a "heads up" on that.

I know some cars have it programmed, but didn't think our Turbo's did this? Never tested so I wouldn't know.

Macster

Haven't come across any artificial RPM limit in Park (or neutral in the case of a manual transmission car) in all my Turbo stuff.

Regardless I would never attempt to rev the engine to even 4K even if it was fully warmed up while stopped with the transmission in neutral so I have no direct experience.

Absent a CEL and any other untoward engine behavior my advice is take the car out on the road and drive it around keeping RPMs down below 4K until the engine is fully up to temperature then when safe accelerate the car moderately hard up to and beyond 4K and see if the engine is ok or there is a problem.

If ok well there you go.

If not ok you'll have to come back for help on that.

Carlo_Carrera

It is possible even though the engine had reached operating temperature that the transmission had not and the ECU cut the power.

napoleon1981

It actually does reach operating temp. It takes a while, but it reaches it.

Berra

Do you go by the water temp? Because that's not operating temp.

napoleon1981

The ECU doesn't let you go above 4k rpm if it thinks the engine or transmission is too cold? Never noticed that, although I don't think I have tried. I don't believe however that temperature has anything to do with the ECU allowing you to rev the engine above 4k.

napoleon1981

Cars can overheat when idling. In fact it is fairly common and happens when the electric radiator fans are not working.

If you let your car idle for 15 mins in the garage, you can actually do the oil measurement as well (the car believes it has reached operating temperature).

Berra

A car that overheats when idling for "too long" has issues! I've had times when I've sat in my M5 for up to an hour in 100+ degrees weather idling and the water temp wouldn't move. The fan did its job but would occasionally shut off.

Sure you can do a measurement but trust me, the engine is far from operating temp. Best way to give it temp is to drive and also pay attention to the oil pressure. Higher temp = lower pressure.

I drive a minimum 30 min before putting load on the engine and even then I won't go high on rpm's.

napoleon1981

You are contradicting yourself.

If an engine would never reach operating temperature idling, it wouldn't need any cooling either. Thus no fans would be needed and cars would never overheat when idling.

My point is that even an idling combustion engine generates enough heat to meet and exceed operating temperature and eventually even needs cooling.

Of course a car that overheats has issues, also when idling. I did not say overheating during idling is normal.

Kevinmacd

Take it out warm it up so you can get an oil level reading and see if your symptom still exists!

Berra

No I'm not, but I understand why you're saying that, my bad. My point with the M5 was after a long trip I did across Europe, wasn't idling from a cold start but waited in line at a border.

T10Chris

The 996TT can reach operating temp in regards to oil temp at idle, but it takes literally 10-15 mins... You can measure oil level after engine oil temp is 165-170* and I think 180* is recommended temperature for the oil..

bansasn

I have not rev mine to 4K in a netural. May be it's like the Cayenne turbo. On my 05 CTT its never be able to rev pass 4k on Park gear. I think it's a safety factor.

Carlo_Carrera

Rev limiting by the ECU because of lower than optimum temperatures is common in modern cars. Especially if the car is standing still. Google it.