m62 surge of power above 4k RPM's (or lack of power below 4k)?

[jgood]

I bought my 2002 X5 4.4 about a month ago, and have noticed that it's either down on power below 4k, or has a surge of power right at 4k. I've never driven an m62 powered vehicle, much less another X5, so I don't know what's normal. It feels strong down low, and up top as well, but I can notice that at full throttle from idle, when it hits 4k, the sound changes, and it begins pulling harder. I'd say it feels like 20-30 whp more between 3900 and 4000. It's not a gradual thing, it's an instant change of some sort. It's not really bad or anything, just something I notice if I pay attention. Looking at stock m62 dyno graphs, I know I shouldn't be feeling that, as the power curve is smooth in that RPM range.

I'm familiar with single vanos engines, as the m50b25tu that I put in my e30 is single vanos. That is an on/off solenoid though, 6 degree advance to 6 degrees retarded, at 1k RPM's and again at 5200 RPM's, depending on throttle load. From what I understand, the vanos in the m62 is continuously variable, and has 20 degrees of motion. Could something potentially be causing it to not operate properly, until 4k?

[jgood]

And just to clarify, it's not a "surge" that hits at 4k then goes away, it's just a general increase in power at 4k, that continues til redline, it feels/sounds exactly like hitting about a 25 shot of nitrous.

[Sundayjumper]

Have you had your car on a diagnostics ?

I noticed a similar surge on mine and the diagnostics has shown up a cam sensor fault. I'm guessing this either stops the VANOS operating, or makes it operate in a limited way. I'm planning to fit new sensors tomorrow.

[Nik]

Do you have SES light on? I had that feeling before, but then my Vanos timings were off.

[o. l. t.]

My Mercedes CLK430 did that as the MAF sensor was going out. The easiest way to figure it out was to disconnect the battery for a few hours to reset the computer. Once the computer was reset and the engine was not running off the ECU's cache and was taking new readings it was immediately obvious which was bad as it wouldn't provide the ECU with information. Most OBDII cars learn your driving style and the ECU cache's info so when you clear it it can't reference the old settings it figures are already there as a baseline.

It's also the cause of the famous line "this wasn't like this before I changed the battery" as faulty products become instantly obvious when the ECU is reset.

[bgsquad]

i slightly feel this on my 3.0i as well... not sure of the exact rpm though...

[jgood]

Originally Posted by Sundayjumper

Have you had your car on a diagnostics?

No I haven't, I assume that means I need to take it to the dealer and have them charge my 6 billions dollars to plug it in and tell me what the computer says?

Originally Posted by Nik

Do you have SES light on?

Nope, no lights.

[Brandond11]

Check you DISA valve and make sure it isn't broken

[jgood]

Originally Posted by Brandond11

Check you DISA valve and make sure it isn't broken

m62's don't have DISA.

[Sundayjumper]

Originally Posted by jgood

No I haven't, I assume that means I need to take it to the dealer and have them charge my 6 billions dollars to plug it in and tell me what the computer says?

That's a possibility, but you can do it yourself if you don't mind getting your hands a little dirty. I'm new on the forum and not sure where the mods stand on this, so won't go into any detail here.

Anyway, FWIW, I've only had mine (2001 4.4i Sport) a fortnight but had noticed a surge at about 4k revs a couple of times. I generally drive pretty sedately though so I couldn't tell you if it was doing it every drive. I checked the error codes a few times and there was consistently an error for the cam sensor on bank 1. I bought and fitted two new sensors today and so far, touch wood, no more error codes, and having deliberately run it well past 4k revs a few times there was no surging. The engine actually seemed smoother generally but that could be simple optimism having spent ££££s on a couple of small pieces of plastic

So based on my experience, I'd say you might need new cam sensor(s), but get the codes read before you chuck money at it.

Steve.