Hi all

My 72 clubman seems to have developed a rough shaking idle. You can feel the vibration throughout the whole car when sitting idle. Most noticeably the steering wheel really gets moving with vibration.

The misfire seems to settle once driving and power seems quite reasonable and smooth. Once coming back to a standstill and idling, the misfire or shaking idle seems to occur in a surging manner. If you then rev the engine it seems to once again run fine with no stutter or backfiring.

I have adjusted the tappets and carb with no luck. Changed spark plugs, leads and the coil once again with no luck. Points have been cleaned up and adjusted, checked the dizzy cap and rotor for obvious cracks or wear, but still no luck.

I'm thinking the issue is still related to the distributor but before shelling out for a new one thought i would see if anyone on here had any thoughts.

Cheers,

Tom

Its odd that it's not down on power, normally a change in the way they run like that means something has crapped itself and the car drives like crap... like eating a set of spark plugs or blowing a head gasket

I'd be removing the plug leads one at a time and see which one (if any) is playing up.

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I'm trying to think of something that is throwing the timing or mixture off at idle but at higher rpm, the fault is not noticed or bypassed.
Like:

Anything broken/unhooked in the vacuum advance unit or tube?
Anything letting excessive air into the carburetor at idle, worn spindle, leaking crankcase ventilation setup?

Beware the poor quality of some reproduction distributors, too.

Although probably not it, you don't mention changing the condenser. Is it a mechanical fuel pump? Do you have any test equipment like a vacuum gauge or dwell meter?



I agree with that, I would much rather a good used distributor. Unless you can actually find something wrong with the distributor I would not replace it with a new one. I have had one cause multiple breakdowns even though it seemed to fix an issue when first installed.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Yes at first I was thinking bad engine mounts or something making contact with the body and transferring engine vibrations through to the body, but looking at the source of the vibration the engine defiantly doesn't look to be ticking over as smooth as it should.

I've pulled the leads off one at a time but didn't notice any particular difference. None of the plugs look different either.

Doesn't appear to be, I've even sprayed a bit of carby cleaner around the vacuum tube and carby to see if the idle changed, but nothing unless directly spraying a fair bit at the spindle (the carby has been rebuilt, although i didn't replace the needle, hmm)

The dizzy on it came with the car when I bought it a few years ago, I'm not sure if it is a quality replacement or not.

Yeah, I haven't changed the condenser or points.

It's a mechanical fuel pump replaced last year

I have a digital timing light with a dwell setting?

Hmmm, you *should* notice a difference - it should drop a few revs and be a bit rougher as each one is removed. Ideally it'll drop off the same way as you take each lead off, then pick up when you put it back on, then drop off when you take the next one off etc. What's it like if you take two leads off?

My dad's car was running like crap and I said "watch this" and took two leads off - no difference - still ran like crap... 4 new spark plugs later and all fine. He had a box of old plugs he'd keep swapping around, I put all but a couple in the bin - after I broke the electrodes off to make sure he didn't "rescue" them

What's the compression like?
Can you post some pictures of the spark plugs?

Without knowing more about your car and history, I'm kinda wondering if it's always been down on power and it's now just getting a bit worse

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did I tell you that I won a trophy?

It will probably test fine but I would check the dwell is correct.

maybe the fuel pump could have an issue and doesn't supply enough fuel at idle.

Hopefully it isn't like this mini I worked on today which hasn't idled very well for a long time but otherwise ran ok:

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis

Check if the jet in the carb isn't stuck down in the lowered (choke) position.
I had one do this in the past week.

Sorry, i didn't notice any difference between the 4. By this, i meant that they all stumbled the same as i took each lead on and off. Taking two leads off at the same time made the engine run like an old tractor.

I did a compression test and they all seem to be a bit down, might be the gauge? or just low compression all together (engine machined and rebuilt 2 years ago with very few km's on it).


There is defiantly something sus happening with cylinder 2 according to the spark plugs. These were changed not long ago in the hope of fixing the problem.

Checked, not the problem unfortunately

I’d try another distributor cap, and perhaps swap the leads around and check the resistance on the leads. Also check the points gap is the same on all 4 cylinders to make sure the cam isn’t worn out

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90psi is very very low.. I'd try another gauge. A mate of mine kept saying his compression with flat top pistons was around 110psi, and the engine was making rattling sounds but it couldn't be pinging because the compression was so low on his flash new gauge.. I took my gauge around, bam, 165psi..

The plug 2nd from the left does look suspicious... but your gauge in the photo is in #3, and assuming the plugs are in order as removed then it's #3 that's dark. Cylinder #1 is closest to the radiator - the water pump is at the front of the motor.

I'd grab 4 new plugs and start trying to move the problem to another cylinder - as Tim said, swap leads, you depending on the distributor you can turn them 90 degrees, or you could reposition the dizzy by pulling the drive out and turning it, then get a different terminal pointing to #3.. but if the compression is really that low I'd be quite concerned and have a serious talk with my engine builder

_________________
did I tell you that I won a trophy?

In your picture with the gauge there is only 1 connection to the coil. there does not appear to be an earth connected to it.

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Cheers Dave.