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Superbad
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Discussion Starter #1
The passed few weeks, i've been having issues w/ boost and my 99 1.8T going into some sort of soft limp. I know i know, rumor has it AEB's don't have LIMP MODE, but..... on a good day, i would spike 15-17PSI WOT, hold 15, and gradually taper down to 10PSI. Some days, it would only spike at 10-12, then hold 8-9. and on other days, it would only spike 7-8 PSI, and hold at 5PSI. It's getting really annoying.

Car in question: 99 B5 1.8T AEB FWD Tip.
ECU: 557P - GIAC 1.1 Bar Chip Flash (93 Octane) thru AWE-Tuning
DV: Forge 007p w/ yellow Spring (installed Normal Orientation)
High temp silicone: FPR to intake manifold, intake manifold to dv
Stock SMIC and Stock Turbo Inlet Hose
Stock Airbox: Mann German Paper Filter

Vacuum:
At startup - 21mmhg
Warm idle - 19-20 mmhg
after letting off gas/throttle will go down from wherever to 28-30mmhg
Turning AC on - vacuum drops to 10mmhg

Idle - between 800-900rpm

True or False ?

Hard Limp - No boost (if any 1-2psi)
Soft Limp - Some boost (5-10psi)

Things i've done:

Sparkplugs - NGK PFR6Q stock gap i think its .032
New ICM - HUCO
EGT/CTS - Coolant Temp sensor (Forrest Green updated from blue)
Cleaned Throttle body plate, clean as whistle, idles super smooth
Complete PCV system replaced: pcv valve, breather tube, check valves, puck valve, etc.
Fuel Filter - Bosch New
I took apart everything to check for leaks, could not FIND anything visually or hear anything.
Checked the L-Hose -GOOD
Checked the TBB hose - GOOD
Checked TIP - GOOD
Checked WASTE GATE ROD (to see if it has any play, NONE, hard to move)
Checked Coil Packs, still running stock - All are seated properly screwed, NO CEL or P03xx/misfire codes)
Unplugged N75, car ran like crap..Plugged it back in (took a couple cycles to get better)
Unplugged MAF, car ran like crap..Plugged it back in (took a couple start cycles to get better, but it did get better)

i wanted to PINCH the hose from the Waste Gate to the N75 Valve, but i dont have/cant find any clamps that could do that w/o tearing the hose itself.


Things i searched that might be the problem:

N75 valve (intermittent could be letting my waste gate to dump excess boost or not build at all)
MAF Sensor (could be getting wrong readings, but its not throwing a CEL)
Sparkplugs (might need to switch to cooler BOSCH FxxLR or NGK PFR7Q gapped at .028)
Clogged Cat (which i searched could be a reason, but wont pop a cel)
O2 Sensor (could be a reason, but it will pop a CEL right?)


What i need before i start purchasing parts, cuz i'm a not soo hood rich college student:

Anyone w/ a VAG-COM, local to 07080 that can lend a hand?

VAG-COM

Block 115 - need Requested boost vs. Actual boost

Block 032 - See how much ECU trying to adjust fuel trims

Block 003 - see what type of MAF readings im getting



Any thoughts, ideas, are welcome. TIA :salute:
 

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Hehe...hard limp...hehehehehe...

...beavith...

- - -

ANYWAY...the vacuum levels look normal, but FYI that doesn't actually indicate a lack of vacuum leaks because the throttle isolates the intake manifold from all but the largest vacuum problems everywhere else in the system. What you're experiencing, if it's consistent throughout the day as opposed to changing constantly during a single trip, sounds either like normal variations due to temperature, or else your N75 is wearing out.
 

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needs more cowbell
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The passed few weeks, i've been having issues w/ boost and my 99 1.8T going into some sort of soft limp. I know i know, rumor has it AEB's don't have LIMP MODE, but..... on a good day, i would spike 15-17PSI WOT, hold 15, and gradually taper down to 10PSI. Some days, it would only spike at 10-12, then hold 8-9. and on other days, it would only spike 7-8 PSI, and hold at 5PSI. It's getting really annoying.

