9 replies to this topic

[minimowta]

Great forum! I wonder if anyone can help me please....

I drive a 2000(X) Cooper 1.3i I think that makes it an MPi. It runs great but occasionally at low speed/revs I get a misfire and kangaroo (especially in a traffic jam) I have fitted new plugs and leads and had it checked over at the garage but they can't find anything wrong.

The other day I pulled the leads off in turn to check that all cylinders were working OK and I noticed I got a lower spark and electric shock from 2 of the leads..... Could I have a dodgy DIS? Or could it be something else?

Any help and advice would be much appriciated.

Cheers, Mike

[taffy1967]

What's the mileage on, because it's possible that the head gasket needs replacing?

[minimowta]

Mileage is about 45k. I've just been out in it again and the misfire is worse at around 1500rpm if I drive along in top at around 1500rpm and try to maintain constant speed it kangaroos something rotton! If I boot it, it lurches off and accelerates like a goodun!

I've changed my mind about the DIS being faulty now because I would expect a dodgy spark to be put out by the sudden infux of fuel when I put my foot down thus causing a misfire - mine pulls away nicely. Could it be fuel or could it be the headgasket? I remember when I was pulling the leads off one by one the revs dropped the same each time suggesting the gasket is OK.

When I took it to my local garage they checked for faults and found none so I am assuming all the sensors are OK and doing their jobs properly. Any ideas? I would really like get it sorted this weekend if possible...... it's starting to be a right pain in the (whiplashed) neck!

Cheers, Mike

[taffy1967]

Well a compression test would rule out the head gasket.

And getting it looked at by a garage with the right diagnostic equipment would really help.

[minimowta]

Thanks, I am going to check the compression tommorrow. The garage has the proper diagnostic equipment. They plugged into the connector by the heater and found everything to be OK - no faults!

Cheers, Mike

[elvisthepizzaman]

Don't ever pull the plug wires off a car that uses a coil pack. the voltages can kill you.

Now to the problem: This may be another case of engine vibration disrupting the maps sensor electrical connection, if it is for long enough of a period then the ecu will throw a fault but wont if it is only intermittent. Disconnect the map sensor plug and clean both the sensor contacts with sandpaper and the connector contacts with electrical contact cleaner. Plug it back in and see if the problem goes away. Be sure the wiring harness is clipped to the throttle body as this takes a lot of engine vibration away from the plug.

Next time do a search for misfire or sputter, etc.. as this has been covered quite a few times, not necessarily fixing the problem in each case but giving out very good advice on what to check.

Edited by elvisthepizzaman, 28 November 2008 - 08:43 PM.

[minimowta]

Thanks for the warning elvisthepizzaman..... I did get a hell of a shock when I pulled the leads off! Sharn't be doing that again! I will definitley try what you suggest tommorrow. Will post the results.

Cheers, Mike

[minimowta]

Here is my update:

I checked the compression - three cylinders were producing 130psi and the other 140psi so I think the head gasket is OK. I also disconnected the MAP sensor and took the sensor off to check the connections. All looked OK, I bent the three pins a fraction of a mm before I put it all back together and there was some reassuring resistance as I pushed the plug back on suggesting a good electrical contact had been made. I re-cleaned the leads and the DIS module (they weren't very dirty anyway) and I cleaned and checked the plugs. I also checked the filter, that was OK. Took it out for a spin and it is still the same

It is definitly worse around 1500rpm when driving at constant speed and therefore very little throttle - you know, when it goes from power to overrun and back, each change from one to the other is greated with a cough and a jolt. Driving hard and fast seems fine.

There is a definite lumpy increase in revs when I slowly open the throttle from tickover and if I boot it from tickover there is a bit of a cough before it revs up.

I also seem to get an irregular decay in revs after reving it - it drops to around 1500rpm, hovers there for a second or two then continues to decay to tickover at 900rpm or so.

Sorry to ramble on. Does anyone have any ideas please?

Cheers, Mike

[Ethel]

MPI's are the only Minis that left the factory with a front mounted radiator.

Check all the air hoses, might be related to the air idle bypass valve?

[elvisthepizzaman]

MPI's are the only Minis that left the factory with a front mounted radiator.

Check all the air hoses, might be related to the air idle bypass valve?

The idle air bypass valve or idle air control valve only takes care of idle and nothing else.

I would suggest that you clean the main ground behind the ecu on the bulkhead. Pull the plug wires off again and inspect the metal part that grips the spark plug caps. I had a wire that had rusted and was causing an intermittent misfire depending on the weather and engine vibrations.