Land Rover Repair: Engine cutting out, throttle position sensor, litre v8

Question
Hello

My 1997 Discovery SE7 4.0 v8 recently started having a problem stumbling or cutting out on the road. It started on a recent extended trip of about 3000 miles. It doesn't seem to be related to engine load. It stumbled up hill and down hill. I thought that it might be related to bad gasoline, but I had the problem across a few tanks and it steadily got worse. I got home with it and now the idle seems rough and it will die while idling. It has about 82,000 miles. I'm afraid it may be the fuel pump. What do you think?

Thanks
Richard  

Answer
Hi Richard,

Nice Disco!  Do you have the 217bhp 4.6 litre V8?  

It could be a fuel pump.  It could also be a number of other problem areas:

If your Disco is lacking power (stumbling) it could be a clogged fuel filter.  

Have you changed your spark plugs and wires lately?  When did you last have it tuned up?

How is the condition of your fuel injectors?  Have them tested and cleaned.  

I know that many early Disco's have had alternator and spark amplifier module (SAM) problems.  Be careful if you are considering an engine wash -  that's when the SAM really fails!

Another culprit could be the Throttle Position Sensor (TPS); signs of this failing are random and rough idle, wild pitching rev's, engine stalls, low's and highs in fuel consumption.

Usually, problems like yours can be traced to spark, fuel or exhaust.  I'm almost certain that you can rule out fuel as the cause (unless you've loaned out your Disco).  Most owner pamper their 4x4's and would never purchase "El Sludge" gasoline!

I have heard of carbon build-up on older Disco's.  This could rob you of spark and compression.  Depends on your mileage, how you drive, where you drive and how you maintain your Disco.

I hope this help you, Richard.  82,000 on your Disco leaves with lots of use remaining.  

Best of luck,
JohnMc