9 replies to this topic

[hystrix cristata]

For the last week or so when trying to get upto speed (mainly on the motorway) my revs will go really high but there will be very little to no acceleration. I'm not sure if it's connected but I think my idle is a little high but only about 13-15, and a few times now after I have been for a drive turn the engine off and take the keys out the engine will keep going for a second or two and splutter to a stop. Any ideas on whats wrong with it. It's a Morris 1968 but I'm pretty sure the engine in it is a 1.3 carb from a 1980s metro

[Ethel]

Contact breaker gap or condenser - also could be running lean. The fast idle suggests an inlet air leak.

[mike.]

Slipping Clutch?

[icklemini]

For the last week or so when trying to get upto speed (mainly on the motorway) my revs will go really high but there will be very little to no acceleration

sounds like a slipping clutch...

I'm not sure if it's connected but I think my idle is a little high but only about 13-15, and a few times now after I have been for a drive turn the engine off and take the keys out the engine will keep going for a second or two and splutter to a stop.

its not connected to the slipping clutch problem..
revs to high can and lead to the engine running on as you describe...

have you tried turning the revs down?

[Ethel]

If the revs go up with the car in gear but it doesn't accelerate correspondingly then it is the clutch. The negine will be working harder and getting hotter which would account for the running on. Where the clutches biting point - on the floor?

[hystrix cristata]

The running on was happening before the over revving. It does accelerate just a lot slower than it should. The first time it did it I did think I hadn't put it in 4th as I was going about 40mph then put my foot down the revs went up higher than normal but wasn't accelerating fully. I think the biting point is in the middle, I've not realy thought about it though, I do think it is higher than my last mini whos biting point was pretty much the floor.If it's the clutch how hard/easy, expensive would it be to fix.

[1275 SPRITE]

the clutches can be changed with the engine still in according to the haynes manual. Clutches are cheap for replacement standard ones. Ignition timing too advanced can cause the run on you described earlier.

[Jack Jones]

high revs no acceleration = clutch slip

high idle and over run = to far advanced, the more you advance it the more the idle will pick up and also over run

i reckon these are your problems, if not that my bad

[finch661]

i had a similar problem, turned out to be bad timing. i use the engine run on as an indication to adjust my timing. though check you mixture as well.... you never know

[benb12]

Lots of info about run-on: http://www.theminifo...ine keeps going

Running on, pre ignition, pinking or what you like has another name that describes it pretty well - dieseling.

Basically something ignites the fuel air mix before the spark does. It could be a hot spot in the combustion chamber be it carbon, a valve or the spark plug itself. Just like a diesel engine the pressure and temperature ignites the fuel, if this is insufficiently before the piston reaches top dead centre the pressure in the cylinder will effectively be pushing against the direction of rotation and the temperature will shoot up as a consequence of the much higher pressure; that's what causes damage like melted pistons and burnt valves.

Lower grade petrol is more prone to dieseling as are high compression engines, like 10.5:1 MG Metro's, hence why an anti run on valve was fitted. Running on isn't likely to cause damage but it is indicative of an engine that could be prone to piston melting pre ignition.

It could be carbon build up in your engine or it could be the ignition timing. Sort your idle out first though because the fast idle could just mean that it's taking longer for the engine to slow to a stop.