Disco 1 '97 with 120,000 miles.

Never had issues with the engine till lately. If the truck is not started for a day or more, it'll start just fine and run normally for 10 - 15 minutes when it starts to misfire and lose power to the point where you've got to get off the road. The engine does not stall and continues to idle but any RPM increase results in very rough engine and notable misfiring in one or more cylinders. After about 10 minutes of this the engine runs normally!
Any suggestions? Thanks

 

Has it had a tune up recently? Plugs,wires, fuel filter.....

 

Nothing has been done recently. The only thing I can come up with is that we've had to leave it outside of the garage around the time this problem started. The curious thing is the transient nature of the misfiring always 10 to 15 min after a normal start for 10 or so min and then presto a normal engine.

 

Does the check eng light come on at all?

 

The check engine light and service engine light have been on for around 5 years. Paid $90.00 each time to clear check engine light twice only to have it reappear. So, I just continue with routine maintenance on a mileage basis. The fuel pump was changed about 8 months ago but I can't draw a link with this problem to the fuel pump.

 

You can reset the red "service engine soon" light yourself, there is a good write up on it on www.discoweb.org, look for the tech section.
As for the amber light, you need to buy or rent a OBDII code reader.
You can buy them for pretty cheap and this will not only let you read the codes but also clear them and turn off the light.

Has it been raining there? Really super humid? Snow? Sprinkler hitting the truck?
What grade of gas are you using?

 

I thought the problem might be rain related but until the weather turns really like summer, I won't know if moisture in any form is the cause. The garage has too much crap to move right now! The gas octane is 89 - 91 octane is crazy expensive here but I did try running the truck on it for a whole tank full - didn't make a diff though.

 

Well it very well could be water in the ECU, it is on the left fender towards the back by the washer fluid tank.
If it has been raining it could very well have water in it.
Unhook the battery and pull it out, dry it out, use silicon to reseal it, put it back and see what happens.

 

Sounds like a plan, BTW, the washer fluid tank in my truck is on the driver's right side fender. I forgot there was a way to reset the Service engine nuisance so - Thanks for the reminder.