Engine hunting when reversing.

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rambo
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Joined: Tue 16 Aug, 2011 18:17
Posts: 82

  Z3 roadster 2.0
Location: Grimsby

Engine hunting when reversing.

Post by rambo » Wed 17 May, 2017 19:23

I've noticed that when I back my 99 2.0/ Z3 into the garage the engine hunts in waves and unless I keep the revs up it stalls. Any ideas as to what causes this?
Regards
Rambo

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pingu
Joined: Fri 30 Apr, 2004 17:01
Posts: 3337

  M roadster S50

Re: Engine hunting when reversing.

Post by pingu » Wed 17 May, 2017 20:19

Hunting is usually an air leak. Strange that it only happens when you are reversing.

It could be that you are driving so slowly. Does it happen when you try to crawl along at very low speed, especially uphill?
Pingu

John Wilson
Joined: Fri 12 Jun, 2009 13:11
Posts: 240

  Z3 roadster 2.0
Location: Diss

Re: Engine hunting when reversing.

Post by John Wilson » Wed 17 May, 2017 23:07

Yes, I think it's just that You are going at a slow speed when going into the garage rather than the fact that you are reversing. It used to happen to my Z3 (a 2litre 2000 so similar to yours) when coming back from a run and going forwards into the garage. It would over rev then drop right down and usually stall. I found it was the idle control valve that just needed cleaning out, in my case, and I now havent had any problems since doing the job a couple of years ago. But I agree with Pingu that it could also be an air leak in the inlet side. If you are doing the valve then you have to remove all the rubber boots from the inlet side anyway so youll be able to check the boots condition at the same time. Just make sure the boots all go back properly as some are a bit tricky to get to. You could also check the butterfly is moving freely and theres no crud around it, at the same time.

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 643

  Z3 roadster 2.2i

Re: Engine hunting when reversing.

Post by motco » Thu 18 May, 2017 07:37

My 2.2 Sport is a real pain to manoeuvre because of the fly-by-wire throttle. The tiny time lag between adjusting the pedal position and the engine's reaction causes a sort of feedback loop of revving and near stalling. My Westfield, with all its crudeness and harshness, is a delight to manoeuvre in comparison because it has a cable throttle and no damned clutch delay valve! (The CDV from my Z is in the bin)

rambo
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Joined: Tue 16 Aug, 2011 18:17
Posts: 82

  Z3 roadster 2.0
Location: Grimsby

Re: Engine hunting when reversing.

Post by rambo » Thu 18 May, 2017 09:05

Driving forwards at slow speed in a traffic queue does become uncomfortable sometimes and I have to lift the revs slightly to compensate but reversing does cause the car to hunt on a light throttle.
Or maybe it's me, as my other car is a Volvo XC90 Diesel auto and I'm getting lazy in my old age!
Thanks for the replies and I'll look into your suggestions.
Regards
Rambo

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