The V8 Owners Forum -

My truck with a 3.9 RV8 has developed a mis-fire whilst i was on holiday for a couple of months. I took it for a MOT this morning and it failed on HC emissions. The tester said that this was caused by a mis-fire and new set of plugs should be a start.

Result Max

CO = 2.97% PASS 3.50
HC = 1812 ppm FAIL 1200
Idle speed PASS
Smoke level PASS


I don't have much knowledge of RV8's. Can anybody work out the likely cause of the high HC and where i should start with trying to rectify this fault?
Should i start with a new set of plugs?
What else should i look at replacing and where should i source it?

Thanks in advance

Ben

Might be an idea to say more about it. Carb or injection? Standard or modified?

Sorry....... as far as i know it's a standard RV8 3.9 EFI still in it's original Range rover classic chassis. It's covered roughly 106,000 miles and i have no service history for it.

I have just been checking all of the connections and found this

Is HC hydrocarbons? i.e. unburned fuel?

If it's misfiring then that's the place to start. Could be the plugs, leads, dizzy etc or it could be that the fuel filter is blocked. Have you ever changed it?

Edit: Just seen you've posted while I was typing. That's a likely culprit

The rest of the connections look like this

First thing to find out is the reason for the misfire. Obviously check the plugs first and replace if worn. If it is a regular miss, try to find out which cylinder it is by removing plug leads one at a time. If you find one which doesn't make a difference, measure its resistance with a DVM. It will be several thousand ohms - compare to another good one about the same length. A bad one will be many times the resistance of a good one.

If nothing found there, look at the dizzy cap for signs of burning etc inside and out, and the rotor arm.

Also measure the king lead between dizzy and coil - it should have the same sort of resistance per foot of length as a plug lead - and look for signs of burning/corrosion on the connectors.

Thought i would remove the Dizzy cap to see what the condition was inside and found this

I'm guessing that the glued back together cover isn't causing much of a problem.

Can anybody tell if the rotor arm is still in good enough condition?

Looks like you've found the problem with that plug lead connector. If you're a tight-arse like me you could find another connector and crimp it on - those look to be Bosch leads which generally have a long life. Or see if you can buy a single one of the correct length.

High mileage rotor arms are often rather crusty. Give it a clean with sandpaper before just buying a new one - some of the new ones are rubbish.

The plastic cover over the reluctor etc in the dizzy is to prevent an HT flash-over harming the electronics. The missing chunk shouldn't much matter.

I'm not tight when it comes to my toys as i like to know they are in top condition. Since this is the only problem i have to sort for the MOT, i can't complain either.

Nope they aren't Bosch.



I will buy a new set of leads to try and prevent this happening again. Are the Mallory leads significantly better than cheap leads?

Can anybody recommend an online supplier or a supplier who deserves the business?

Well look below on the main page of this site...
Id say Real Steel would sell you proper leads.

Stay away from those red Magnecore leads as they have way to much resistance. You Need a very big coil to fire the plugs with These leads.

I usually buy an universal MSD superconductor 8.5mm kit and make them my self. They come complete with all the parts and tools to crimp them your self in a vise.
MSD 8.5m superconductor cables have very low resistance creating a big spark even on a stock coil.

I have been looking at the suppliers at the bottom of the main page and there seem to be 2 main ones, Realsteel and V8tuner.
I was just about to ask about the Magnecore leads as they were recommended on a Land rover forum.
Would Realsteel sell the good quality Dizzy caps and arms ? Just thinking for the price of them, if they are good i might was well replace them and hopefully forget about the ignition system for a while.
Thanks for all the help and replies so far.

I'd advise against just throwing new parts at it. Especially since there is so much rubbish out there. Think you'd need to go to a Range Rover main dealer to be certain of getting OEM quality.

IMHO, most of these expensive plugs leads are just that - expensive. If Bosch was good enough for a car maker, it's good enough for me.

Got some new leads and plugs from V8tuner, after fitting the engine was noticeably smoother........too smooth.
Took it back for a retest today and it passed.

HC 1812 to 219
but
CO 2.97% to 3.43%

I hope the CO doesn't go up next year as 3.5% is a fail