[Cyberaction]

Should have sold my 2002 406 with 2.2i petrol engine FH and 320k a long time ago, but cannot get it over my heart (wallet). Great performance and light on fuel, use car mainly for long distance touring and I drive it real hard. For some months now when going uphill or over a rough patch of road, the car starts to run on three cylinders only. Sometimes it auto-corrects within minutes, other times only after 20 or 30 km or so. This is a very annoying problem as the car does not have normal power when in this mode. Repair shop is baffled and tell me they can only do a diagnostics test on the car when the problem is current. I stay 60km from the repair shop and the chance of getting the car to the mechanics when in 3 cylinder mode is almost nil. Diagnostic tests already done when the car does not have the problem, have not shown anything wrong. Any ideas how to fix this issue will be greatly appreciated!

 

[IanML]

Inspect the plugs - if one looks different to the others, that should indicate which cylinder. You could try a new plug there.

If that doesn't help, I would try a new coil pack.

 

[Old Pug]

Fitting a new set of spark plugs is the first job,making sure the four plug contacts of the coil pack are clean.
The fact that`s its an intermittent fault makes diagnosis and suggestions difficult. I`ll list probable causes of an engine running on three cylinders.
A. Spark plug
B. Coil pack.
C. intake manifold air leak. (when its misfiring try the brakes to see if the pedal is hard? I`m thinking of the valve by the brake servo)
D. Hydraulic valve lifter. (highly unlikely,I`ve never known one go ).
E. Fuel injector,or the wiring to them.

Normally faults with B and E would cause a fault code to be stored.

 

[Cyberaction]

Peugeot 406 running in three cylinders

Thank you guys for your advises.

The car has new spark plugs so the plugs can be ruled out. I noticed some oil in the spark plug wells though.

Seems that an intake manifold air leak as mentioned by Old Pug may be the most probable cause of the problem. I will check it out. A couple of days ago when driving the car and stopping at a toll gate, the brakes suddenly lost power, the ABS light came on and the engine died. Started again and the fault was cleared with the brakes working normally again.

What puzzles me most is that the car starts to run on three cylinders the moment one goes uphill or sometimes when hitting a rough patch of road.