I have a 1997 Discovery XD. Everything was working fine before till I washed the engine bay today. I applied the engine degreaser and let it soaking for about 20 minutes and then power washed. Then I air blew the entire engine bay and let it sit and dried for about an hour before I started the car. The car started right away with perfect idle as before. I let it idled for about 20 minutes while I was cleaning up my driveway, but suddenly I heard the car lost idle. It then idled up and down for about 5 minutes and died. I switched it off and then started again. The car started right away with no problem, but it couldn't maintain the idle which immediately dropped unless I kept stepping on the gas pedal a little bit which was the only way I could keep the car running. I tried to drive on the street a bit. The first one or two miles seemed ok but then at the stop sign the car started to become rough running. So I didn't go further but managed to get back before it died. After, I could still start the car but it wont maintain idle unless I keep pedaling the gas.

Can someone help me out of this? What are the possible causes? Where should I start with to diagnosis this?

Many thanks!

 

You got something wet, let it dry out, and see how it does. Also if you have a scantool see if it set any fault codes or pending codes.

 

The most likely cause is water somewhere it shouldn’t be.

is the car throwing any error codes ? Poor running issues could be due to a spark plug/wire and/or coil that’s wet. Otherwise, if it’s just the idle, check the idle air control at the top of the plenum to make sure the connector isn’t wet. How about the MAF? Is it nice and dry ?

 

So, quick updates here.

Started the car this morning and everything seemed good at the beginning. The car started up right away as before and ran smoothly. I let it idled for about 20 minutes and the rpm started to drop and the car eventually died. I checked the battery and it was at 12.6v. I started the car again. The car started right away but died after about 2 minutes. Before it died, I checked the voltage on battery terminals and it was at 13.86v. It seemed to me the alternator didn't work properly as it used provide about 14.2v output. So, I turned my auxiliary battery on and started the car again. It started right away and this time it lasted for about 30 minutes and then died. I checked the alternator a couple of times when the car was running, the output never came up higher then 13.9v and kept dropping.

It seemed the alternator's problem, probably when I pressure washed the engine bay got the alternator broken. Since I was running two Optima deep cycle batteries, the car will start and run for some time till the battery juice drop to the certain point that the spark output is not enough (I have 10mm heavy duty spark plug wires on so it requires higher power).

I will take the alternator off and give it a test, and will probably swap to a new alternator and see what happens (I was about to put a new 160amp alternator on in anyway), and let you know.

Thank you all for quick responses and help!

 

To be honest 14.1v is about as high as you want to see on an older LR. 13.4v to 13.9v is completely within the normal range of output.

I had an alternator die on my 98 LSE D1 while driving and she ran fine thru stop n go traffic all the way down to 10.9v & when I pulled into my driveway it hit 8.6v and of coarse it finally died.

I would be looking at the MAF, IAC, TPS, or heck even the CPS as I think your charging system is ok unless while running you see 12.9v or less.

 

Replaced the alternator and got the car up running good. So it was the alternator. I took apart the alternator and switched the voltage regulator with an old one I have, it output 14.1v during a bench testing. But I have my new 160amp alternator installed already so will keep using it.

 

100% normal numbers for the alternator