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Eratic idle
#1
Hi all,
After visiting the UK & buying some spare parts, crank shaft sensor, brake cylinders & thermostat sensor I have now replaced the old with new ones but still have an erratic idle on start up. Could this be due to the throttle housing having a vacuum leak or is it due to another sensor playing up.
Another thing I have noticed is that a small round sensor? near the power steering reservoir with two inlet pipes one hard plastic and two outlet pipes is making a clicking noise which I have not heard before, what is this part is it a sensor or something else, it is made by sagem and is brown in colour. Should it make a clicking noise.
Thanks for any help.
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#2
It's your carbon canister purge solenoid. Yes, it should click.
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#3
Ok, so as far as my erratic idle goes I have changed the driveshaft sensor & thermostat sensor, the battery is ok and earthing is fine.

After reading some of the older posts by DIVING SCUBA BOY the next sensor to change is the Idle Control Valve which I have no idea is located.

When I disconnected the MAP sensor when the engine was running it had no effect on the idling as it still ran high. Is this a clue to if it works fine or not & how do you test it.

Which other sensors could cause such a problem or if there is a vacuum leak in the throttle housing how do I diagnose it.

If I take it to Citroen do you think they would be able to diagnose the fault or not as they said it was due to a "Flat Spot"

Any Help is much appreciated.
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#4
New update,

After visiting a Citroen dealer for advice, it turns out that the idle control valve is the stepper motor which is located on the back of the throttle housing, they advised me to change it, then if that does not resolve the problem change the potentiometer then MAP sensor. Afterwards the van should be taken back in to them for a retune of the ECU as it often keeps the old settings in memory which need to be wiped clean and new ones downloaded. It was also mentioned that the Lambda sensor,can cause problems with air mixture plus the carbon canister can become blocked which can also cause problems.
My quest for a non erratic idle continues.
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#5
Instead of playing parts bingo, I'd advise hooking the van up to lexia diagnostics. If the Citroen dealer you visited has already done this and is still advising you to keep changing parts until it's resolved, I'd start looking for a more competent dealer.
Somedays you're the pigeon, Somedays you're the statue.
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#6
The ECU software version should be checked for most up-to-date, and if it isn't correct a dealer can download the updates.

The most common cause of erratic idling I know, is poor battery connections; the old crimped lead terminals especially are a source of unreliable current capacity. If you have the newer style lever-clamp terminals with the wires soldered in, you can ignore this one. A good battery is one that's been tested on a battery load tester and passed.

Assuming all plugs are good, look at the coil dwell times on Lexia or Diagbox, they should be very close to each other.

Watch your sensor voltages on the diagnostic, ideal is 5V, you may see 4.9 or so but that's OK.

Don't write off mechanical faults such as a vacuum leak from hardened O-rings where the inlet meets the head.

Throttle body faults on an electric throttle body are usually logged as being out of range for throttle position vs RPM. You can also read the throttle position as a percentage off the pedal movement in your parameter measurements, with the motor off.

As it is probably the Sagem ECU, these are somewhat known for dodgy idle/low speed issues. I don't know what causes it but several companies offer a fix for a few hundred.
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#7
Thanks guys, that's what is going to happen, but before the van can be hooked up to the lexia, Citroen suggested changing the parts I have mentioned as they say that any part could cause the vault and may not necessary be the one diagnosed. if it does turn out to be the ECU then the names of companies would be helpful.
The coils have been changed the battery load tested and terminals are of the clamp kind and the plugs are new,
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#8
There are several sensors fed by the same 5V reference voltage. Yes, a fault in one can affect the others but the crank sensor is the only one (I think) of the sensor "set" that must be plugged in for the motor to run. You can operate without ovygen sensors, coolant temp, MAP, knock and it will carry on a treat with fault codes but you shouldn't get any effect greater than a safely rich mixture and slightly laggy performance.
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#9
Ok thanks Addo, just another question, i was browsing eBay for a potentiometer & one of the sellers mentions that they can turn both ways clockwise and anti clockwise, if I remove it is there a way to test which way it turns or do they all turn the same way? I have to remove it to get the part No:
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