3.0 Hdi 160 With Poor Idle And Starting

[pikesrelaybus]

Hi Guys,

I started a new thread yesterday but ironically as I explained my problem I stumbled across the fault but I thought I'd still post anyway. For months now my relay has intermittent "hunting" engine, especially at tick over. If you engage cruise control you can feel the vehicle surging as the power comes and goes. If you stomp on the accelerator your rewarded with a sooty puff of smoke which means these days a MOT failure. It's like it's running rich and those of you out there, like me, might place blame on the EGR valve since there's so much crap circulating around modern diesels. Sometimes, not always, she was a complete bugger to start and I'd get a engine warning light, more often than not she won't start first turn which is unusual. Yep, she rattles away at 140k miles but this is what I found.

 

As I finished off my original post, post fitting a new EGR valve and then having to refit the thing due to coolant leaks, I noticed a "include file" option at the base of the post and thought a quick video of the thing hunting away might help. Upon switching off the engine I hear the familiar sound of the throttle body closing about 3-4s after ignition off and also a buzzing sound coming from the valve which feeds vacuum to the EGR valve. As the vacuum reduced the buzzing noise faded and went up in frequency. That caught my attention and I pulled off the vacuum hose from the EGR and immediately there was air flowing when it was ticking over, that shouldn't be at tick over. SO... what I'm saying is I was spot on diagnosing the EGR problem, the poor running was due to it sniffing it's own farts but it wasn't the EGR valve, it was the sodding valve. Both items are quite expensive, EGR was £160 (pattern part), £280 for OEM (if memory serves me right) and that valve, which looks like if you open it up it'll be broke forever is £120, on my 2008 it's fitted above the engine behind a metal plate. I've got a 2nd hand one off eBay. After I removed it I could blow/suck air through it, so I guess it's opened and stuck open. Having taken it off I get the engine light but it seems the hunting has gone away, well it did for the 6 mile journey I did this morning. I could of course blank the bloody thing off but then I increase engine temperature, so I'm led to believe. Still, worth checking that valve before you remove the EGR valve, which incidentally is much easier if you remove the heat ex-changer it's bolted onto. The worse part was the lower seal, I opted to leave the lower half bolted to the exhaust where the hex bolts had rusted.

[paul.h]

Thankyou for posting this, it might help another member with a similar problem on a petrol C8 who has cleaned the egr valve and done other things but still has similar symptoms to yours.

[pikesrelaybus]

That's not a problem... however!!!. Having received the new valve which has the part number 46524556, looks like this. I checked it against the old one and it behaved similar. Of course I wrecked the old one to find out why it failed. I fitted the valve along with a pressure meter on it's output. When you switch the engine on I measured -30mBar, most of the vacuum is sucked through the third hole the other side of the valve which has a small boot with a little filter fitted. Moments later, the the engine's note changed (became throatier) and the vacuum was now 700-800mBar so obviously on but why? It's ticking over... Also even without the egr valve hooked up to the vacuum, I'm still get this hunting which has now really confused me. If you disconnect the valve electrically it goes back to running smoothly and the vacuum is -30mBar. So, I can connect all the pipes up and leave the electrical connection loose and all is ok. What I'm worried about now is what controls this valve? or maybe it's getting duff info from another sensor which fools the ECU to operate this valve. And why is it running rough even while the EGR valve is closed.? When the valve is connected it buzzes. You think Citroen will find this?

[paul.h]

The sensors involved in getting the air flow right will be the coolant temperature, the inlet air temperature, the air flow meter MAF - this probably also contains the inlet air temperature, the manifold pressure MAP. To check these would need a code reader that gives live data. It is possible these do not give a fault code but could be giving wrong values.

