Only 6 or 7 cylinders in the morning

fett · Aug 12, 2009

My 1990 3.9 classic is only running on 6 or 7 cylinders in the morning , for about half a mile.

I have done all the service items with new quality parts.

It seems to dirty the plugs with coke after about 500 miles , not fully sooted up but they are too dark to be right.

I have removed and cleaned the air bypass which had improved the idle but not the poor running in the morning. WhenI remove and clean the plugs this seems to help for a couple of weeks.

Any ideas?

The Mad Hat Man · Aug 12, 2009

try changing to the next hotter plugs

fett · Aug 13, 2009

Any ideas how to work out which plug that is, as I dont trust the 8 year old working in halfords to work that one out and thats the only supplier in town now.

I am currently running the standard champions for the 3.9 and also I have a set of ngks for it as well.

I will go and have a look tomorrow in the light and see which ones it currently has running in it.

Out of interest who reckons ngk are better than champion or vice versa?

classic kev · Aug 13, 2009

It might be a long shot but you may be getting a small amount of condensation inside the distributor cap. Before you set off just quickly take the cap off and give it a wipe with a cloth and maybe a spray of WD40.

norseman · Aug 13, 2009

Sorry to sound a sour note but could be head-gasket. Coolant on one (or more) plugs prevent firing but heat build-up dries it out rapidly. Had this same problem on a 3.9 myself, check if any of the plugs looks cleaner than the rest as this type of fault has the effect of 'steam cleaning' the plug. I'd go for Champions every time, my last 3.5efi went through several NGK's with a previous owner, I did thousands of miles on a set of Champs, never missed a beat.

fett · Aug 13, 2009

One is cleaner

I thought that was good lol)

whats the best way to tell if it is head gasket? as I am sure the compressions will be diffrent from the manual after the miles its done. there is no old in the water or water in the oil.

K- seal it is!

norseman · Aug 14, 2009

fett said:
One is cleaner I thought that was good lol)

whats the best way to tell if it is head gasket? as I am sure the compressions will be diffrent from the manual after the miles its done. there is no old in the water or water in the oil.

K- seal it is!

Stangely enough various tests ie. compression/hydro-carbon etc. can be inconclusive (as mine was) & the symptoms I had were: pressure still present when removing rad cap, even after an overnight stand & slight coolant loss (but no overheating) Eventually when carrying out a daily oil level check I found a water oil/water mix.

fett · Aug 14, 2009

Ok the plugs its running are Champion OE001 N9YC , so how do you work which is the next hotter grade up then?

I saw today the one of the hoses was not attached to that big plastic sphere under the bonnet , it was the smaller of the two. what does that do then? lol

I have found that it really helps to let it idle for a min or two in the morning before I set off, but it is not a definate fix though

norseman · Aug 17, 2009

'Plastic sphere' is probably the vacuum tank that operates the fresh/recirculate air flap on the heating system. With the engine running (or shortly after switched off) you should hear a 'clunk' as the flap operates when you move the lever. If there is still no obvious change, check that the rubber pipe has not come off the valve that operates the solenoid (on the lefthand side of the heater unit) which is accessible after removing the parcel shelf. Pre '86 cars had a simple lever 'n rod set up, but of course that had to be 'improved' on for later years.

classic kev · Aug 17, 2009

fett said:
I saw today the one of the hoses was not attached to that big plastic sphere under the bonnet , it was the smaller of the two. what does that do then? lol

I have found that it really helps to let it idle for a min or two in the morning before I set off, but it is not a definate fix though

Only spheres under the bonnet of a classic I am aware of are the pressure accumulator for the ABS braking system and the vacuum accumulator behind the nearside headlight.

Any vacuum leak will give some rough running so best to check all the hoses especially at the ends, including the one on the brake pedal if you have cruise.

norseman · Aug 19, 2009

classic kev said:
Only spheres under the bonnet of a classic I am aware of are the pressure accumulator for the ABS braking system and the vacuum accumulator behind the nearside headlight.

The latter is the sphere I was refering to when explaining the air flap operation. My '87 & '89 don't have ABS.

fett · Jan 21, 2010

Well sorted , I know it took a while and yes alot of other things broke and needed fixing in the mean time.

So it turns out that genuine lucas cap leads and rotor are not the same as genuine landrover lucas leads cap and rotor.

It now starts and drives like any other car first thing in the morning instead of needing a min warming up.

Stupid me for thinking that a black cap made by lucas and black cap made by lucas and sold by landrover for twice the price were the same!

Only 6 or 7 cylinders in the morning

fett

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The Mad Hat Man

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fett

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classic kev

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norseman

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fett

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fett

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