Jamieee

2007 GB270 Wagon

On normal acceleration it feels like it's jerking slightly like it's not smooth acceleration. If you stick at the same speed it's fine, if you floor it that's fine to no hesitation etc. It only happens when for example keeping up with traffic speed.

It had plugs & maf sensor last year.

Any ideas, thanks in advance.

Bazil_SW

iTrader: (4)

02 sensor maybe? During wide open throttle accel it will switch to open loop fuelling (not using the 02 sensor) but under light accel and cruise it will operate in closed loop which means it's using readings from the o2 sensors in the exhaust header and in the downpipe to adjust fuelling and keep the air fuel ratio on target.

Also might be worth resetting the ecu to see what happens then. Google it, there are lots of posts on how to do it.

hedgecutter

iTrader: (5)

I have something similar on my hatch going on, it misses if you accelerate without changing down, in casual driving, but in wot it is fine. No codes or cel. The hesitation was like hitting a wall initially, but has become less violent. I went back to mapper who suggested an ignition issue, so now changing plugs to one colder, but the explanation above sounds a better explanation. Let me know your outcome, cheers

Jamieee

Thanks for the advice, just rang a motor parts place about getting hold of one they asked if its the front or rear? Didn't know there was two....

TECHNOPUG

iTrader: (1)

They'll be a CEL light if one of the sensors is at fault. A code reader will tell you which one.

Jamieee

No lights on the dash

TECHNOPUG

iTrader: (1)

Probably not an O2 sensor then. I've had both fail on mine and they both gave consistent CEL lights with fault codes.

Jamieee

Maybe I'll just have to bite bullet & take it in somewhere! Thanks anyway.

TECHNOPUG

iTrader: (1)

Might be cheaper in the long run to pay to get it diagnosed, rather than just replacing parts until you find the culprit.

Bazil_SW

iTrader: (4)

I think it is possible for a failing sensor to affect fuelling without the ecu throwing a cel or code. It would only throw it if it sees signals outside of the predefined limits, voltage, open/closed circuit etc but a sluggish responding sensor wouldn't trigger these.

There are 2 sensors pre turbo and post cat, both are used to trim fuel but the front is mostly responsible with the post cat one being mostly for checking the condition of the cats.

It might be worth trying a cheap logger to see if there are codes stored that aren't triggering cel before taking it to someone. Bluetooth ones are cheap on ebay and work with your phone or laptop.

hedgecutter

iTrader: (5)

No cel on mine either ; will get it looked at end of month and let you know

Cambs_Stuart

iTrader: (3)

Possible boost solenoid?

Jamieee

Something like this?

https://www.ebay.co.uk/itm/181888553312

Tidgy

Just get it to a specialist for them to have a look, put it on a dyno. Saves chasing it round the engine bay

TECHNOPUG

iTrader: (1)

This:


And this:

https://play.google.com/store/apps/d...orque&hl=en_GB

Bazil_SW

iTrader: (4)

I keep one of these in the boot: http://www.ebay.co.uk/itm/2016-Unive...QAAOSw4CFY25RN

It works well on my hawk and has helped me out a few times for clearing and reading codes when I've been out and about, but you can also get bluetooth obd 2 dongles that can log to your phone or laptop (using Torque or other apps). Some are really cheap, like <£5 delivered.

Jamieee

Update: It would seem my car was stuck in valet mode via the map, & was only running 0.5bar, now at 1.3bar.

Thanks to the good people of Scoobyworld Loughborough, now a different drive all together.