Engine and Transmission Tech

Hey great site i`m impressed everything in detail and all here together fantastic stuff.
I am in England not far from Land Rover and i have to go to our Yanky cousins to find what i need on a Landy Engine. Well the top half of it i guess because you sold us the bottom bit i believe.
Guys i am pulling my hair out at the moment with a sick running 3.9 1993 Rangey.
Suddenly she has begun to develop a gentle miss fire which has got much worse over a week or so and i can`t find the problem.
All ignition parts were changed Plugs,leads,cap,rotor and dizzy just before this began because of a light back fire and the fact that they were quite old so i do not believe its the regular culprits.
She ran beautifully smooth on Petrol or LPG but now at best poorly on either, though as petrol is easier to burn a little better on the petrol but not much.
Is there a garage that will have a diagnostic test book for these engines or did they not have such things back then.
If so where is the port to plug into.
I am told there is maybe a connector to display simple fault codes under the seat, is that true.
If so how do you use it.
I have cleaned the stepper motor and rechecked all the new ignition parts i replaced including the vacum on the dizzy and even plug gaps.
Remember it ran beautifly for a couple of weeks after the parts were changed this is something else but what i have no clue.
Can you help as to what you might think it is or how i can find the problem.
Thanks i look forward to any help replies you might have and in anticipation of that i am so grateful.

Hi Anthony, I know you said you replaced the ignition parts but verify you have replaced your ignition module which is bolted to the side of the distributor? Those have a tendancy to go bad and cause running issues. Was any work done on the car recently? If not I would not think that you would have a vacuum leak that would be causing the issue and I doubt that it would be an issue that changing the fuel filter would cure if it runs well besides the occasional misfire. My bet would be with that amplifier module. have you noticed a change weather the engine is cold or warm? There is a code reader under the passenger side seat, it is a square black plastic piece and if a code is thrown it will display a number, if no code is thrown it will be blank. I have a feeling that this particular issue probably did not throw a code but that is a good place to start the search.
Randy

here is a picture of the code reader, look for the section labeled fault code reader in bold just about half way down the page
[www.britishv8.org]

Thanks Randy good American name that but you have to know here in the UK it means your always up for sex :).
Seriously i appreitiate the reply and your input.
I did just find out about that little box you mention that`s under the seat from your site actually but i think it is only supplied to U.S vehicles strangely, i am going to look NOW!
The new dizzy came with a new amp and vac, i have swapped the amp over with the spare and no joy.
Tested vac by sucking on its pipe and popping my tounge on it ,works fine.
So many things i see after reading your very informative sight that it could be.
Loads of sensors like the MAF, TPS and coolant temp.
I do not have the equipment or skill to use it to determain what is the problem.
Got it in to a friend and indy garage tomorrow ,he thinks maybe even fuel supply but agreed unlikely as you say just the filter.
I`m depressed with out her i love the old dog, neigbors think i`m a nut i spend so much time messing with it.
I will get some pics up asap.

Sorry Randy forgot to add answer to your direct question.
No work done recently on the engine except the ignition parts but i have removed the exhausts center box and replaced it with straight pipe for a better sound.
Cats are still in and the oxygen sensors.
I do have a habit of cleaning the engine bay but NOT! with the power washer maybe i have wet an electrical part or connection.
The occasional misfire is now a spluttering hesertating burble and it is very rough when i accelerate or rev it.
Seems to clear when at high speed or higher revs but that might just be that its masked.
Friend at garage said "he will be looking to find which cylinder or cylinders are not firing"

British weather its thunder and lightning here with torrential rain can't get out under the seat as yet but if it shoud stop raining i will update.
Failing that I will let you know what happens at the independant tomorrow.
Please still add anything known from experience I would be grateful

Anthony, let us know what happens, I am sure someone here with more experience troubleshooting the system will be along soon. Im gonna keep mulling it over and see if I can come up with anything else. I would replace the coolant temp sensor as a matter of course, they are cheap enough only a few dollars.
Randy

Randy maybe a few dollars but here in rip off Britain even for that little thing its costly.
So far the boys at my Indy say I have a weak spark from some of the leads.
They do not like the leads either said they were poor even if silicon.
Ordered LR genuine ones.
They can not find the problem as yet so kept her over night.
They have said when ignition is turned off sometimes the dash lights stay on very dim could mean a bad earth.
Looking at electrics today also.
I trust these guys known them along time and they are very good.
Pointed him to that resistor on the EFI loom I found on your site he will check it also.
I really miss my Rangey and her rumble
Let you know how things are going could even help someone else.

Oh my Randy turns out one of the new spark plugs had damage.
After a second set of new ones were put in and genuine LR leads the horrible symptoms have gone.
Read it so many times over and over plugs plugs plugs leads leads leads then cap arm amp.
I'm a little embarrest to say the least.
There is something not quite right though.
She's as smooth as a baby's bum under any load and cruises sweet but hunts on tick over at stand still almost stalling at timed.
What should look at guys.
Regards
Anthony

Well thats great news Anthony! hmmm as far as hunting, thats a tough one, Im just starting to mess with that myself. I know the road speed sensor being disconnected will do that, check and make sure the plug wasnt disconnected accidentally, should be on the chassis rail somewhere and is driven by the speedo cable. Most likely a long shot but who knows? These are very sensitive to air leaks and that could be a cause somewhere in the system, also sticky idle valve.
Randy