Hesitation after 4k rpm

T

thecremeegg

Active member
 North Hampshire
So I have a high mileage (135k) 3.0 that idles smoothly and up to 4k rpm is very smooth, but at the 4k point it hesitates and surges.

I thought I had fixed it when I changed the DISA but it seems not. So for the car has had:

Vanos rebuilt
New DISA
New spark plugs

It always runs on premium unleaded if that makes any difference.

Any ideas what it could be as I'm stuck!

Thanks

Edit: As an update, I just checked the MAF and the plastic grille thing in front of it was completely detached....is it required, I presume so hence it being there? Could this cause the issue?
 
It could cause an issue as it smooths the airflow to the MAF so that it gets a consistent reading.

Other issues could be as simple as leak in the intake boot.
 
mmm-five said:
It could cause an issue as it smooths the airflow to the MAF so that it gets a consistent reading.

Other issues could be as simple as leak in the intake boot.
Click to expand...

The intake boot is an interesting one as it does look a bit old - no obvious leaks though but worth a shot as they're only cheap
 
Leaking intake boot should [?] ping up an EML light [as mine did].
Common fault on these girls, changed mine in a few minutes, bought the elbow from a main dealer & wasn't silly expensive.
Coil pack could be the next port of call?
 
Might be worth checking the battery, changed mine a few months back and it was quite surprising how much it improved the cars responsiveness :thumbsup:
 
Update time: The intake boot was the cause. I put duct tape round the top where it looked suspect and the problem has vanished, no longer feel any hesitation at 4k rpm. Thanks mmm-five!
 
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