low boost, low power

[2000blk1.8t]

2003 1.8T stage 1 tune. I feel like im always working on this dang thing. So, When i first got it running after an engine swap(before the tune), it ran great at around 10-11 psi. after awhile, It started spiking 15-16 psi and than instantly fading to 5. I found a tear in the line going to the waste gate. OK, I fixed that. Now, the thing will not run over 6 psi. It might spike to 7, but always ends up at 6 psi. I have checked all of the boost lines and vac lines. I found a few faulty check valves, and I also found my diverter valve had failed. I replaced the check valves and the DV. Still, 6 psi. Tried swapping the N75 valve from my parts car with no change. I only have 2 codes tripped, and they are both in relation to the test pipe and rear 02 sensor I removed. I should note I had an underboost code once, but I cleared it and i have not seen it in awhile. I figured i was possibly in a soft limp mode, so I would clear the codes and no change. It runs ok, but I Feel it is definitely under powered compared to my all stock 2002 passat I had that ran right at 11 PSI stock.

[ShogunR32]

Im having the same issue on my stock avant. I fixed a couple faulty check valves and even threw a FMIC on. I know for a fact its a boost leak tho because I can hear a weird sound boosting past around 5psi. Sounds like its a leak on a hard surface. I only get about 8psi. Doing a boost leak test is the only way to resolve this I think.

[2000blk1.8t]

i hear no strange air rush noises from my car that i can tell. I have had some boost leaks before and it made noticable moving air sounds, and it idled rough.

[diagnosticator]

There are two types of intake air leaks. The most common is a boost air/vacuum leak after the throttle valve, the second is before the throttle valve. The first type leaks the most when the throttle is closed or at low opening angles. The second type leaks boost charge air only with boost pressure in the charge air plumbing. Make sure there are no cracks or splits in the 2" charge air hoses.

[2000blk1.8t]

update. I finally found time to do a boost leak check. the car will hold 5-6 psi well. taking around a minute to drop to zero from 5 or 6. If i pump the compressor up higher, I found a large air leak that seems to blow all of the boost off past 6 psi. the map sensor in the intercooler. I'm wondering if I pinched the O ring when I installed it. Now I just need to find time to pull the front bumper and intercooler off to see what is going on. I will update this thread once I have that fixed.

[2000blk1.8t]

well. I tore into it tonight. I fixed the leak at the map sensor. I also had another small leak at the N75 valve that presented its self around 10 psi. Now, I have no leaks in the plumbing system. I sprayed soapy water on every connection that I could find or see to assure. The only air i'm loosing now is in the engine. Probably from the air leaking by the piston rings and out my crank case vent hose. After another test drive, STILL runs around 6-7 psi. I also checked the codes before I tore it all apart and it did trip another P299 low boost code. Any ideas here guys?

[2000blk1.8t]

bumping this up. Car tripped another P0299 code. It also tripped a P0455 code? I think its a vacuum leak code. If the vacuum leak didnt show up in my boost leak check, how would I find it? unless that code is related to my PVC system delete.

[diagnosticator]

bumping this up. Car tripped another P0299 code. It also tripped a P0455 code? I think its a vacuum leak code. If the vacuum leak didnt show up in my boost leak check, how would I find it? unless that code is related to my PVC system delete.

PCV system delete? Reinstall the removed PCV plumbing. You have not done yourself any favors by removing the PCV. Removing the PCV (and SAI, EVAP purge systems if this is the case also,) is misguided and has no practical merit.

BTW, the "MAP" sensor in the intercooler end tank is not an actual MAP (manifold absolute pressure) sensor because the sensor is upstream from the throttle body and cannot sense manifold pressure, it only senses boost pressure, so it is properly called a boost pressure sensor for this application.

[2000blk1.8t]

PCV system delete? Reinstall the removed PCV plumbing. You have not done yourself any favors by removing the PCV. Removing the PCV (and SAI, EVAP purge systems if this is the case also,) is misguided and has no practical merit.

