RRC 3.9 rough running on petrol

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Khryztal

Khryztal

New Member
Posts
725
Location
Felcourt. Surrey
Evening all, just started having problems with my Classic when on petrol, but runs ok on LPG. Smells like hell on petrol too. I'm thinking it maybe over fuelling somehow. Is the a way of turning down the fuel flow? Or would it be down to something else? All plugs, leads etc are in very good condition.
As I say, it runs pretty good on LPG, but badly on petrol.
Oh, it stalls if left to idle on petrol and if you try to hold it at 1000 rpm with throttle it revs up and down by about 300rpm either way.
Thanks for any advice or ideas
 
he is saying it good on lpg isnt he?

I think if its bad on petrol mate it sounds like its gone in to limp home mode if its that rich, and or base idle needs setting.

So maybe check the coolant temp sender for the ecu (which is on the inlet manifold by where you had that leak :p ) buy a genuine LR one as they are about £25 but actually work- any other make seem not to work at all well!!!

also the base idle setting procedure is in the thread.
http://www.landyzone.co.uk/lz/f10/idle-problems-157563.html

from memory me old mate isnt this the truck you had to adjust the throttle cable stop on to keep it running? if so you will find it will have stored/recorded a throtttle pot fault code for the last year lol , I am not sure if it repeatedly flagging that code when you drove it could have caused a problem in some way? unplug ecu after doing those other two jobs to clear and see what it says?

I will go halves on a fault code reader with ya if you want. Joe found them on ebay for £50 if memory seves me right :p
 
Last edited:
Yep, this is the type I got;
14CUX ECU fault code reader TVR Range Rover Land V8 | eBay

It might seem like a lot of moeny for a box with LED on it, but its well worth it, not just saving on buying needless parts, but for me it is a sanity saver!!!
It comes with a plug set and extra wires to splice into the loom if yours hasn't got the same socket on it (some 14CUX hotwire ECUs dont). Also comes with the codes key to tell ya what it means and what direction to take.
A usefull bit of gear. I have to admit I was a little scared of the ECU injection system on classics before I got one of these. I'm not big into auto electrics and this is about as complex electronics as the classics have. Turns out its not THAT complex afterall.
Get one....you wont regret it ;)
(no, I'm not the seller or connected with the seller!!!)
 
....and if ya need a replacement ECU for the 14CUX hotwire system, let me know. I got 4x spare that I know are good (its dead easy to plug-unplug them on me bobtailed RR) ;)
 
Khryztal said:
Evening all, just started having problems with my Classic when on petrol, but runs ok on LPG. Smells like hell on petrol too. I'm thinking it maybe over fuelling somehow. Is the a way of turning down the fuel flow? Or would it be down to something else? All plugs, leads etc are in very good condition.
As I say, it runs pretty good on LPG, but badly on petrol.
Oh, it stalls if left to idle on petrol and if you try to hold it at 1000 rpm with throttle it revs up and down by about 300rpm either way.
Thanks for any advice or ideas
Click to expand...

As you know there coud be all sorts of influences. FWIW I would start by checking the operation of the vac and mechanical advance on the dizzy and check ignition timing - I think it should be slightly advanced if you've got LPG.

Next I think I would check the air flow meter as Fett suggested but don't necessarily rely on the resistance setting - that is only a base setting, you should check air flow signal and CO trim values. I could be wring, but most LPG set ups I've seen on Classics don't use the AFM for the LPG. If this is the case with yours, then it seems logical the AFM could be at fault when the engine is O.K. on gas but plays up on petrol.

The other option is unfortunately an ECU problem. I had an ECU that had an intermittent fault where it didn't read the AFM signal. It might be worth plugging in a known good ECU to see if it makes a difference.

Next I would be tempted to take the plenum off, give the plenum, ram housing, stepper and throttle butterfly a good clean. Check stepper motor is working properly. Reassemble and make sure there are no inlet air leaks then see if it will idle. If it does then check/set base idle. Hope that helps ya.

Nearly forgot to ask is your EFI Warning light coming on at all?
 
Last edited:
thanks for the advice guys. Already replaced stepper - slight improvement.
New rotor arm and cap. good leads put on all plugs are good.
Found the fault is down to AFM. swapping that out today. Hopefully that should be it.
If not I have a good ECU here I can swap out.
Going to wales tomorrow morning so I'll keep y'all posted lol.
 
Khryztal said:
thanks for the advice guys. Already replaced stepper - slight improvement.
New rotor arm and cap. good leads put on all plugs are good.
Found the fault is down to AFM. swapping that out today. Hopefully that should be it.
If not I have a good ECU here I can swap out.
Going to wales tomorrow morning so I'll keep y'all posted lol.
Click to expand...

Sounds promising. Where in Wales you going? I'm going to be in North Wales this weekend but not taking the Rangie.
 
Right got the fault sourced down to the AFM area. It runs like crap, but if you remove plug from AFM it smooths out. Reattach Plug and runs quite nice..
If you shut the engine off wait a few minutes it'll run rough on re start. Remove plug etc runs well.
Swapped, ecu no difference. Swapped AFM no difference. Swapped stepper no difference. Only thing that stops the rough running is pulling the plug and putting it back.
Bad wiring in plug?
 
maybe clean it and see. also what are the afms set to? check with your meter.

if you unplug it puts it in to limp home mode, so it prob isnt in that mode when fault occurs as you say it smooths out.

does it make any differance when hot or cold?

did you ever get your throttle pot set right?
 
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