Running Problems. carb icing?

[jonny555]

Hi folks

Got another contribution to the cold weather running problems on here:

My 1989 mk2 1.8 carb rocco has been running fine but took it on a couple of long runs over the christmas period and it developed an intermittent running problem. Its a standard carb on it.

It usually starts well but after about 30mins - 1 hour running, usually crusing at around 60, it would lose a little power - you wouldn't be able to rev above approx 3,200rpm even with your foot flat to the floor. Also if you went to change gear, while your foot was on the clutch the revs would drop to approx 200rpm and the engine would barely tick over. If you continued to run it would start to struggle and stutter a little. I noticed that when the whole process started the engine temperature would drop ever so slightly.

I found that by pulling over and revving the engine while stationary the problem would mysteriously disappear and the idle and engine temperature would return to normal. This pattern continued throughout the journeys.

Intially i thought it was an ignition problem with damp getting into the plugs and dizzy, but inspection of dizzy cap showed it was bone dry inside and the plugs are no more than 6 months old. Have replaced the old leads as they looked a bit weary and sprayed the whole lot with ignition sealant but problem returned on the next trip. Also had a look at the fuel filter and it appears to be sediment free.

Now think it is to do with the carb icing up - the warm air intake pipe from around the exhaust manifold is barely connected to the air intake and probably not functioning and not sure of the status of the carb heater but it may not be working - going to investigate this next but thought I would raise the issue to see if you guys had any other thoughts.

Cheers
Jonny

[Chaps]

good chance it will be carb icing.. that air feed from the exhaust manifold is meant to cure your problems, i'd try getting that fixed. I had carb icing problems loads on a old nova during winter, a DIY warm air feed using tin foil, a plastic bottle and tie wraps sorted me out and got me 100 miles home with no further problems. And when you pull over it improves, its because the heat from the engine thaws out your carb jets.

[captainwow15]

Mine was doing the same as the ducting perished a while ago, and I fixed it yesterday, couldn't wait for the ducting to come from ebay as had to drive it today so i chopped a carlsberg can up and used a couple of jubilee clips to hold it into place and its all sorted now.