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> Rough idle after engine rebuild
donutty
post 19th April 2019 17:49
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As those who have been following my misadventures may know, the purple wonder recently suffered from a blown head gasket. This has been replaced, the head skimmed, all engine rebuild service parts renewed (bolts, other gaskets etc) and now all 4 cylinders are fine and no oil/water contamination, water blowback or nasty smoke.

But now we have a bad idling problem. It was kinda evident before the gasket issue but not as bad as this.
At first from cold the engine hunts erratically on idle. Giving throttle is smooth and no hiccups there. Returning back from throttle to idle, as it slows down it is gradual and smooth but then when at idle back to hunting. After warming up for a couple of minutes the hunting is consistent like a bass drum beat.

Things tried (while running):

1. Unplug MAF = gets a little bit better (less clumpy but still very not right)
2. Unplug ICV = no change. Sprayed inside with carb cleaner. Noticed it rattles when had it removed, like the plunger is free moving inside, not held by a spring. New gasket as part of service kit
3. Unplug variator solenoid = no change. Didn't think the variator is in play when at idle anyway.
4. Unplug crank sensor (brown) / cam sensor (blue), cant remember which one was unplugged = kills engine (I guess crank). Other unplugged made no difference
5. Unplug lambda sensor = no difference

Also, exhaust fumes are quite strong; unburned fuel = Air mixture too lean??

OBD shows nothing, apart from all the errors from when we were unplugging the sensors with the car running. After clearing errors nothing shows even after minutes of bad idling.


Anybody got any clues? Is this a typical 'sensor x' problem? Otherwise, this may mean more hundreds of quids shotgunning sensors until I find the one that causes this.

This post has been edited by donutty: 19th April 2019 17:51
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JeremyG
post 20th April 2019 22:28
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Can you describe the hunting (rev range, timescale)?

A couple of thoughts:

- Did you check the inlet hose for air leaks between MAF and throttle body?

- Re. the ICV, if it makes no difference when you disconnect it, that could mean it isnít working. When you removed it, did the valve drum rotate freely? Did you check the ICV resistance values as per the manual?

- On the sensor side, and especially since you mentioned potential over-fuelling, have you checked the temp sender to the ECU (Iím thinking of Danteís recent post re. his temp sensor issues)? If you can trace the signal from the sensor you might even find it is cycling in sync with your idle hunting. MultiECUScan will allows you to track a parameter over time like this.

- You could also track MAF readings this way too.

Hope that helps...
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Ganz
post 21st April 2019 19:51
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Take the ICV out and clean it out with some cotton wool and carb cleaner. Make sure it's clean of carbon deposits etc. My icv needed this treatment but mine would hunt when the engine got hot not cold. Air intake manifold ok and inlet manifold rubbers not cracked?


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dante giacosa
post 22nd April 2019 04:27
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and did that nail it Ganz?

The ICV was affecting the car hunting at hot..?
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donutty
post 22nd April 2019 06:27
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Thanks everybody, all suggestions will be considered. Just to confirm, the hunting at from cold idle is erratic and as the engine warms up after 2 to 3 minutes it becomes more rhythmical - you can see the engine throbbing to the beat on it's mounts. When accelerator is pressed it is smooth and hums along nicely, it just won't idle nice.

This post has been edited by donutty: 22nd April 2019 07:06
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donutty
post 22nd April 2019 06:53
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All air intake hose seems airtight. The ICV vanes were resting in a middle position so you could see half of the curved metal flap and it could be poked either way. I guess this makes sense. I am going to read up again about the cleaning of the potentiometer tracks in the valve assembly and see if it makes sense to attempt that procedure. I am thinking of the right thing, yeah? There was a Russian web page that described the opening and cleaning in detail... or was that the throttle position sensor??

Also, daft question, maybe, but not having the aux belt connected thus no alternator and a diminishing strength battery is making the system not happy with low voltages?

I am heading off soon to do more probing poking cleaning and head scratching so hope to at last come back today with some hard evidence

This post has been edited by donutty: 22nd April 2019 07:00
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dante giacosa
post 22nd April 2019 07:31
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er-

running without the alternator is going to be a constantly diminishing state-of-run until the car can't generate the voltage to either start or develop spark to fire the cylinders.

So yes; that's not going to run in the healthiest manner- you should disconnect the battery in-between tries, donutty- and try and charge it in-between times.