BTW, the "MAP" sensor in the intercooler end tank is not an actual MAP (manifold absolute pressure) sensor because the sensor is upstream from the throttle body and cannot sense manifold pressure, it only senses boost pressure, so it is properly called a boost pressure sensor for this application.

Does removing the PVC system have anything to do with my problem? they system was pretty much all junk on the car when I got it. It may not be doing me any "favors", but I cant see how it is hurting me either.

[2000blk1.8t]

to the top again. I cannot seem to figure out this problem. The car keeps tripping P0299 codes and a P0455.

[Captain_Panic]

In situations like this I usually give little shots of brake cleaner around the vacuum lines. Once/if your idle changes, you found your problematic area.

[texasboy21]

to the top again. I cannot seem to figure out this problem. The car keeps tripping P0299 codes and a P0455.

With your 'delete' did you alter the EVAP system? Code P0455 is for a large EVAP leak. P0299 is underboost.

http://wiki.ross-tech.com/wiki/index...9/P0455/001109

It always seems that folks who choose to 'delete' various vac and crankcase breather systems have vacuum, low boost, etc, issues.

[2000blk1.8t]

Left the evap system alone. No reason to mess with it.

[2000blk1.8t]

wondering if I messed something up when I installed the passat engine in this car. It just has not been right since I got it running. Can anyone point me in the direction of a good emissions direction image? I have a bentley manual for a passat but the audi is different for sure. I did the brake cleaner trick with no good results.

[2000blk1.8t]

some more info. I clamped the wastegate hose shut. car will boost 15 psi and up easily. I ran a datalog with a vcds. its commanding in the 2100ish mbar range but actual is only in the 1300-1500 range wide open. did an ohm check on the n75 and its 29-30 which is within spec. I had the car remote tuned and that did help raising the boost to 7-8 up from the 6. I also bypassed the n249 valve just to make sure that wasnt an issue and it didnt help. did another boost leak check this morning with no leaks found. I used soapy water on every connection I could get to with no leaks. the duty cycle on the N75 is 95% while wide open. any ideas guys? im going crazy trying to narrow this down.

also things I forgot to add. I replaced the fuel filter awhile ago. I checked the air filter. Heck I tried running it wide open from the MAF sensor housing. it spools fast and sounds normal. I have a test pipe in place of the cat. Pulled the diverter valve and did a vacuum check on that. it's brand new, but you never know.

[old guy]

It sounds like you may have the N75 ports installed incorrectly and instead of shunting the pressure signal to the TIP during the high duty cycle it's passing it along to the wastegate.

[2000blk1.8t]

I wish. Checked that last night. The longest port on the valve is in the tip.

[old guy]

OK. Here's what we know. If you clamp off the pressure signal to the wastegate you can easily build boost so you know your turbo is mechanically capable of operating properly. You know that your ECM is calling for boost as evidenced by the requested boost of 2100 mbar but all you are getting is 1500 mbar. You checked the resistance of the N75 and confirmed that the coils are intact and working properly. You are also seeing a 95% duty cycle on the N75.

So the problem seems to be that even though the ECM is doing everything properly to build boost the pressure signal is still getting through the N75 and on to the wastegate. One possible explanation would be that the N75 is stuck in the closed position and consequently not dumping the pressure signal into the TIP as requested by the ECM. But you did mention that you tried two different N75's with the same result. So another possibility is that the wiring to the N75 is defective and isn't getting the required signal. Although in this case I would expect a DTC for an open or short to ground.

Two suggestions. Unplug the N75 and see if you get a DTC for open or short to ground. Hopefully you do. If not we can address that separately. Then take your spare N75 and blow into the high pressure port. You should be able to feel air exiting out of the wastegate port. Next apply an electrical signal to the N75 and do the same thing with your finger over the wastegate port. Now you should be able to feel air exiting through the TIP port. This will confirm that the N75 is functioning properly.

If you received a DTC for an open circuit you know that you are getting power to the N75 since the ECM recognized the open circuit. Then replace the N75 with the one you just confirmed as working and see if you have boost.

Good luck!