Car in question: 99 B5 1.8T AEB FWD Tip.
ECU: 557P - GIAC 1.1 Bar Chip Flash (93 Octane) thru AWE-Tuning
DV: Forge 007p w/ yellow Spring (installed Normal Orientation)
High temp silicone: FPR to intake manifold, intake manifold to dv
Stock SMIC and Stock Turbo Inlet Hose
Stock Airbox: Mann German Paper Filter

Vacuum:
At startup - 21mmhg
Warm idle - 19-20 mmhg
after letting off gas/throttle will go down from wherever to 28-30mmhg
Turning AC on - vacuum drops to 10mmhg

Idle - between 800-900rpm

True or False ?

Hard Limp - No boost (if any 1-2psi)
Soft Limp - Some boost (5-10psi)

Things i've done:

Sparkplugs - NGK PFR6Q stock gap i think its .032
New ICM - HUCO
EGT/CTS - Coolant Temp sensor (Forrest Green updated from blue)
Cleaned Throttle body plate, clean as whistle, idles super smooth
Complete PCV system replaced: pcv valve, breather tube, check valves, puck valve, etc.
Fuel Filter - Bosch New
I took apart everything to check for leaks, could not FIND anything visually or hear anything.
Checked the L-Hose -GOOD
Checked the TBB hose - GOOD
Checked TIP - GOOD
Checked WASTE GATE ROD (to see if it has any play, NONE, hard to move)
Checked Coil Packs, still running stock - All are seated properly screwed, NO CEL or P03xx/misfire codes)
Unplugged N75, car ran like crap..Plugged it back in (took a couple cycles to get better)
Unplugged MAF, car ran like crap..Plugged it back in (took a couple start cycles to get better, but it did get better)

i wanted to PINCH the hose from the Waste Gate to the N75 Valve, but i dont have/cant find any clamps that could do that w/o tearing the hose itself.


Things i searched that might be the problem:

N75 valve (intermittent could be letting my waste gate to dump excess boost or not build at all)
MAF Sensor (could be getting wrong readings, but its not throwing a CEL)
Sparkplugs (might need to switch to cooler BOSCH FxxLR or NGK PFR7Q gapped at .028)
Clogged Cat (which i searched could be a reason, but wont pop a cel)
O2 Sensor (could be a reason, but it will pop a CEL right?)


What i need before i start purchasing parts, cuz i'm a not soo hood rich college student:

Anyone w/ a VAG-COM, local to 07080 that can lend a hand?

VAG-COM

Block 115 - need Requested boost vs. Actual boost

Block 032 - See how much ECU trying to adjust fuel trims

Block 003 - see what type of MAF readings im getting



Any thoughts, ideas, are welcome. TIA :salute:
that's all we need to know. any K03 chipped 1.8t will heat soak after 2-3 runs. you don't have a problem, you have too much power for your formerly adequate intercooler.
 

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that's all we need to know. any K03 chipped 1.8t will heat soak after 2-3 runs. you don't have a problem, you have too much power for your formerly adequate intercooler.
That's not what he's describing, though. He said "some days it does this, some days it does that, etc." If it actually behaves like that all day, then it has nothing to do with heatsoak.
 

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Superbad
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1,456 Posts
Discussion Starter #6
ANYWAY...the vacuum levels look normal, but FYI that doesn't actually indicate a lack of vacuum leaks because the throttle isolates the intake manifold from all but the largest vacuum problems everywhere else in the system. What you're experiencing, if it's consistent throughout the day as opposed to changing constantly during a single trip, sounds either like normal variations due to temperature, or else your N75 is wearing out.
I am well aware of the effects of ambient temperature to the turbo. but what i'm describing is sporadic and inconsistent.

Given:

hot/humid air = higher PSI
Cold/Dense air = lower PSI

Higher PSI doesn't always equate to more POWER; because higher PSI also = more HEAT right?

Colder / Cooler Air especially for a turbo engine = more responsive throttle, quicker spool, overall much better gradient for the turbo to reach its programmed power curve efficiently right?

So here's my situation:

Some days when its hot outside, 85-95 F and humid, i can go WOT and hit 15-17PSI, hold at 15 and taper at 10 PSI. And other days i can barely get it to go passed 10 PSI and hold 8-9.


