Engine in limp mode when warm

[Arvid]

Hi all,

My QP Evo 3.2 has started to act up recently. It will go into a kind of limp mode when engine is all warmed up. Not sure if it's limp mode but it will suddenly start to run very uneven and not on all cylinders. There is also a strong smell of fuel and engine is very down on power. This will only happen when engine is up to operating temp - 85/90 dgr. When cold and up to operating temp it will run perfecty normal.

No warnings or check engine light either.

I suspected one of the O2 censors and disconnected them when problem appeared but no change. I then swapped the cam position sensors - no change. Last I swapped the upper crank sensor but no cure there either. I have not changed the lower crank sensor as this has to be done from under the car and I have no lift. I also tried a new throttle position potensiometer but there was no change.

Could it be one of the water temp sensors that is failing ? What other sensors could create this problem when reaching 80/90 dgr. ?

Regards,
Arvid

 

[Oneball]

I’d look at the coil packs.

 

[Arvid]

I’d look at the coil packs.

That might be a very good advice. There are separate coils for each cylinder but in my case there must be more than one coil failing. If it was just one coil it should feel more powerful than it feels now. If there is a coil problem it almost feels like it's on all coils on one side of engine.

Does these engines have one common ignition ECU or one for each side ?

 

[Arvid]

I had a go at the coils today and 7 of them measures 0.8 Ohm and the last one 1.2 Ohm. This is 50% deviation and I don't think this helps. They where measured cold. But missing just one cylinder shouldn't make the engine run as poorly as it does.

Maybe it causes some problems for the ignition ECU and makes the engine run in limp mode ? I've ordered a new coil and hope it solves the issue. Coils are the same as for Citroen/Peugeot so easy to source.

 

[Zep]

Do the readings from the coils change when hot?

 

[Arvid]

Do the readings from the coils change when hot?

Don't know yet. That is next step when engine is ready to fire.

 

[Arvid]

A big thank you to Oneball which guided me in the right direction. The one coil that measured out of spec crashed totally when warm. It went from aprox 1 Ohm to infinite ohm.

Not sure why one defetive coil makes the engine seem like it's down 200 BHP. The ignition ECU might go in limp mode but there is no "check engine" light. Either way problem solved

 

[midlifecrisis]

A big thank you to Oneball which guided me in the right direction. The one coil that measured out of spec crashed totally when warm. It went from aprox 1 Ohm to infinite ohm.

Not sure why one defetive coil makes the engine seem like it's down 200 BHP. The ignition ECU might go in limp mode but there is no "check engine" light. Either way problem solved

Good detective work there. As for Limp Mode, it's Italian, it gives up whenever something goes wrong. I've seen it in Radars too...

 

[Arvid]

I could ad that coils are part nr. 571084200 for original Magneti Marelli and is about £100 a pc. from Maserati. The same coil is used in a variety of Citroen/Peugeot with part.nr. 597050 which again is Valeo 245127 at about £20. Rubber extension is a Beru part with nr. 0300132103.