Technical Rough idle/misfire?

[Ducatomick1988]

Evening all,

I recently started a thread asking for some advice on what I presume to be a misfire, someone suggested a crankshaft sensor but symptoms of that also include loss of power which my van doesn’t seem to suffer with, I only notice the rough idle when i am stationery.

The reason I’ve started this new thread is because I’ve taken a little video in hope someone has a look and could advise me any further.

Also one of the injectors looked ‘damp’ compared to the other 3, could this be part of the problem?

I’ve scanned the forum and I can’t seem to find any answers so any help would be greatly appreciated.

 

[Ducatomick1988]

Anyone help?

 

[Anthony489]

Hi Ducatomick

I agree that one injector is "damp" with fuel, but unless it's been cleaned off recently that slight mist corresponds to a very small leak and is probably unrelated to the idling.

From the sound on the video, I would describe the behaviour more as surging or hunting, i.e. there is no misfire in the traditional sense, but the idling speed is unstable in a cyclic rather than a random way. As you will appreciate, there are a large number of things which could potentially cause this and they won't necessarily be enough to trigger a fault code. One easy check would be to remove the rubber air hose feeding the throttle body and watch the action of the flap at idle (you will be temporarily running without turbo boost) to see if it is cycling or sticking due to oily deposits.

I think your best bet is to find a diesel specialist with the skills to read the dynamic parameters (e.g. fuel pressure) whilst the engine is running, to pinpoint any abnormal behaviour. I appreciate that finding someone like this isn't straightforward, as too many workshops are of the "read the codes, change parts and hope" school of thinking.

 

[Ducatomick1988]

Hi Ducatomick

I agree that one injector is "damp" with fuel, but unless it's been cleaned off recently that slight mist corresponds to a very small leak and is probably unrelated to the idling.

From the sound on the video, I would describe the behaviour more as surging or hunting, i.e. there is no misfire in the traditional sense, but the idling speed is unstable in a cyclic rather than a random way. As you will appreciate, there are a large number of things which could potentially cause this and they won't necessarily be enough to trigger a fault code. One easy check would be to remove the rubber air hose feeding the throttle body and watch the action of the flap at idle (you will be temporarily running without turbo boost) to see if it is cycling or sticking due to oily deposits.

I think your best bet is to find a diesel specialist with the skills to read the dynamic parameters (e.g. fuel pressure) whilst the engine is running, to pinpoint any abnormal behaviour. I appreciate that finding someone like this isn't straightforward, as too many workshops are of the "read the codes, change parts and hope" school of thinking.

Hi Anthony,

Thanks so much for the reply.

I will get out today and remove the hose from the throttle body and give it an inspection.

I have read on a few threads with idle problems, it could be the EGR valve and a quick fix is to blank it. I know this isn’t the right way to go about things and isn’t technically legal but it would be a cheap fix.

I’ve looked into a diesel specialist and there is one about 40 minutes away from me so once pay day comes I’ll get in touch with them, as Once you put specialist up in your name you can charge what you want

Once again thank you.

 

[cris1117]

I would get the injector leak sorted first, probably the copper washer seal between the injector and the cylinder head letting by, this could easily be the cause of your problem and in any case needs sorting out.

 

[Ducatomick1988]

I would get the injector leak sorted first, probably the copper washer seal between the injector and the cylinder head letting by, this could easily be the cause of your problem and in any case needs sorting out.

Yeah I’m going to get that sorted asap I’ve read they’re a nightmare when they get worse to get out when they get seized in

 

[Womo793]

Hi
It may or may not be of help but I recall some years ago when I had a problem with a Toyota d4d (common rail) engine. A diesel injection technician said the hunting at idle was caused by the Surge Control Vavle (SCV). I don't know if your engine has that but it may be a pointer for you to investigate.

As for the EGR, a sticking valve was a fairly common occurrence with that engine, it would lose power, run erratically, but only when the engine warmed up. The remedy on that engine was to remove the valve and clean it.
Regards

 

[Ducatomick1988]

Hi
It may or may not be of help but I recall some years ago when I had a problem with a Toyota d4d (common rail) engine. A diesel injection technician said the hunting at idle was caused by the Surge Control Vavle (SCV). I don't know if your engine has that but it may be a pointer for you to investigate.

As for the EGR, a sticking valve was a fairly common occurrence with that engine, it would lose power, run erratically, but only when the engine warmed up. The remedy on that engine was to remove the valve and clean it.
Regards

Hi, thanks for your reply,

Do you mean a suction control valve? If so a Google search suggests the Ducato does have one, thanks for the heads up on that. I’m waiting for a blanking plate for the EGR valve to arrive if that cures the problem I’ll get the Egr removed and cleaned up, if not I’ll move on to the next least expensive thing would would be the suction control valve then the damp fuel injector.

 

[Anthony489]

Hi

If I have got things right, the "Suction Control Valve" (SCV) in Fiat-speak is the "Fuel Flow Rate Regulator", a solenoid valve under the control of the ECU which adjusts the input pressure to the high pressure pump according to engine demand. Presumably the ECU sends a varying pulse width to the valve to allow it to open at regular brief intervals.

