Hi everyone,
I am a newbie here and female so please be patient with me while i try to describe an issue i am having with my 97 discovery (172000 miles).
about a month ago this issue started, up until then it has been a great running vehicle which i have owned for 4 years.
The problem is when started and when idling it runs perfect! But when revving the engine or driving it acts awful! Literally like its gonna blow! It backfires, very sluggish and will not get aBove 25 mph.
This seems to happen after the engine gets warmed up.
Since doing some work on it, we are able to get it to drive a few miles now before it starts to act up real bad!

Work that has been done in past few weeks:
Heads. gaskets, etc...
timing chain and gears
waterpump
fuel pump
fuel filter
cam position sensor
ect sensor
plugs, wires, etc
probably some others i'm not able to think of at the moment.

We had a diagnostics machine put on it about a week ago (after replacement of all parts above except fuel pump and 2 sensors) it showed multiple misfires, multiple ignition misfires, many sensors, including the few we replaced since this. It showed the vss sensor also, which we have yet to replace. The diagnostics machine was one from a local auto parts store though.
we also had to cut the cats off, and since this like stated above we are able to get it to drive further, a few miles now before it is back to the same bad running car!
Any help or suggestions would be GREATLY appreciated!!
Was also hoping someone knew of a place to get the vss sensor at a very decent price.
It stinks that we are in a place that is absolutely no where near a dealer or mechanic who has any clue how to work on rovers!!
Again thanks in advance for any help or suggestion!!

 

Have you had the ECU checked out? If you look at the connectors on the ECU you will see a large black connector. This is known as Connection A. This connection is where all your Injectors get thier signal. Checkout this connector for corrosion or damage. Open up the ECU and look around this connection area for shorts. Also If you expect the problem to be coil related then the connection is the small black connector and is known as Connection B. Look around for shorts or corrosion. The big red connection is Connection C. and it is mostly signal wires to and from your sensors. Is your malfunction indicator light on? Sounds alot like it may be injector misfire. This could happen if wires are damaged, mis-connected or the ECU is sending and recieving bad signal voltage. Have you checked your fuel rail pressure?

 

Where the O2 sensors changed or might it still be tryong to run on possibly the original ones?

Thanks for the detailed ECU explanation LRD!

 

Post all the 4 digit fault codes so we may better try and help you.

 

Your VSS (vehicle speed sensor) is bad, it is the speed limiter for the truck, when it fails it sends a false signal to the ECU.
It slows the truck by killing the spark plugs one at a time until the truck has slowed below the limited top speed (110mph), thats why you are getting the random misfire codes, cam code, etc.
The ECU does nto know what it going on, all it knows is that something serious is wrong and whatever it is is causing misfires and other poor run conditions.
When it fails it will cut the spark at random and for no apparent reason but almost always while under load since it thinks you are trying to go faster and faster.
Replace the VSS.

 

hooked it back up to the diagnostic machine today. Reset the ECU and then drove the vehicle until the problem started again. The only codes showing up now are:
Random multiple cylinder misfire
manufacturer control ignition system or misfire
camshaft position sensor A- bank 1 circuit malfunction.

We also had a mechanic (admittedly not specifically a LR mechanic) look at it today. He checked everything he could think of and said it it dumping fuel into one side of the injectors and restricting fuel to the other side.

Although the VSS code did not come up, alot of people are leaning toward this option also... anyone know of a place to get one at a decent price? Also same with the ECU either work on it, or a new one?

Again thanks so much in advance for everyones help!!!

 

There are a couple places.

RockAuto Parts Catalog
Speed Sensor / Transducer - Vehicle - Road - Vss | Land Rover Electrical Parts, Batteries, Relays, Lamps & More

 

The injectors are all connected by one wire, a Brown/Orange stripe. This wire starts at the fuse panel under the hood. I would check continuity from the fuse panel to all the injector plugs. Follow the wires from the ECU and check in that direction all the way to the last injector in the circuit. Also if you look at the first injector behind the alternator. This is where the connection is to the drivers side injectors. The wire connection is bare, meaning it does not have a solid insulation on it, All the drivers side injectors connect at this point. This area can come apart or corrosion can cause problems. The yellow wires to the injectors are signal wires that go to the ECU. You can check the large black connection on the ECU for signal voltage. Looking down at the connection from the passenger fender side, #1 pin starts from the top left and counts over to the right, and so on until you get to #36. Under #1 is #13 and under #13 is pin 25. Look at pins#6,#8,#9,#12, #19, #20, #24, #35 are the injector signal pins. Just cross reference the injector wire color with the pin wire color and check for signal voltage. No voltage-no circuit. Good luck.

 

Does anyone know of a way to check the VSS before I just buy one?
We are also checking the ECU today as stated above and will let everyone know what we find.
Thanks so much for everyones help and great knowledge!!! It is much appreciated!!

 

http://www.cartserver.com/sc/cart.cgi

RovahFarm - Land Rover Parts and Accessories - Discovery, Range Rover, LR3, LR2, Defender, Freelander and Land Rover Series

Before you do anything with the ECU take it out of the truck and open it up and see if there is water inside it.
If there is dry it out and then put it back.
But its the VSS thats bad.

EDIT:search vehicle speed transducer on Rovahfarms web site, it is $70 plus shipping.