C4 Hesitation

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Captain Slow
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C4 Hesitation

Post by Captain Slow »

Hi All

Thought I would just write a few lines about what I would class as bogging down or hesitation on my petrol VTS.

Ever since I purchased my car I noticed that unless I had the revs in exactly the right place when pulling away from a junction the car bogged down. It was if the car was from the late eighties, with massive turbo lag. You would put your foot down, get nothing, get nothing, and then suddenly it would surge forward.

Clearly this wasn't ideal, and at times quite frightening.

Whilst at Citroen yesterday having another unrelated issue looked at I asked for the ECU to be "flashed" and updated. They didn't think this would do much, but I insisted. Low and behold, upon jumping back in the car last night it was a revelation.

Flashing the ECU and updating it has cured the issue. Driving it home was a real pleasure and the bogging down has disappeared. It's much happier upon pulling away, and the "lag" has been cured. It seems much better through the rev range too.

I urge you all with this problem to get your car plugged in, and get it updated.
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Re: C4 Hesitation

Post by daviemck2006 »

Mine seems all right when pulling away, although I find it does need revs to do so. It's very easy to stall. Doesn't help that I come out of drive on the level, 50 yards to stop junction which is uphill and the car's always cold!
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Captain Slow
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Re: C4 Hesitation

Post by Captain Slow »

daviemck2006 wrote:Mine seems all right when pulling away, although I find it does need revs to do so. It's very easy to stall. Doesn't help that I come out of drive on the level, 50 yards to stop junction which is uphill and the car's always cold!
I'd suggest you have this issue too. Exactly the same as mine was in the mornings.
Last edited by Captain Slow on 28 Mar 2013, 14:55, edited 1 time in total.
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daviemck2006
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Re: C4 Hesitation

Post by daviemck2006 »

I'll phone nearest dealer and speak to them. Thanks.
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Re: C4 Hesitation

Post by Fake Concern »

I think mine must have already been done as it's eager to go from the off!
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Re: C4 Hesitation

Post by Mandrake »

Its unlikely the new software version itself has made any real difference, however as part of the flashing process the temporary memory of the ECU is cleared, this includes all fuel trim data that the ECU has learnt over time by monitoring the oxygen sensor(s).

If that is what has happened, the same result could have been achieved by disconnecting the battery for half an hour...

Its possible that a dodgy oxygen sensor (or MAP or TPS) has caused it to learn bad fuel trim corrections, for example if the oxygen sensor constantly reports richer than reality it will try to lean the mixture.

Depending on the original cause the symptoms may come back over time. If so you'd want to get a proper diagnostic session done including looking at fuel trim figures and sensor data.
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Re: C4 Hesitation

Post by daviemck2006 »

Mandrake wrote:If that is what has happened, the same result could have been achieved by disconnecting the battery for half an hour..
Is there a special technique for disconnecting the battery on these, or is it a simple disconnect?
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Re: C4 Hesitation

Post by Hell Razor5543 »

While this is mainly for the C5, it should be do-able on a C4. The main trick is to allow all the ECUs to 'shut down' cleanly, in a similar way you shut down a PC. This normally can clear down any glitches;

http://www.frenchcarforum.co.uk/forum/v ... 11&t=40407" onclick="window.open(this.href);return false;
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Post by addo »

I'm confident that updated versions of the PSA ECU software are not placebos. Most are instituted to correct a shortfall in the mapping (as opposed to changes from learnt behaviour). Learned characteristics are tweaks of the tables - which, if they're flawed to begin with, are going to give flawed results.
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Re: C4 Hesitation

Post by Mandrake »

I'm sure there could be small tweaks in newer firmware versions that may improve running but if you read the original post the original complaint was symptoms like "bogging down" and "massive turbo lag", somehow I don't think Citroen would let a firmware version out the door that caused "massive turbo lag" that was present all the time and plainly obvious, and I doubt the symptoms were there from new either.

Its more likely there is an undiagnosed fault or there WAS a fault like a faulty oxygen sensor that was repaired before the car was purchased but the ECU's non volatile temporary memory was not cleared. (Clearing the fault codes is not sufficient to reset learned mapping data in some newer ECUs)

My V6 has the exact same symptoms by the way, bogging if I snap the throttle and a large amount of throttle lag at certain rpm/load/throttle combinations, and I know its not a firmware issue...its only because its an automatic with a torque converter that its still drivable, I'm sure if it was a manual it would have similar drivability issues to the OP's car on take off.

As you know, exhaust restriction is the current theory on my throttle lag issue, it could be that a restriction upsets the map sensor reading thus confusing the ECU into under fuelling.

Its possible for example that the OP's car has an exhaust restriction and that the firmware update has made the ECU less dependant on the MAP sensor data or less easily fooled by incorrect readings from the sensor.

I still believe its likely that either there is an undiagnosed fault that the firmware update has disguised or worked around, or there was a fault that was already repaired some time ago but bad learnt data had not been cleared from the ECU non volatile memory.
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Re: C4 Hesitation

Post by Autunois »

Hello all,

Our c4 2 later petrol automatic is lagging when pulling away in 1st gear or reverse. It stutters a bit , sometimes the engine stalls, and the suddenly jumps to speed away.
No problems with higher speeds or more revs.

We had this issue in a slight form 40.000 km ago but it went away by itself. Now since 4 months the issue came back and makes driving in town very stressful.

The local Citroen dealer doesn't know the issue, there are no faults when reading out the car. They told us it is an automatic car deal with it, we do not touch automatic gear boxes.

Went to another garage they changed a valve, no improvement. They also found no faults on the computer.

Back to Citroen garage, you might start by changing the gear box oil, although normally it has a life guarantee. Go to a specialist who can pump out the oil. We did this €280 later, no change. Same issue.

Although we are in France the local garages do not seem to know what to do.
The engine has 120.000 km on it and runs really smoothly.
So far had to change timing belt, battery, interior heater, heat exchanger connecting the heater. Tires, brakes, window wipers. Nothing out of the ordinary.

Can somebody tell me what is wrong with our car and how to get it fixed?

Thanks in advance,

Hjalmar
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Re: C4 Hesitation

Post by GiveMeABreak »

Please provide the VIN so we can identify the exact gearbox type as I'm not seeing any AL4s on a C4 II. Please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff.
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