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V8 sometimes cuts out coming to a stop


Turtlepudding
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Hello and thank you for letting me join this Forum,

I have recently purchased a 1997 3.9 V8i automatic Discovery 1 and all seemed well for the first few weeks but for the last 2 weeks it has been very Jekyll & Hyde, one minute it can be perfectly fine with no issues (apart from the ABS warning light which is down to a front speed sensor on the right side that needs replacing)

the next time i use the car it seems to idle low on start up and cuts out on me when I come off the loud pedal and start braking. I changed the fuel from tesco to shell v-power in the hope it would be just a bit of build up and the fuel would clear it out but after a week it still remains the same, I can go to the shops and it runs fine but for the return trip it just cuts out at most junctions and it is doing my head in and the other half is moaning saying its a piece of junk.

what could be the main issue causing this? any help or pointers in the right direction would be great.

it may help to know that I am not sure when its last service was but from looking at the oil it looks like it could do with a change, distributor cap looks new and is from Lucas, the leads look ok and are in the correct order with number 1 at 4 o'clock, has had new exhaust fitted from last owner with cats.

I am not the most tech minded when it comes to cars so please explain like i am a 10 year old lol

thanks for reading this

Daniel

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Hi, unscrew the crankcase breather from the top of the offside rocker cover along with it's hose to the plenum and clean both in petrol, dry and refit, or even replace the 'flame trap' if really coaked up u should be able to see a bit of daylight through it.

Also stick some injector cleaner in the fuel, it simple things first then if you still have the issue move on to part two.

You then go on with cleaning the idle control valve and checking/ resetting the base idle if part one isn't successful.

A Haynes manual for the D1 will show you how and what if u don't know.

Part three will involve checking the various sensors the engine has.

Of course check that all the vacuum hoses are securely fitted and with any holes, but then that usually increases the idle speed... But look anyway.

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You could have a blocked fuel pump filter.

Lift up the rear carpet, unscrew the cover-plate and the very large (5" dia.) plastic nut and remove the fuel sender/fuel pump assembly. There is a "stocking" filter on the inlet to the pump, if this is blocked with crud it can lead to occasional fuel starvation = no fuel = no go --- Oh, and change your service station !

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Inactive oxygen sensors will cause this, before you buy loads of new parts get someone to stick it on a diagnostic machine and do some live data displays,or get a voltmeter onto the black wire from each sensor and make sure their output varies from 0-1v about once second while the engine is idling in neutral,hot all loads off.

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  • 2 weeks later...

There is a vehicle speed sensor in the speedo cable. ...

This tells the ecu if you're moving and alters the fuelling to suit. ... sounds like yours has failed. ..

There isn't, 1997 models don't have a speedo cable but the earlier 200 series did, what they do have is a the Road Speed Transducer bolted to the transfer box and wired to the ECU.

When the Road Speed Transducer fails or is disconnected the engine goes into idle mode, that's something the OP would like to have.

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