[2000blk1.8t]

Took it for another drive this morning. Pulled the codes. P0238 and p0106. First time for those codes. Possible bad boost sensor? Also, my partial fuel trim is at 11.7%. would that indicate a leak?

[2000blk1.8t]

OK. Here's what we know. If you clamp off the pressure signal to the wastegate you can easily build boost so you know your turbo is mechanically capable of operating properly. You know that your ECM is calling for boost as evidenced by the requested boost of 2100 mbar but all you are getting is 1500 mbar. You checked the resistance of the N75 and confirmed that the coils are intact and working properly. You are also seeing a 95% duty cycle on the N75.

So the problem seems to be that even though the ECM is doing everything properly to build boost the pressure signal is still getting through the N75 and on to the wastegate. One possible explanation would be that the N75 is stuck in the closed position and consequently not dumping the pressure signal into the TIP as requested by the ECM. But you did mention that you tried two different N75's with the same result. So another possibility is that the wiring to the N75 is defective and isn't getting the required signal. Although in this case I would expect a DTC for an open or short to ground.

Two suggestions. Unplug the N75 and see if you get a DTC for open or short to ground. Hopefully you do. If not we can address that separately. Then take your spare N75 and blow into the high pressure port. You should be able to feel air exiting out of the wastegate port. Next apply an electrical signal to the N75 and do the same thing with your finger over the wastegate port. Now you should be able to feel air exiting through the TIP port. This will confirm that the N75 is functioning properly.

If you received a DTC for an open circuit you know that you are getting power to the N75 since the ECM recognized the open circuit. Then replace the N75 with the one you just confirmed as working and see if you have boost.

Good luck!

Didn't see your reply. Will check it out. Thanks!

[old guy]

Took it for another drive this morning. Pulled the codes. P0238 and p0106. First time for those codes. Possible bad boost sensor? Also, my partial fuel trim is at 11.7%. would that indicate a leak?

Did you clear all codes after clamping the wastegate hose? If not, these codes would be expected. Clear them and see if they come back.

The 11.7% partial LTFT could indicate a small amount of false air entering after the MAF sensor.

[agentsmith988]

update. I finally found time to do a boost leak check. the car will hold 5-6 psi well. taking around a minute to drop to zero from 5 or 6. If i pump the compressor up higher, I found a large air leak that seems to blow all of the boost off past 6 psi. the map sensor in the intercooler. I'm wondering if I pinched the O ring when I installed it. Now I just need to find time to pull the front bumper and intercooler off to see what is going on. I will update this thread once I have that fixed.

I've always wondered what the normal bleed down rate is when leak testing. If we pressurize to 15-20psi, how long should it take to come back down after removing the air source?

[2000blk1.8t]

Did you clear all codes after clamping the wastegate hose? If not, these codes would be expected. Clear them and see if they come back.

The 11.7% partial LTFT could indicate a small amount of false air entering after the MAF sensor.

I cannot remember. I think I did. well, I took it on the interstate up to 90. it will run about 10 psi with a large load in the higher gears. I cleaned the MAF sensor again really well this time incase I did a poor job last time. No change. I did your trick with the n75. Clicks cleanly with 12v going to it and I can then blow through all of the ports when it opens, when it closes I can only blow through the 2 shorter wastegate ports. I then swapped the N75 in the car with the one i know worked. No change and the other one tested fine also. the 11% fuel trim has nothing to do with the boost right? its just adjusting fuel for partial throttle under vacuum right? the MAF sensor readings are in the low 100 range. 130sh wide open.

[2000blk1.8t]

might sound like a long shot, but would a damaged exhaust cause my problem? the previous owner high centered this car at one point. The evap lines were damaged, and i see the resonator has a fairly large dent in it. I cant image how the dent would block air flow but i'm running out of ideas.

[old guy]

130ish MAF readings at WOT are pretty normal for a stock tune. You mentioned that when you clamped off the wastegate line "the car will boost 15 psi and up easily". That's a pretty good indication that you aren't dealing with any restrictions and that mechanically everything is OK.

