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Discussion Starter #1
Guys, sorry I had to use the 'Anna K./bump card,' but my post got buried 3 pages back within 24 hrs. of posting. I just gotta give it one more shot.

She's a '99 GIAC'd GLS. In first gear I'm only getting about 4-5 psi; don't know if this is norm as I never took note before (only gauged about 2 mos.). In second I typically get 4-5 psi, but can get 15-18 if I get the timing right... but for the majority of time she'll only give about 5 psi in 2nd. What type of boost is expected for a chipped 1.8t? Third, fourth and fifth I'm spiking up to 18 as expected. One thing that's blatantly obvious is that torque is veeerrrrryyy minimal, and boost comes on slow. I hear the turbo spooling, or releasing, or whatever the Whoosh indicates, but the butt dyno says the torque just ain't there. I used to get pushed back in the seat, to some extent, in practically every gear. And when I am able to boost beyond 5 psi (3,4,5 gears), the boost gauge needle almost seems to be moving in slow motion. Seems I remember it jumping rather quickly when I first installed the boost gauge, but now it seems laborious trying to generate boost. FYI, I recently installed new OE Bosch plugs (trying to remedy) as well as a new DV (Forge 006 to TT DV). Any thoughts or suggestions would be greatly appreciated.
 

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SmittyVIP said:
Guys, sorry I had to use the 'Anna K./bump card,' but my post got buried 3 pages back within 24 hrs. of posting. ...
Yet another dang good reason to have a technical forum...

Sorry but I can't help you with this - do you have access to a VAG-COM? It would help you pinpoint the problem. AA's stab at it is a good one, however, on a '99 you should have an AEB engine and I don't think there's any such thing as "limp mode" - I think that's a DBW exclusive. But I could easily be wrong.

I think she may be right about the N75 - if you are getting full boost, but it's coming on real slow (unless you get the timing right?????) that looks like a boost regulation problem. I would have guessed a leaking DV right off the bat, but you've swapped it out. Double-check your connections on both the DV and the N75. And all your vacuum lines - you could have a hairline leak somewhere that could be causing weird stuff.

Interesting that AA was the first to bite on Anna... (hee-hee!) :wink:
 

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Discussion Starter #5
Thanks for your feedback, Alex. I don't think it's going into limp mode, unless the progamming is smart enough to do so in selective gears. Once I get to 3rd gear the boost is fine (just no torque), but in first and second I can't boost beyond 4-5 psi. FYI, my car has gone into limp mode before and it prevented boost in all gears... not the case now. It is also my understanding that the '99 B5 doesn't have a boost sensor so the N75 valve is not what sends my car into limp mode. Thanks again, Alex.
SmittyVIP
 

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Discussion Starter #7
Thanks for the feedback Rusty. I've checked the connections on the DV, but I'll have to check the N75 connections. Now, are all connections to the N75 electrical, or is there a vacuum component to it? Not even sureI know where it is, but I'll find it. You mentioned boost regulation... Is it the N75 valve that regulates boost? Again, any and all feedback is much appreciated.
SmittyVIP
 

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Yeah Scuba, a few weeks ago I changed plugs (coincidence :???: ) and my car started cutting boost off at 4psi, whenever would generate over 12-13psi. This was true for all gears. I was fine as long as I didn't boost higher than 8-9psi. After about 40-50 miles of driving or 1-2 hours of sitting, I could generate more than 4psi... aslong as didn't go over 8-9psi. Well, I changed the plugs back to a set of OE Bosch plugs which brings me to my current situation: plenty of boost (although slow) in the high gears with no limping out, but nothing in low gears, with poor butt dyno results.

Maybe I'll try swapping N75 to see what happens. Just that finances are a little tigt right now, so I hoped to maye narrow before dishing out, more. Thanks again for the feedback.
SmittyVIP

Wow, when I checked my post this morning there were 38 peeks. Within 20 minutes of re-phrasing my topic title there have been 57 additional peeks. :lol:
 

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If you have a spark plug gap gauge, I would check the propper gaps for the plugs. If there isnt enough, or too large of a gap, then the plugs arent going to perform to the amount that they are meant to be used for. But dont ask me what the gap should be at, thats one thing I dont have.
 

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Lisa Simpson
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The boost is very load dependent. I have trouble hitting much more than 6-7 psi in 1 and 2 because the gears are so low.

Something is going on with boost regulation. Between Rusty and I, we are thinking the same thing, just not sure of why...
 

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SmittyVIP said:
... but I'll have to check the N75 connections. Now, are all connections to the N75 electrical, or is there a vacuum component to it?...
The N75 sits between the turbo nipple and the wastegate, connected by vacuum (actually boost) lines. It has an electrical connection to the ECU, and it sits in the turbo inlet pipe (TIP), with an opening into the TIP.

Now, I'm still fuzzy how a wastegate works - whether boost closes it or opens it. But somehow boost pressure from the turbo nipple is involved. The N75 regulates the wastegate by bleeding pressure back into the TIP according to the electrical signal sent by the ECU. And this is a cyclical phenomenon - the ECU is constantly, rapidly modulating the N75 valve to keep a certain level of boost.

So, other than the wastegate, the N75 is the number one control over your boost. (If the wastegate was bad, I think you'd either have no boost, full boost, or totally erratic, random boost). Which leaves the N75, or its connections, as the probable source of your problems. Unless your ECU has somehow got its programming jumbled, which is unlikely.

But having read your subsequent posts, I understand that all this started immediately after changing plugs. I think it is more likely that you have knocked or jarred something loose during the change, especially since putting the old plugs back in didn't cure the problem. Look careful for loose wires, kinked wires, vacuum lines, etc. that might have gotten "pinged" while changing spark plugs. For example - did you drop a wrench down the front pax side of the engine? It could have hit your N75 and knocked the connector or a hose loose, or actually damaged it.

atomicalex said:
The boost is very load dependent. I have trouble hitting much more than 6-7 psi in 1 and 2 because the gears are so low.
Hmmm... with my Dawes MBC I get 10-12 psi in 1st easy. :shock: and a solid 12 in 2nd :shock: :shock: Hmmm... the more I live with it and read about chipped cars, the more I like my MBC setup... :D

Oooo - views up to 320 now. I have to admit that it got my attention, although if I hadn't seen AA's tag as a post, I might have passed it up... Thanks, Kathy!
 

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What...NO pictures??? :mad: (view count now reads 398)

Rusty said:
...But having read your subsequent posts, I understand that all this started immediately after changing plugs. I think it is more likely that you have knocked or jarred something loose during the change, especially since putting the old plugs back in didn't cure the problem. Look careful for loose wires, kinked wires, vacuum lines, etc. that might have gotten "pinged" while changing spark plugs. For example - did you drop a wrench down the front pax side of the engine? It could have hit your N75 and knocked the connector or a hose loose, or actually damaged it...
Seriously, I'm with Rusty on this one...Like you, I've got a '99 and those braided horsehair and gum rubber (or whatever they're made of) vacuum lines are a must-go item! Replace them with some quality aftermarket vacuum lines and proceed from there. You might also want to check the condition of your wastegate actuator rod, N75, DV, etc. I think the wastegate problems of early 1.8T's was cured by '99, but it can't hurt to check.

:poke: BTW, Rusty loves his MBC...but I guess you already knew that!

Also...if you ever throw down the Anna K card again, you BETTER have at least a bad timing belt tensioner or a lunched turbo to back it up! Anything less and I'll ask the Mods to have you banned, keelhauled, or at least demoted to "Newbie"!
 

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Gimps Unlimited said:
False advertising!!! At least include a good picture of her.
here you go!
 
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