Flat Spots

[JDF]

Hi All,

 

I was wondering if anyone could shed some light on what I should look for regarding flat spots.

Engine (Mk1 2.3 petrol) starts and runs fine under normal conditions, however if you give it some heavy right foot then I get a slight flat spot / miss fire starting around 4,000rpm but disapears at around 5,000rpm.

Any ideas e.g. Plugs, MAF, Spark Pack/s

 

Thanks in advance.

J.

[JDF]

Hi All,

 

I was wondering if anyone could shed some light on what I should look for regarding flat spots.

Engine (Mk1 2.3 petrol) starts and runs fine under normal conditions, however if you give it some heavy right foot then I get a slight flat spot / miss fire starting around 4,000rpm but disapears at around 5,000rpm.

Any ideas e.g. Plugs, MAF, Spark Pack/s

 

Thanks in advance.

J.

63 views, no comments !!!

Can anyone help Please.

Cheers

J.

[sepulchrave]

That'll be because you have experienced that rare thing on this forum, a problem no-one else has had before.

 

I'll take a stab that it's the spark breaking down since 4000 rpm is where you're just coming on the cam and your effective C/R is increasing putting the ignition under additional pressure.

 

Replace the plugs first unless you know they're newish, after that one of your coil packs may be deteriorating, this is difficult to test for TBH but look for one of your plugs being slightly darker than the rest for a clue as to which cylinders pack may be failing, buy a new coil pack and swap it out but keep the old one to swap with the other cylinders until the problem goes away.

 

It's somewhere to start.

[JDF]

That'll be because you have experienced that rare thing on this forum, a problem no-one else has had before.

 

I'll take a stab that it's the spark breaking down since 4000 rpm is where you're just coming on the cam and your effective C/R is increasing putting the ignition under additional pressure.

 

Replace the plugs first unless you know they're newish, after that one of your coil packs may be deteriorating, this is difficult to test for TBH but look for one of your plugs being slightly darker than the rest for a clue as to which cylinders pack may be failing, buy a new coil pack and swap it out but keep the old one to swap with the other cylinders until the problem goes away.

 

It's somewhere to start.

 

Thanks for your advice Sepulchrave.

The problem did come form one of the coil/spark packs. It was the low voltage connector had broken away from the main body exposing a bit of the internal wiring (bright metal connection). Changed the spark pack for a new one & fitted a new set of plugs (although one of the new plugs was duff - but that's another story.....). The old bus now runs fine!!!

 

Cheers again

J.