Hi there, desperate and skint now. My new scoobs hesitating, it feels like im lifting the foot off the gas then re-applying it. I changed the dump valve, as it was first suggested it could be that, then was told it was the MAF, changed that, still the same. I have no engine check light up ever, and its very intermittant The hesitation can be felt in all gears, in all rev ranges, ie, could be in first slowly moving off, or 5th at 80mph cruising steadily.

Anyone have a clue as to where to look next?

(appologies to any SIDC`ers, also posted this up there too)


Cliff

 

spark plugs and coil pack are normally hesitation culprits, they should be your first check

 

Boost Solenoid may be the culprit ? Might need a clean if its been contaminated by oil ?

 

coil packs being borrowed this week (cheers customscoobyIOM). It wont be the boost solenoid as the fault can happen before the boost is even thinking about coming in, ie, from 0-10 mph slowly pulling away from stationary in 1st gear.

Any more ideas? Lambda sensor?

 

I would say Lambda sensor.

Grant

 

Maybe try unplugging Lambda sensor and see if problem persits ?

 

is it only hesitating on light throttle?

if not forget the lambda.

i would first do an ECU fault check to see if it gives a fault code, if nothing then i would go right through the ignition system plugs then leads etc.....

i take it your car is a v5 but what model is it?

 

On very light throttle it is normal to be able to feel the slight pulses as the air to fuel ratio rocks back and forth about the perfect stoichometric point, the car holds back a little when its rich and pulls a little more when it's lean. These pulses might be something like once a second. If you have an air to fuel ratio meter you can see the meter moving in time with the pulses. Normally you should only be able to feel it to any degree when the car, and hence the lambda are cold, but it may still just be perceptible when warm. If the lambda sensor is on it's way out the pulsing can be stronger as the worn lambda sensor doesn't respond so well or so fast, so the variations are bigger.

If it is strong enough for passengers to notice without it being pointed out, your lambda is probably on the way out, if it's just a very faint pulsing, then that is normal.

If it does it on boost or unser any conditions other than very light throttle cruise or acceleration then the problem is something else.

 

Mine does the same "pulsing" thing but can be worse or better under any condition whether warm or cold.Sometimes when its cold it`s fine and then after a run,stop for a minute and go again it`s very noticeable.Lambda was changed with no noteable difference.Is it me being paranoid or do i need to look at something else ie the boost solenoid?coil packs?
cheers
Robbie

 

Is this the front lamda or the rear you refer to?
Thanks
Mark

 

My Scoob only has one lambda sensor, are you sure one of yours isn't an exhaust temperature sensor - a "catalyst on fire" warning sensor? This is the one that can be removed when fitting a de-cat, the lambda sensor is required. I'm not 100%, but I'd be very surprised if it does have two lambda sensors, I'm not sure what the ECU would need 2 lambdas for, or which one to check if there are two.

 

I have a newage car - perhaps there's a difference?

I thought there was 1 sensor in the headers and 1 in the catpipe (immeadiately after the downpipe).

Perhaps I'm mistaken.

 

There could be, not fully conversant with the new age cars. Still not sure why there would be though.