V8 trouble!

[skip]

Hi again

Now i've had my disco for a bit and got used to it, i've identified a problem that originally I thought was just a characteristic of the engine.

first off it runs fine when being laboured and fine when being ranted. The fun happens when I drive moderatley which contrary to popular belief is the mojority of the time :lol:

Say i'm  traveling at around 30mph in 3rd gear and i want to accelerate, the engine will start to pickup ok then hesitate and then lurch, it'll keep doing it until about 2500revs then it clears up. or if i lift off the throttle a touch and it'll pickup again. and on other occations it just doesn't want to accelerate :?

I think it's a miss fire but I don't think it's ignition related as it runs fine on LPG.  Aslo I've been through the ignition system but ive stopped short of checking timing.

Are these motors known to suffer with fuel pressure or injector problems?
Oh it's a 3.9 hotwire BTW.


Pete.

[Skibum346]

I'd try putting some forte fuel treatment through in the first instance before looking for dodgy compnents/systems. Could just be crap in the fuel filter or pipes.

When was it last serviced?

[skip]

Skibum it was last serviced 3k ago, I don't know what was done as the dealer I bought it from did the work.

 TBH i've had enough of the thing now. I bought it becuase i've always wanted a V8 but it's a big let down in just about everyway conciveable.

The gearbox is notchy and doesn't like going into first, just like the 110 I drive at work, the switch gear is impossible to see without peering round the steering wheel and the engine is lack lustre even when it's runnning well. that's the main points.

Sorry to moan i'm a bit fed up  

[Skibum346]

No worries matey, by the way, is it a carbed v8 or efi?

[skip]

tas got the lucas hotwire effort on it.

[Skibum346]

Whilst an efi engine will generally sort itself out, the ECU is only as good as the readings it's getting from the sensors... see if you can "borrow" a known working air flow meter and change it, see what happens.

The other place you could look is at the Lambda sensors on the exhaust. If they give false readings then the ECU will try to make the mixture leaner or richer affecting performance.

There will be loads of other sensors but these are starting points.

Good luck

[Sheddy]

I'd be measuring the TPS output, it sounds like you've got a dead spot.

[Skibum346]

I'd be measuring the TPS output, it sounds like you've got a dead spot.

TPS Output....?   :(scared):

[skip]

Throttle position sensor :D  

both your suggestions make sense, there is a landy specialist near me with a rovacom, I think an hour of his time doing some realtime diagnostics could be money well spent.

I'll get the multimeter on the TPS first as it's free. unfortunatley I don't know anyone with another V8 I can swap stuff from. :(

[Blakey]

Hey skip!

My bro's got a P38 4.6 LPG but his wont run on petrol because the engine has been tunned to suit LPG. this maybe the same for urs if it wont run on petrol but will on LPG, but if its the other way round then it may need re-tunning to suit.

[skip]

Thanks for the input Blakey, It's just a missfire or some sort of hesitation problem I'm having on peterol.


I found a brilliant link for the lucas hotwire system, it gives a good overview of how it's all put together.

http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

[Skibum346]

Thanks for the input Blakey, It's just a missfire or some sort of hesitation problem I'm having on peterol.


I found a brilliant link for the lucas hotwire system, it gives a good overview of how it's all put together.

http://www.britishv8.org/Articles/Rover-14CUX-EFI.htm

Brilliant aint the word!

A quick five minute speed read and I've learnt a pile already! Just in time to apply it over Summer rebuilding the engine on or V8 RRC Vogue SE!

Thanks matey!

[skip]

No worries, spread the word :D

I've also got some good news, I think i've sorted my woes .
I tested the TPS as described on that link I posted and had apart the MAF, no obvious problems there, infact it was really clean. So I decided to have a play with the ignition timing.

I marked the block and dizzy base so I've still got a reference if I cock it up 8)  after abit of messing around I've settled on around 2-3 degrees of advance, I don't know exactly cos I ain't got a strobe. TBH I'm baffled why a 98 motor has still got old an school timing system as opposed to full engine managment :?

Anyway end  result is much better pickup when free revving the engine, it used to stumble all the way up to about 2k, and it pulled like a train when I took it round the block. it stuck being put in 5th gear at 15mph although it did pink quite alot, but under those conditions any normal car would kangroo and stall. The proof will be in the drive to work tomorrow :D  can't wait.

Only downer now is I found I need a new viscous coupling for the cooling fan. I can stop the blades with the engine running, wobble it around and spin it wrong direction :lol:  DOH!!!

Cheers

Pete.

[Rossko]

Only downer now is I found I need a new viscous coupling for the cooling fan. I can stop the blades with the engine running, wobble it around and spin it wrong direction :lol:  DOH!!!

Fix that before it goes really wobbly, blades catch and explode through the radiator ....  lucky me when it happened on my old stage one at speed the shards didn't do any damage, but they should have done.

cheers Ross K

[skip]

Thanks for the tip 8)

I was thinking of putting an electric fan on anyway. Now i've got no reason not too as even like it is she's not getting hot 8)

I can get a 14" from work for nuthin :D  I reckon it'd be ok with just a switch on the dash for emergencys, any thoughts?

Pete.

[Range Rover Blues]

A apir of 14s would be better.

FYI a stock 3.9 with cats should be 4 deg BTDC, a pre-cat should be 6deg and the 4.2 is 10deg (same dizzy).

Could also be cam timing/wear

[skip]

Hi RRB,

I did wonder if the timing problem could be related to general valvetrain wear. However she's running well now with no nasty noises, If it starts playing up again i'll have to look a bit deeper. Hope not though

Hmmm two 14" fans, I think it maybe cheaper to just get a new viscous unit, although eblag might come up with somthing 8)

Cheers

Pete.

[daveyravey]

One here Skip
http://cgi.ebay.co.uk/LANDROVER-DISCOVERY-3-9-EFI-94-98-VISCOUS-COUPLING_W0QQitemZ150023575222QQihZ005QQcategoryZ31348QQrdZ1QQssPageNameZWD1VQQcmdZViewItem

[skip]

That seems like a good price 8) , Thanks.

[daveyravey]

No worries, that's what we're all here for innit   :D

[Range Rover Blues]

I picked up a pair of brand new PAcet style fans from E-Bay for £40 each.  Designed for Fiat vans or something but massive air movers :D

[daveyravey]

Jammy git   :lol:
I'm looking for a set too   :D

[skip]

I've managed to get the old viscous unit off, it was well shot :lol:

 Been driving around without a fan for a couple of days now and the temp guage stays where it always sat (just under half way) It's quite a pleasant surprise as my old jeep used to overheat really easily 8)  i've not been doing anything taxing for the engine, only my daily commute, I would imagine that a bit of towing would get things to warm up a bit.

So I've got my eye on a pair of series 1 ES  aircon fans at the moment, I don't know if they'll be upto the job or no, also i'd like to know if fitting will be easy? BTW My diso doesn't have air con.

[daveyravey]

What size are they Skip ?

[skip]

As it's an ebay auction i'm only guessing they're about 12 inch looing at the photos.