measured air flow

[richieski]

Sorry another question,

I am trying to diagnose a fault. I connected diagbox and looked at some readings. I am getting egr fault codes but could my air intake valve/sensor be at fault triggering these?
at 700 rpm
measured air flow 229 mg/impulse
air flow ref value 212 mg/impulse

at 1700 rpm (this is when it hesitates the most)
measured air flow 200 mg/impulse
air flow ref value 204 mg/impulse

seems to rise when i go past 2000 rpm and this is when it does not hesitate and drives smoothly

It's actually less!

What is going on?

[MikeT]

While I don't have answers to your specific questions, and given the obvious lack of posts/advice so far, perhaps it would help you to consider my thoughts on this...

1. The MAF only measures air drawn through it. Leaks are not taken into account.

2. The EGR sneaks exhaust gases back into the intake without the MAF being aware.

3. The reported air values are per impulse, which I understand to mean per stroke. If I'm correct, this is a very pertinent point to make as diesels are not throttled in the traditional sense like petrol engines. Without the compressor (turbo), the measured air entering the cylinder per stroke I would expect to be pretty constant, regardless of rpm's. (Obviously compressed air will increase this figure respectively).

Can you post the EGR faults you're getting?

[richieski]

P1459
p0490
p0401

I have had a complete new egr fitted, does it need to be programmed to the ecu?
It only hesitates between 1300 - 2k rpm and only at constant speed, if i accelerate at any time it's ok. It only happens under load too.

[richieski]

Today i tried measuring the MAF
results,
Tested the wiring loom with ignition on unplugged from sensor
1-green + 5v
2-yellow - ground -12v
3-empty
4-red +12v
5-blue - 6.3v

1-green + 1.83v
2-yellow - ground -12v
3-empty
4-red +12v
5-blue - 7.8v

Can't get my head around these results

[richieski]

I replaced the MAP as the sensor was reading 2.4v at idle, the new one is 1.4v at idle.

[richieski]

Also, i had a new battery fitted 8 months ago and now i can only have the radio on for 5 min before it goes into eco mode. Could i have an electrical fault that is bringing the battery down too?

[MikeT]

P1459
p0490
p0401

I have had a complete new egr fitted, does it need to be programmed to the ecu?
It only hesitates between 1300 - 2k rpm and only at constant speed, if i accelerate at any time it's ok. It only happens under load too.

Again, I can't answer if yours has to be programmed but I know mine does. Perhaps this should be done and don't forget to erase those codes too, see if they come back after.

[richieski]

Any ideas how it is programmed?

[MikeT]

I know the lexia diagnostics will do it.

[richieski]

Programmed it, no difference.

[RichardW]

Presume this is a 1.6? No need to program the EGR - it does it automatically at key off by cycling the EGR valve open and closed. Check in the live data what the EGR valve is doing - The reported copy position should closely track the requested position. If it doesn't then either the EGR is faulty (what did you fit?) or there is a wiring fault between the ECU and the EGR. This could be wires around the underbonnet fusebox, or the fusebox itself.

[MikeT]

Presume this is a 1.6? No need to program the EGR - it does it automatically at key off by cycling the EGR valve open and closed.

Interesting, my lexia states you do have to carry out auto-adaption after change of EGR.

[RichardW]

Interesting.... I didn't do anything when I replaced the valve on our C4 - I'll have to have a look in Diagbox sometime and see if there is an option. It doesn't say anything about doing it when replacing the valve in the service.citroen docs I have.

[MikeT]

Interesting.... I didn't do anything when I replaced the valve on our C4 - I'll have to have a look in Diagbox sometime and see if there is an option. It doesn't say anything about doing it when replacing the valve in the service.citroen docs I have.

Purely speculation on my part but I have noticed that my copy signal is often a fraction different to the command signal, especially when it's closed. I wonder if I were to follow the procedure, this minor discrepancy would disappear and, perhaps, the annoying hesistation/flatspot.

[MikeT]

Auto-adaption table according to model.