Bouncing Idle revs during warm-up period

[wickedwillie]

All, I know this has been covered before but during these threads, the initial thoughts on culprit were fuel pressure regulator valve. However, reading further into these threads, when replaced, some still reported the same fault, therefore, all in all, was inconclusive. So, just starting this thread as a work in progress

So to my car: - 2.0 DTH, 2013, 67k mileage. First became aware of this about 6 months ago (circa 60k miles) but only for part of the warm up period and otherwise, the car drives perfectly - and it is still the same today.

I finally managed to get my op-com working in Windows 10, therefore do not now have to swap images with Windows 7 on my laptop (much more convenient for me now) and therefore decided to capture some engine data on Saturday from a cold start.

Data: -

No Fault codes stored on any of the car modules.

Foot totally off the accelerator pedal at all times during this test.

When the engine coolant temperature is below 18C, the idle is rock steady stable and always pretty darned close to the desired rpm but as soon as it reaches 18C, the fluctuating revs begin (between +50 rpm to -50 rpm of ECU's desired rpm) - from the data,you can also see the engine load fluctuate and the MAF data fluctuate in harmony with the different engine demands. As the coolant temperature rises toward 25C the idle steadies again and just as the glowplug command switches to off (I think they are in the 'afterglow' period at that point), the idle is once again rock steady and will be until the next cold start cycle. It is pretty repeatable that the rough idle begins spot on at 18C and evens out at Glowplug off point (i.e. does not look to be time related but rather temp related).

That is much as I have done thus far and fast becoming an old bugger, I like my creature comfort in the cozy house rather than be out in the cold, so unless this develops into a driveability problem I cannot see me doing much more until warmer days.

I wonder though, if one or more of the Glow Plugs is going slightly out of spec and demanding incorrect engine load. I did check the engine pressures with OP-COM when the engine was hot and they are fine, maybe will do the same check when it is going through this problem temperature range and see if it gives any cylinder imbalance.

[MJSROOFING]

First thing I'd be doing is putting a multimeter over the heater plugs.

[wickedwillie]

Yes, thanks. I will do that at some point.

Its like a specific event which happens at that particular engine temp (you can feel something kicking-in as the engine note changes and the wobble begins). So, I have just had another look at the captured data and what I noticed was that just half a second prior to this effect starting, the intake airflow valve (whatever that may be) position starts reducing from 100% and the problem manifests when this reaches the 28% position. Its % continues to fall and by the time is reaches the 21% position, the revs have stabilised totally and it then remains at that 21% position until the accelerator is pressed.

Maybe on a complete wild duck chase but better than watching political posturing on TV IMO.

[lizzard-t]

Hello, dose your car start ok from cold ?
If so then the glow plugs are ok , the glow plugs will only light on initial start up , once started then they will go out
What have you done so far for this issue ? Have you replaced any parts yet ?
Simple things first .
Try cleaning the MAF and MAP sensor with some electrical contact cleaner. With the MAP use a cotton wool bud to clean around the probe , but don't poke it .
Remove the hose to the intake manifold, and get some MR mussel oven cleaner and spray in there , get a bottle brush and work it in and out a bit , then get some carb cleaner and spray in there to dilute the oven cleaner, use some paper towel and clean as much as you can out of it .
Remove EGR valve and repeat the process .
Of course wear suitable gloves when using thease products.
Then take the car for a bit of a run to clear out any dislodge carbon which will pass through exhaust system .

[wickedwillie]

Thanks for the reply Lizard. You raise a few points there so will take these one at a time.

Glowplugs: - I am sure they do work for a few minutes after initial start up (and my recorded engine data supports this), when engine stone cold. They have an initial white hot phase to aid the engine start up, then they are pulsed on and off until a pre-determined temperature point is reached (usually in UK climate anywhere up to 4 minutes) to aid in the cold running scenario. The pulsed phase, if I remember my theory correctly, is sometimes called the 'afterglow period.

No parts replaced. It is just a niggle at the moment but past experience tells me that niggles can develop into larger problems with the passing of time. I am not the sort who usually throws money at my car without trying to understand some of the issues. You win some, you lose some but that is me.

The other parts you mention seem logical steps and when the weather improves (spring or summer) I will tackle these (unless it develops into a show stopper).
But from the recorded engine data alone, it could be feasible that the problem is linked to the throttle body mechanism (contamination?) or inlet manifold sensor (as you have eluded to). Its many years since I last played about in this area and that was petrol normally aspirated engines so am trying to establish just how the throttle body butterfly works in a diesel i.e. is it simply there to restrict the airflow during warm-up periods. If this is the case, then it may become sticky with the passing of time and from the oil misting air coming out of the intercooler from the turbo.

