I have had this issue for a while, its had it since I bought the car. Its intermitant and there is only one circumstance where I can almost be sure its going to do it.

 

The problem:

 

When driving along at light throttle the car feels like its holding back, and almost sounds like its missing. If you increase throttle a little bit the car doesnt respond as you would expect until you put a little more throttle on and then it accelerate away cleanly and as normal.

Its annoying in traffic as it just feels sluggish and it can begin to jump/vibrate as if it had a miss.

 

The "fix"

 

If I accelerate, or just put my foot down for a couple of seconds its gone and then its fine again for a while but then sometimes it returns.

 

The cause:

 

If I drive the car quietly off boost from start up and dont actually work it hard it generally DOESNT do this issue. However, if I have a couple of fast gear changes full boost etc then it almost certainly WILL do this weird thing once its all calmed down again.

 

I have a feeling that its o2 sensors telling the ecu the wrong signals so its trying to do all sorts of stuff with the mixture and that hence why higher throttle settings (when as I understand it the car ignores the o2 sensors) does it clear.

 

It doesnt really affect the car just feels weird.

Edited October 22, 201015 yr by Quavey

Are you sure it's not a fueling problem? When you say 'it feels like it's holding back' is there enough fuel getting through? Other thing could it be an injector?

Edited October 22, 201015 yr by WelshZ

I dont think so, as there is no issue at all when driving under full throttle when the injectors would be working the hardest.

 

It is strange in the fact that as you put your foot down not much if anythnig happens although the vacuum on the boost gauge changes so the throttle is opening obviously. It then seems to "realise" that its open and of it goes. Quite strange, my old grey one did exactly the same from time to time (although the silver one does do it more than the grey one did)

 

I did read somewhere that if the o2 sensors were unplugged it had no huge affect on the car so could I try this? Or will it cause more problems?

 

One thing I did forget to mention before was that one time when it was doing this. I pulled into a car park and held the car at a fast idle, I did video it but it was dark and didnt come out well and the revs in this case would fluctuate between 2600rpm and 3000rpm (I was trying to hold it at 3000) on its own with no change in "input" from me, obviously some sort of weird sensor issue.

My car does exactly the same thing, you explained it alot better than I could. Its going to be a sensor of some sort

My car does exactly the same thing, you explained it alot better than I could. Its going to be a sensor of some sort

 

Good lol glad im not alone.

 

Its such an odd sensation isnt it? Yet when giving it a boot full all is well!

Do you still have the EGR still fitted? if so remove the vacuum pipe and seal it off, see if that cures the issue.

 

Jeff TT

Ah okay, will give that a go... Just one minor problem, which vacuum pipe is the egr? Is there a diagram? I just looked at engine bay by numbers thread but couldnt see it on there.

Used to get this with mine. Hooked it up to the conzult and it told me the O2 sensor had died. replaced and fixed issue.

Used to get this with mine. Hooked it up to the conzult and it told me the O2 sensor had died. replaced and fixed issue.

 

Thats interesting, they were my suspects although last time on conzult it showed 55, and its always had the issue.

 

What would happen if i simply unplugged them to test?

deffo O2 sensor, part throttle it's trying to adjust the AFR based on the feedback then open the throttle up and it goes to a different map that doesn't use the O2 feedback