On the same day, after it cools down at night 70-77F cool air, (car is warm of course, Temp gauge is where its supposed to be) i would try to go WOT and spike only at 10 PSI, hold 8-9 and taper off. As i continue to drive, and stop at a stop light, i dont floor it, i go from a roll, easing the throttle, the car will surge w/ boost, not even going WOT, and it'll go from 0-10 PSI in a blink of an eye, then rapidly climb to 15-17 and really pull you. (mind you this is at half throttle not WOT)

Still same day, hour or two later, i start the car, and drive it, (slowly pressing on the throttle to build boost) feels like it wants to boost, needle goes from 0-5PSI and then stays there. It wont go passed 5 PSI, and if i go WOT it will spike at 10 PSI slowly and then bounce back down to 5 PSI.

This is at Night, where the ambient air is cooler, after the car cools off a few hours, and heat soak should not take place immediately. when it hits 5 PSI, the car feels like it falls on its face. could the Waste gate be stuck open because of an intermittent N75 valve?

I know the N75 valve is a Solenoid, and its not a sensor. could a bad spring/mechanism within the valve be causing the intermittent Boost i'm getting?


Another scenario:


Sometimes, when i vacuum the pickup / snow screen on the air filter duct, it improves throttle response, as if its sucking more air, less obstructions from dead bugs/all sorts of other particles, it'll boost really well to 15-17 PSI, hold 15,taper 10. And after that, if i try to gradually increase the throttle it falls on its face back to not being able to go passed 5 PSI. could an intermittent/faulty MAF Sensor be the cause of this? that's why i would need to do some VAG-COM logs to make certain my MAF readings are where they're supposed to be.


Stealership wants $110 for updated N75 Valve. according to them N75 C is discontinued and the replacement for it is (N75F) 058 906 283 F. Would a MBC be a cheaper fix?
 

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Superbad
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1,456 Posts
Discussion Starter #7
I pulled the DV plenty of times, and did the DV Test, by pushing on the one side, and holding thumb sealing the nipple, if it holds the piston in place, valve is still good/sealed. And it did. also serviced it w/ Mobil 1 synthetic grease, and i tried it w/ the stock green spring, then moved to a yellow spring.

Green rated 5-12 PSI
Yellow rated 12-20 PSI
 

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Mine does the low boost problem whenever my car is heated up. Cold it runs fine, but after an hour or so of driving the turbo will not or barely spool. It happened ever since i was chipped. About a month in it started to happen, then I pulled the chip and it stil happens. I went through the same steps you did and we had about 4 pages of options and none of them worked. I have resorted it to being my wastegate not sealing all of the way when heated up.

Time for a K04. I know I know money, I am acollege student and have been needing the K04 for about 16monthes now, haha. Funny thing is when I have 5 people in the car and stuff in the trunk the car will barely make it up some hills.

I could ahve gotten a K04 this last week but I decided to get new suspension for my Rabbit ($800).

Good Luck with finding the source if I am wrong.
 

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sounds like ur n75 may jst be goin out.. if anything. if u have a mbc just try that. if u dont. there not expensive at all and good for adjusting that spike out. search for MBC or related words and see what comes up. theres a write up on it. i no rusty did one and it was A+ in my book.
 

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Superbad
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1,456 Posts
Discussion Starter #10
Mine does the low boost problem whenever my car is heated up. Cold it runs fine, but after an hour or so of driving the turbo will not or barely spool. It happened ever since i was chipped. About a month in it started to happen, then I pulled the chip and it stil happens. I went through the same steps you did and we had about 4 pages of options and none of them worked. I have resorted it to being my wastegate not sealing all of the way when heated up.

Time for a K04. I know I know money, I am acollege student and have been needing the K04 for about 16monthes now, haha. Funny thing is when I have 5 people in the car and stuff in the trunk the car will barely make it up some hills.

I could ahve gotten a K04 this last week but I decided to get new suspension for my Rabbit ($800).

Good Luck with finding the source if I am wrong.
Trust me, if i could i would get/upgrade to a K04 in a heartbeat. but it is completely out of stock almost everywhere. And if you do CALL FOR PRICING, avg price is between 1000-1200$ for turbo alone.

