Startup "grunt"

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TdiRN

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2002 VW Jetta, 5 speed, 400k milesish
I've had this minor issue since I inherited this car last July. When I start the car in the morning (it starts fine) it will surge ever so slightly which I refer to as a grunt. It will "grunt" 2 or 3 times and that is the end of it.

Is this an issue, something I should be worried about?
 
eb2143

eb2143

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I have from a startup grunt too, especially before 7

I'd be inclined not to dive into it if it's been stable over the last year. Surging on startup (revs rising well above idle momentarily) is classically the injection pump fuel shutoff valve solenoid or the coolant temperature sensor on the ALH.

Most people don't refer to these as grunts, which makes me thinkmore that your car is stumbling a few times. A video might be helpful. Any correlation to engine temp or is it the same every time you start it?
 
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TdiRN

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eb2143 said:
I have from a startup grunt too, especially before 7
I'd be inclined not to dive into it if it's been stable over the last year. Surging on startup (revs rising well above idle momentarily) is classically the injection pump fuel shutoff valve solenoid or the coolant temperature sensor on the ALH.
Most people don't refer to these as grunts, which makes me think more that your car is stumbling a few times. A video might be helpful. Any correlation to engine temp or is it the same every time you start it?
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It only seems to happen on the first start of the day which is usually around 6:20 :) so the motor is dead cold.

I don't have any CELs or anything. And I guess I call it a grunt because its a diesel and the accompanying exhaust sound. If it happened in my other two vehicles I guess you would call it a mini surge. I guess I should not over-scrutinize as I tend to do with my vehicles as it is still running fine. I do like to be proactive though so if this were to be a sign of things to come I like to be on top of it.
 
UhOh

UhOh

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Maybe the initial crank speed is a little slow and when the engine fires it's over-compensating a bit.
 
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TdiRN

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Ok here is a video of what happens on a cold start. Hopefully the video works.

Edit. Well nevermind the camera didn't start apparently. I'll try to get one after work.
 
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TdiRN

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No its surging. Its gotten worse the last two days. Now it will do it when I start the car in the parking garage after work. It used to only do it first thing in the morning. It blows smoke in the morning. I'm going to try the diesel purge thing on saturday and if that doesn't do it i'm going to throw an MAF at it. When I first acquired the car from dad it had a CEL on and code for MAF. I replaced air filter and cleaned the snow screen, cleared the code, and it never came back. Maybe its just bad.
 
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gatz

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Just a thought, what was the MAF code for? I just thought because I sometimes start the engine with the MAF sensor unplugged, or the airbox completely removed when I'm in the middle of a big job. Then I clear it generated code afterwards. If the code didn't return possibly previous owner did the same thing.
 
bmwM5power

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Post up a video, i might have the same thing youre describing, interested to know what this might be as well
 
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TdiRN

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gatz said:
Just a thought, what was the MAF code for? I just thought because I sometimes start the engine with the MAF sensor unplugged, or the airbox completely removed when I'm in the middle of a big job. Then I clear it generated code afterwards. If the code didn't return possibly previous owner did the same thing.
Click to expand...
Previous owner was my dad. He doesn't work on cars - always took to mechanic/dealer
 
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TdiRN

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Damn it. Ok I'll try to upload it off my pc. Where is good place to host video?
 
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TdiRN

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Update: diesel purge didn't fix it
 
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TdiRN

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Rembrant said:
I just did a quick search and found this...
https://forums.tdiclub.com/showthread.php?t=413868
He posted a video as well, and it looks a lot like yours. Looks like an IQ adjustment cured his funky idle.
Have you checked/adjusted your IQ yet?
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It's at 1.4 I set it to 3.0 via vcds once and next morning it sounded odd when I started it so I set it back. And what u saw in that video is all it is. 10 seconds on pretty much first start.
 
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bmwM5power

bmwM5power

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TdiRN said:
Is this what yours is doing?
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Honestly i dont see a lot on that video, try to close the door so it doesnt chime so we can hear it. I will try to make a vid of mine and post it
 
UhOh

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Just about anything should run (esp at idle) fine with an IQ of 3.0. If 3.0 made it worse (scratch head) then I have to wonder what your timing is at.

Could there be an issue with the EGR valve? Have VCDS?
 
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TdiRN

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When I made that change to 3.0 and I started it the next morning the power was down and the clatter from the engine was much increased.
 
UhOh

UhOh

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I think that bumping the timing to around 50 (given a fuel temp of 160) should help.
 
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TdiRN

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UhOh said:
I think that bumping the timing to around 50 (given a fuel temp of 160) should help.
Click to expand...
This is back from the dead i know. But would changing the timing to 50 be a drastic change? This issue is still present for me.
 
BobnOH

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No, but it won't help, you're timing is fine.
Read post #1, but bit seems the issue has changed from a grunt after start to engine noise and low power?
 
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TdiRN

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It's still the "grunt" or surge. It does it for 5-10 seconds every morning.

The noise/engine noise came when I changed the IQ. I drove it for a mile pulled over at a gas station and changed it back.
 
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TdiRN

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IQ is 1.0-1.4. That cant be normal....
 
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eddieleephd

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I think you need to do the timing and IQ at the same time to match them properly.
Bump the timing up to the line after adjusting the IQ which is insanely low, which means over fueling.
I'm going to guess that your timing is causing the issue and the IQ is compensating.

Basically the surge is the ECM fueling to keep it running as the timing is to far down on the graph.
In my experience the IQ changes when I set the timing. I would set the computer default, 32765 if I remember correctly, and then set the timing to where it should be. Finally I would hammer mod it to the right IQ of 3 and then drive and adjust the IQ ONLY to the best setting.

You're fighting one aspect with the other and adjustment to one throws off the other, they're not in balance and it of spec together causing surge.
 
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