3.5 v8 efi power loss of 10 mins and hunting

Hi, New to the site and looking to see if anyone can offer some advice. Have a 3.5 efi (flapper) with 4 speed auto box from 1988 RR classic in 1986 Ninety.

Was running great but went a bit rough last year so had a bit of an overhaul, new dizzy, HT leads, plugs etc - was hunting badly so all vacuum pipes replaced. timing and mixture was adjusted and passed emissions on MOT no problem, new timing etc seemed less powerfull than original setup but nearer factory default so advised to leave it 'as is' as original was way out and hunting was now only just detectable. Had run like that fine for a year but recently after about 5-10 mins driving the engine loses power and even with foot to the floor a motorway run will see you decline from a speed of 70 to 35 within a couple of miles. pulling off motorway and accelerating hard - loads of power and revs. stop and tickover is fine (altough was hunting again slightly). turn off wait 5mins and all back to normal. fuel consumption poor at 9mpg.

initial thoughts were fuel pump as this is one item that had never been replaced so had another weekend on the drive last week. replaced fuel pump, fuel filter and regulator - new fse unit installed from rpi and tests at 2.5bar at tickover. slight improvement was made but not a cure. new plugs were next, old ones werent bad (mix of brown and black, not oily, pure soot or burnt to a crisp) but as they were out to be checked changed any way with NGK BP6ES. rotor and cap good in dizzy and leads genuine LR less than a year old. on checking for air leaks spotted rear rocker cover breather blocked, on checking MAF this was full of oil, suspected lack off breather meant oil being sucked up from flame trap side, yep full of oil also. mushroom breather wouldn't drill so removed ram housing to remove rocker cover and hammer out brass bung. first issue - ram housing full of oil and petrol mix; second issue - rocker cover completely sooted up inside. Cleaned everyting up and replaced.

Now running slightly better...But ...low gears some power, accelerates cleanly from standstill (better than before fse) however as soon as 4th kicks in engine is once again guttless and accelerating from 30 reqiures full throttle and kickdown to acheive splutterlessly . once hot - excessive hunting has returned although the gradual loss of power now just a general gutlessness all the time. still smells very fuelly in engine bay. have a warning light on dashbord that now comes and goes (unfortunetely defender dash and RR loom so could be wired to anything at one end but looks like a heated windscreen icon on the dash).

Any ideas where to go next whilst i try and trace fault light through the loom to whereever its attached?

Hi there.
Has the engine ever been cooked/ overheated?
Engine on my bobtail went through a period of being pretty gutless. A combination of fuel injector faults (one wasn't opening properly), distributor not doing what it should do through the rev range (vacuum advance etc) and ECU replacement saw most of the issues resolved.
Through general lack of proper servicing and a sketchy past the engine looked much more worn and tired than the odometer indicated.
I've only just finished replacing the cylinder heads with some 'better' secondhand ones mounted on composite gaskets. The intake gasket was also leaking, this has now been remounted,again, on a composite valley gasket (I don't care what anyone says, those tin ones are ****e!)
The engine still doesn't pull as a 3.9 V8 should do....but its better than it was. Ultimately I shall eventually be looking for a replacement engine..., but still not where I really want to be, compared to other RRC V8s I've had/have

Oh, and I also found the parking /transmission brake
was partially siezed on....freeing this off obviuosly helped!!!

Hope this helps??

Hi Thanks for the reply. engine has never overheated when i've had it, even in morocco at 40 degrees. the engine was changed before i went for 60,000 miler as a precaution as i wasn't sure about the original as i didn't do the conversion and the local LR guys (Foleys) said it was a good known running unit and was a better bet than what was there. the old engine however never hunted. dizzy was new last year, again just eliminating possibilities as old one checked out ok anyway and makes no difference if you swap back over. the only engine issue i had on the trek was that the champion spark plugs they fitted were ****e and destroyed coil and HT leads. NGKs, new leads and coil sorted issue.

confident on dizzy and vacuum pipes so looking at your comments gave me a few things to look at / think about this morning. looking at the back of the block the seems to be some oily petrol mix collecting in the valley so possible that intake gasket (tin) leaking? any quick test suggestions? looking at the RRC wiring diagram last night i notice there is an ECU fault light so this could be my heated windscreen light, i need to find time to trace, i have a spare 4CU so will swap test that also. i thought injectors which is why took plugs out to see if one was burnt, oily, unused etc but all looked good. Any way of testing injectors? my other thoughts due to amount of fuel in ram housing was cold start injector so going to try disconnecting that also. hadn't considered park/tran brake as the guy who converted the beast was not a good electrician and doesn't seem to have even wired the park / handbrake lights so possible.

I bought myself a fault code reader on the back of the trouble with the bobtail, I've had a fair few classics now, so my thoughts are that it'll save a lot of potential unneccessary parts replacement. Mine have mainly been the later 14CUX ECU type Hotwire EFi type engines, so I foudn someone selling the readers on ebay. think it was about £50.
I also bought a relatively cheap (about a fiver) EFi noid light...which is basically an LED with two contacts. Unplug the electrical plug from the top of an injector, plug the light into the plug. This tests that the injector is getting a signal from the ECU.
Another useful gadget is a UEFI Quick probe. A bit more expensive (about £60). Its a touch sensitive probe with variable sensitivity. Hold it against an injector and it reacts giving a light and sound 'blip' as and when the injector opens, then closes. It doesn't help check detailed interval times as full laptop diagnostic gear would, but it does atleast tell you if an injector is opening and closing.

