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Throttle Hesitation in Xsara HDi - mph_turbo
Hi Folks,

I have an intermittent poor throttle response with my vehicle, a Citroen Xsara HDi. Apologies for the long post but I'd really like to hear from anyone that had experienced a similar problem.

The symptoms are:

· The engine can fail to respond to a re opening of the throttle from closed for a period of 1 to 5 seconds. This is particularly happen when reapplying throttle when coming out of a bend or roundabout.

· It does not matter if the throttle application is light or heavy

·But it is really bad in terms of its frequency and duration when the car has a trailer attached or has an internal load. In this case, the car just ?chugs? as if it?s just getting intermittent spurts of fuel.

·The revs level where this tends to happen most is around 1400 to 1800 r.p.m. It does not seem to matter if the engine is cold or warm.

·It also tends to happen for a much shorter time period, say 1 second, when reapplying throttle on open road, say after coasting downhill and re opening the throttle to overtake. This can occur at any r.p.m.

·The problem also can manifest itself when trying to pull away from a standstill from a junction. In this case, the engine is way down on power and is very slow to respond to the throttle.

·The problem never happens when increasing the throttle opening from an already open position.

·Its possible to drive the car for, say, 5 miles, with hardly any evidence of the problem. But driving the same distance on another occasion could see the problem reoccurring a few times. It really does depend on the road type in terms of whether throttle re openings are a common occurrence. Apart from that it?s random except that the only time it occurs is with a throttle re opening.


·In all cases, it?s like as if the engine electronics is failing to recognise a change of load and is very slow to change from a lean mixture to a richer mixture. Once the engine gets fuel, then it?s away as normal. My understanding is that Hdi engines have an ?overrun? valve that reduces the fuel to the engine when the engine load is low. Am I right?

When the problem happens, the engine management light on the dashboard remains off. The vehicle was checked three times by a Citroen garage but no error codes are being logged .

One other thing is that the cars overall performance in terms of acceleration seems to be down slightly.

At this stage, I've lost all confidence with the Citroen dealer and my patience is rapidly running out with the national importer. Nothing has been done in the last three months other than check the diagnostics.

All ideas are most welcome

Top Reply

Throttle Hesitation in Xsara HDi - garage2u.co.uk

Recently had a customer with this same problem, no throttle response for up to five seconds more evident after hard cornering, after exhaustive testing i sourced the fault to a miss adjusted brake pedal switch, customer had spent alot of money previously and had been told ecu fault, 'fly by wire' throttle housing, egr valve etc etc.

The brake switch cuts throttle action when depressed hence being miss adjusted a signal was being sent to the ecu telling it both the throttle and brake were being pressed together, with this information the ecu cuts throttle opening. It appears this is a common problem that is costing customers hundreds of pounds when a quick adjustment is all the is needed, even a new switch is only £8.00.

Hope this helps.

All Replies

Throttle Hesitation in Xsara HDi - Screwloose
mph

Until I got to the bit about "no codes" I'd have put good money on P0120/220 or 0121/221 being there. Those are very common HDi accelerator position sensor codes; there's even a wiring mod to [try] and stop them recurring.

With no codes to help, there's a very odd [almost Citroen only] HDi fault that might fit. The plastic air intake pipe between the filter and the turbo gets warm, softens and sucks flat on re-application of power. It's more usual to occur on leaving a fast stretch of road; but... Try briefly removing the air filter element and trying it.

Some later HDi's have an [obvious] vacuum-operated butterfly valve where the intercooler hose joins the inlet manifold; they do stick, but more usually at a consistent level.

What's your year and engine code? It's incorporated in the VIN number letters; either RHY or RHZ.
Throttle Hesitation in Xsara HDi - mph_turbo
Screwloose,

Many thanks for your post. Your theory about the air intake pipe is interesting since I have noticed that the problem can be worse than usual on a warm day. Will check this as soon as I can after a 10 or 20 mile spin at a decent pace.

My vehicle's year of manufacture is 2004. Will get the engine code asap.

Thanks again

MPH
Throttle Hesitation in Xsara HDi - mph_turbo
Screwloose,

Just got a chance to check the engine code from the VIN number. It's RHY.

There's just one other thing:

The car was off the road for 6 days or so for repairs after a minor bump. The parts replaced were essentially a bumper and bonnet after a 15 mph bump.