I'm surprised to hear that you could move the ICV vanes..? I would have expected it to be reasonable 'fixed' in the adjusted position...
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JeremyG
post 22nd April 2019 10:12
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QUOTE(donutty @ 22nd April 2019 07:53) *
All air intake hose seems airtight. The ICV vanes were resting in a middle position so you could see half of the curved metal flap and it could be poked either way. I guess this makes sense. I am going to read up again about the cleaning of the potentiometer tracks in the valve assembly and see if it makes sense to attempt that procedure. I am thinking of the right thing, yeah? There was a Russian web page that described the opening and cleaning in detail... or was that the throttle position sensor??

Also, daft question, maybe, but not having the aux belt connected thus no alternator and a diminishing strength battery is making the system not happy with low voltages?

I am heading off soon to do more probing poking cleaning and head scratching so hope to at last come back today with some hard evidence


The Russian web page re. potentiometer tracks was for the CF2 plastic-top motor... from the age of your car and your previous post (re. removing the ICV) yours is a CF1 alloy-top motor, right?

But it does also have a separate throttle position sensor - resistance details for the TPS and the ICV are in the workshop guides to give you something to test against.

See the pic below - this is as seen from the bulkhead side - ICV on top, TPS below on the right.

Attached Image


If you need one, I have an ICV you could test with (I bought it second hand when mine was playing up but never fitted it. The valve drum moves very easily, however.)

This post has been edited by JeremyG: 22nd April 2019 10:18
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donutty
post 22nd April 2019 10:36
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Reporting live car-side...

Aux belt is being fitted to get it charging again and I have had the throttle body off and gave it a good clean. I'll not remove the TPS as it is attached to the big vane and don't want any springs boinging out. I'll check the resistance on both the opening and closing coils of the ICV, which has the spring loaded vane in the middle position. It can be moved either side with a light poke of a screwdriver tip and returns to centre with poke pressure off.

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donutty
post 22nd April 2019 10:50
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OK, TPS readings are opposite of what the docs say.

I read correct 2k between pins 1 and 2 when at rest, but 1.1 at full open and 2.7 at closed when tech manual says 2.7 for open and 1.0 for closed..

I guess they just got it wrong way round in the paperwork. Wouldn't be the first time...


Couldnt find specs for ICV to hand but I measured both pin 1 and 3 to, guessing common is 2 centre pin and either side coils to fully open or fully close are 1 and 3. 1 to 2 and 2 to 3 both 0.012 ohms or thereabouts, which seems OK

This post has been edited by donutty: 22nd April 2019 12:43
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JeremyG
post 22nd April 2019 13:04
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Do you have a diagnostic tool that will allow you to trace ECU parameters?

eg for MES you could track these (FYI this is just dummy data):

Attached Image


This post has been edited by JeremyG: 22nd April 2019 13:05
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donutty
post 22nd April 2019 13:17
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Did the secret throttle reset procedure and great idle after the first 10minute blast. Left to cool for an hour and a bit and upon next start back to being lumpy

This post has been edited by donutty: 22nd April 2019 15:34
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donutty
post 22nd April 2019 19:25
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OK, so. I thought I was on to a winner with the reset / learning procedure. I guess all I did was warm up the engine. When bedded in for 10 minutes it idles fine but on cooling down after ignition off for an hour its back to it's old tricks.

I have ordered a KKL cable for MultiEcuScan and will hopefully be able to see some numbers. My dad has a decent OBD system but does loooads of ECUs and does not support live data read of the Bosch 2.10.4 which is in my CF1 car. As suggested, I agree that I need to be able to plot some graphs and see some real-time values to make sense of what is going on.

@JeremyG - hold onto that ICV.. I might need it at some point!!
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JeremyG
post 23rd April 2019 10:19
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QUOTE(donutty @ 22nd April 2019 20:25) *
@JeremyG - hold onto that ICV.. I might need it at some point!!


No problem, I will do.

BTW - how much did you spend having the head skimmed? And did you get anything else done at the time - valves reseated, replacement seals etc?
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donutty
post 23rd April 2019 11:49
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QUOTE(JeremyG @ 23rd April 2019 11:19) *
No problem, I will do.

BTW - how much did you spend having the head skimmed? And did you get anything else done at the time - valves reseated, replacement seals etc?


I think the skimming was around £75. The valves have all been lapped and new stem seals fitted. All gaskets used were good quality Payen (bought the full kit).
Had a bit of problem at first with the hydraulic adjusters not compressing fully but they worked themselves out.

