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VW MKIII-A3/B4 TDIs This is a discussion about MKIII-A3/MkIII Jetta/Golf (<99.5) and B4 Passats (96,97) TDI's. Non TDI related postings will be moved or removed.

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Old May 14th, 2018, 08:25   #1
Josh_WA
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Join Date: May 2015
Location: Mountlake Terrace WA
Default Excessive vibration at idle, AHU Eurovan

I've had my AHU (160K miles) swapped into my 93 Eurovan weekender for a few years now. I've always had what seems like excessive vibration at idle. It shakes the van through the floor, stick, steering wheel, doors, everything. Once underway, everything is great vibration wise and drives great. Pretty much once I get above 1000 rpm. I've just lived with it for the most part, after trying a number of changes to try and relieve the vibes, and since this was the first diesel engine I've owned. Late last year I built another TDI Eurovan, but with a 1Z (326K miles) and it didn't nearly have the same amount of shake at idle as my weekender. The 2nd van was built with little/less replacement of existing parts to the engine or mounts, so this has brought me back to seeing if I can figure out what I've got that needs replacement or adjustment on my current. The van builds are in my signature. Here's some things I've already looked at or replaced.



Mounts are all new

Single mass flywheel with no changes whether clutch in or out

I don't see any air in the fuel lines

Fuel filter is new

Harmonic balancer is new

I don't see any wobble or shake with any of belts or rotating shafts

The engine is not contacting the body/frame/firewall

Compression is 400, 420, 420, 400 on letting it turn over 5-6 times

I went from stock injectors with 170K to Bosio DLC 520 injector with no changes in vibration (power at the pedal went up though!)

K03 Turbo is new, but only because the original was leaking.

Injection pump doesn't appear to have ever been serviced, but the van starts instantly, and the IP is not leaking.

VCDS-
Timing is dead on the middle line, but jumps up and down to the next upper and lower line interval

IQ is 3.4, but theres not much change if I move it up to 3.8 or down to 2.6.

Injector values are 0.14, -0.21, 0.12 (bosio DLC 520)




So I'm open to any advise to help remedy some vibrations. Or if someone knows a trusted mechanic in the North Seattle area to look at the engine. Could it be fuel delivery in some way? Are there ways to test fuel flow or the IP? Its the last part to make this van perfect mechanically, to me. Thanks if you have some advise.

Last edited by Josh_WA; May 14th, 2018 at 11:54.
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Old May 14th, 2018, 19:28   #2
goose737700
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Fuel Economy: 43 summer, 46 winter
Default eurovan Vibe.

Hey Josh, we should get together and compare, mine vibrates as well at idle. I posted a similar question a couple weeks ago in regards to AHU vibration VS ALH vibrations. I cannot say I was entirely satisfied with the amount of answers i received as not many people are running around in '96 VW's anymore. But the general consensus was that they are a little more shakey.

Some days a little more than others, temperature seems to come into play as well as i think the solid rubber mounts are pretty stiff, not like AHU mounts which are a lot bigger and have more complex shapes built into them.
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Old May 14th, 2018, 20:24   #3
Josh_WA
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I’d love to meetup, but I’m in WA. I’d think that i could just put it to the engine having more vibes than newer engines, but mine seems to have gotten even worse as of late. I had another van that I converted also, and it wasn’t close to the same, although it still had some vibrations.

Again, I have put all new mounts on my white(I’ll call white). They are solid rubber, but that is standard. The 2nd van (red) I just put in with the old mounts it already had, and it was great. With twice as many miles on the engine. I tried putting in older mounts on white, but it just makes it worse. Its just shaking everything right now.

I’ll try pulling off the serpentine and power steering belt tomorrow to see if there is anything with the clutched pulley on the alternator. I don’t see the belt jumping at all but who knows. Does the tensioning arm require a particular torque rating of its hold on the belt?
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Old May 15th, 2018, 18:55   #4
Abacus
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Location: Nobleboro, Maine
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Default

No, the tensioner arm is automatic.

Taking off the belts is a good idea. While they're off, rotate the alternator and power steering by hand to see if they feel smooth or not.
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Old May 15th, 2018, 21:16   #5
Josh_WA
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Thanks. Tension arm seemed to have plenty of spring force. Rotated all the pulleys that would spin and all seemed smooth enough. Alt pulley held in the driven direction and freewheeled the opposite. Vibration was still there after starting the van with the belts removed. Then same when back on. So that area doesn’t seem to be an issue.

I don’t want to arbitrarily start messing with the IP, but it’s the only thing left. Any simple mechanical tests that can be done to test its health?

On another note, at least for my van, I’ll need an even stiffer mount on my drivers side. I’ve got an older mount in there and the torque of the engine is crushing it, causing it to have metal casing contact on acceleration in 1st and 2nd. I’ve got some newer mounts to put in there. Thinking about putting some extra urethane in one to get it real stiff. Probably be counter productive to my idle engine vibration.
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Old May 29th, 2018, 09:01   #6
Josh_WA
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I installed a T4b style drivers side transmission mount that's hydraulic as opposed to solid rubber. Pain to get in and had to elongate one of the tower holes for it to fit. My idle seemed the same outside of the van, but noticeably better inside the van. No more vibration in my seat, but the stick and steering wheel still shake quite a bit.

At the same time, I was preparing to run diesel purge, and had disconnected the fuel feed at the pump, but didn't end up having time. I reattached the line and noticed my fuel return line at the fuel filter was not tight. tightened that up and restarted the van. it was about the same as the test with the new mount. I watched a small segment of clear fuel line coming out of the fuel filter towards the pump and saw a good amount of air bubbles for a good five minutes. Does it take a long time to purge air after having the lines apart? I'm going to look later today to see if there are still bubbles going through. I had a good 100 mile drive yesterday and would think that all air would have been purged.

Any suggestions or methods to test the fuel lines for air ingress? I don't see any leaking fuel anywhere.
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