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Discussion Starter #1
Greetings,

I'm a member of the tdiclub forums, and have followed many of the excellent write-ups on this page. I have a problem with my 1996 Passat TDI that has me a bit puzzled...

I have developed a bad shake that comes about with certain throttle conditions, typically light-to medium throttle, regardless of gear, engine speed or vehicle speed. Sometimes when it's really bad it feels as though the whole engine is hitting its resonant frequency. I can always make it go away if I stomp on the accelerator, and can keep it smooth if I very gently let got of the pedal until I restore the desired throttle.

Within the same time frame, my idle has been getting rough (correlation is unmistakable). With my VCDS, I can see that my IQ fluctuates between 0 and 6 (or more). If I *slightly* give it throttle at idle and raise it to about 950 rpm, it becomes smooth and I get a solid IQ reading of about 4.0. I've played with the IQ range, both with VCDS adaptation and hammer mod, without any big improvements. My injector balance (Meas. block 13) reads out-of-spec numbers, and these numbers are different every time I check!

A bit of history:
326K miles.
Freshly-rebuilt IP from DFIS
Freshly re-balanced injector bodies with new Sprint 520 nozzles (I did this after my symptoms started, and this had no effect).
Timing belt replaced less than 10k miles ago (the new IP was installed at the same time).

Based on some write-ups I've read o this page, a bouncy IQ reading at idle points at either the IP or the ECU. But my IP has just been rebuilt, and my ECU shows no other signs of failure. Any help or insight would be much appreciated!

P.S. Sorry for the long post. I've been battling with this for months now and this is my daily-driver!
 

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My best guess: unknown electrical problem. Check all the wiring harnesses. Some places they like to break: the big group to the driver's side of the injection pump. There are a bunch of grounds there too. Look above the starter- a bunch of wires pass through there and a bad wire killed my injection pump which is why I have an injection pump swap article for mk3. Look under the air filter box. There is some wiring that likes to rub through there. And all the grounds.
 

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Discussion Starter #3
Thanks, that is certainly a good possibility. I'll check the harnesses and grounds thoroughly... certainly possible with a 15 year old car! I'll post back with updates.
 

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Just a quick "non-update" with a couple of more questions...

I actually bought a 2002 Jetta Wagon TDI since, so I've been in much less of a hurry to fix the B4. But I'm about to set some time to do this soon. In case all my electrical points check out fine, the pump rebuilders at DFIS offered to take a look at my pump as part of the warranty, so I may end up sending it back out to them.

Question about the IP removal how-to page: It instructs to remove the TB first. I was wondering if I could just as easily loosen the TB tensioner and simply slip the IP sprocket out? I realize the amount of belt going through the IP sprocket will still be "sandwiched" between the cam and crank sprockets, but I lack the first-hand experience to know whether this would make it difficult for the IP sprocket to slip out. Doing it this way would obviously save me tremendous amounts of time :eek:.

Thanks!
 

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Question about the IP removal how-to page: It instructs to remove the TB first. I was wondering if I could just as easily loosen the TB tensioner and simply slip the IP sprocket out? I realize the amount of belt going through the IP sprocket will still be "sandwiched" between the cam and crank sprockets, but I lack the first-hand experience to know whether this would make it difficult for the IP sprocket to slip out. Doing it this way would obviously save me tremendous amounts of time :eek:.

Thanks!
On the 2002? Yes, you can just slip it off. You still have to reindex the timing belt position but you don't have to remove the belt completely from the engine. The reason you have to remove the motor mount is because the belt is looped around it. In other words, you basically have to do a full timing belt job except instead of removing the mount to get the belt off you just leave the mount on but still have to reset all the TDC marks.

You can't just remove the pump and put it back on without indexing and resetting the other points.
 

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Discussion Starter #6
Thanks for the response. I actually meant for the 96 Passat... I realize I would have to index everything with the proper tools, but can I just slip off the IP sprocket without having to remove all the belts?
 
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