Not such smooth acceleration.

[Heat Seeking Missile]

I've noticed for a few weeks now that when I accelerate on WOT, as the revs increase, it feels like I get lots of small flat spots and doesn't accelerate smoothly.

Accelerating on part throttle seems to be alot better but it sometimes still feels like its there.

I will try it on VAGCOM when I find my disc, but I'm thinking its the knock sensor for some reason. I'm pretty sure I read on here ages ago about someone having a similar problem.

Any ideas?

Mark

[S2central.net]

Coil packs or POS (or bad earthing) ?
Lambda or MAF ?
Air leak ?

[Heat Seeking Missile]

Lambda and MAF are less than a year old, wouldn't be one of them would it?

Whats a POS? Could be the coil packs I guess. What is easiest and cheapest to check first?

Mark

[S2central.net]

POS - Primary Output Stage... Search here for more info - its an amplifier for the coil signals from the ECU. If you can get a couple of spares to try that will help rule it out... Or swap in another cars coils complete with cover if you can... You might have one or two bad uns - quite hard to separte them. If one is dead/dying then the others can't be far away.

[Rusty]

Plugs?

[Heat Seeking Missile]

Thanks Paul, might be time to try a shout out then, try and get some spares first then. Would any of this come up on VAGCOM perhaps? I dont think it would but no harm in asking.

Mark

[Heat Seeking Missile]

Andy, the plugs were replaced this time last year but they are a "consumable" I guess. I dont know why I didn't think of them before. I used to have a 1300 Hyundai Accent that used to munch through plugs for some reason.

Mark

[Fat Audi 80]

Sounds like a weak spark at higher boost levels to me. Also check plugs are new and tight and that the plug/coilpack rubber connector boots are in good shape...

Cheers,

Steve.

[Greg_S]

Do you have NGK or Bosch plugs fitted?

[Heat Seeking Missile]

I'm not sure what plugs it has, QRSport did the service last year on it. What difference does it make?

Mark

[Greg_S]

I had a similar problem recently with NGK plugs which seem to go off a bit after a year or so and the bosch ones work and last alot better. It would be worth checking though

[Heat Seeking Missile]

Ah right fair enough, might not be a bad start then I suppose. Thanks for the replies everyone.

Mark

[Rusty]

Bosch Platinum plugs F5DPOR, make sure they're tight (but not too tight), can't remember the proper figure, something like 30Nm but DON'T quote me on that. Inspect the wiring, earths, boots and check the plugs at the back of the enginebay if you don't get any other ideas...

Other things to do are to disconnect the breather pipe and plug the MAF - Turbo hose as a leak on the inlet before the turbo can cause funny running.

Clean the MAF, I use carb cleaner, some think that's a bit harsh.

Check every clug you can get your hands on, make sure it's secure.

Check the earths on the back of IM.

That lot should keep you busy, even if it doesn't solve the problem you'll know it's all 100% (ish )

[wilywyg]

flat spots

mine was the same and it was the pos.
under wot when warm it would seem to have flat spots. then after chasing my a**h around for two weeks,trying to find the fault, it started to run lumpy after the engine had been run hot then turned off for 15 mins or so. its when the pos has got hot and the pixie's start moving in
hope this helps

[macspring]

Also consider this,

mine had a pinking sound on WOT at say 5.5K+ rpm and sometimes felt a little reluctant / small bit hesitant to rev out completely cleanly, and so I felt it might be fuel related.

I'd already cured a POS issue when it dropped onto four cylinders a few months previously, i.e. BTDT re POS.

So decided to change the fuel filter on the Avant and because it is out of sight and out of mind, and is not the easiest or most pleasant job to do, so they tend to get overlooked, and on both of my Avants they were the original fuel filter as indicated by the date on the two respective filters.

Changing them is not an impossible job, but be prepared to be patient and for the bolt that clamps the filter to be seized and to spin. (I think also one of the three tank "straps is NLA?). You appreciate what's involved better after you've done it. I know this isn't a great help on how to change it, but the job is worth doing IMHO.

The car seems, I say seems, to be better for having changed the fuel filter, so while it may not be the cause with yours, if you have not changed the fuel filter yourself recently you may wish to consider doing so, if only to rule it out as a possible cause and to know that it is done.

Additionally, the improvement was not instant, but it is like as if the ECU adjusted itself to take account of the change in the filter. Don't use WOT at 6k+ that much, but when I do pinking does appear to be gone, but a tiny bit of the hesitancy is sometimes there, this could be related to the quality of petrol, don't always fill up at the same garage / with the same brand.

Want to change the knock sensors as I'm sure they're original and new ones can only be better after 13 odd years of heat cycles, but too busy driving it.

Hope the above waffle is useful to someone?

Kind regards.