weirdbeardmt

Active Member
Hi all.

Car is a 2004 FL1 V6. On the whole it's brilliant. Full service history, no coolant leaks and no lights on the dash. No codes stored in the ECU.

There's a strange idle issue. The symptoms are that when you let off the gas and the engine revs drop, then you can see that it sticks a little returning to idle, then when idling, the power sort of dips off a bit every now and then, a bit like a misfire. It's strong enough that it makes the stereo speakers crack a bit!

After searching and reading a bit, I figured the IACV was most likely fault. Under the bonnet, the first thing I found was that the t-piece style engine breather that runs across the top of the engine had broken in one place. I've taped it up until I can get a replacement, but i don't think that's causing it.

IACV - have sprayed a decent amount of carb cleaner in to what I think is the right place on the IACV. See attached - is the highlighted pipe the right one? Do you squirt it down in to the pipe... or into the body itself? I did this, and it hasn't resolved it. Any more tips on cleaning this?

Other things I've looked at - checked the air filter - looks in good condition. Have checked all of the cables running to the coils and all look in good order. I pulled one of the more easily accessible spark plugs out and generally looks fine. All the evidence that the car has been maintained well over the years. The throttle cable seems OK - it's possibly a bit loose but the amount of play in it doesn't seem excessive. Have checked the top VIS motor and the actuator arm in the inlet manifold. Arm looks and feels solid. VIS motor appears fine. It is a bit noisy on tick over but not the usual death rattle.

A couple of other things I noticed - when the car was idling, and it had been running for less than 5 minutes, is that there's an obvious bubble in the expansion tank... and also the power steering tank. Is this normal? See attached for some videos. Another thing i noticed is that when killing the engine after idling, but without the air filter mech on, there's a big whoosh of air. (And on that subject, there's always a big whoosh of air when I open the fuel filler cap.) I think these things are all normal, but keen for thoughts - and of course, other things to look for / at?

Vid 1: Car idling, whoosh of air after https://www.dropbox.com/s/p16u4bb21fz45qy/IMG_1556.MOV

Vid 2: Car idling. Afraid the blip in power isn't really perceptible :(
https://www.dropbox.com/s/uaomqnnddxy0bpu/IMG_1555.MOV

Vid 3: Bubble in expansion tank
https://www.dropbox.com/s/1wmsnjvgnnflcpb/IMG_1505.MOV
 

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Can you post a picture of the broken breather and its location. The IACV does get clogged. Symptoms are normally low or erratic idle particularly after revving. It shouldn't cause any hesitation while driving as the valve closes as soon as the throttle is depressed. Opening again when the engine returns to idle.
 
Can you post a picture of the broken breather and its location.

See attached. Lines indicate the pipe. The circle is approximately where it has broken.

The IACV does get clogged. Symptoms are normally low or erratic idle particularly after revving. It shouldn't cause any hesitation while driving as the valve closes as soon as the throttle is depressed. Opening again when the engine returns to idle.

These are definitely the symptoms I have - goes away with power, and indeed, you don't see it when the engine revs are dropping. It's only when it's actually idling that it happens.

Did I put the carb cleaner in the right place then to try and clean it out? How liberal should I be with it?
 

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A split in the large breather won't upset the ECU so is no real cause for concern. It can allow a small amount of unfiltered air to pass into the engine but nothing more than that.
The pipe circled is where you can spray carb cleaner and or WD40. I use both with equally good success. You can be quite generous but use short bursts, repeated every few seconds. It spray doesn't fix the fault, the valve can be removed and cleaned.
 
Just a thought. The underside of the fuse box can corrode. This causes momentary power loss. I can't see how a sticking IACV can cause a problem with the speakers.
 
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The main fuse box in the cabin under the steering wheel?

No the engine bay fuse box.
Also check the wiring to the IACV. If the plenum has been removed in the past, very often the wiring isn't clipped back into place correctly. This can cause all manor of shorts on the wiring. This might explain your interference through the speakers.
 
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No the engine bay fuse box.

That's good, I was wondering how the one in the cabin would start to rot!

Also check the wiring to the IACV. If the plenum has been removed in the past, very often the wiring isn't clipped back into place correctly. This can cause all manor of shorts on the wiring. This might explain your interference through the speakers.

This was the first thing i did... unclipped it and reclipped and clean it all up. There was some crap in there but did seem to seat properly on the clip.

Will check out the fuse box later and keep digging.
 
OK, so this continues to torment me. As far as I can tell on the whole things are fine. But the engine is definitely down on power. The weird "crack" through the stereo only occurs when the engine is running (i.e., not with power on) so it definitely feels like it's electrical. The way it cracks, made me think maybe it's a short somewhere.

But then yesterday I noticed the MIL came on! Hurrah! Finally, I might get something. Hooked up the scan tool and the ECU is showing nothing :(

Connected to the auto gearbox and found two reported issues:

* P1605 - EEProm fault
* P1844 - Engine speed (RPM) sensor - incorrect signal

I'm going to hunt the forums now for anything similar, but again, if anyone's encountered this any intel would be great.
 

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Reading through various threads, tends to point initially at the loom for the gearbox...

This may arbitrarily make sense as it SEEMS the problem is more prevalent when the car is in gear rather than neutral.

And definitely worse in reverse.

Might pull apart the gear connectors and see what it's like.
 
I'm sure those faults are ones in the TCM (which can also bring the MIL on on later cars)

Ideally you'll need a decent oscilloscope and some ignition adaptors and try and measure the volts/amps on the coil on plug packs to determine if ones breaking one under load etc
 
Reading through various threads, tends to point initially at the loom for the gearbox...

This may arbitrarily make sense as it SEEMS the problem is more prevalent when the car is in gear rather than neutral.

And definitely worse in reverse.

Might pull apart the gear connectors and see what it's like.

Well worth giving the contacts in the box barrel connections a good clean. They can cause some odd faults. Bad electrical connections can cause some very strange faults.
I've just sorted out my fuel pump connections and filter that was causing all sorts of weird running faults.
 
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Pulled both barrel connectors apart this morning. The internals of the connectors look fine. The cables coming out the ends are a bit gunked up. Gave it all a decent soaking in ACF 50 and reconnected. Will check how it drives later.
 
There's not much on the forums about these two. P1605 seems to be a generic fault. P1844 looks more interesting - is the "engine speed sensor" a replaceable part?

No and yes! It's not part of the engine, that's for sure. I suspect it's referring to the turbine speed sensor in the box. This could well point to the barrel connections. One of our American contributors has just cured some weird faults caused by barrel connectors that seemingly looked in good condition. In manufacture a contract grease seems to have been used, this hardens with age, causing odd connection problems.
 

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