Rover V8 rough running when hot

[Harleyboy]

Hi,
My 91 Range Rover 3.9 efi is running very badly when it’s hot. Starts fine, runs fine but then on restart it is ropey. Once cooled down it’s fine.

It’s so bad it is cutting out especially manoeuvring Any ideas what it could be? I wonder if some sort of temperature sensor is faulty?

This pesky car seems to have constant running issues! But I suppose that’s old cars for you!

Cheers

[Boosted LS1]

Coolant temp sensor perhaps? What would happen if you disconnected it as a means to test?

[NMNeil]

Any check engine lights on?

[Harleyboy]

No warning lights have come on. Not sure it has a check engine light though.

I haven’t done any form of testing or disconnected anything yet

[Saleen836]

Coil pack breaking down when hot?

[Harleyboy]

Saleen836 said:

Coil pack breaking down when hot?

Stupid question but is coil pack different to the ignition coil?

[stevieturbo]

Harleyboy said:

Stupid question but is coil pack different to the ignition coil?

Ignition coil as you're thinking would generally refer to a car with a single coil, and a distributor etc. Like most old cars.

Coil pack tends to mean a coil unit which is capable of feeding more than one cylinder, or indeed all cylinders from a single unit.

There can be deviations around that though, but in general that's about it.

[Harleyboy]

stevieturbo said:

Ignition coil as you're thinking would generally refer to a car with a single coil, and a distributor etc. Like most old cars.

Coil pack tends to mean a coil unit which is capable of feeding more than one cylinder, or indeed all cylinders from a single unit.

There can be deviations around that though, but in general that's about it.

Ok, thanks. Mine has distributor (relatively new) and a single coil pack. If I keep it running even when hot, it runs fine, It's once its been stopped and restarted that it all goes wrong.

[Vixpy1]

Had same problem with mine, turned out to be a cheap coil, fitted a proper Bosch one and all good

[paintman]

You would be best getting a copy of the Land Rover factory manual & working through the tests given. Otherwise you may end up throwing parts at it in the hope one will solve the issue.

Other causes could be a sticking stepper motor or a faulty ignition amplifier, the ones mounted on the side of the dizzy suffer from heat & it does come up fairly regularly.
LR eventually came up with a modification kit to allow it to be mounted on the inner wing away from the heat.

[Harleyboy]

Thanks, good point. I’ve been down the road before of throwing money at parts with no impact

[HealeyV8]

The Rover V8 came with 2 types of distributors the SD1 early type have an amplifier behind the coil which was less prone to heat problems. Later , I assume yours have the amplifier bolted to distributor where they breakdown due to heat giving problems. Swap out your amplifier.

[paintman]

The earlier RRC EFi amplifiers are mounted on top of the left hand inner wing underneath the coil.
Later ones are mounted on the side of the dizzy & are supposed to have a heat resistant paste between the mounting faces.

The remote kit for the later ones is LR part number STC1856:
https://blog.simonbbc.com/2014/12/10/761/

Edited by paintman on Sunday 9th August 13:32

[GreenV8S]

Rather than replacing parts speculatively, I suggest you try the 'bag of frozen peas' trick to see if you can make the problem go away by cooling components down.

[paintman]

He needs to work through the tests in the manual.

'Bag of frozen peas'. Never thought of that. Every day's a school day!

[Harleyboy]

Love the frozen peas trick! Mine has the amp on the distributor.

Will try and source the manual.

Thanks all

[paintman]

You may well be able to find it online, the later RRC LR workshop manuals which would cover yours were on a CD called 'RAVE'.
There was a good online site but it's now plastered with ads & not worth the effort.

This is from the earlier paper manual, it may help. From page 15/146.
https://www.landroverweb.com/Pdf-files/Manuals/Ran...

[Tony1963]

Could it be a problem with fuel vaporising in the fuel pipes in the hot engine bay? Many years ago I had two vehicles suffer with that, and with time and/or copious amounts of water, they would fire up ok and stay ok if just driven.