QuestionJohn,
I've owned a 1996 Land Rover Discovery Series 1 automatic (US
model) for about 3 years now. Generally there have been no
problems except for this one problem when the engine stumbles
once in a while. It usually occurs when I'm driving on the freeway
at a constant 70-75 mph, but it is very infrequent. It probably
happens a couple of times per year, but this last week it has
been happening a lot - every day on my 45mile commute. The
symptom is that when I have the accelerator peddle at a set
position the engine will reduce speed like it is fighting itself and
then it will speed up suddenly and then reduce speed. Last week
the engine check light came on. I took it to the dealer and they
said that the code said it was an engine misfire, but it did not
specify which cylinder. They suggested I have the ignition cables
replaced because they were the original ones and looked very
old. I had them replaced. However, it is still stumbling
occasionally at the high speed. The dealer suggested that I have
the speed sensor replaced next. My question is, is this correct,
should I have the speed sensor replaced or could it be
something else like the fuel pump?
AnswerHi David,
I've seen this before on my '95 Disco. The dealership will run you thru various part swaps in HOPES of fixing the problem. It may be true that your spark plug wires are old but there is no garantee that it will fix this problem. What they are doing is isolating the problem by eliminating the possible causes.
I've seen the TPS (throttle position sensor) cause this problem, vacuum leaks, idle adjuster failure, and various sensor failures.
If it was your wires, you'd think your engine woes would increase, especially on humid days! As for the speed sensor, I suppose it could happend but very few owners I've chatted with have had the speed sensor fail.
Ask the dealer: "If its NOT the speed sensor, will you put back the original and not charge me for the part?"
Best of luck,
JohnMc
