3.9 V8 efi running rich from start up

Hi All,
My 1994 Discovery V8 has fired up, I have reset the dizzy into the correct position, new leads, new cap, new rotor arm and a new Mass airflow metre fitted.
firing order is correct and dizzy in roughly correct position.
After I have attempted to fire the engine up - ( it does run at revs of 2000 rpm + and dies after letting off throttle) the plugs are black - really black so its running rich or unregulated?
I was thinking clean out the Plenum and associated plumbing and attachments - would this be a good starting point?
Engine does sound good when I do get it away so its the fuelling or sensors?
would a faulty throttle position sensor make it run rich?

Any thoughts appreciated,
Ta Ian

How did it run before you did the work

pete1987RRC said:

How did it run before you did the work

Click to expand...

He bought it as a non runner :
Hello, new to the site, looks good.
just bought a Discovery 1 3.9 V8 - and it does not run - I like challenge.
Bloke reckons it ran and then he changed leads, rotor arm, cap and plugs, I have checked and all in correct place.
Next need to check if its 180 degrees out - do this tomorrow.

Tps and AFM need to be set correctly but timing could still be an issue. From 2000-3000 rpm you should be seeing timing advancing from 14-21deg btdc

http://www.actproducts.co.uk/2011/l...n-system-–-installation-and-diagnostic-notes/

I would be looking to get a diagnostic run as there are a numbere of components which can cause this, rave will give pointers also.
If it was my 87RRC I would be swapping the ecu.,

Hello, thanks for the replies and sorry for not copying and pasting my intro from the other part of the forum.
OK I'm new to fuel injection and modern cars to be honest but I'm reading up on it most nights.
I did think about pugging it into a diagnostic machine - does it need to be running or will the faults already be logged?
I am a bike mechanic and I have seen tps's going down and it gives an erratic rev up and does not run rich, its just guess work so I will get hold of a diagnostic machine.
I'll keep you informed of the results,

ta ian

It is possible there is no bulb in the engine management fault indicator (main dealer trick). Faults are cleared by removing battery power for a minute or two. Assuming it has cats / exhaust sensors, it will switch closed loop fuelling when up to temp

Pete and cooltide, just been out and disconnected the battery, left it 10 minutes, and it fired up much better than it has the whole time i've been working on it but it is still misfiring slightly, tweaked the dizzy back and forward a bit and got the over revving down on start up.
I can hear the inside of the dizzy rattling so suspect a faulty dizzy, going to take it back off and take it to bits, sounds like the springs are not doing their job.
Closed loop is lambda sensors working - yes?
Progress of sorts

Ian

IandiscoV8 said:

Closed loop is lambda sensors working - yes?

Click to expand...

yes

Lambda sensors, there are 2 used ones in the back of the truck so I am assuming they have been changed and they do look quite new

ian

In the post 93 land rovers I have owned, I've never had problems, most of the tinkering I do is with precat prelambdas. As I understand it, until the engine is up to temp - presumably indicated by coolant temp sensor - the fuelling is controlled by the traditional parts, fuel temp, afm, tps.
The point being your problems from start up mean lambdas are out of the equation unless the ecu is faulty as suggested or is being told the engine is up to temp.

A noisy dizzy can't be right. It could also be that it is not engaged with the oil pump drive gear properly and is bouncing up and down whilst running

Hello, Update of sorts about the V8.
I bought a lead and a Rovergauge disc which connects to my laptop.
Its communicating with the ECU, and seems to do everything else. but I cannot seem to access fault codes with it, should there be a way of ID ing fault codes on the vehicle?
On the Rovergauge screen its telling me its running fuel map 5, I have found out from the previous owner that the catalysts have been removed and replaced with normal boxes, surely this; as has been suggested would not give over rich mixture on start up and only be an issue when warmed up?
One puzzling thing which could indicate a dodgy ECU is; on the Rovergauge screen, both temperature gauges are reading 69 degrees - the engine is not running.
I will check the temperature sensors when I have some time later in the week.

Ian

Check the AFM setting and operation as per the link I posted above, afm cat setting is richer (1.8v) and map 5 is cat tune. Personally I would adjust AFM co trim to 1.4v and see if it makes a difference, and check operation as per link.
Without a cat, you no longer need to use the lambda sensors and map 5. You can change to non cat tune by replacing the white tune resistor with green map3 (it is taped into the ecu loom inside the cabin). However I would check emissions requirements for your model year. You need to comply with these and cat visual inspection for an mot.

I did think that maybe an issue for the MOT greatful you reminded me, think its going up for sale and I'll find a decent running one, it needs a bit of welding for mot too and the interior has seen better days mm
Thought I got a bargain

One more question, are there 2 sets of lambda sensors on the downpipes and on the cats?

Ta Ian