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JeremyG
post 23rd April 2019 15:53
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QUOTE(donutty @ 22nd April 2019 11:36) *
I'll check the resistance on both the opening and closing coils of the ICV, which has the spring loaded vane in the middle position. It can be moved either side with a light poke of a screwdriver tip and returns to centre with poke pressure off.


I've just had a look at my spare ICV... and with mine (and also with the one that's currently on the car) the resting position for the shutter is to one side, not central - from this view.

In the pic below you can see the shutter is partly obscuring the right hand hole - and by using a small blade you can move the shutter to the left, obscuring more of the hole.

The way you've described yours sounds different...?

This post has been edited by JeremyG: 23rd April 2019 15:54
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donutty
post 23rd April 2019 17:37
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QUOTE(JeremyG @ 23rd April 2019 16:53) *
I've just had a look at my spare ICV... and with mine (and also with the one that's currently on the car) the resting position for the shutter is to one side, not central - from this view.

In the pic below you can see the shutter is partly obscuring the right hand hole - and by using a small blade you can move the shutter to the left, obscuring more of the hole.

The way you've described yours sounds different...?


Your pic is invisible!

Here's mine...
Attached Image


As you can see at rest the vane is half open half closed. It can be opened more by poking the vane from the left hand side moving it to the right. Also does yours rattle?

I forgot to mention before, but I don't know if its this ICV that is making a repetitive clicking noise in the first 10 seconds of a cold start. When the engine is started, I can hear a sporadic click click...click click click...click...click...click click type of thing and then it stops clicking. If it is faulty maybe the ECU is trying to make it move one direction and it isn't responding and it doesn't see the change it expected in engine performance and tries a few more times and gives up?

Not sure. Can't exactly pin-point where the clicking is coming from but its around the air intake plenum / manifold area (i.e. right hand back side of the engine bay).

One thing that puzzles me about this vehicle is despite all it has been through (head gasket + this), it has never offered up an engine management warning light on the dash! What will it take to make it officially complain!?

This post has been edited by donutty: 23rd April 2019 17:45
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JeremyG
post 24th April 2019 03:17
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Ah yes, I forgot to attach the picture - here's mine (so same as yours):

Attached Image


The resistances should be as follows (from the Motronic 2.10.4 manual):

Attached Image


The readings I got on my spare ICV were:

Pins 1-3: 32.6 ohms
Pins 1-2: 17.1 ohms
Pins 2-3: 15.0 ohms

... which is about right.

My ICV also rattles (if you shake it "vertically", in the orientation of the picture above).

On the clicking - MES has a function whereby you can test the operation of the ICV. It sends an open/close signal which is audible as a series of clicks. Might be worth trying this to see if the noise is the same as the one you're hearing?

On the engine warning light - I'm assuming it comes on when you turn the ignition light on, right? And when you were triggering all of the sensor errors above it must also have been coming on, surely???

Finally - if you suspect your ICV and you want to borrow my spare, then let me know and I'll post it up to you...

This post has been edited by JeremyG: 24th April 2019 03:33
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donutty
post 29th April 2019 10:11
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I managed to do a bit of investigative work on Sunday - car started and idled properly from cold (~12C) and after a 5 minute run idled lumpy (rhythmically). Then went for a 10 minute run to warm up more and idle was fine. So there is a temperature range where the idle problem manifests?

After battling with my new Toughbook + MultiECUScan + KKL dongle + OBD2 to Fiat 3-pin adaptor setup, (short story here as it might help others)...

Could not get the damn thing to connect to ECU (leftmost diagnostic plug in the engine bay) but did get some life out of the ?ABS? CU - right hand side, I finally figured out that the ECU connector only had 2 wires and the ABS had 3 - the 3rd (blue + white) was power. Strange that the ECU didn't have this. That is what the 2 crocodile clips on the OBD to Fiat adaptor are for - Red to Battery+ and Black to Gnd,


MultiECUScan could then connect to ECU and we could read the parameters!

I did a minute or so of logging with rough idle and then after the extra 10 minute warm up and good idle got another chunk of data which I still have to analyse.
Some graphs n stuff to follow later today / tomorrow..
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donutty
post 30th April 2019 09:06
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OK, I did a poor job at remembering which set of data was for what condition, but I think this is the rough idle after a short 5 minute drive:

https://docs.google.com/spreadsheets/d/e/2P...mat=interactive


And Chart 2 is better idle after a longer 10 minute drive:

https://docs.google.com/spreadsheets/d/e/2P...mat=interactive


I will repeat the tests this weekend and properly note down what the condition is so we have some reliable data.
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