 

[Ducatomick1988]

Hi

If I have got things right, the "Suction Control Valve" (SCV) in Fiat-speak is the "Fuel Flow Rate Regulator", a solenoid valve under the control of the ECU which adjusts the input pressure to the high pressure pump according to engine demand. Presumably the ECU sends a varying pulse width to the valve to allow it to open at regular brief intervals.

If it was something to do with this valve and it’s in connection with the ECU, would it not though up some fault codes or warning lights?

 

[Anthony489]

Hi

There is no direct feedback to the ECU from the Fuel Flow Regulator, so if the solenoid coil and wiring is intact the ECU has to "assume" that the fuel control part of the regulator is doing what it is told. Its behaviour will affect the high pressure in the common rail, which is monitored by a separate high pressure sensor. I guess if the high pressure is too far out of spec it will trigger a fault code/warning. Minor deviations may not be serious enough to trigger this, but could still have an adverse effect on idling/running. This is only my educated guesswork, if anyone knows better let's hear from you !

 

[Womo793]

I'm sure the technician called it surge but it sounds like the same thing.

With the d4d engine, the EGR valve was fed by coolant pipes so it only operated when the engine was up to temperature, this aided the diagnosis. The problem caused by a sticking valve didn't occur when the engine was cold. If I remember rightly it was less than an hour to take it of, dismantle, clean it and put it back on.

I would agree with the point Anthony makes, the ECU may well be able to sense the electrical load presented by the coil, and if it within the expected range it will energise it as normal. But I don't think a fault in the mechanical function of the vavle could be sensed in the same way.

 

[chaaarlieee]

Hi mate, did you ever get to the bottom of this? I've got the exact same idling issue. I have found the measured values state that tge air flow measured is alot higher than the air flow target, I've replaced the MAF and checked all wiring all OK. I've blanked off the egr however when I unplug the vacuum valve for the egr the faults does go away so this is making me think the egr is at fault?

Wondering if you ever found your fault?

Thanks

 

[Ducatomick1988]

hi mate, I haven’t sorted it yet,

Hi mate, did you ever get to the bottom of this? I've got the exact same idling issue. I have found the measured values state that tge air flow measured is alot higher than the air flow target, I've replaced the MAF and checked all wiring all OK. I've blanked off the egr however when I unplug the vacuum valve for the egr the faults does go away so this is making me think the egr is at fault?

Wondering if you ever found your fault?

Thanks

hi mate, I haven’t yet, I thought I fixed the issue I noticed a small hose was disconnected from something just under the windscreen that went into the Egr valve, I also removed the MAF and sprayed in some carb cleaner into the intake at 2000rpm for a while, the problem then went away for a month so I assumed it was due to the small disconnected hose/tube, but recently the problem has started again so im not thinking it’s a blocked Egr and the cleaner worked for a while.

I’ve purchased a blanking plate but haven’t got around to fitting it yet. When you fitted yours did it throw up any fault codes? I was told it would so would have to get a remap that would electronically bypass the Egr after it’s been blanked so stop any fault codes.

 

[Ducatomick1988]

Hi mate, did you ever get to the bottom of this? I've got the exact same idling issue. I have found the measured values state that tge air flow measured is alot higher than the air flow target, I've replaced the MAF and checked all wiring all OK. I've blanked off the egr however when I unplug the vacuum valve for the egr the faults does go away so this is making me think the egr is at fault?

Wondering if you ever found your fault?

Thanks

Hi mate, did you ever get to the bottom of this?

 

[chaaarlieee]

Hi mate, did you ever get to the bottom of this?





Still no luck, I'm looking at it again this week, what about yourself any luck?

 

[Ducatomick1988]

Hi mate, did you ever get to the bottom of this?





Still no luck, I'm looking at it again this week, what about yourself any luck?

I’ve put a blanking plate in the EGR Vvalve but the problem is still there. My next course of action was going to be the fuel pressure sensor and fuel pressure regulator, but if you click on the YouTube video I shared at the start and read the comments someone has just commented and seem pretty certain what the problem is. So I’ll try his suggestion when I return from work in a couple of weeks, might be worth trying what he says also

 

[LandyAndy]

The black unit with the small pipes attached is the egr solenoid and allows a vacuum to pass through it, that then opens the egr. The system also alters the the air intake flap whilst it is operating, or “thinks” it is operating the egr. Disconnection of the egr vacuum solenoid is often to deal with a failed, misbehaving, throttle body, which appears to be a very common issue if you have the older style part, which was soon updated due to issues.

 

[bugsymike]

Did you sort the leaking injector?
Even a small leak of fuel out, can let air in and diesels hate air in the fuel system.
It would have to be a very small leak, as modern common rail diesels only operate at extremely high pressures so normally any leak would shut the whole engine down.

 

[chaaarlieee]

@Ducatomick1988



Where I'm at..



Blank of EGR no fix



Replaced EGR control valve (pressure convertor valve) no fix



Noticed I had no vaccum on the pipe from the vaccum pipe to the control valve (Connected by a black T piece)



Saw your video and the comments so looks for a blockage, couldn't see anything, removed the pipe, clear out as much as I could, refitted, now have a vaccum to the ci trolley valve, van is running better but still not 100%, my assumption is there is still a partial blockage or a valve within the T piece has failed, I have ordered a new pipe from fiat £40 I'll let you know how I get on. Definitely worth checking if you've got a vaccum there, just pull off pipe and start teh engine you should feel it 'suck'