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Discussion Starter #1
My car: 2000 GLS 1.8T manual. Upsolute chip is the only engine mod.

It only started this winter... sometimes during full throttle acceleration in 4th and 5th gear, the car would hesitate or hiccup between ~2500 and 3000. Feels like something yanking backwards on the car, and it went away once you got past 3000 rpms. At first I thought it was something caught underneath the car, or maybe something getting in the way of the exhaust, which would cause the turbo to stutter. Then I thought maybe it was the clutch going, but the RPM's don't go up.

So I go easy for a while, and after a month or two it starts doing it in 3rd gear, too. And happening up to about 3300 rpm's. I switched my stock ECU back in for a couple of weeks, and no problems. Never hesitated. Now I have the chip back in and it's doing it again.

It doesn't do it all the time, just sometimes under full throttle in 3rd, 4th, and 5th. Most noticeable in 3rd and 4th, not so much in 5th. I looked at all of my vacuum lines, they looked fine. I opened up my airbox - everything is clean. No check engine lights. Changed oil about 3,000 miles ago. Looked over car when I was doing that, didn't see anything out of the ordinary. Ran bottle of BG44k fuel injector cleaner through - no change.

I have no idea what the problem with this car is, and I have no idea how to fix it short of buying new parts and swapping things out, like DV, vacuum lines, spark plugs. That could be a waste of time, though. Any thoughts?

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Update:

Well today something new happened. Car felt slower than usual with the chip in. Seemed to degrade slowly, not like a sudden BOOM and no boost. Car now feels like it is not chipped. Turbo is definitely working, I can hear it whiiirrrring, but its the whir it made when I wasn't chipped. After driving it around for a while, I got the dreaded "EMISSIONS WORKSHOP" light.

All of these things have to be related. I'm thinking I'll get a new DV valve and replace all of the vacuum lines. It sounds like it's worth doing it anyway.
 

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Some strange reason, N75-J valve seems to gotten rid of the slight hesitation feel. It's been awhile, but I believe the N75-J valve helped with this. At least, you'll get smoother turbo response, if nothing.
 

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Discussion Starter #5
Rusty said:
pancreas said:
diverter valve?
I second that.
Why though? From what I've read, a bad diverter valve makes noticeable noise. The car doesn't sound any different at all. And I thought the diverter valve only did its thing when you lift the throttle? Maybe its a bad wastegate dumping pressure before its supposed to?

That's the problem, there are just so many things that it could be. Swapping them all out would get too expensive.
 

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FWIW, I had this problem, and swapped out my DV this weekend. I do not think it fixed the problem.
Oh, and I'm not chipped. YMMV
jimbob
 

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This may be old school, but check the timing and total advance. I don't see any info. as to when you may have done a recent tune-up. That should be simple and inexpensive if you do it yourself 8) .
 

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RachaPassat said:
This may be old school, but check the timing and total advance. I don't see any info. as to when you may have done a recent tune-up. That should be simple and inexpensive if you do it yourself 8) .
Car is at 56,000 miles, so no "tune up" since 40,000 when I changed the spark plugs.

I don't know how to check the timing, though. Don't I need a timing gun?
 

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N75-J valve will help with the surge. For $65, it's worth a try.
 

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Triumph said:
Rusty said:
pancreas said:
diverter valve?
I second that.
Why though? From what I've read, a bad diverter valve makes noticeable noise. The car doesn't sound any different at all. And I thought the diverter valve only did its thing when you lift the throttle?...
A bad DV only makes noise if it is so bad that you should have replaced it a long time ago. If you have the OEM DV, and you're chipped, you should get a heavier-duty DV anyway, so you won't waste money if you swap out the DV. Use the "TT" DV, the "710" valve, or if you want to go even heavier-duty, get the "110" valve available at SAAB (and Porsche?) dealers:

Bosch 0 280 142 110, Saab 4441895 equivalent.

Either of these diaphragm-type valves should not cost you over $40.
 

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Triumph said:
PASSAT2001.5 said:
N75-J valve will help with the surge. For $65, it's worth a try.
it's not surging, its hesitating.

Hesitation will result from a surge in many cases. If you stabolize/smooth out your boost out put, then it will help with the hesitation from premature surge. From what you have described, it sounds like the case of premature surging or you're hitting a soft limp mode, but I wouldn't think you're current set up is capable of hitting 23 PSI to trigger that. Also, if your 2000 has AEB(?), then soft limp won't be an issue due to lack of boost sensor for your year model.
 

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Check all the hoses....especially turbo ones.

Ribbed VW hoses should be replaced at that milage....heck they should be replaced with 0 milage. Im talking about the little ones that come off the intake manifold. Check them....

Also not sure when you changed the spark plugs....or air filter.

BTW, my car does that too.....in 3rd gear....its like a backfire with no boom. Its common on turbocharged cars from what I understand.....might be wrong though.

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Discussion Starter #15
Checked hoses already. Did spark plugs and air filter at 40k. Again, I could go spending money swapping out all these components that it *might* be, but that's not the correct way to diagnose a problem. Time consuming and expensive.

But I probably should look at the DV first. That thing failing is so common that the odds are it could just be that.
 

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Triumph said:
Checked hoses already. Did spark plugs and air filter at 40k. Again, I could go spending money swapping out all these components that it *might* be, but that's not the correct way to diagnose a problem. Time consuming and expensive.

But I probably should look at the DV first. That thing failing is so common that the odds are it could just be that.
Well if you havent checked that yet...then the odds are it is that.

Do you have VAG....or know anyone that has it?

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Discussion Starter #17
No VAG. I could find one around here if I tried, but I haven't gotten any CEL's or anything. Does the computer ever throw codes and not tell you about it through the display?
 

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Discussion Starter #18
one more thing, my secondary air pump runs ALL THE TIME now after startup, for like 30 seconds to a minute, and the idle sits at 1200 rpm. it'll do this even if the cars only been sitting for 3 hours or so, so it isn't exactly cold. it used to only run at 1200 rpm idle when it was below about 35 degrees, and i never heard the secondary air pump.

i'm wondering if these are somehow related. like the problem causing the hesitation is also making the car think it needs to run the secondary air pump at startup. i dunno.
 
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