4.8is won't rev over 5000rpm

centurion · Post by **centurion** » Tue Dec 23, 2014 11:20 pm

Hi guys.. Today i spent some time polishing up front headlights and upon testing couple points i noticed that car won't rev over 5000rpm in P/N. I didn't have a chance to go for a ride but guess it would behave the same in D too. Any hints as to what could be the cause of it?

Checked the obd... No errors and lights on the dash

.

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Lee4.8is · Post by **Lee4.8is** » Tue Dec 23, 2014 11:42 pm

Some BMW`s do this for some reason and maybe its to protect the engine and my E92 M3 would only rev to 7000rpm in neutral yet it redlined at 8400rpm.

I don't think its much to worry about and I have read similar with other models too.

Horizon · Post by **Horizon** » Tue Dec 23, 2014 11:43 pm

My Vw Golf has a Rev ,Init of 2.5 K in park And neutral. Maybe yours has a Rev limit Cohen stopped too

Denis O · Post by **Denis O** » Wed Dec 24, 2014 6:16 am

Had the engine warmed up enough. I'm guessing the 4.8 is like the 4.6 in that the rev counter lights go out, as the engine warms, and allows greater revs. Perhaps that restricts revs until the engine is warmed up.

pvr · Post by **pvr** » Wed Dec 24, 2014 8:52 am

Just curious why you would rev it in neutral that high ...

Lee4.8is · Post by **Lee4.8is** » Wed Dec 24, 2014 10:12 am

[quote="pvr"]
Just curious why you would rev it in neutral that high ...
[/quote]
I used to enjoy revving my old one on the drive but I never went that high with the revs I just used to enjoy the rumble.

I only knew my M3 only revved to 7k in neutral from reading about it.

sunnydude959 · Post by **sunnydude959** » Wed Dec 24, 2014 11:12 am

Its to protect the gearbox when in park or neutral as it heats up considerably when revving, if I remember correctly reading somewhere. Most modern auto's have a similar feature.

It will rev higher when in D, S or M

X5Sport · Post by **X5Sport** » Wed Dec 24, 2014 3:39 pm

+1 for transmission protection system. Very quick way of doing damage in the same way as towing an auto.

Richard

centurion · Post by **centurion** » Wed Dec 24, 2014 5:08 pm

Thx for your feedback... Eng was warmed up to a nominal working temp and have revved it to see how far it can go (out of curiosity

).

Still curios why it won't go all the way!? And not sure why g'box has to be protected in N as it is 'inactive' so to speak.

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X5Sport · Post by **X5Sport** » Wed Dec 24, 2014 6:14 pm

Because the torque converter is never inactive and neither is the input shaft. This can cause all sorts of internal issues within the various clutch, brake and planet sets and so the box needs protecting. There is no need to run an engine at those speeds in normal operation in Neutral or park.

Richard

shadrack · Post by **shadrack** » Thu Dec 25, 2014 12:06 am

[quote="X5Sport"]
+1 for transmission protection system. Very quick way of doing damage in the same way as towing an auto.

Richard
[/quote]

what damage can be done towing in an auto, just i noticed my ml has a 6400kg train weight so must be rated to 3.5t and has a mercedes detachable towbar fitted

sleepyfolk · Post by **sleepyfolk** » Thu Dec 25, 2014 12:03 pm

I think he means towing an auto not towing with an auto

X5Sport · Post by **X5Sport** » Thu Dec 25, 2014 12:36 pm

Correct.

shadrack · Post by **shadrack** » Thu Dec 25, 2014 8:47 pm

[quote="sleepyfolk"]
I think he means towing an auto not towing with an auto
[/quote]

ahhh, i was pissed

centurion · Post by **centurion** » Mon Jan 05, 2015 1:28 pm

I tried driving over the weekend in both auto [D] and tiptronic and simply won't go over 5k... something I noticed is that it downshifts really quickly and very odd feeling of not 'breathing' properly. I had that feeling during the student days in dad's Astra where exhaust section was so clogged that no gasses were coming out?!

I replaced vacuum hoses/CCV's and have done the scan with INPA [no issues]. Only tiny bit I noticed is that voltage is slightly off on cylinders 3 and 7... replacement coils+spark plugs will go in over the weekend to see if that's the cause but I doubt it would be. any hints?

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4.8is won't rev over 5000rpm

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