By pjkbrit on Wednesday, August 01, 2001 - 05:23 am: Edit

94 Disco...had it a year and still can't get a nice even idle...

Done the following;
1. Magnacor wires, platinum plugs, ( even and normal light brown deposits on all plugs, no carbon fouling etc.).
2. New stepper motor, (no difference)
3. New Distributor, cap and rotor
4. New uprated piper camshaft/ ignition amp/ECU chip from RPI, all of which made it go faster but made no diff to the idle.
5. Engine pulls very strongly as soon as you are off idle. Compression test checks out OK with no major differences across all 8 cylinders....does 16-18mpg constantly.

SOOOOOO.....what's next....fuel pump, injectors, what...it's driving me nuts...and injectors are expensive as hell...even from RPI in England.

The continuum goes on....
Pete

By Perrone Ford on Thursday, August 02, 2001 - 07:21 pm: Edit

Well,

You seemed to have spent a ton of money without really looking at your problem. So lets do that. You need three things for smooth combustion:

1. Good spark
2. Adequate fuel supply
3. Good air flow

Checking the air flow is easiest. Remove the air filter canister and just leave the mass air sensor. Does it idle any better? How about if you examine the butterfly in the intake. Is it gummy and dirty? If so clean it and see if your idle improves. Most idle problems are air related.

If the air system check out, then move to spark. Adding Magnecors was a good idea, but are they grounding out? Are the properly seperated? The #5 wire has a tendency to ground out to the oil dipstick. Check it. How's the coil? Are you getting a STRONG spark to the plugs if you check with a properly gapped spark tester? Spark problems tend to show up much more under throttle so I doubt your problem is here.

Assuming your ignition is now in order, we need to look at fuel. If you are getting good performance at speed, then you need to look at the idle circuit, the pressure regulator, and perhaps dirty injectors. When's the last time you changed the fuel filter? You should probably start there if its been over 10k miles since the last change or you don't know when the last change was. After that, try using a good fuel system cleaner like Red Line's "Complete fuel system cleaner". Beyond that, fuel problems get expensive.

Have you checked your timing to be sure its in spec? Does the idle improve if you retard the timing? If so, you are either using bad gas, or you are running too rich. How's that oxygen sensor?

Try this and hopefully it helps.

-Perrone

By Daniel on Friday, August 03, 2001 - 03:43 am: Edit

Perrone,
I am planning to replace my fuel filter this weekend, but I have a couple questions.
I read your article on the Spanish trail site. I want to be sure the "fuel relay" location and removal instructions apply to a 98 Disco. Also, can I get the filter at any parts store/what is the part number?
Thanks,
Daniel

By Tate on Friday, August 03, 2001 - 06:11 am: Edit

Daniel,
You can also just pull the fuel pump fuse in the engine compartment and crank it till it dies, and then crank it a little more. I used a Wix #33481 on my 98. A "good" auto parts place had it. I usually have less luck at Autozone with rover parts. One tip: have a rag because regardless of what happens, you'll get gas all over.

If this shows up, here's the wix filters for 98:
http://www.wixfilters.com/filterlookup/index2.asp?Section=2&Make=88&Model=&SubModel=&Engine=1218&Year=1998&TempSection=2&TempMake=88&TempModel=&TempEngine=1218&TempYear=1998

By Perrone Ford on Friday, August 03, 2001 - 07:18 am: Edit

I cannot verify the location of anything in the Disco so I would take the advice from Tate. I tend to use Purolator filters because they are good and widely available. Even if a place doesn't have them, you can almost always cross reference one. Here are the filters for your truck:

Oil Filter L25195
Air Filter A35252
Fuel Filter F33144
Breather Element N/R
PCV Valve N/R
Transmission Filter P1266

By Alex Schubow (Alex) on Friday, August 03, 2001 - 12:44 pm: Edit

You do not need to pull the fuel pump relay on a 4.0 engine disco. Just disconnect the fuel filter (some fuel will spill) and replace it. This is per the factory manual.

Alex

By pk on Friday, August 03, 2001 - 12:52 pm: Edit

I have found that platinum plugs run fine but they do make the idle a little rough. If you are anal about smooth idle, go by some cheap plugs.

Does the smoothness of idle really matter? Disco can climb small buildings in a single bound... idling is kind of an afterthought.

pk

By Daniel on Saturday, August 04, 2001 - 10:43 am: Edit

Thanks for the info everyone.
Daniel

By pjkbrit on Monday, August 06, 2001 - 09:36 am: Edit

Thanks Perrone...I don't know when the fuel filter was done....a while back is my feeling...but wouldn't you get fuel starvation under load if the filter was bad rather than a lumpy idle??

By pjk on Wednesday, August 08, 2001 - 01:35 pm: Edit

Thanks for your responses....the throttle pos sensor checked out with smooth scaling and the right numbers...I guess I'm looking at fuel issues then!!