Thread: Discovery 1 running rough when warm

Originally Posted by Utemad

I had similar problems with mine. I pulled my hair out looking for the cause. Turned out it was the new aftermarket rotor button.
Started running rough on lpg first and later it did it on petrol. Ran fine for months with the Bosch part so even though everyone said to swap it for a genuine one it took me a while to do so.
So fit a genuine one if you haven't already $45 delivered from Karkraft.
Alternatively ask Beeutey for the Ford Bosch part that fits.

GB864

Hi All

I changed the coolant sensor this morning and it made no difference at all.

I would be surprised if this was the problem because the problem is now happening when the engine is cold. As I mentioned last night the engine will not free rev past 3500 when cold now.

As I first mentioned the car had a new fuel pump about 2 months ago. I cracked the fuel connector on the injector rail and the pressure seems quite high although I don't have a fuel pressure gauge to get a pressure reading.

The car also had a new fuel filter when the pump was changed.

Is this still sounding like a fuel problem?

Regards to all who are offering suggestions

Originally Posted by rickl

Hi All

I changed the coolant sensor this morning and it made no difference at all.

I would be surprised if this was the problem because the problem is now happening when the engine is cold. As I mentioned last night the engine will not free rev past 3500 when cold now.

As I first mentioned the car had a new fuel pump about 2 months ago. I cracked the fuel connector on the injector rail and the pressure seems quite high although I don't have a fuel pressure gauge to get a pressure reading.

The car also had a new fuel filter when the pump was changed.

Is this still sounding like a fuel problem?

Regards to all who are offering suggestions

It is not unknown for replacement pumps to fail quickly, or the hose to burst inside the tank. It should be possible to fit a tee piece and a pressure gauge, the turbo boys frequently fit adjustable regulators with gauges. I bought one on ebay for not very much to replace a failed Volvo regulator for which I didn't know the design pressure.

Not withstanding the pressure problem, how does it run under light load? What about low RPM and acceleration? If it splutters under load then it could be a failed coil, that is common enough to warrant repeat mentions.

Hi All

The car runs fine under light load and acceleration is as good as it always was until it hits just over 3000 rpm and then it starts to misfire. As it gets warm it gets worse

Vacuum leak? It really sounds like its not getting enough fuel or it may be the inverse in that its getting too much air, either way its too lean. Like you say it was running fine before so I doubt its some major failure and more a simple sensor or pipe is at fault.

Originally Posted by nzlandies

Vacuum leak? It really sounds like its not getting enough fuel or it may be the inverse in that its getting too much air, either way its too lean. Like you say it was running fine before so I doubt its some major failure and more a simple sensor or pipe is at fault.

Vacuum leak will cause poor running at idle, from what you say I would say fuel delivery rate is a problem. Take your fuel filter off and see what is in it after 2 months. Just let it drain backwards into a clean container, shake it a bit. If you see lumps they have been through your pump. If its clean then the pump is probably OK. Was it a genuine pump? Maybe its too low a volume aftermarket thingy, as it wears it gets worse.

Last night I tried the suggestion of pinching off the vacuum line to the fuel pressure regulator. This made no difference I could detect at any point in the rev range.

I will try the fuel filter tonight as I have a spare new one.

Originally Posted by rickl

Last night I tried the suggestion of pinching off the vacuum line to the fuel pressure regulator. This made no difference I could detect at any point in the rev range.

I will try the fuel filter tonight as I have a spare new one.

Removing not pinching the vacuum hose will raise the pressure if it is operating. In any case, no vacuum equals full power setting.