C5 2.0. Hdi rough tick over and stalling

[Peter.N.]

Hi Folks. More trouble or more of the same. With Jim and Micks assistance we found a faulty lead to the crankshaft sensor, replaced it and the sensor, the car now starts and runs and doesn't drive to badly but still has these throttle flat spots. If I disconnect the MAF sensor it virtually stops the problem but it then has a rough tickover and sometimes stalls. Someone on Aussie Frogs suggested the EGR valve, any thoughts?

Peter

[aerodynamica]

Hi Peter, I have similar. A few months ago mine was stalling when hot. I blanked the egr off and it improved. I removed and cleaned the throttle body and cleaned the temperature sensor and it improved further. Replaced the vacuum solenoid and no change. I still have a flat spot in throttle response and no fault codes. I disconnected the MAF sensor and it seemed to run better. I reconnect the MAF and the improved throttle remained. For a while. Still no fault codes so I'm none the wiser

[aerodynamica]

It is back to its old ways now however. Annoying throttle lag from stationary, driving or from idle in neutral.

Out of interest: where abouts in the wiring harness did you find the bad connection/ break to the crank sensor?

[Gibbo2286]

This might help: https://mechanicbase.com/engine/mass-ai ... ptoms-maf/

[Peter.N.]

Graeme.

Pleased to know I am not alone, yes mine is much better with the MAF disconnected except that it runs a bit rough at tick over and sometimes stalls.
The electrical fault was right where the cable went into the sensor plug, I used the one from the scrap car and it started immediatly and ran fine - apart from the above.

Gibbo

Thanks for that but I have already tried another MAF and it still runs the same.

Peter

[aerodynamica]

Graeme.

Pleased to know I am not alone, yes mine is much better with the MAF disconnected except that it runs a bit rough at tick over and sometimes stalls.
The electrical fault was right where the cable went into the sensor plug, I used the one from the scrap car and it started immediatly and ran fine - apart from the above.

Gibbo

Thanks for that but I have already tried another MAF and it still runs the same.

Peter

Hi Peter, yes thanks for the info on where the wiring was bad. Just curious as to what to expect when mine finally goes
It's all quite easy to reach though and that's good. Unlike some other C5 things I could mention...

[aerodynamica]

Not sure if it's of any help but I had read somewhere there could be a connection between rough running, no fault codes and problems with the fuel pressure regulator. I decided to change mine. It's fiddly to do but not too bad. The replacement was a no name Chinese number. Started up and it ran well but noisy idle. Drove better though.
Live data showed idle fuel pressure up at 900bar!

Decided to change it back to the original delphi regulator. After blowing through the old one with compressed air. Started up and ran very well. Fuel pressure read at around 300bar. In fact it seems 'cured' although who knows if it'll last.

Not saying this is the cause but the improvement is very noticeable

[aerodynamica]

Another day off driving and it is still running well. No longer showing the annoying delay in throttle response.
I've wasted £50 on the new part but it has shown the cause might have been that the regulator only needed cleaning.

[Peter.N.]

I think mine is something to do with the DPF system as it doesn't appear to be working. I changed to complete pump on mine on mine, made no difference.

Peter