Hello, I have a 1995 Rover 220SLi with almost 60,000 miles on the clock. During the colder weather it suffers from a bad misfire during warmup.

Starting from cold it runs OK but after about half a mile driving it starts to misfire. This gets gradually worse and is worse still at low revs in the higher gears. Then it starts to improve and after about 2 miles into the journey it has gone. In really cold weather it starts to misfire again after about 4 miles, getting worse again before it gets better and then stops. If the journey is broken during the warmup period for say 10 minutes, usually on restarting the misfire does not occur again even though the engine has not fully warmed up. The colder the weather, the worse the misfire is and the longer it takes to go away.

When this first occured last winter I took the car to a Rover agent and explained the problem. They investigated including an engine diagnostic check and the only fault they could find was the TPS which they replaced. When the car was returned it was no different and over the next few weeks I replaced the spark plugs, HT leads, distributor cap and rotor arm, oil and filter and gave it a good dose of fuel system/valve cleaner, all with little or no effect. By the time I was through with that lot, I had come to realise the temperature dependence nature of the problem and the weather was starting to warm up. Needless to say it ran fine all through the summer but the problem started again in November.

The first winter that I had the car I had no problems whatsoever.

Has anyone else experienced this or have any suggestions?

Thanks,

NJONES7054

Could this be sticky valves?

Hi mate,

I have the exact same problem with my 220GSi, and I've done the exact same things as you have to no avail. In Rover dealers now checking to see if they can tell what it is for the 3rd time but this time asked to check for sticking valves so i'll let you know what they come up with.

Cheers Jason.

P.S not holding my breath tho.

Cheers Jason.

Hope you get it sorted this time round. If they manage to fix, please let me know. I will do the same.

Nick.

Sounds like youve replaced the electrical items for the HT system.

I have seen Dave recommend some stuff to clear any water from the fuel tank. This may be a next step.

Other item could be the crank sensor.

Stu

When this misfire occurs it is very constant like the engine is only running 3 (or less) cylinders.

I think this rules out any dodgy sensors or water in the tank as Stu has suggested. I suppose the crankshaft sensor could be the problem as this might not affect all cylinders.

This evening I looked at the plugs again. They haven't been out for quite some time. Three were nice and clean as all the books would have us believe they should be, the fourth had a lot of dry black deposits as though that cylinder was running very rich.

I fitted a new plug, still got the misfire.

Could it be a dodgy injector not closing properly (hence one cylnder running rich). Does anyone know if the injectors fire sequentially or simultaneously????

Could be oiling I suppose but consumption is not unduly high about half a litre every 1500-1600 miles and most of that i suspect from the inevitable head gasket leak adjacent to no. 4 cylinder. Why always just there?

Inside the distributor was dry as bone and clean. No moisture or oil here.

Thanks to all who have responded,

Puzzled and frustrated of Surrey.

Success (I think).

Changed the plugs and leads (yet again). Definite improvement in engine response but misfire bad as ever.

Decided sooty plug reported earlier was symptomatic of over rich mixture. Therefore concluded problem was an injector sometimes not closing properly.

Gave it good dose of fuel system/injector cleaner and took it for a spin down the motorway. Seems much improved although not completely cured yet. Hopefully a few more miles will see it right.

This bears all the hallmarks of sticking exhaust valves.......

Hi mate,

Getting back to you about misfire on my 220. Dealer checked for sticking valves and said it didn't show symptons for sticking valves and they were at a loss, it was in for a service so they changed plugs etc. hoping it was the plugs but to no avail so I've done the same as you and bought for injector and valve cleaner in the hope that sorts it. I've been reading about a product called 'red line valve and injector cleaner' which is suppose to work. Somebody with an 800 fitted with T'series recommends it highly. Perhaps worth a try.

Cheers Jason.

I've never had any luck with these potions but they're worth a shot I guess.

Hi Dr Dave,

I've read alot of different stories about this, sounds like a very common problem with these engines what causes it is it a build up of carbon, short journeys etc. Or is it a weakness of the engine itself.

Cheers Jason

A combination of cheap fuel, tight tolerances and short trips........

Give it some Shell Optimax. Now I have heard all of the stories about the old T16 and the sticky valves I use Optimax because of its properties (engine runs much cleaner).

Do you drive your car gently/around town alot? If you do you may have to adjust your driving slightly or once a week let the engine warm up to normal operating temp and give it blast at high rpm which loosens carbon inside of the engine.

Dan.

Hi Dan,

Yes I do drive steady around town etc. will try optimax and give it a blast. Just come back from holiday, alot of motorway driving and it doesn't sound as rough now.

Cheers Jason

Nice long motorway journey's do it the world of good. I gave mine a good workout traveling from home to uni and I dipped the oil last week and it had gone dark. I am assuming it's because on the motorway I put my foot to the floor for a good minute and it cleaned out the engine.

Oh well, it's due a service now.

Dan.