In term of checking for leaks around the intake, lots of advise on here about different stuff to spray around the engine to check as and when it changes the engine running tone (sprays like wd40 or intake cleaner with engine running and cold/cool). Slightly different if theres an oil leak around the base of the valley gasket which just covers n seals the oil splashes from cam n push rods...as its further up the valley where the intake butts up and seals against the cylinder heads where in theory a leak would cause the hunting.
To be honest, its probably not what ya want to hear, but I'd have the valley gasket replaced anyways

Cheers Joe, going to Billing on saturday so will see if i can pick up some of these tools there, if not ebay next week! Just picked up some recon heads as they were a bargain and a friends diagnosis was that due to the amount of crud in the rocker covers that mine are probably history anyway. Looks like this will end up turning into a bigger project than intended - if i decide to fit them soonish then valley gasket is going to get done by default. To be honest seeing that a recon 4CU, 2AM and Injectors seem to work out over a grand to replace/maintain in the long run begining to wander if brand new weber wouldn't work out cheaper and if it all coming off to replace the heads anyway...well !!!

Tried tracking down my non existant heated rear windscreen warning light last night as its still coming on after 10mins of driving and i need to find out what is connected to the other end - dashboard now in bits!! (that's no easy task)

New problem - found loose connection on oil pressure guage and finally got that working again but the oil pressure is running around 70 whilst driving at a few thousand rpm, startup to tickover sees the normal 5 but i'm sure this used to run between 25-50 once i got up to speed. Is oil pressure to high? Anyone know what it should be?

FrankTheTank said:

Tried tracking down my non existant heated rear windscreen warning light last night as its still coming on after 10mins of driving and i need to find out what is connected to the other end - dashboard now in bits!! (that's no easy task)

New problem - found loose connection on oil pressure guage and finally got that working again but the oil pressure is running around 70 whilst driving at a few thousand rpm, startup to tickover sees the normal 5 but i'm sure this used to run between 25-50 once i got up to speed. Is oil pressure to high? Anyone know what it should be?

Click to expand...

Taking the dashboard out of a ninety is not a 5 minute job! Finally got to my wiring loom and after multiple cable colour changes traced it through the bulk head to a black box that turns out to be a thermo control unit for a kenlowe copy electric fan - needless to say don't have a heated rear windscreen or and electric fan! power to the box shorting on exhaust manifold - hey presto - warning light! will set about completely removing unit and wiring at the weekend along with a complete rewire of the dashboard.

This still leaves me with a possible high oil pressure question and waiting on the posty for a noid light to continue diagnosing what feels more and more like a choking issue resulting in loss of power whilst cruising once the engine is warm. can anyone help with the oil pressure query?

you want at least 15 psi at hot tick over.

does the oil light come on at all? should be on a seperate sender.

have you mixed up the two?

Ok start at the top
Are the cap leads and rotor original dealer kit?
Does it have e massive amp under the coil?
Is the vac unit working on the dissy?
Have you done a throttle pot set up and the set up of the Afm?
Have you eliminated all the air leaks?
If you can run the car up on axle stands run at a constant 60 mph and watch the manifolds if they glow cherry then you have a leaning off of mixture which means either a ignition fault or a fuel fault I suspect a ignition fault properly amp or coil are all the earths ok on the engine to chassis?
The 14cu does not have any diagnostic capability so if you suspect the ecu or sensor it is a case of sending away to test

Tbh the easier course of action when it comes to 14 cu is ditch it and upgrade to 14cux from a 3.9 range rover or from a disco 1 as they had hot-wire on the 3.5 engine
This may seem as a drastick idea but with the amount of failed 14cu units put up for sale and the lack of repairers that can fix then the 14cux is a better system and can be talked to

At the moment i have the whole dashboard out so trace thed wiring and confirmed connections to correct senders. Crimped new connector along the way.Oil light comes on with ignition and goes out when running.

Did a 30 mile trip today. hot tickover is about 25 , cruising is about 50 and never got much over that unless booting it, but never got up to 70 as before so looks like maybe bad wiring. The interesting bit is that there was no power loss today, hunting is still there but only just noticable. haven't touched anything else under the bonnet that should effect this, all i've been doing in the last 24hrs is cutting out the crap from the wiring loom that goes nowhere before i start rebuilding the dash (eg door light switches, toggle switch etc where i have no interior light (softtop)).

Puzzled? but sure it will be back to running like crap tomorrow!

Are the cap leads and rotor original dealer kit?

lead genuine land rover, cap is the blue one that came with remanufactured dissy from RPI

Does it have e massive amp under the coil?

No has small amp on side of dissy

Is the vac unit working on the dissy?

yep

Have you done a throttle pot set up and the set up of the Afm?

no, will google this unless you can post a procedure?

Have you eliminated all the air leaks?

will recheck everything this weekend but think so

If you can run the car up on axle stands run at a constant 60 mph and watch the manifolds if they glow cherry then you have a leaning off of mixture which means either a ignition fault or a fuel fault I suspect a ignition fault properly amp or coil are all the earths ok on the engine to chassis?

only got a pair of stands but there's a rolling road round the corner so will see if i can sweet talk them into a freebee!

The 14cu does not have any diagnostic capability so if you suspect the ecu or sensor it is a case of sending away to test



Tbh the easier course of action when it comes to 14 cu is ditch it and upgrade to 14cux from a 3.9 range rover or from a disco 1 as they had hot-wire on the 3.5 engine

This may seem as a drastick idea but with the amount of failed 14cu units put up for sale and the lack of repairers that can fix then the 14cux is a better system and can be talked to

sounds like a plan at this rate - also thinking of just going old school carbs, seems to be less to go wrong and cheaper/easier to maintain and for the amount of miles i do the differnce in mpg per year probably wouldn't even cost me the price of a replacement ecu when it does go wrong