Ugly lull on highway

d1driver

Well-known member
Oct 19, 2005
3,153
1
Pittsburgh, PA
At highway speeds, my 98 Disco(107k miles) seems to be having an issue. Particularly when decelerating after running 70+ mph. It acts like the engine just stauls out, then comes back to life after a second or two. If I hit the gas while this happens, nothing. Then it just picks right back up and away I go. It starts fine, no lights on dash, has new air filter, fuel filter, etc. It otherwise runs just fine. A little sluggish on low end, but runs smooth.

Anyone experience this before? Fuel pump problem? Spark problem? I'm not sure what to look at first.

Got an offroading trip 3 hours away next weekend and need fixing asap.
 

NHESS81

Well-known member
Mar 23, 2006
650
0
CA
Yeah, pretty common issue, most of the time it is just the Vehicle Speed Sensor going bad...VSS shouldnt run you too much a lil under 100, and I think its somewhat easy to get to...I dont have the material with the details right now, but it is not a 'critical component' and as long as your truck isnt doing it EVERY time you are up to speed, I wouldnt worry about it till i got back...my 97 does it, maybe...once every 20 hours of 70-75MPH driving at most...
 

maxyedor

Well-known member
May 9, 2006
1,353
0
I have a similar problem, when going uphill or passing, if I start at 60-70 mph I can floor it and nothoing happens for a few seconds, then it takes off. Could this also be the VSS? I have a 98 D1 w/96k miles.
 

NHESS81

Well-known member
Mar 23, 2006
650
0
CA
max..your problem could also be your kickdown cable setting...you can test this by driving...eh...around 50-60, then floor if, seem if the transmission shifts to the lower gear...it should do this to help out passing/uphill...if it doesnt downshift on acceleration from speed, then id say its the kickdown cable....try it out...VSS issues are: you are driving, then it feels like you let off the gas, VERY noticible deceleration feeling--scary the first few times lol--but the RPMs say up and you dont lose much speed, and after about 2 seconds it all jumps back up to normal...I think this is because the clutch is engaging as the VSS gets confused?
 

robbyb20

Well-known member
Oct 2, 2019
70
12
Seattle
Yesterday I finished replacing the fuel injectors (new bosch gen 3 ones from this link that i can find atm https://landroverforums.com/forum/d...ctor-comparison-stock-vs-ford-vs-volvo-78787/) and also the valve cover gaskets.

I was getting a P1179 code but that has resolved itself after a few drives. The new issue is highway speed. When i reached 70, everything was ok but then it started to act like I had taken my foot off the pedal but the speedometer didnt drop and my RPMs only dropped by 1-300prm. Any sort of acceleration after that was sluggish. i had replaced them due to gas contaminating the oil (small levels) and gas smell outside the engine. The vehicle wont get above 65 or above 2200rpm.

Im going to check out the VSS shortly here and see if there are any loose connections.

Thoughts?
 
Last edited:

robbyb20

Well-known member
Oct 2, 2019
70
12
Seattle
Cleaned the contacts off, didnt have same problem on HW speeds. Will monitor but that seems to have been the issue.
 

WaltNYC

Well-known member
Mar 3, 2010
500
22
NYC
if you find yourself 'in the field' and can't deal with the VSS right away, just disconnect it. You will lose the speedometer on the dash but the truck should run fine without it. If you unplug the VSS and the truck runs as it should, you can bet the VSS is the issue.
 
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robbyb20

Well-known member
Oct 2, 2019
70
12
Seattle
New VSS installed and things appear to be sorted out. I have yet to get on the HW but the MPH displayed on the ultragauge is consistent again.