K04 setup needs:
Upgraded Programming (PC_16) = i guess AWE can give me a Discount but still $$$
Bigger Injectors (225 or 318 cc) = $$$$
2.5'' downpipe + Cat back exhaust = $$$$
FMIC = $$$ even tho ebay ones or 1fish2fish can make one for 500$ish still $$$$

i know you gotta pay to play... but school is more important rite now, once i get a real job w/ a real big kid's salary then i can play w/ the big kids.

As for now i'm leaning on replacing the N75 valve and go from there. I'm just afraid that i'm gonna end up having to randomly buy parts and use process of elimination to solve my problem.
 

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Superbad
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Discussion Starter #11
sounds like ur n75 may jst be goin out.. if anything. if u have a mbc just try that. if u dont. there not expensive at all and good for adjusting that spike out. search for MBC or related words and see what comes up. theres a write up on it. i no rusty did one and it was A+ in my book.
I don't have a MBC, i know you can get a Boostvalve kit for 50$ shipped, which is relatively cheaper than a brand new N75 Valve. i've read countless threads on Faulty N75 valves, N75 J, N75 H, etc etc ... i even read Rusty's thread on installing his Dawes MBC and why you shouldn't get an N75 J or H for an AEB thread.

MBC set at 15-17 PSI, yes that would be awesome to have boost come in at 1500-2000 rpm, instead of 2500-3000rpm, but the having that much power on tap w/o a middle ground is not gonna be fun when driving / stuck in traffic. My understanding is people use MBC's to control spikes. my spikes aren't that high, 17 PSI highest. I know some people get it because they use a slower N75 valve, which is a "race valve" i.e N75 H or J, they will spike at 21-23, so they need to get a MBC to turn that spike down to 16-17 PSI, so they don't go into LIMP Mode. Lithiumfox, scwcrow, to name a few use it on their b5.5, and have good results.

Also, i know Deusexethera uses it as well, he bypassed his N75 valve all together but kept it plugged in, in conjunction w/ his GIAC chip. and according to him works well. this is on his B5, im assuming its an AEB.

I may have to just bite the bullet and pay the Stealership the $$ and get a new N75 valve. :cry:
 

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well... i know a lot of mbc goes for 35. hell i peiced mine together from a hardware store for roughly 25 dollars.
i have a 99 1.8 aeb.
in stop and go traffic it really isnt bad. as long as your not punchin it u wont build much boost...
im not sure about the whole surpassing thing with the valves.
but i no a mbc is nice. i like it. give u what u want when u want it.

for the n75...
058-906-283-F is the part number world impex gives me for the 99 aeb 1.8t wastegate solenoid valve. so... i searched that on 1stvwparts.com and its 79.07.. soo...
its all up to u.
 

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Don't get a manual boost controller. They're more trouble than they're worth. Just replace the N75.

Have you ever replaced the intake temperature sensor? Do you have a crush-proof turbo inlet hose?

I actually used to get erratic boost when I used my MBC; that's what convinced me to get rid of it. N75 is much more consistent.
 

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hmm.. did not know that deus. yea i switches back to my n75. but i cant deny i liked the mbc. i just didnt want to accidently fuck something up... (since i finally got the car running good).
 

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I had the same problem and just took out my turbo for a K04 and the actuator was bad so that is your problem too, I am 90% sure.
 

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I had the same problem and just took out my turbo for a K04 and the actuator was bad so that is your problem too, I am 90% sure.
how do you tell if the actuator is bad? i remember reading somthing about how to do that while ago. i had an old blown KO3 but i gooked it up to a air pump to move the wasgate. is tehre any way to test it while the turbo is still attached?
im having similiar problems but with my KO4. i was spiking and boosting higher with my KO3 with KO4 chip. i gota re-freash my memory about the N75 for leaks etc...
TIA
 

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hmm.. did not know that deus. yea i switches back to my n75. but i cant deny i liked the mbc. i just didnt want to accidently fuck something up... (since i finally got the car running good).
Yeah, sometimes the turbo would start coughing (for lack of a better word) -- lots of noise, no boost, then suddenly it would peg the boost gauge and then shoot back to 0 in the same instant, repeating this over and over until I took my foot off the gas to let it calm down or I stomped the gas to let the engine suck in the boost spikes. It was much more likely to do it with cold air, even after the engine was nice and hot.

I put the N75 back in the loop and it never happened again.
 
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