96 Disco 1 SE7 120k miles. A month ago I drove her for a 2 hour drive. 3/4 of the way there she starts misfiring when barely giving her gas. Uphill or flat didn't matter. If I gave a little gas to maintain speed it would run rough, but if I nearly floored it (no shifting) she would return back to normal until I let off the gas. Next day, just driving through town at 35MPH, she started running VERY rough. Funky noises, bouncing, the whole deal. Let her sit for a couple hours then drover her 2 hours back and she ran fine the whole way.

Haven't drove her far until today. She ran fine for 45mins of 65MPH highway. Got to town and she started stumbling at a red light like before. Pulled into a parking lot, shut her down for a minute, started her up, and she ran fine again until I hit the highway where she started running rough ONLY if I gave a little gas.

Codes I've got when these happen:
P1314
P1193
and whatever Cylinder 7 misfire is.

What gives? I'm assuming it's a fuel/air problem but correct me if I'm wrong.

Things that are new for fuel/air:
MAF
Fuel Pump
Fuel Filter
Fuel Injectors
Previous owner put new Magnecor wire on the Spark Plugs
Spark plugs looks good
Cats were removed by previous owner.

I don't have a vacuum leak that I can see. However, the hose from the Fuel Pressure Regulator to Intake is damp and has a fuel smell. Inside of Intake housing had a decent fuel aroma as well. Could this be my problem?

Engine Temp is well below overheating. I don't know if it matters, but the transfer case was dropped and resealed and new output bearings installed. New water pump and front cover gasket as well.

I'm completely stumped and open and thankful to all input!

 

If you have fuel in the vacuum line for the fuel pressure regulator that means that it is failing and can cause a random misfire like you are describing. I would replace it and see if the problems persist. If they do there are other things on these disco's that can give the exact same problems.

 

ever find your problem? Sounds like the VSS (Vehicle Speed Sensor)
Based on the description, and Technical Service bulletin TEC190397, malfunction of the VSS can cause misfiring or stalling of the engine. The VSS itself consists of a magnet mounted on the speedometer input shaft that triggers a magnetic reed switch. The reed switch provides input to the speedometer, the cruise control system ,and the engine ECU. A defective VSS may cause a codes P0500, P0300, P1316 and any combination of P0301, P0303, P0305 and P0307. It may also show no codes at all.

Hard to get to , on the underside of passenger side of transmission, unplug it, see if vehicle runs good. (you will loose your speedometer while doing this, but will know if the VSS is your problem.

 

https://landroverforums.com/forum/di...cut-off-45273/

 

Thanks for the input!

I took the sensor out, took it apart, and replaced the plastic with an extremely small ball bearing and machined shim for it as well. It didn’t fix the problem but it didn’t make it worse either.

Drove her today and same thing. Only this time I measured throttle position percentage with my ultra gauge.

These are my findings:
ONLY happens in 4th and above 50mph

ONLY happens when throttle position is between 30% and 69%. Once the throttle reaches 70+% the rough running stops IMMEDIATELY.

When i hit 70% and she runs better, if I release the throttle, she continues to accelerate until I completely let off. There is no in between.

Have yet to get codes for anything since the problem showed up.

I’m starting to think it may be a throttle position sensor issue. I ran seafoam spray through the intake per the directions and the throttle body itself is clean now.

i noticed too, on the throttle cable assembly, a rubber boot/diaphragm. There’s a paper clip looking thing that attaches to the throttle on one end and a nipple on the other end with nothing attached to it. Is there a vacuum line that needs to be attached?

thanks again!

 

vacuum line here, you referring too? at number 7 ???If so, yes there is, it goes back to a T connector up against the wheel well about 12" away. One end of the T conn goes to brake inside vehicle (above shroud over brake and gas pedal) and the other side of T conn goes to front of air leaner box then down to a small motor . (hard to see it under the metal). All for cruise control, believe when you hit the brake it cause the cruise control to release, shut off).

 

That's what I started thinking it was after looking at it! Makes sense as to why my cruise control doesn't work lol I'm sure this wouldn't have an effect on running the engine correct? If so, does the TPS being at fault sound like a potential cause? I have another VSS on the way just in case the rebuild crapped out too. Perhaps the original VSS was just too worn out that a rebuild like what I did wouldn't do anything.

 

I rebuilt my VSS, it worked a day or so, then back to the same sputtering, etc. Bought a new one from Rover Farms, problem solved. I had just over 200k on mine at the time. Even rebuilt it was loose, wobble feeling.
If you just unplug the wire from the VSS and if the VSS is at fault, it will run okay, as mentioned, you will loose speedometer (and cruise control) but you will know if it is the culprit.

That vacuum hose off, I do not think it will cause the vehicle to run as you described, just cruise control will e messed up.

 

I drove once with it unplugged but I don't recall the outcome as it's been a while. I'll unplug and test again this weekend on the highway. Thanks for the help!

 

Tps ???? Throttle Sensor?