2200 TC sooty plug

My 2200 TC doesn't do many miles nowadays but, after a 30 mile run to clear the cobwebs, during which I noticed slight misfiring under acceleration when warming up, I took the plugs out to check their condition. To my surprise, 1, 3 and 4 were the expected colour, but 2 was very sooty (incidentally, the misfire went away once the engine was hot).

I have a couple of Colortunes from earlier motoring days and put them in 1 and 2, then into 3 and 4. Cylinders 1, 3 and 4 were the correct shade of Bunsen blue, but 2 was distinctly yellow (rich mixture). I appreciate the old Colortunes, which go back to leaded days, are not accurate but they seemed to confirm the visual inspection of plug two. Any ideas guys how the mixture to three cylinders is OK but one is rich?

For info, the car is running on relatively new super grade fuel with lead additive, and ignition and carb settings appear OK.
Yes I have one and I'll do a check. Are you thinking no.1 cylinder is pulling in extra air from somewhere else as well as through the carb and is actually running lean rather than 2 being rich?
The colortune works just fine on unleaded. It simply allows you to view the combustion process, there is nothing magic about it. A blue flame indicates correct ratio of air and fuel; fuel burn is complete. A yellow/amber flame indicates fuel burn is incomplete.
wet and dry compression checks come to mind. air /fuel imbalance from fuel system seems unlikely. soot can be oil burning as well as fuel. ( rich mix) so a valve stem seal leak? oil control ring defect etc .
Did a compression test yesterday and the good news is the figures are all within 5 psi. The bad news is the range is 30 to 35 psi.........!!

Used jump leads from my daily drive, which I know has a good battery, to ensure consistent starter speed over the test, so assumed a problem with the pressure gauge. However, the gauge inlet thread is the same as a tyre valve and with a bit of frantic foot pumping got it up to 100 psi, a reading which agreed with the foot pump gauge. So the compression gauge is OK.

On the face of it the engine has some pretty serious problems. BUT, it starts easily, runs smoothly, keeps up with modern traffic and reaches 70 without problems. It's certainly not a flying machine and guzzles petrol but is no slouch either. Not a problem in itself as it only does a handful of miles a year. Is this a testament to Rover engineering? or am I missing something. Maybe I'll get my local garage to check the compression and take it from there.
Yes, all done by the book. The gauge moved up in pulses over about 6 or 7 seconds until it stabilized at 30/35. I didn't do a wet test. The next step I think will be to go to my local garage which specialises in classics, and get a second opinion.


Well-Known Member
Something doesn't add up here. A car which had cylinder compression's of 30psi would not start easily, run smoothly or keep up with modern traffic.
I agree, if compression was that low it wouldn’t even start. Having experienced cars with bad intake valves (thanks GM for screw Saab over again).

Fingers crossed it’s a bad gauge or something silly. Best of luck!