You also mentioned that you could eventually get to 10 psi of boost under high load. Stock tuning is typically around 10→11psi max. So you are getting there, just not quickly. Yet you are showing a high N75 duty cycle. Does the duty cycle go to 90%+ at the same time your throttle position goes to full open?

[2000blk1.8t]

yes. Looking at the log, anytime the throttle is in the high 90's to 100 the duty cycle is right up there with the throttle percentage. I did a more proper boost leak check. I plugged the crank case breather off this time. It takes about 1 minute to go from 13 psi to 5. I noticed a have a leaky valve cover gasket and my oil fill cap was also leaking. after 5 I quit timing because it took forever to drop below that. Can I attach a copy of my logs to this thread? here is a screen shot of part of my log. Hopefully you know what your looking at. left to right is RPM, accel. pedal position, throttle valve angle, requested boost, time, rpm, intake temp, duty cycle, and actual boost.

[2000blk1.8t]

1 more thing I forgot to mension. When I unplug the n75 I immediately get an open circuit fault for wastegate valve.

[old guy]

I think you have a problem with your wastegate setting. Your ECM is doing everything it can to build boost and it just isn't getting there. If the wastegate setting is too low it will start to open at a very low pressure. When you clamp off the wastegate line you aren't getting any pressure to the wastegate and consequently you can build boost.

Use an air nozzle and apply regulated air to the wastegate pressure line. Slowly turn up the pressure while you reach up underneath the turbo and either feel or observe when the wastegate actuating arm starts to move. That would be your wastegate setting. You can also get an approximation by simply unplugging the N75 and observing your maximum boost.

You should not perform a boost leak test with the engine enclosed. The block was not designed to be pressurized. Always leave the oil cap open and block the PRV line. Otherwise you pressurize the block and risk blowing out your oil seals and gaskets.

[2000blk1.8t]

good to know thanks. I will try simply running it with valve unplugged. From what I have read, it should run 3-5 psi on just the wastegate setting?

[old guy]

0.37 bar (5.36 psi)

[2000blk1.8t]

P0238 and p0106 came back again. Thinking my boost/map sensor may be bad. I ran it with the valve unplugged. max I ever saw with a hard loaded spike was barley 4 psi. Normal wide open run i was only getting in the 3 psi range. If you think that is out of spec, I need to adjust it. Can that be done with the turbo in the car?

[old guy]

I remember Walky_Talky20 stating that it could be done with the turbo in place. No way in hell I could do it without removing it.

[2000blk1.8t]

Looking at my spare k03 and holding it how it sits in the car, Ya right. Looks like it's atleast getting unbolted from the manifold. Hopefully I can roll it down enough to avoid taking coolant and oil lines off. So the actuator arm should start moving at what psi?

[old guy]

I would set it for 6 psi.

[2000blk1.8t]

So at 6 the arm just starts to move? Or the gate is actually open at 6

[old guy]

When it first starts to move. You can experiment with your spare K 03 and see how sensitive the adjustment is.

[2000blk1.8t]

I couldn't seem to figure out a happy medium on how to adjust it. I ended up just going about 1/4 inch tighter. There isn't a whole lot more adjustment available. Car is running better now. consistant 12 psi now. MAF is around 140's. What would you suggenst now? turning the wastegate up more? the flap it's self was opening about 1/8th inch at 6psi. If you need me to say what is what on the log don't hesitate to ask. I blocked the hose off again just to make sure nothing has changed. Car hit 20 psi right away.

[old guy]

You did say you were running a stock tune, correct? If so it looks like you are right where you should be. Stock is typically 135 g/s. You are running in the 140's. Stock boost is typically around 11 psi. You are at 12 psi. Overall it looks pretty good.

[2000blk1.8t]

No, stage 1 tune. 17 psi file. Doing the math, the requested 2100 mbar it's calling for is about 18 psi.

[old guy]

OK. I see that now. Your last log is asking for 18 psi and not getting it.

Let's take a look at your MAP sensor in relation to the actual and requested boost. Read through this short thread and use the information in posts #2 and #9 to see how yours is performing. Clicky click®