[minisprint4230]

Will work similar to a choke, so if it is fluctuating, air flow will go up and down.

[wickedwillie]

Thanks for that. The actual engine RPM is definitely tracking the desired RPM, homing in on it constantly but between the coolant temperatures of 18 to 31 C, this has a marked variation between + 50 and - 50 RPM, whereas at other temperatures, the variation is negligible. As I said up-front this is a work in progress for me so will update this thread as and when I have any more information. I have seen this problem reported quite a lot on the web but I can see no real concrete conclusion as yet.

[minisprint4230]

Once you have eliminated mechanical issues with valve you need to find what controls it.

[Butt0ns]

My Biturbo does the same, you have shed a lot of light on the issue, thank you.

[wickedwillie]

Update: - Had waited for the car to do its normal regen before performing this so I knew the starting point.
I warmed the engine up, disconnected the turbo inlet pipe and slowly sprayed 150ml of EGR cleaner into the air intake system as the car idled. Put it all back together, cleared the MAF code (which I had caused by running with the pipe disconnected) and took it for a drive. Certainly felt a bit more responsive.

I have been monitoring the idle revs at warm up since and; although the needle still begins to bounce when the engine coolant temperature reaches 18 degrees, it now appears to stabilise much quicker at about 22 degrees. I maybe will run another can of EGR cleaner through it in the next few weeks but just want to monitor to see if this is a constant improvement (it seems to be so far).

The EGR cleaner must have done something (dumped crap into the exhaust) as my DPF regen intervals are always between 300 to 500 miles but this one has happened after 100 miles (and that is 50 miles since introducing the EGR Cleaner).

Whilst I fully realise that this in no way will be as effective as physically dismantling and cleaning, for a tenner, worth a try as an interim measure IMO.

[wickedwillie]

Pre-EGR cleaning graph

Hopefully this has attached (1st time I have attempted to attach anything to the forum in years). This is the Opcom captured data of the troublesome warm up phase and prior to me running any EGR cleaner through the air intake.

The vertical axis is engine load (throttle at 0% i.e. the engine ECU is controlling this without input from me) . The horizontal axis is engine coolant temperature. You will note that all is normal until the coolant temperature reaches 18 and then the engine load starts to hunt (this corresponds with the RPM hunting at + - 50rpm) and settles somewhere when the coolant temperature gets into the low 30s.

I will try and capture the same data again but this time it will be after running through a can of EGR cleaner and see if there is a difference. It certainly feels now that the bouncing revs settles down at approx 22 degrees.

[gaundvd]

Insignia B 2.0L on start up revs at 1000 after about 1/2 hour driving will return to about 800. If I turn on the heater it will then put the revs back to 1000 at idle. Why does it do this anyone know

[gaundvd]

Forgot to mention I’m only getting about 30 miles to the gallon and a slight vibration running through the car whilst standstill

[lizzard-t]

Hello. This thread is about the insignia A .not the B as yours is .
but how long at idle are the revs at 1000 rpm before you set off in the morning?
your is a diesel, and especially if you have consumers on ( ie headlights ,heater air con then the revs will., be higher due to the fact that there is a lot of load on the alternator ,the alternator load is monitored by the cars ECU which will adjust the idle speed to compensate
so in theory the more load the harder the alternator has to work to put back into the battery what is being taken out by the consumers.
the biggest consumers are
Heated rear screen
Air con compressor
Heater fan on full





56-345555555 roofing felt !

[wickedwillie]

Hi all, I promised an update on this issue when I had something significant to report but due to working at home since March 2020 and car only covering a couple of K miles since 2019, I did nothing to it and the idle remained bouncing as described earlier in this thread. However, a couple of weeks ago, I had the SVS message pop up and OPCOM'd it, which pointed me to number 2 Cylinder Glow Plug Circuit. So out with the multi-meter and Glow plug number 2 was sitting at 987 ohms, all others were less than 1 ohm. So I replaced the duffer (pressure sensors on all 4), low and behold, the bouncing revs during warm-up are now gone. I have purposely waited for 7 cold starts before reporting this to ensure consistency. I can only assume the resistance of this glow plug has been high for some time but not high enough to trigger an SVS until now.
So, my advice to anyone suffering bouncing revs at warm-up, check the resistance of each glow plug.