Intermittant rough running - inspiration reqd

[gifdy]

Hi - hoping someone can suggest some things to try to cure rough running of my V8S. It doesn't happen all the time but when it does it's as if it's running a few cylinders short. That's the best way to describe it although I'm not sure if that's what it is.

There's also a strong smell of unburnt fuel when it is in this state so I initially thought it was ignition related. I've put in new rotor arm, coil, new dist cap and new leads (they were needed anyway). Cleaned and regapped the plugs. No difference. Then took out the throttle pot and cleaned that up.

I've just been out checking through the ECU checks from the bible and the only thing I can find which is not in spec is the output from the speed sensor. It only toggles between 2.7V and GND rather than 12V but the speedo works OK. The injector resistances etc are OK.

Any clues ? I'm about to chuck in the towel and take it to APM although I'm not sure if it will make it there. Also dont want to damage anything by running it in this state

Cheers

kenny

[Barkychoc]

Its all armchair guesswork but the electronic ignition thingmybob on the side of the distributor can breakdown, I don't think its a very expensive part.

[gifdy]

Ah yes - the amplifier thingy ? Yep - can try swapping that out.

[M3CHA-MONK3Y]

While we're playing the guess work game, maybe injectors? They could be gummed up or loose wiring.
Does the fault occur from start up? Does the rough running start and stop?
Best thing to do is give as much information as possible, no matter how small.

HTH

[Barkychoc]

Also there are some rubbish rotor arms about too.

My engine was running well when I took the car apart - I don't mind sending you some known working parts off my car to try for the cost of the postage (and send them back please!)

Edited by Barkychoc on Saturday 6th June 20:17

[gifdy]

Thanks for replies so far :

Bit more info:-

It can occur from start up when cold and also occurs when the car is warm so haven't been able to correlate it with temperature. I once noticed smoke out the right exhaust but not the left after it had run like this for about 60 seconds which is why I started looking at ignition. It'll idle like this,but only just. Sometimes it seems fine but get 50yds down the road and it'll go lumpy again. When lumpy it can sometime clear itself but I think this has only happened when I've switched it off and started it up again ( from memory )

What else - I've recently replaced the fuel pump relay. The speedo has stopped working in the past but is OK now (didn't change anything). That's all I can think of just now.

I'm going to have another crack at it tomorrow so any more suggestions for stuff to try will be welcome. On the injectors - can you clean them with basic tools or do you need an ultrasonic bath or similar ?

Thanks for the offer Barckychoc - if I dont get anywhere soon I may take you up on that

Cheers

[K4000JB]

hi just a guess hear but you could check the fuel pressure regulator if this is duff it can cause overfueling.Or a faulty temp sensor making the ecu think the engine is cooler than it is and it putting more fuel in to compensate.
HTH
i hope you get it sorted soon

Edited by K4000JB on Saturday 6th June 23:04

[Last S4]

Hi,
My V6 had al sorts of rough running problems until I removed the multiplug/socket and replaced it with solder connections. When removing it I could actually pull the cables out leaving the crimp in the plastic housing. It is the one above plug No.1 at the top. Carries info from the throttle pot etc.
I am sure I read about a sensor to the speedo which was involved in the mixture too? It was in the Steve Heath book - I will try and find it.

[Barkychoc]

gifdy said:

I once noticed smoke out the right exhaust but not the left after it had run like this for about 60 seconds which is why I started looking at ignition.

You've red herring'd yourself here - the exhaust is a single pipe from the front of the car to the exhaust box - then it splits to 2 tail pipes.

[gifdy]

Barkychoc said:

gifdy said:

I once noticed smoke out the right exhaust but not the left after it had run like this for about 60 seconds which is why I started looking at ignition.

You've red herring'd yourself here - the exhaust is a single pipe from the front of the car to the exhaust box - then it splits to 2 tail pipes.

bum !

Think I need to leave it a day and go back to it - confusing myself !

[gifdy]

I've managed to get hold of one of those Landrover fault display units. Unfortuntely my car doesn't have the corresponding connector wired into the loom. Pins are not in the connector to the ECU - does anyone know where I can get hold of some pins to put into the connector to wire the unit in ?

Thanks

[Barkychoc]

One of these might fit, which one I'm not entirely sure.

http://www.vehicle-wiring-products.eu/VWP-onlinest...

[gifdy]

This is turning into a nightmare ! Managed to get the fault display connected - didn't flag up anything other than 'ECU lost supply' when the volts dipped as the battery was getting low.

I noticed a strange gurgly noise and hissy coming from inside the head/plenum area that I've never noticed before - maybe coolant but I'm now suspicious about the fuel regulator. I don't know the failure mode of these but it seems to tie in with the overfuelling and gurgly noise. Anyway, I may be putting 2 and 2 together and getting 5 but I got hold of a secondhand regulator of a Chimeara to try.

Thought this would be a 10minute job but couldn't for the life of me get a spanner on the bottom bolt to take it off. I've now dropped a socket into the gap between the 'V' and can't get to it. Ever started something and wished you hadn't ?

Given up for the night. Need to get a magnet or grabby thing to retrieve my socket then have another go at that bolt. Beer therapy needed

[ketvrin]

I know what you mean...the magnet on the end of my telescopic-dropped-nut retriever stuck to the nut but came off the telescope what a job I had rescuing that lot... duct tape eventually saved the day

hope the therapy worked

K

[Barkychoc]

gifdy said:

I noticed a strange gurgly noise and hissy coming from inside the head/plenum area that I've never noticed before - maybe coolant but I'm now suspicious about the fuel regulator.

There is coolant circulating through a water jacker near to the plenum air inlet - maybe it was water runing through there that you heard. If its running rough you may be generating turbulence / bubbles in the cooling system.

[gifdy]

Yes, did consider that. However I believe I've ruled out a lot of other things so my current focus is on the fuel supply. Sensor inputs seem to be within spec, there is a good spark, I've been unable to find an air leak (including the brake servo)... . I may have missed something so will go round the loop again if the regulator swap out doesn't help

Cheers for the help, and yes, the beer did improve matters

[Elfit]

I'm not sure if it's the same on my V6 as your V8 but my rough running problems were caused by the wire in the top of the fuel relay. One of the contacts was not fully pushed in. Took 2 seconds to fix but over a month to find.

[gifdy]

Well - don't want to celebrate too early but just managed to replace the fuel regulator, put it all back together and the car is running really nicely !! Immediately there were no gurgly/hissy noises and it fired up first time. Unfortunately I have to head off for the weekend so no time for a test drive but looking good so far.

All the makings of a good weekend. British GP, Paul Weller concert on Sat night and potentially a hoon on Sunday evening if the old girl is fixed

Cheers everyone

Edited by gifdy on Friday 19th June 17:23