406oc.co.uk

Hi there geniusses!

I need help identifying a problem. I recently bought an 'S' plate 406 2.0 petrol manual which I'm pretty happy with. It's the old chestnut of one owner from new, serviced regardless of cost and only 56k on the clock.
Anyway, it's got a slight issue. Whenever I come off the throttle or get back on it there is a slight hesitation. It doesn't seem to be every time but it does it a lot. At first i thought it was an engine mount as it was fairly 'jolty'. But the car has just sailed through it's MOT so it's not that.
Can anyone tell me if there are any sensors that i need to check (i.e MAF, lambda etc) or does it sound like something else? Any help or suggestions is much appreciated!

Cheers, Mike.

Ah, the engine hesitation issues - I've had two bouts of this on my '99 1.8 petrol. The first was a chaffed wire sparking on the engine - the wire went to one of the sensors on the throttle body housing. After this was fixed, a few months later it started hesitating again. I replaced the stepper motor and the throttle position sensor (TPS) at the same time and it was solved. Unfortunately I can't tell you which solved the problem though. I did have a very bad idle, but I'm told that the stepper motor won't cause hesitation at revs, but I can't be sure...

Hope this helps.

pphilpot wrote:but I'm told that the stepper motor won't cause hesitation at revs, but I can't be sure...

I wouldn't have thought so as these usually just control the idle, once your foot starts moving the throttle they don't do anything.

Don't seem to have any 'shorting' of cables/wires anywhere.

Any other suggestions? I'm pretty convinced it's a sensor issue but which one would give these symptoms. It's not a FBW throttle (the cable goes through the bulkhead out to engine )

Ta, Mike.

They do on the fly by wire throttles too, they end on a big potentiometer near the air filter. Yours is on the throttle body so I think it has a traditional butterfly.

When I was trying to track down my first hesitation issue (cause by a shorting sensor wire) when I ran the car with the lambda probe temporarily disconnected the problem went away. This wasn't due to a faulty lambda probe as the problem returned when I fitted a replacement - but I believe that the ECU compensated for not having the lambda probe signal by shutting off other sensors - namely the cluster on the throttle body. I suppose that you could try disconnecting the lambda probe temporarily to see if your problem goes away in the same manner...

Thanks pphilpot, I'll give it a go when I get the time.