Jerky Under Acceleration

[NickP]

Picked my car up after a month at the garage following a new from end including oil cooler, air conditioner and bumper being fitted. On way home after it had warmed up a bit I gave it some beans and it lurched like a kangaroo. I left it for a bit to warm up more but it does the same thing all the time. The car is going back to the garage and I'm hoping it will be covered as it wasn't doing this when I last drove it. Anyone have any ideas what might cause this?

And to top it all off the bumper colour match is awful.....

 

[onlinesys]

Morning NickP, sorry to hear this. Do you mean it is jerky when you change to lower gear/press on the throttle?

 

[onlinesys]

I had the same issue if you are referring to accelerate/press the throttle especially in 1st or 2nd gear in lower rpm.
I did a throttle reset and found the throttle became heavier and finally the car was in dead limp mode (1000rpm) with
CEL on. The previous owner had done the contactless throttle potentiometer and the pedal-pot wirings so not sure
if it is connection problem. Hope you are covered with warranty by the garage as mine was towed back to garage!

 

[NickP]

No, if you accelerate in 2nd/3rd/4th with full throttle it suddenly loses all power, then regains it, then loses it, on and off, it causes the ASR lights to come on as the wheels start to spin.

 

[onlinesys]

I C. Guess it is a different issue then. How about in Sport mode?

 

[NickP]

No sport mode on mine.

 

[ledlights]

Nick,

If you're comfortable try it with ASR off (obviously be careful with wheelspin) to see if it's ASR related.

Other than that, is it popping any codes or are any lights coming on? There are the ECU/Fuel pump fuses on the LHS under the bonnet and the relays in the boot can give trouble. Only other thought is fuel starvation caused by dodgy fuel pump connector or from blocked fuel filter. Now I've written them down, it probably won't be any of these......

Hope this helps,

Steve

 

[NickP]

I'll give that a go, it feels more like turbo / fuel problem, it did exactly the same thing when I once tried full throttle before it had warmed up properly but now it does it all the time.

 

[rossyl]

FYI - Nick's got a 3200 I'm fairly sure (with tubi exhausts if I remember correctly)

Hope you get it sorted.

 

[ledlights]

Nick,

In that case, def have a look at fuelling as the engine would be running rich when cold so it would show up more. Have you had any dirty fuel?

Steve

 

[StuartW]

Hi Nick

I had the exact same thing with mine. It has a contactless TB but the EOBD light came on which when read, came back as a throttle pot. I had this replaced and everything was fine for all of 15 minutes when the EOBD light came back on. The jerkiness occurred a few weeks later and continued pretty much for every journey since plus hunting and revving too high at idle (1500prm +)
I have just got back from Shiltech who plugged it in again and it came back with an unknown error code, very useful! But at least it was a yellow code and not a red one. They then did a full re-set on the throttle pot and we test drove it for a while so that the TB & the TP could learn & synch up with each other.
The 70 mile / hour and half drive home which was a mixture of bumper to bumper traffic and fast twisty roads was faultless and in fact the throttle seems more responsive than at any time since I've had it and no disco lights on either so hopefully it has been cured.

Maybe this could be your issue too? Good luck with whatever it is and I hope it works out soon.

 

[NickP]

Took it back to the garage yesterday and they said that the battery had been on/off over the past few weeks so possibly things with pots and air intake might be out of sync, they were going to run it on their diagnostics today and will let me know. Fingers crossed it nothing serious.

 

[StuartW]

Fingers crossed indeed Nick, keep us posted

 

[conaero]

Took it back to the garage yesterday and they said that the battery had been on/off over the past few weeks so possibly things with pots and air intake might be out of sync, they were going to run it on their diagnostics today and will let me know. Fingers crossed it nothing serious.

I take it your nose is all fixed now?....happy with it?

 

[NickP]

Nose is new, colour match is awful... Letting them have another go... It looks fine from the side, but the difference where it meets the rest of the car from the front is really noticeable. Was given some spiel about chemicals having changed over the last 10 years in paints... Surely they just use a reader, it provides a code and the factors make the paint? I did read on here that others have had similar issues with bumper colour matching.

 

[Maser Sod]

Jerky acceleration ... hmmm, possibility of paint particles having polluted the MAF?

If it happens at around 3000 RPM then check that the turbos are engaging, the 3200 engine management system will back them off it is unhappy with any readings/stored codes (though this is usually accompanied by a CEL).

 

[NickP]

The bumper was painted off the car as its new. It was done at the paint shop and then replaced at the garage so unlikey there are paint particles in the MAF. There is no CEL, just ASR when the wheels spin when the power re-engages! I'm going to give them a call today and ask if they have figured it out.

 

[Maser Sod]

If your car is not pre-OBD II, and they haven't figured it out, you could always plug in a scanner yourself and see what codes it comes up with.

Having said that, I'm sure the first thing that the garage will do is check for stored codes.

 

[rossyl]

Hi Nick - hope it's all sorted for you?

 

[conaero]

Nick, if they are using the correct PPG paint code and using PPG pre mixed paint rather than doing it themselves and the match is poor, you will have to have the bonnet and wing tops blended then all of it lacquered.

Its the only way to do it properly.

If they give you the speil that there paint mix in house is PPG, dont listen to them and go buy the paint yourself, there is a Brown Brothers in Basingstoke that are an official PPG supplier.