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VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old March 11th, 2016, 18:29   #1
jorioux
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Default [video] ALH Rough idle, IQ jumping around

A couple of months ago I noticed a rough idle with RPM jumping from ~880 to ~930, and IQ jumping from 6 to 8 (see video), but it was only occasional.

But this week, whenever Im idling, its always rough! Except when I give a quick blip on the throttle, the idling returns to normal for a couple of seconds, then its rough again.

Whenever I apply throttle, its all smooth. The rough idle only starts a couple of seconds after being idle.

On the video, the rough idle starts suddently at 15 seconds. You can also hear it, and inside the car, it shakes a little bit.

VIDEO: https://goo.gl/photos/BCafRcTeTgraArsf8

In case it might help, here is another video showing the MAF values: https://goo.gl/photos/VZXWmGzZJPRKG8vi6

Last edited by jorioux; March 11th, 2016 at 18:35.
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Old March 11th, 2016, 18:55   #2
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Can't watch the video (don't have the bandwidth), but this seems to sound like a failing IP or some bad wires in the IP wiring harness.

Search around for a thread by "ILL_NAMED," he had a VERY lengthly battle with a similar situation and it ended up being chafed IP wires inside his wire loom. These cars are aging and the wiring's insulation is breaking down.
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Old March 11th, 2016, 19:41   #3
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Yep, look for my thread. Look there first, before buying many parts like I did...
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Old April 3rd, 2016, 09:31   #4
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Sorry for the delay, but I think the cause is a leaking injector. When I start the car, there is white smoke from the exhaust.

Do you think that could be the cause of my rough idle?

Last edited by jorioux; April 3rd, 2016 at 09:54.
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Old April 3rd, 2016, 14:20   #5
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I doubt it. That is either your timing off or one or more of your injectors leaking down into their cylinders while the car sits for a while. If the timing is off, I'd think that it would start rough.

Did you check the wiring?
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Old April 3rd, 2016, 15:09   #6
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I did check for any wire damage to the IP but everything looked fine.

I changed the timing belt at a vw specialist last summer. When I start the engine, it always starts instantly even during the winter.

I will check the timing with vagcom and post the results.

Last edited by jorioux; April 3rd, 2016 at 15:12.
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Old April 3rd, 2016, 15:29   #7
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Quote:
Originally Posted by Ill Named View Post
I doubt it. That is either your timing off or one or more of your injectors leaking down into their cylinders while the car sits for a while. If the timing is off, I'd think that it would start rough.

Did you check the wiring?
That's what I said, I suspect a leaking injector. How can I test my injectors?
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Old April 5th, 2016, 12:09   #8
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What's Group 013 look like? You may try to isolate via swapping around injectors to see if the problem follows the injectors or stays at the cylinders.

I'd still lean toward this being an IP issue. I think that if the injectors were messed up (or cylinder problems- low compression, that starting wouldn't be as brisk as you say it is).
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Old April 5th, 2016, 19:55   #9
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Quote:
Originally Posted by UhOh View Post
What's Group 013 look like? You may try to isolate via swapping around injectors to see if the problem follows the injectors or stays at the cylinders.

I'd still lean toward this being an IP issue. I think that if the injectors were messed up (or cylinder problems- low compression, that starting wouldn't be as brisk as you say it is).
Here is the video showing Group 013 (i opened the window so you can hear the random engine studder):
https://youtu.be/UTiRyJYdb5A

And here is the video showing the TDI-Timing graph:
https://youtu.be/WqEbP6dNmwY

You can also notice the camera shaking when the studder happens.
The issue is present whether the clutch is depressed or not, and whether the engine is hot or cold.

Though, I noticed the engine studders a lot more while im braking abruptly to come to a stop (ie.: stop sign or red light)

Here is a screenshot of the scan for CEL:
http://i.imgur.com/wcWCdbB.jpg

@Ill Named
I checked the wiring thoroughly, but if it were a wiring issue, wouldnt I get a CEL about implausible signal or short to ground? Honestly I really checked all the wiring running from the IP to under the battery tray. I even let the engine running while I wiggled all the IP wires one by one and nothing happened.

What should I do ?

Last edited by jorioux; April 5th, 2016 at 20:10.
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Old April 5th, 2016, 22:06   #10
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Yes, I think that you should get a CEL if there's a wiring issues.

Group 013 seems OK.

Timing, while moving around a bit, appears to be OK.

I noticed that you didn't have the engine up to operating temp. This is important.

Are your radiator fans coming on? (shouldn't given engine temp around 61, but I still want to know) My wife's car had this horrendous shudder at idle that took me the longest time to track down. Turned out the small radiator fan had a chunk missing from the outer ring. When that fan kicked on and you were at idle (our cars don't idle much, and here it doesn't get all that warm) is when it would happen.

Does this happen when idling and the engine is cold, cold?

IP temperature sensor?

ASV messing up?

Clutch?
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Old April 5th, 2016, 22:13   #11
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I had 4 wires rubbed through and no CEL. Your symptoms sound very familiar to mine, but you say you checked the wiring, so I guess that it can't be the issue. Pop the top off of the pump and check for schmeg in there. Pull the little case pressure relief valve and see if it is still in one piece. There is also another valve that is on the front of the pump that can only be changed by pulling the pump off, I can't recall it's name. But if it fails, it'll exhibit the same symptoms as you are having...
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Old April 5th, 2016, 22:20   #12
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Does it shudder while the car is moving? Mine would shudder and stumble when cruising at a constant speed, but was fine when accelerating.
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Old April 6th, 2016, 11:07   #13
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Quote:
Originally Posted by Ill Named View Post
Does it shudder while the car is moving? Mine would shudder and stumble when cruising at a constant speed, but was fine when accelerating.
As soon as my foot hits the throttle pedal, the engine stops studdering. Whether the car is cruising or accelerating, all is good, no studder at all. Even if I apply full throttle, there is not a single studder.

@UhOh, I don't think it's the fans because the issue happens whether the fans are running or not.

Also, the issue is present wheter the engine is freezing cold or after-30-miles-of-highway hot.

I will check the IP as stated by ILL NAMED

Last edited by jorioux; April 6th, 2016 at 11:17.
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Old April 6th, 2016, 11:12   #14
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How about starting by setting the IQ down to about 4? This is done with the hammer mod.
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Old April 6th, 2016, 11:21   #15
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Originally Posted by whitedog View Post
How about starting by setting the IQ down to about 4? This is done with the hammer mod.
I already adjusted it using VAGCOM, but it won't let me get the IQ to 4.

I will do the hammer mod this week and let you know about the result.
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