The hesitation problem was very much in evident before I had the bump.

And the hesitation problem had disappeared totally when I got the car back.

After 12 weeks or so, the problem slowly re emerged.
And it has been worsening ever since.


Thanks

MPH
Throttle Hesitation in Xsara HDi - Screwloose
MPH

The improvement after a small impact is interesting. I've seen particle filters block-up and cause major loss of power. Can't say that I've seen many '04 Xsara's yet; but the late C5's have the inlet butterfly and the Eolys anti-pollution system fitted.

If your's has Eolys [I'm not sure if the late RHY's do]; ask your dealer to verify from the ECU's memories that it has automatically regenerated at proper intervals. If there's any doubt get them to carry out a "forced regeneration" to clean-out the particle filter.

Haven't they ever replaced the accelerator position sensor? It would seem the obvious, if a bit knee-jerk, reaction to this fault.
Throttle Hesitation in Xsara HDi - mph_turbo
Screwloose,

Many thanks for your valuable input. The dealer has done nothing so far other than check the diagnostics. He claims he's waiting for technical information/support from the importer in order to pin point the problem..........

Anyway, it will a week or so by the time I can get the dealer to check if my vehicle has the Eolys system and perform the "forced regeneration"

I will post any update as soon as I get it.

Thanks again,


MPH
Throttle Hesitation in Xsara HDi - mph_turbo
A delayed update on the throttle hesitation............

After much hassle and heated discusion, Citroen took my vehicle back to headquarters for a three week period in Jan 06 to further examine the throttle hesitation issue.

The problem was very much in evidence when I handed over the car but they claimed that they could not find/reproduce the hesitation. I drove the car in the company of their technical manager and it behaved perfectly. They claimed that they had done nothing to it.

However, the problem re emerged within 5 weeks of getting the car back. I immediately informed Citroen but their response was not committal. So after numerous near accidents due to the hesitation problem, I decided to take the car to an independent diesel injection specialist. After explaining the characteristics of the problem, he was able to reproduce it while driving and traced it using his diagnostic gear to be an issue with the EGR valve sticking open or 'appearing' to stick open..........so with the valve 'open', the injection ECU was not allowing fuel into the injectors and hence the definite lack of any acceleration when teh problem occurred.

He recommended that the injection ECU should be changed. This diagnosis and recommendation was arrived at in the space of 1 hour.

So, armed with this information, I again contacted Citroen who eventually agreed to replace the ECU. This was done in August 06 and the problem has not occurred since.

The amazing thing is that Citroen's own diagnostic gear was unable to read diagnostic information that an independent specialist was able to get at...............what really annoyed me is that I had discussed the possibility of an EGR related issue at lenght with the technical manager only to be told that this was not the case.

The amount of time and effort expended chasing down a solution to this issue was horrendous..............so my advice is that, if you have an issue with a vehicle that the distributer claims is non existent, take your vehicle immediately to a reputable, independent specialist to diagnose the issue and then send the findings to the distributor along with your incurred costs.

MPH
Throttle Hesitation in Xsara HDi - Screwloose
mph

Thanks for taking the trouble to come back with the outcome. It's always worth knowing what the cause was for future use.

As to main dealers being unable to fault-find; that's almost normal. They've all the gear - it's diagnostic ability that they're lacking.

But their lack is often my gain; I get called in to fix their customer's cars for them - so it's an ill wind...
Throttle Hesitation in Xsara HDi - kerbiquet

I've had exactly the same problem with my 2002 2.0 hdi Citroen Relay van, so I'm pleased to read this post and will follow your recommendation. Will inform you of the results later.

Throttle Hesitation in Xsara HDi - garage2u.co.uk

Recently had a customer with this same problem, no throttle response for up to five seconds more evident after hard cornering, after exhaustive testing i sourced the fault to a miss adjusted brake pedal switch, customer had spent alot of money previously and had been told ecu fault, 'fly by wire' throttle housing, egr valve etc etc.

The brake switch cuts throttle action when depressed hence being miss adjusted a signal was being sent to the ecu telling it both the throttle and brake were being pressed together, with this information the ecu cuts throttle opening. It appears this is a common problem that is costing customers hundreds of pounds when a quick adjustment is all the is needed, even a new switch is only £8.00.

Hope this helps.

 

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