Thread: D2 running rough under load after 4.6 conversion

When you say that it runs rough under acceleration, I gather you are at least making the vehicle kick back a gear? In all other circumstances, the engine runs fine?

I believe that you can rule out any cam wear or other mechanical wear because this in itself wont make a car from happy to grumpy in the way you describe.

You also say you have new ignition leads on it too. While you have the inlet off, try throwing on your old tried and true leads as I'm leaning towards ignition spark breakdown. Did you also replace your spark plugs? If so, see if they are the correct spec. While you're at it, check that your coil plugs are firmly all pushed in.

The motronic OBD2 is pretty thorough when it comes to fault finding and as you only get a intermittent O2 sensor fault, my bet is ignition breakdown under load.

Keep us updated!

Pulled the engine on Sunday as it all just looked to hard to work on in the car (bleeding knuckles, sore back and the swearing that go's with it).

So last night I pulled the intake off to check the cam, lifters, rockers and valves. Also the sump and a bearing cap. And guess what I found Absolutely nothing out of place I hate that. I'd prefer to find something major wrong than nothing at all.

Tonight I'll check and flexigauge all the bearings and measure all the clearances. Then I'll pull the heads and see if I can find anything in the there.

On spark plugs. I'm using the platinum plugs from my 4.0 at the moment cause they were not very old, but I've noticed the book states the 4.6 uses standards one temp range lower. Can't seeing making to much of a difference but I'll put a set of BPR5ES in it when it goes back together.

OEM 4.6 Cam, lifters and gaskets on the way from the UK . I like opening new parts, feels like Christmas.

Originally Posted by FisherX

OEM 4.6 Cam, lifters and gaskets on the way from the UK . I like opening new parts, feels like Christmas.

I know how you feel,,
I imported a complete engine (less heads) and never even saw the box!!

Found your ECU yet? My fuel consumption may have mysteriously improved.

But lets not kid ourselves, it's still over 30.

after XXXX Klms of towing the 2Tvan over the last 6 months ( at mostly WOT) I can say that the 4.6 eats more fuel than the 4L,, it also tows mucho betterero.
3.4L per K on LPG.
But thats driven pretty hard,, with the SPORT switch off. (the reason is the change-down under load goes straight to 3rd locked)
why have all this torque and not use it?

So you're getting my consumption on LPG?

Wow , 340 litres per hundred kilometers ..... You guys should really get a diesel

I've found the problem me thinks.

I'm won't say what it was yet till its confirmed cause it's a little embarrassing.