[pikesrelaybus]

Thank you for your reply paul.h, I totally agree/think your right. I'd lost my code reader (for months) until today as a result of the many "tidy up" that happen. Anyway, the situation is thus, I have the electro-valve disconnected (electrically/vacuum) and my engine purrs away happily for a 140k engine, like a little rattly. However, the EML is illuminated. So, without my reader I kinda gave up and called into the local dealership who promptly told me how busy they were and frowned upon my changing of anything, let along the EGR valve. Said, they'd have a look so long as it was put back with the original parts, ranting on about pattern parts etc. Now I've found my reader I can do some checks, so, vehicle not stone cold as it's been for a drive today gave me the following live data calc-load 25%, Coolent Temp 44oC, MAP 98Kpa, Eng-speed 800rpm, IAT 31oC, maybe slightly high, temp today at the hottest was 30oC and it's now 22:00. MAF 21.5g/s. These figures are reasonably steady/easy to read.

 

So, The figures above are with the electro-valve disconnected, basically isolated the EGR valve. Plug it in, clear the P0403 error and re-do the live data. Apart from the fact the engine is now surging and thus the figures are not stable, I'm getting 65% calc-load, which seems bonkers but it's calculated, Coolent temp gone up a bit to 52oC, MAP is 45Kpa, engine speed round about 800rpm, IAT slightly more at 33oC and the MAF is 8.04g/s, most figures are bouncing about and difficult to nail a average.

 

I'd be more than happy to nail this myself as the main dealer is SOOOOO busy they can only sort out my problem in one slot/booking, servicing means another booking on a different day and I still need to recharge my AC, I'm hoping it's simply run out and not a leak, it's lasted 9 years.

[paul.h]

I would do the readings again first thing in the morning and leave the code reader plugged in when you go out to see how the temperatures change as the engine warms up. First thoughts are though the values seem ok although I am not sure about the calc load. I have found the IAT is a bit higher than outside since it is measuring the temperature under the bonnet. You would think the MAF would be similar at the same rpm or maybe with the egr open the MAF value will be less since less fresh air is being sucked in to the engine.

 

https://www.ericthecarguy.com/faq/solving-automotive-idle-problems/egr-problems this suggests if an egr is causing a poor idle it must be part open or stuck open but it can be tested using diagnostic equipment to actuate the valve - this would need a dealer type tool.

 

P0403 Exhaust Gas Recirculation Circuit Malfunction - at least you get a correct fault code when the valve is not connected.

 

Chances are the air con needs regassing. I had our C5 done a few weeks ago since it had stopped working and once regassed was ok. It was 4 years since it was last done.

[pikesrelaybus]

re-gasses and enjoying the coolness in this hot weather. It's difficult to understand what is right/wrong with regards readings. I have (as it was only £20) a MAP sensor, very easy to change but I'm also looking for a MAS, possibly the culprit. Obviously the various sensors vary which is a good sign but I have no idea if the readings I'm looking at are right/wrong. I've been searching on-line for some info on a F1C Iveco engine, found a full blown PDF on the engine but nothing obvious. I do have a pressure meter but no Anemometer. Even if I did I'm not sure where one can place it. Best removing the sensor and testing it on some sort of test jig.

[paul.h]

You could see if the MAF/MAS is giving a false reading by disconnecting it. It would then go to limp mode and if the sensor was faulty then it ought to run a bit better but with limited performance. The eml will come on with a fault code that will need deleting once the sensor is plugged back in.

 

However, you can approximately calculate the air flow. Air density is approx 1 gram per litre, you have a 3 litre engine running at 800 rpm, the turbo will not be doing much at idle, it is a 4 stroke engine so 400 rpm sucking in air = 6.67 revs per second, times 3 litres = 20 litres per second which is approx 20 grams per second. So it would appear with the egr disconnected the MAF is giving the right value. For this to drop to 8 g/s with the egr connected, there must be a lot of exhaust gas being recycled or the engine would not run at such a low flow.

