Intermittent Launching and Power Problem

[antman 0]

Hey guys,

I have been reading up about VANOS seals and the like but I'm still not 100% convinced if this is issue.

I've only owned the car for about a month. I've noticed when putting my foot flat on accelerator from a stand still the car slowly sets off then surges through the rev range. If I kick it down to 1st gear while rolling it seems to pull much better. This surging also happens mid range when full throttle while moving too.

I've also noticed a small rough idle when the cars cold, this goes away completely once the car has warmed up.

Sometimes the car will launch perfect off the line like a bullet and give me a surprise so I can't figure out why sometimes it perfectly fine

The problem is pretty unnoticeable while doing light city driving why I didn't notice it in test drive It does seem to be lacking low down power sometimes and changing down gears unnecessarily.

Any advice will be appreciated!

Car is a 2001 530i Motorsport

Cheers

[kwhelan 241]

2001 so guessing high mileage, I'm guessing auto trans and or sensors are a little fatigued, you can't expect an auto box to work as new forever or the myriad of sensors

but even the new specially the multi geared ones it is definitely possible to confuse them at times ,more so if your coasting along like a nana,you lift off for a roundabout and apply power and its not always 100% the same experience,and slowing down they can downshift at odd times,driving them harder and the bugs seem to disappear.

but the vanos are cheap and it will only improve any situation so if its bugging you get it done.

[*Glenn* 854]

Start by getting it scanned by a person who understands what they are doing

[antman 0]

It has 150,000ks. NZ New with Full Dealer Service history. Trans shifts perfectly and can't feel any issue with it.

[antman 0]

Start by getting it scanned by a person who understands what they are doing

What I was thinking. My mate uses BM Workshop so might take it there to get scanned. Would at least save me hopefully going down wrong path.

[KwS 2425]

Sounds similar to my 523i before i did the vanos on it. Need to get it scanned first though, otherwise its just throwing money at a problem hoping it sticks.

Mine was a real dog when cold, surging and was damn near impossible to cruise smoothly at low-mid throttle (would surge and jerk until i let off or gave it more gas). Made it interesting leaving my old parking building when cold.

Edited March 7, 2016 by KwS

[antman 0]

Sounds similar to my 523i before i did the vanos on it. Need to get it scanned first though, otherwise its just throwing money at a problem hoping it sticks.

Mine was a real dog when cold, surging and was damn near impossible to cruise smoothly at low-mid throttle (would surge and jerk until i let off or gave it more gas). Made it interesting leaving my old parking building when cold.

Yeah that's one thing I've heard different to other peoples problems. Unless you notice it while stationary and cold it isn't really that noticeable when you're driving nicely. Only with.. spirited driving. But hey maybe they seals aren't quite gone yet. I'll try find someone to scan it.

[Herbmiester 928]

Could be the idle Air Control Valve (possibly in conjunction with other things), at that mileage it could probably use a clean.

Edited March 12, 2016 by Herbmiester

[antman 0]

Could be the idle Air Control Valve (possibly in conjunction with other things), at that mileage it could probably use a clean.

Cheers for the suggestion. I put my cheap scanner on it and found some lean codes. Had a Google and checked the intake pipes. Found the intake boot closest to engine was cracked so replaced that and the power and launching is perfect now.

I just noticed this morning that the cold idle is still a little rough so might be another thing.

[Allanw 1071]

It's not unusual for them to idle a little rough (no misfires, just not prefectly even)- when cold. They alter the cam timing at cold idle, and dump in fuel to heat the cats up.

It doesn't usually help with the rough idle (unless it really bad!), but I'd suggest getting the Vanos seals done - they're complete crap from new. It's not so noticable in an auto, but it made a MASSIVE difference to our manual. It smoothed out the power, and gave a noticable improvement to low revs responsiveness, plus it was much harder to stall (which was really easy prior to this.

Check the DISA valves for rattles, or remove it and check it physically - it's a 3 minute job. A DISA that falls apart can destroy an engine in seconds, and they're not a "lifetime" item either.

Don't assume everything has been done, just because it's got "full dealer history" - the dealer only does what the customer pays for, and Kiwis are crap at servicing cars, on average.