'Missing a beat' every 6 or 7 seconds

[Big_Nige]

3.5 efi (flapper i think) 89' RRC, auto with no mods i can see. Whils't driving I get a 'miss' for a second or so. The previous owner had had the dizzy replaced, all the leads, the coil,  the plugs all to no avail. To be honest it doesent feel like ignition to me, it feels like momentary fuel starvatiion, but I could be wrong? Anyone got any ideas?

Ta

Nige

[Range Rover Blues]

If you're happy it isn't ignition then try the fuel pump and or pressure reg.  Start with the fuel pump wiring.
Have to admit it's one of the things I keep putting off with ours, runs fine on LPG but on petrol it pulls like a train but won't cruise, I have been told it could be a weak pump, and given the age it's not a surprise.

[Big_Nige]

If you're happy it isn't ignition then try the fuel pump and or pressure reg.  Start with the fuel pump wiring.
Have to admit it's one of the things I keep putting off with ours, runs fine on LPG but on petrol it pulls like a train but won't cruise, I have been told it could be a weak pump, and given the age it's not a surprise.

 This will idle ok all day with no missing, once it needs the petrol it does the missing, i also noticed it doesn't do it whilst cold??? Is the pump in the petrol tank or is that just a lifter/primer pump? I'll have a look after i get the welding done!!!

[Merlin]

Nige, did you get your mis-fire sorted?, mine does the same so I am wastching with gr8 interest--Tony

[Range Rover Blues]

When cold the EFi over-fuels the engine to act as choke, or on the 3.5 EFi you have an extra injector, either way it runs rich so when cold the problem is not as bad.  Spoke to a guy who had very similar probs to me and cured it with a new pump, have a S/H tank to fit but every time I lift a spanner it rains.

[Merlin]

Thanks, am hoping to buy a Workshop Manuel off "E" bay so at least Ii'l know where the pump is, I know most things about Series Motors but minus things about Rangies.---Cogs

[Range Rover Blues]

Sorry, meant to tell you.  The fuel pump is in the top of the tank and it's a tank out job with the 3.5 EFi.  The later 3.9 hot wire system has an access panel under the boot floor.  Lucky so and so's.
Our 88 model was built as a 3.5 but has the later hot-wire EFi and a 3.9 lump retro fitted.  It did run smoothly when we bought it!
I am told the early flapper EFi is a cow if anything is slightly wrong.
Have you checked for air leaks in the inlet side?  check ALL the vacuum pipes, servo and that funny little pipe that goes into the heating system to close the recirc' valve.
Also check the flame trap doesn't need cleaning and there's no oil in the bottom of the plenum.
Also try a bottle of injector cleaner, follow the instructions.  Made a huge difference to the Mondeo!

[Merlin]

Done the In jector bit, misfire still there so will work my way through the rest this week. Plug leads have been suggested as well, this mis-fire is starting to get expensive!!!! :(  :(

[Range Rover Blues]

If it's the leads then start by checking they are layed-out properly.  If they are laced up like knitting this, I am told, can cause cross-firing or arcing.  Honestly though if this were the case I'd fit new leads anyway, but it cost nowt to check.

[Merlin]

And the saga goes on!!! All the electrical side has been done (under the bonnet) & still the intermitant mis-fire.
More on that--
1) It seems to be only after the motor is fully warmed up
2) It comes on AFTER going round a 90 left/right turn ( this may be in my head but am sure I am right)

Possibly fuel filter?
Do you have to de-pressurise the system to replace the filter(s), if so how & how do you re-pressurise it?
Where are the filters you need to replace.

Arn,t workshop manuels bloo-y expensive!!!, looking for one on "E" bay but no luck yet.  Are Haynes any good for a 1990 3.9efi ?, or is that a stupid question.-- :(  :( --Tony

[SPIKEY]

Hi Cogs.
             My motor ran a bit erratically until I changed the fuel filter.

It is situated on the o/s/r chassis rail, and I changed it without taking the wheel off.

As I work in a car salvage / spares yard where petrol out of scrappers is plentiful, I used to put 10 odd gallons a week into the car.

After tipping brown sludge out of the filter when I changed it, and the misfire being sorted, I only fill up at petrol stations now.

Hope this is some help.

Cheers,

SPIKEY.

[Merlin]

Thanks Spikey, do I just swap old for new?, have heard about letting off fuel pressure or am I being over cautious.  
Funny one, I got the "Workshop manuel" on CD & was checking handbrake adjustment but the pages on screen are to small to read so I went to print the page off.  A few pages later I checked the "Print Setup" & found it was printing the whole manuel, 160+ pages, stopped sharpish!!!--Tony PS-How much is a filter, any idea?

[muddyweb]

Tony PS-How much is a filter, any idea?

Just over 8 quid from Mansfield :

http://www.mansfieldmotorsltd.co.uk/shop/en/browse/Range+Rover+Classic/1/0/1/3/411

[Range Rover Blues]

Depressurising is easy, run the engine and pull the fuel pump fuse out, when the engine's stopped it's safe to swap the filter.  No joke it says this in the manual!

The Haynes manual is better than useless for an EFi, it has a useful set of basic checks for all the sensors on both flapper and hot-wire systems that are probably the scope of most mechanics with some knowledge of electronics.

[Merlin]

Thanks, I just used my brake flexy-pipe clamps on either side of the filter & swopped them over.  It seems to have worked OK.
Have yet to try it on the roads to see if the mis-fire has gone.  The petrol in the old filter looked clead, not so good eh!!