C5 throttle lag

deesse

deesse

Active member
Fellow Frogger
Joined
Dec 1, 2010
Messages
603
Location
Melbourne Australia
My 2003 C5 wagon with a 2l 16V petrol engine and auto gearbox has what I can only describe as a dangerous throttle lag when re-excellerating from an almost stop. Say for instance I brake at an intersection to prepare to stop but see that I am free to continue and put my foot on the gas there is an at least 1 second pause before anything happens. When this first happened I thought the car has stalled. It really is dangerous as 1 second can be a long time when another vehicle is bearing down on you. I have got used to it to a certain extent and anticipate it, but I cannot believe that this is normal. My mechanic dismissed my concerns and said it was because of the electric throttle linkage but if this is modern technology then give me back a cable.
Has anyone else experienced this problem and if so do you have a remedy?
Thanks
Tony
 
Has it always done it? I had a peugeot (2 of them actually) that did this sometimes and it was intermittent faults in the computer which controls the transmission/engine. They got confused and didn't know which gear to select so it did nothing. Check it out?.
 
You're not driving left foot on brake, right foot on accelerator are you?

Regards, Rossie
 
Thanks big Kev - yes it has always done it

and Rossie I am quite sure I do not have my foot on the brake at the same time but good try.

cheers

Tony
 
Tony,

I was not being facetious - my 2.2 Hdi TT gives me grief if I drive that way; and I don't mean both braking and accelerating at once! Riding the brake with left foot (as in approaching an intersection) and lifting off the brake at the same instant as accelerating away seems to confuse the computer.

It was just a thought.

Rossie
 
I’ve always had this lag, and it may be two seconds, which is a very long time.
It looks like it’s when the transmission is in second gear and wonders if it has to downshift to first gear.
You can reduce the lag by lightly throttling the pedal.

There is something of it too in higher gears at the lowest throttle opening.
I’m suspecting a break at the low end of the track in the pedal sensor, with the ECU resetting new values around the break.

The sensor is under the fuse box and has at least three wires that I’ll try to follow into the fuse/ECU box.
Removal would be simplest from the front by removing the air filter box.
No question of a new one, it’s about $400 :mad: if it fixes it at all.
 
deesse said:
My 2003 C5 wagon with a 2l 16V petrol engine and auto gearbox has what I can only describe as a dangerous throttle lag when re-excellerating from an almost stop. Say for instance I brake at an intersection to prepare to stop but see that I am free to continue and put my foot on the gas there is an at least 1 second pause before anything happens. When this first happened I thought the car has stalled. It really is dangerous as 1 second can be a long time when another vehicle is bearing down on you. I have got used to it to a certain extent and anticipate it, but I cannot believe that this is normal. My mechanic dismissed my concerns and said it was because of the electric throttle linkage but if this is modern technology then give me back a cable.
Has anyone else experienced this problem and if so do you have a remedy?
Thanks
Tony
Click to expand...
Bit late for reply maybe, but my "04 C5 Hdi has done this from new. It is most annoying and dangerous. And you're right it's caused by indecision from the Trans ECU. Nothing you can do to fix. I find it's a livable condition in traffic when driven in manual shift, and doesn't seem to do it at all with the Air Con off, although it still has the usual diesel sluggyness under 1200 rpm. In my case the trick seems to be removing any extra load imposed on the motor at low revs by turning off the air con. I hate driving in manual shift around town. Hope this helps.:cheers:
 
My 2003 C5 petrol has always had this lag also. very annoying. I have always thought that its mainly due to the 2.0 L engine not having enough power to shift the weight of the wagon from stop until the car is actually rolling.
 
Clogzz said:
I’ve always had this lag, and it may be two seconds, which is a very long time.
It looks like it’s when the transmission is in second gear and wonders if it has to downshift to first gear.
You can reduce the lag by lightly throttling the pedal.

There is something of it too in higher gears at the lowest throttle opening.
I’m suspecting a break at the low end of the track in the pedal sensor, with the ECU resetting new values around the break.

The sensor is under the fuse box and has at least three wires that I’ll try to follow into the fuse/ECU box.
Removal would be simplest from the front by removing the air filter box.
No question of a new one, it’s about $400 :mad: if it fixes it at all.
Click to expand...


If it's not a really early car, it would have the motorised throttle and the pedal is presumably at least a dual track device. So, it's likely to record a fault if one track has failed. There is an initialisation procedure for the pedal too. Two foot driving an pumping the pedal when starting can cause problems, so should be avoided.
 
