Lumpy Engine

[debaron]

Been having a problem with my 400 Chim for a while now. Have posted stuff on earlier threads and tried all the advice given but still got it!

It's a vibration and lumpyness in the engine at around 2000 rpm like it's low fuelling a cylinder. Some times it's worse - sometimes it's not there at all! tends to get more noticeable after an hour or so on the motorway.

Tends to 'come or go' only when starting the engine though. - ie - I can be going along fine, pop in to get some petrol. Switch off - Start up - LUMPY! It will tend to stay like this then. It can also go the other way. And before the engine even comes to life I can tell whether it's going to be lumpy or not - I can feel it while the starter is cranking! This would then suggest a mechanical problem though....

When it is running, you can hear it too as a slightly different tone from the exhaust. It's like a misfire i guess but have been over the leads, plugs, rotor and HT numerous times. Only thing not changed is those plug boot extender things and the coil.

I'm on to thinking it's a fuelling problem now - dirty/leaking injector or possibly something in the top end mechanicals? Maybe a fuel pressure regulator on the way out.....It's the intermittentcy of it all that pisses me off - I wish it would either do it all the time or not at all!!!!


Next stop Mark Adams if I can't cure it!

Any advice gratefully received.

[jonny_c]

I had a similar problem a while back - started out occasionally lumpy at low revs, left it a while and it got worse - sometimes stalling at idle. My gut feeling was a fuel issue, I reckoned i was down on power as it has 'lost it's sparkle' at higher revs. So I cleaned the stepper motor, and spent ages with cotton buds and rags and carb cleaner, cleaning up the housing. Put it back together with thread tape. Bought some fairly expensive injector cleaner that the local cab drivers recomended (said on the tin it was fine for cats/petrol engines). And after good run, i swear it transformed the car, it was now properly quick, idled well, no more 'shunting' when travelling at low speeds. Haven't had any problems since.

[rev-erend]

I would also recommend the fuel injector cleaner..

There are some where you add a whole 1/2 bottle to a tank full..

I ran out of fuel once and after refueling - it ran on 7 and sometimes 8..

That cleaner saved me a fortune..

Well worth spending <£10 on.

[Chimjunkie]

I've had problems with the plug extenders, so don't think they are infallible. What you say about the cranking is interesting. But the problem is intermittent? Can you explain more about this feel?

[bigdods]

Happened to me last night, bit of a misfire and lumpy running. Checked this morning and I have a cracked plug extender. With the engine running I could see sparks tracking all over the place from that extender even in daylight.

Suggest you run it in the dark and have a good look around the extenders and leads see if you can see any sparks.

[debaron]

Ok, after a little more investigating, seems to do it much less when the tank is full up rather than lower than 1/4. Possible Fuel Pressure problem? Does the pump not just pump at 100% regardless of tank volume and lets the fuel pressure regulator sort it out to 37 PSI?

I have run it low on fuel a few times so it's possible that the crud and muck in tank bottom has bunged up an injector too. How easy is it to drain/clean the tank?

Also, where can I find the pressure regulator and filter?

Thanks,


Ryan