Surging/Jerky Acceleration

[Ruofdez]

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]

Well, obviously use inpa to check for codes.

How many miles on the plugs?

 

[Ruofdez]

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]

What about the throttle peddle/potentiometer?

 

[Wookster78]

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]

What about the throttle peddle/potentiometer?

I will research this thanks.

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]

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]

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]

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]

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]

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

 

[Ruofdez]

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]

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]

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]

N/A Thanks for help

 

[bigwinn]

Of course the danger is with a fault like this you can be sent off in many different directions- to no avail!

But- based on enuff_zed' experiences this week with vanos solenoids sticking, is it worth checking these?

 

[enuff_zed]

Of course the danger is with a fault like this you can be sent off in many different directions- to no avail!

But- based on enuff_zed' experiences this week with vanos solenoids sticking, is it worth checking these?

Would be a hell of a coincidence, but easy to check.
Take off the solenoid, stick your finger in the end of the valve and make sure it pushes in freely and springs back out again.
Inlet is easy, exhaust will be trickier to reach and you'll get a bit oily.

 

[colb]

What about the throttle peddle/potentiometer?

You should be able to check this out using INPA, seems a likely culprit as you can get it to do what its doing in a certain position on the throttle pedal. I suspect the pedal or the throttle body end of things.

 

[Mike6]

Spark Plugs?? or plug lead. I dont think these will give an error code so worth checking how long ago the plugs were replaced.

 

[Ruofdez]

Apologies for the delay in replying, things have been a bit mad but thank you once again everyone for the suggestions. I shall do some research on everything mentioned. I’ve been driving with sports button on and it’s actually seemed a fair bit better though if I look for it I can still occasionally notice it. One of those very subtle issues that most people would never notice but once you know it’s there it’s irritating!