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Hesitation after 4k rpm

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thecremeegg
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Hesitation after 4k rpm

Post by thecremeegg » Mon Jul 30, 2018 1:29 pm

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?

mmm-five
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Hesitation after 4k rpm

Post by mmm-five » Mon Jul 30, 2018 2:07 pm

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.
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thecremeegg
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Hesitation after 4k rpm

Post by thecremeegg » Mon Jul 30, 2018 2:27 pm

mmm-five wrote: Mon Jul 30, 2018 2:07 pm 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.
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

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Fox889
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Hesitation after 4k rpm

Post by Fox889 » Tue Jul 31, 2018 10:25 am

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?
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Hesitation after 4k rpm

Post by aquarianone » Tue Jul 31, 2018 9:59 pm

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:
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Hesitation after 4k rpm

Post by AveZ4coop » Wed Aug 08, 2018 4:28 am

Sounds like a coil pack? I had exactly the same symptoms. New coil packs/plugs, all now good. :driving:
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Hesitation after 4k rpm

Post by thecremeegg » Fri Aug 17, 2018 1:43 pm

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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