Citroen XM Forum

I did wonder about that Will but yes they are identical. The only difference you were thinking presumably would be in the sensor ring? I am fairly sure it is a fuel starvation issue and I have just added a couple more items checked to the above list! With regard, Matthew T.

What happens when it doesn't rev, is it a gradual reduction of power, or sudden at 3200 rpm, is it smooth, does it stutter or misfire, also have you tried it in neutral and lower gears, which would reduce fuel demand, but the ignition side would still be operating at the same revs.

When it drives normally, what changes, revs only, smoothness, power?

Thanks for your further comments Will and at 3,200rpm it basically just goes flat and sort of misfires and the effect is the same in or out of gear. The engine is completely normal up to that point all very smooth and pulling well etc. I shall try and upload a video later. With regards, Matthew T.

A further revised list of items checked:

plugs
injectors
sensors to crankshaft, map, temperature, manifold, throttle, oxygen etc.
idle valve
alternator
ecu
fuel filter
fuel pump
pulsation damper
pressure regulator
ignition coil and module
distributor cap and rotor arm

Regards,

Matthew T.

MTXM wrote:Thanks for your further comments Will and at 3,200rpm it basically just goes flat and sort of misfires and the effect is the same in or out of gear. The engine is completely normal up to that point all very smooth and pulling well etc. I shall try and upload a video later. With regards, Matthew T.

That reads as if it is hitting a rev limiter and cutting the fuel. It's as if the limiter should be at 6400rpm, but is being activated at half engine speed.

Just one last thought. Check for any chafing wires that are moving due to the engine moving. I have known that cause running issues on another brand of car as the spark trigger wire gets shorted out.

What would cause that then Will I wonder? Regards, Matthew T.

Check the connection under the LHM tank. possibly if it loses any signal, especially crank position, it forces the ECU into a limp home mode.

If it is doing the same both in and out of gear, it's not load related, so we can pretty well rule fuel delivery out, as well as mixtrure strength.

Bad coil? bad engine earth?

If its missing it could well be ignition breaking down under load.

The limiter will be controlled by the ecu i would think and i doubt it could get revs that wrong or there would be other issues.

I would think its something thats gone back together wrong or not connected rather than component failure.

D

Matthew - does the engine ecu set any fault codes due to the event? i'd try a temporary additional engine earth - e.g. jump lead to battery -ve. Plug leads are another possibility for ignition fault as is a known good coil/ign module steve

Thanks Will and I will recheck the connections under the LHM tank that were obviously disturbed by the recent removal. In relation to mixture, based on the plugs if anything it is running a bit lean. I have tried other coils Dean and checked and rechecked all earths and battery connections and I think you may be correct about it being a wiring issue. There are no fault codes or engine light at present Steve, although initially I did get codes oddly for the air temp and throttle position sensors. I have tried other coils and modules but not ht leads that I shall also now explore. With regards, Matthew T.