It has the motorised throttle and I hope that it has the dual track pedal sensor, but has never indicated a pedal sensing fault.
I’ve tried the initialisation many times and always start without touching the pedal.
I also only ever drive with one foot at a time. :D
I’ve experimented with the crankcase vacuum intake to see if the throttle was moving at idle and also squirted the throttle spindles.

The car feels like a dirty old bomb with three on the tree and an unsynchronised first gear.
It’s faster to stop to allow the transmission to return to first gear than to wait for the lag to come good.

Coming from a Xantia, the C5 felt like being back in a Holden HG Belmont. :evil:
 
Dismal Sunday afternoon, ideal weather to tinker.
Opened the pedal sensor to find a Hall Effect sensor with two magnets.
Nothing to see that can go wrong.
Removing the back plate was no use, it’s resin inside.
There are four numbered pins in the socket.

1 to 3 measures 41 kilo Ohms.
1 to 4 ... 40 kΩ.
3 to 4 ... 1 kΩ.

These are not readings that we would expect from pick-up coils, so I think that there’s an amplifier inside.
So, we’re no further with it except for knowing that there are no potentiometer tracks.

 
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lag

i had a xantia 16v manual wagon fantastic car sold it bought a c5 16v petrol auto wagon throttle lag was shocking as were other parts of the car sold it bought another xantia
 
Also a problem with Xsara 1.6 AL4 Auto

AXGT and I are having a similar problem with the above combo. The NFU engine also has a fly by wire throttle control.

With air con on and starting from stopped, there is quite a bit of a hesitation from the engine and by looking with the Lexia, we seem to be able to detect a big pull back in the ignition timing. It is 0 degrees at idle and then seems to go about 10 degrees negative before starting to go positive and then the engine pulls OK. It does not seem to do it as badly with the aircon off. It is very offputting to learner drivers! Anyone have any ideas what is going on here?

I think all ''smart'' autos seem to get confused when you slow down, then plant the foot. They have to think about getting into the right gear before they let the engine go. My first real expereince of this problem was in a work commodore but I have since had it in this Xsara and the new C5X7 (to which you have to add turbo lag). It is a much better idea to soft acelerate to get stuff happening and then to increase the throttle.

But I would agree, there is nothing like the great throttle response of a good 16Valve manual Xantia. My wife spins the wheels taking off from intersections by mistake after driving the diesel C5X7 auto.

Cheers, :cheers:

Ken W
 
:mad:

The 8V automatic Xantia didn’t have that problem.
The Nissan Pulsar 2005 with motorised throttle reacts strongly and instantly.
If the C5X7 also has that lag, it must be built-in but how then do those cars make it past the new car buyer’s test drive ?

My lag isn’t affected by the air conditioning.
It’s only there when slowing down to unlocked second gear.
Starting from standstill in first gear is always instantaneous.
I’ve trawled to no avail in three languages to find out if the lagged cars are all like that from new or if the fault appears along the way.
Some say that it’s inbuilt to reduce the torque when downshifting to first gear … just like granddad’s old bomb.

In today’s cool weather, the lag seemed a bit more obvious.
There’s apparently a thermostat inside the AL4 box, but if it also has an accessible temperature sensor, I may explore around there.
 
I had a 2005 C5 facelift petrol wagon which I liked a lot, except for the throttle lag.
My spouse hated that aspect so much that she insisted we get rid of the car once the lease was up.
I think someone told me that it was due to the old tranmission?
The 08 diesel C5 wagon that we have now does not have the same problem.
 
I've also got an 03 c5 with the 16v auto that does this too. It's one of the few things that makes me want to sell the car a t times. (along with the turning circle of a house boat and not being able to find a towbar)
My guess is it would be there by design as part of the throttle maping for the auto, but it's way to long and dangerous from a stand still or very low speed.
 
There seems to be a lot of talk here about lag with autos, but I've experienced it with manuals too.

My Dad's 1989 Mi16 had atrocious lag. My grandfather's 306 HDi (in warmer weather) would switch on the air con unexpectedly when it mattered most, leaving you sitting like a duck in front of oncoming traffic before finally waking up and whisking you to safety. And most recently, my Dad's 406 coupe also has some lag.

My experience suggests two things:

1 - There's nothing quite like direct cable throttle response, and

2 - There is possibly some way to change this shortfall by changing computer chips... :confused:


:cheers:

Binky.
 
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