[paul.h]

If you have an exhaust particle filter (dpf) then it could be blocked - have a read of this topic http://www.citroen-owners-club.co.uk/citroen/topic/22909-c5-hunting/?do=findComment&comment=95329

[pikesrelaybus]

Paul, you've been a great help. I took some MAF readings @ 800, 1000, 1500 & 2000rpm and the maximum error was 0.5g/s with the electro-valve disconnected, so I'm happy with the MAF. I've noticed the IAT temp is higher than expected and after an hour I checked with a thermometer stuck in the air-intake. When I started IAT was 40oC, I measured 35.6oC, after 2-3 minutes running the IAT was 32oC, I measured 26oC. However, one thing I've seen again, so it's repeatable, is the reduction of MAF reading when I reconnect the electro-valve, it dropped to 6.33g/s. Unlike yesterday I didn't get the erratic readings but all the signs are there it's in the back ground, just lucky I got some stable readings.

 

So, basically the air flow is right but the MAF sensor is reporting wrongly when I reconnect the electro-valve. Which is worrying! The electro valve also gets ruddy hot quite quickly. I don't think it's supposed to be energized 100%

[pikesrelaybus]

I also forgot to mention, I have a spare electro-valve, I believe it's operated pulse width, so either it uses the exhaust sensor or it calculates what % pulse width it requires. Either way, I need to break the coil and insert a small value resistor, hook it up to my oscilloscope. If I don't see pulses I guess there's a problem with the EMU..

 

I do have a DPF, at least I think I have. There's no light to suggest I have a blockage problem, I know a friend with a Volvo had issues with his DPF and he was alerted by it's whinging/light display. I used to do quite a bit of M'way work using the cruise in an attempt to save fuel, these days I don't care so when I can will drive at 70mph. This surging engine has been with me for some time spread over many, many miles.

 

What I'm worried is that the drive from the EMU (assuming PWM) to the electro-valve is stuck 100% which potentially, by design shouldn't be the case, in doing so has effected things like the 5v reference for some of the other sensors. I would be able to measure for pulses and indeed calculate what the current is.

Edited June 27, 2018 by pikesrelaybus

[pikesrelaybus]

I'd have thought if I had a DPF then I would have seen a DPG warning light, pre-starting. There's no such warning light.

[paul.h]

If it has a dpf it will look similar to this in the front underneath section of the exhaust https://www.ebay.co.uk/itm/CITROEN-JUMPER-Bus-Catalytic-converter-Particlefilter-2010-89049km-1731TV/352274532525?hash=item520532c8ad:g:9aQAAOSwjytaeda4  If you have one the part number will depend on your VIN.

 

I do not think the slight variation in IAT is anything to worry about. The value will be used to calculate the air flow to get the fuel flow right. SInce it will work in absolute temperatures in calculations (ie add 273 degrees to the 30 to 40 degrees), a few degrees out would only give a small percentage out in calculated air flow.

 

Have you checked all the wiring to the egr valve/sensors, just in case a fault with it is causing the valve to open when it should be closed ? Is it possible to fit a blanking plate to the egr valve but whilst leaving it in place - whilst not the right way to sort the problem it could be a fix ?

[pikesrelaybus]

Hi Paul, Sorry for the long delay. It's off to Citreon anyway but to answer your question, the EGR valve is disconnected from the vacuum pipe so it can't open and the electro-valve if disconnected allows the engine to run normally and I get normal MAF readings. It's only when you refit the electrical connection to the electro-valve do the MAF readings go super low, like you said, if they were that low the engine wouldn't run BUT!, I think they're not actually that low but since the EMU "thinks" it's low, it's compensating elsewhere (Fuel) which then causes the engine to run poorly. My live data only really shows the MAF, IAT etc. not the exhaust oxygen sensor. I also looked up the details of my engine and it only stated it has a cat and there's no mention of DPF nor any lights so safe to say, I ain't got one (Thankfully!!). I will of course, subject to Citreon BS return what was actually wrong and I'm really hoping it's a sensor and not the EMU itself. I will of course obtain the old one and repair it if possible, depends on how much crap there is between me and the components within..!

