Turns out I had the timing set at 12 degrees btdc. Remedied that with a new timing light. Reset basic idle and it still stumbles. Fuel pressure is good, looked in the cap and it looks like it is wearing funny. Picking up a new cap and rotor and the recommended plugs.

 

Ok. Replaced the NGK R coppers with Bosch +4 plugs, ran sluggish bu eventually smoothed out. Smoothed out a lot, like the smoothest idle I have ever had on the disco! Took it for a drive and she falls flat on her face on WOT.. If I stop and shift into neutral it is fine. Idles and I can rev the engine no problem.

Thoughts?

 

Fuel filter? Fuel PSI at WOT (is it holding up)? TPS not providing reliable input to ECU? Clean MAF?

 

I thought maf, you said use CRC to clean, can you elaborate?

 

Take air hose off each end of MAF after it has sat overnight. DO NOT SWITCH ON TRUCK (or that heats up sensor inside to 350F). Take pair of needlenose pliers, grip edge of plastic sleeve that holds screen in. Pull straight out a little at a time, working around the whole circumference. Tiny plastic notches you can't see at this point hold it in place. Do not pry on screen. Once ring is out screen will fall out into you hands. Take it away from truck and spray off both sides with CRC MAF cleaner. Don't use anything except something rated for MAFs. Don't use carb cleaner. Spray the MAF cleaner down the hole in the center of the rod that points at the center of the screen. 10 seconds. Then tip over and drain out liquid. Repeat two more times. I take a paper towel soaked in MAF spray and wipe out the plastic tube on the inside of the bore. Let dry a few minutes, then put back together, and snug up the rubber hoses. When you crank truck it will be using ECU adaptations from old dirty sensor, so may idle higher, this will smooth out in a short drive.

BTW - a new sensor is like $1400. I got a spare from salvage yard for $30, on my spares shelf.

 

You can get aftermarket D1 MAFs in the 200-300 dollar range. The only place I can find that sells an OEM GEMS MAF is roversnorth and it's $1700!

Also the lucas and gems use different parts.

Check this site out:
Range Rover Remedies

a lot of the range rover stuff will apply to 94-95 discos too.

They talk about flame trap needing cleaning and also the advance weights in the distributor that I mentioned earlier. Also ignition pickup, coil, and amplifier. I think the ignition amplifier is junk in these trucks. My buddy converted his RRC to an MSD setup because he kept burning them out.... of course his was still on the side of the distributor, and not relocated remotely.

 

Cleaned MAF, and it is idling very smoothly. I test drove and still stalls out on WOT. Removed the VSS and tested it using AC Hz setting and it is generating signal. Plugged it back in, now it is stalling at WOT when sitting in my driveway. Of course this decided to happen after I tested the VSS. Fuel pressure is good. Bumps to 2.9 bar when I rev but the engine does not follow. I am sure that there is fuel as I let off the gas and it goes back to idle and I get a rich smell from the exhaust. I am beginning to suspect spark arrest at WOT.

 

Update. If I slowly depress the throttle it will go up in RPM's. So I don't think it is spark. What I am narrowing this down to is TPS or ECM. It is being starved of fuel when I depress the gas however the FPR and the fuel pump is working.

Am I correct in saying the fuel injector pulse is not opening in accordance with the demand for fuel? The controlling components which directly effect this signal are, MAF (cleaned and working, does not effect a change when run unplugged), TPS (no test available for this component), ECM (unsure of signal from TPS, would have to test wires for continuity.).

 

see attached. You can measure for volts at the TPS wires, between the red wire and ground; or disconnect sensor plug and meter it for resistance. Green to yellow wire should read a fixed resiatance. Either yellow or green to red should read a resistance that changes as the throttle is moved thru the range. What you are looking for is smooth, with no jumps or drop outs. It is just like volume control on old radio, if dirty or not making good connections, it will make static and annoy the listener. The only thing that listens to the TPS is the ECU. When you boil it down, this is the man/machine interface. The ECU knows more air is coming in (the MAF told it), but it takes the TPS to tell it why (the human has punched the pedal) and how much throttle angle after that a few calculations the proper size squirt of fuel is authorized.

 

Thanks! Excellent info! I am going to test it and will report back in a few.