BX 16 Engine light idle fluctuate

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Re: BX 16 Engine light idle fluctuate

Post by Dave_16v »

That's it.👍
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Re: BX 16 Engine light idle fluctuate

Post by Kitch »

RobC wrote: Tue Sep 07, 2021 3:51 pm In that case you have the BOSCH motronic ML4.1 ECU.

Pretty sure he doesn't if it has an EML. Could be a DFW engine, being it's in Oz?
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Re: BX 16 Engine light idle fluctuate

Post by RobC »

Yeah, if Oz perhaps things were different…

I note the relays in his pic are in the engine bay though, as per ml4.1
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Re: BX 16 Engine light idle fluctuate

Post by white exec »

If the VIN can be posted here, we can check which engine and other ex-factory details.
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Re: BX 16 Engine light idle fluctuate

Post by frog »

Hey Glenn,

I'm not sure if you use facebook but I made a video in the BX Club group there showing how I test the error codes on my series 2 16v without a reader/without using the plug. facebook.com/708380267/videos/10165536223470268/

We use to have a home made error code reader but I found I can trigger the error code diagnostic reading sequence with just the ignition key.
Turn your ignition past accessory to ON;
Then turn the key very slightly clockwise as if to engage the starter motor but not all the way, only a few degrees and the dash will go blank/quiet;
Hold this for ~3 seconds and then let the key return anticlockwise back to ON;
This begins the error code sequence.
Repeat this process between codes.
My video shows error Code 12 (Test start)
Code 44 (Knock sensor)
Code 11 (Test end)

The following page has been very useful over my BX ownership - it's a long scroll down to the EMS error codes heading but it goes through fault code reading and interpreting.
https://citroen.tramontana.co.hu/fuel-e ... components

I haven't got much to add on the idle problem, like Rob I sort of gave up trying to cure mine; I think it has mostly resolved but I'll have to drive it on a few hot days this summer to be sure. Mine only seemed to happen when the engine got quite hot or was started again shortly after a long drive.

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Re: BX 16 Engine light idle fluctuate

Post by krekov »

I have a 1989 16v as well, it has the 3 row ECU and a lambda sensor, it's the DFW 147hp engine.

I've installed a new idle air valve, leads, coil, spark plugs, reconditioned AFM, lambda, all new sensors on it, tested compression (~0.5bar variation between cylinders, lowest was 11.5bar), checked for intake and exaust leaks (didn't find any), reconditioned the injectors.

The ECU throws no codes and the car drives like a rocket.

Using an ECU that disregards lambda sensor input and relies solely on the AFM for proper mixture, the car will idle perfectly smooth if the AFM is tuned right, smooth just like the non-cat 16 valves.

I'm not an expert, but my opinion is the catalytic and lambda equipped 16 valves have always run lumpy on idle and there's nothing you can do about it.
But, it should be a "regular lumpy" idle - if it's irregular then you've got some slight issues.
Many people overlook that the AFM needs to have proper dampening, as vibration from the engine carries onto the rotor arm inside and introduces fluctuating readings to the ECU.
You can check that by simply holding the rotor arm still with your fingers.