[pikesrelaybus]

So its trip to the main dealer resulted in a software update. It is running smoother for sure and hasn't hunted since however, the MAF readings when the electro valve is electrically connected results in a reduction in readings, I'm now getting 11g/s rather than 6g/s and she's still a bugger to start when warm. So, I guess it's solved my problem for MOT time but I don't think this problem has gone away, just postponed..

[paul.h]

Sounds as if the update has increased the air flow slightly which would help the idle - has the idle speed gone up a bit ? Maybe this is a common problem if there is a software update.

 

Does holding the accelerator pedal down a bit help starting, just in case it is running a bit rich ?

[pikesrelaybus]

Idle same, 800rpm. Although it doesn't hunt now and I can have the electro-pnumatic valve connected all the time, no EMU light. Valve still gets very hot but then I don't know if that's normal. What's started happening more often is it won't start when warm. That happened once in the blue moon and a switch off, count to 5 and try again it would start. Once it's warm it point blank wants to run, it coughs and splutters but won't catch and continue. I'd also say that normally I would turn the key, two churns later it would fire up but now (when cold) it does the two churns but then thumps into life. Like the time is bad. I've thought about this while driving, if there was a fuel pressure situation or lack of, then I'd have poor acceleration but this isn't the case. It's going to a specialist on Wednesday who I'm rather hoping has a shed load of test equipment and can get to the bottom of the problem, of course I'll come back with anything new. In a way I guess Citreon has sorted the hunting issue BUT!, I'd say in updating the firmware has merely hidden the fault (The quick option!). When you plug the electro-valve back in, you still get a drop in readings and the engine changes it's tone to a deeper intake noise. What would be really good is if someone with the same engine and a code reader to reset the error afterwards is to check they're engines behavior and noting the "live" data...

[pikesrelaybus]

I forgot to say, doing anything with the accelerator makes no difference.. It's a pattern of switch off, wait a bit, switch on, wait for the Glow plug light to go out and then re-try. A few days ago I'd repeated that pattern for about 3 minutes before it finally caught and ran. Once it's going, it's fine..

[paul.h]

Maybe there is a glow plug problem but often that gives P1353 fault codes. Fingers crossed it gets sorted tomorrow.

[pikesrelaybus]

I think we can put this one to bed now, It appears to be fixed and I was somewhat gobsmacked when I was told what it was. Of course now I know it kind of makes sense. So, firstly the dearlership's attitude put me in a negative frame of mind, the reason I took it to a Diesel Specialists today. Going on about how busy they were and owners doing DIY etc. made me highly suspicious of the work they'd done. It's just they're attitude sucks. As it turns out the whole of the drive train, sensors etc were all working fine and in spec. I did have some Errors which did not illuminate the EM lamp nor come up on my reader, P0335 - Crankshaft Sensor, P0520 Engine oil Pressure sensor & P0530 Refrigerant pressure sensor, no surprise, that's leaked out recently. So, I'm pleased about that, the firmware upgrade did actually work fair play to Citroen. My new starting issue was down to the starter motor, which cranked ok, maybe not as enthusiastic as when it was new and I still have my original battery, now 10 years old and showing signs of replacement each winter but that's been going on 3 years now and it still survives. The starter motor was drawing more current than normal, maybe my battery doesn't help but that was enough to screw up the electronics due to excessive voltage drop, possibly why there's a few weird errors stuck in the EMU. Maybe if I spent more than £20 on a reader I might have found them!!. So, somewhere within the forums I remember reading something about poor starting and it made me think, it might sound and crank normal (ish) but if it's drawing too much current then they too will have issues. It seems a plausible reason and the specialists I went to had a new Lucas starter within the hour and had fitted it while I waited. It certainly turns and starts like I remember..

[paul.h]

Pleased it is sorted, we have learnt something new, plus you have found a specialist who seems to know their stuff.

 

I will pin this topic and change the title slightly so it does not get lost in the forum.