Surging/Jerky Acceleration

Ruofdez · Post by **Ruofdez** » Thu Sep 03, 2020 3:52 pm

This is a bit of an ongoing issue and one I haven't been able to find from searching. Basically when accelerating fairly slowly and around 60-70% throttle the power surges on and off as if I'm lifting off and pressing down when the pedal is static or barely moving. Don't really notice it with city driving, just when I'm holding the throttle at 60-70% in higher gears which tends to be the motorway. If I push the pedal down a bit more it's then fine and the same if I lift off, there's just a narrow band where it's an issue with a certain speed of pedal movement or if holding it.

Others that have driven the car haven't even noticed it on a long drive but as I'm aware of it I can notice it quite clearly and 'balance' the throttle right in the spot where it does it to make it happen repeatedly.

Occasionally it will happen when accelerating at moderate speed around a long bend, which wouldn't be ideal in the wet.

Now the strange thing is I've replaced the MAF (3 times). Every time the MAF is replaced it seems improved for a month or more and then it gradually goes back to doing it again. I thought it must be faulty MAFs (Hella branded) so bought a VDO one and it's starting to do it again, so it seems the MAF isn't the issue however if the MAF is unplugged the issue goes away.

I have INPA should anyone have any ideas with that, though I've not delved into that yet as it's all in German so not easy to use!

Car is manual gearbox.

Any ideas would be brilliant.

javis20 · Post by **javis20** » Thu Sep 03, 2020 4:52 pm

Well, obviously use inpa to check for codes.

How many miles on the plugs?

Ruofdez · Post by **Ruofdez** » Fri Sep 04, 2020 9:28 am

javis20 wrote: ↑Thu Sep 03, 2020 4:52 pm Well, obviously use inpa to check for codes.

How many miles on the plugs?

Yeah no codes on standard code reader but I'll see if that picks anything up. Only changed them just over a year ago, maybe 10,000 since then. The fact it doesn't do it when the maf is unplugged makes me think they're probably ok.

Chippie · Post by **Chippie** » Fri Sep 04, 2020 9:48 am

What about the throttle peddle/potentiometer?

Wookster78 · Post by **Wookster78** » Fri Sep 04, 2020 10:02 am

Hi,

Had similar issues with mine and bogging down in power. This was down to a failing DISA valve and VANOS which needed the seals replacing. Has this been done on your car? If not I would suggest these two would be the first place to look as it resolved my issues.

Neither of these showed as a fault in Carly or INPA so I wouldn’t expect any codes to come up. Couple of threads of here to do both jobs.

Ruofdez · Post by **Ruofdez** » Mon Sep 07, 2020 8:34 pm

Chippie wrote: ↑Fri Sep 04, 2020 9:48 am What about the throttle peddle/potentiometer?

I will research this thanks.

Wookster78 wrote: ↑Fri Sep 04, 2020 10:02 am Hi,

Had similar issues with mine and bogging down in power. This was down to a failing DISA valve and VANOS which needed the seals replacing. Has this been done on your car? If not I would suggest these two would be the first place to look as it resolved my issues.

Neither of these showed as a fault in Carly or INPA so I wouldn’t expect any codes to come up. Couple of threads of here to do both jobs.

Mine doesn't bog down in power, it really is quite subtle and I doubt most people would even notice it, needs some very particular circumstances though thank you for the suggestions. I changed my DISA for the metal flap as a precaution. The VANOS seals I don't believe have been replaced though. What I don't understand though is that when the MAF is unplugged (or replaced for the first month or so) the issue disappears completely. That makes me think it's something electronic rather than mechanical but perhaps I'm wrong with that, any thoughts?

Wookster78 · Post by **Wookster78** » Mon Sep 07, 2020 8:47 pm

Assume you don’t have an after market induction kit or K & N filter installed as the oil is sometimes known to coat the MAF and damage it over time?

Maybe a failing coil pack?

Ruofdez · Post by **Ruofdez** » Mon Sep 07, 2020 9:42 pm

Wookster78 wrote: ↑Mon Sep 07, 2020 8:47 pm Assume you don’t have an after market induction kit or K & N filter installed as the oil is sometimes known to coat the MAF and damage it over time?

Maybe a failing coil pack?

I thought the same and switched to a standard air filter on the first maf replacement so unfortunately not that.

I do have a spare coil pack I could try but would a code not be showing if one was having issues?

I plugged into INPA to check for any issues and need to decipher it. There were only a couple of things but I’ll post them up in case anyone spots something.

Ruofdez · Post by **Ruofdez** » Wed Sep 16, 2020 3:35 pm

Well finally got round to modifying the cable and getting the codes from INPA. Need to research them myself however if anyone spots anything from experience and would like to offer any advice I'd be very grateful.

Ruofdez · Post by **Ruofdez** » Thu Sep 17, 2020 8:27 am

Those messages seem to relate to lights and windows. Not sure exactly what, though both are fine and doesn't help me with this issue so drawing a bit of a blank. Damn!

ph001 · Post by **ph001** » Thu Sep 17, 2020 10:39 am

First thing to check on the M54 is for any splits in the concertina elbow on the intake...

: split elbow.jpg (92.73 KiB) Viewed 777 times

Ruofdez · Post by **Ruofdez** » Thu Sep 17, 2020 10:57 am

ph001 wrote: ↑Thu Sep 17, 2020 10:39 am First thing to check on the M54 is for any splits in the concertina elbow on the intake...
split elbow.jpg

Thank you for the suggestion. I replaced this part last year due to there being a split however I will double check for any issue with new one.

enuff_zed · Post by **enuff_zed** » Thu Sep 17, 2020 11:02 am

Ruofdez wrote: ↑Thu Sep 17, 2020 10:57 am
ph001 wrote: ↑Thu Sep 17, 2020 10:39 am First thing to check on the M54 is for any splits in the concertina elbow on the intake...
split elbow.jpg
Thank you for the suggestion. I replaced this part last year due to there being a split however I will double check for any issue with new one.

Fingers crossed then that it's something simple like that bit not being aligned properly, clips not tight etc.

Ruofdez · Post by **Ruofdez** » Thu Oct 15, 2020 9:51 am

enuff_zed wrote: ↑Thu Sep 17, 2020 11:02 am
Ruofdez wrote: ↑Thu Sep 17, 2020 10:57 am
ph001 wrote: ↑Thu Sep 17, 2020 10:39 am First thing to check on the M54 is for any splits in the concertina elbow on the intake...
split elbow.jpg
Thank you for the suggestion. I replaced this part last year due to there being a split however I will double check for any issue with new one.
Fingers crossed then that it's something simple like that bit not being aligned properly, clips not tight etc.

Well I checked the intake pipes and tightened up a few jubilee clips and was quite optimistic as seemed a bit better the next day but the day after (today) it seems to be doing it again. Really weird. There is one clip missing from the airbox but don't think that's the culprit. Will repeat the exercise one more time to make absolutely sure it's nothing that's loose but not looking hopeful, damn!

Ruofdez · Post by **Ruofdez** » Thu Oct 29, 2020 11:52 am

N/A Thanks for help

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