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so i did a couple mods over the summer including a td-04 3" exhaust TMIC msd coil de snork and coffee cup...
and i did one thing at a time to make sure if there were problems it wouldnt be hard to pick out what caused it.
everything was fine until winter hit...
at first it would only happen until the car was warmed up for about 10 mins (the temp needle at the middle for at least 10 minutes of driving so all in all usually about a half hour since i would start the car) but now it just happens sometimes and other times not regardless of engine coolant temperature.
its mostly obvious going up a hill a.k.a. under load

between 0 and 5 psi of boost the car bogs down so badly that going up a hill it actually starts to slow down. if i put it in power mode and the revs come up its fine if i push the throttle down so that boost builds past 5 psi it'll jolt me back powerfully. and if i let go of the throttle a bit so that it goes back to 0 psi the bogging stops and it starts to accelerate normally.

i had a code 23 so i swapped out the maf 2 days ago and now the code is gone but the problem never changed.

the knock sensor is the updated version(age unknown) the maf is clean, I tuned up the car in the summer it has a fairly new o2 sensor. i've been thinking the coolant temp sensor but i didnt think it could cause such a randomly occuring problem so dependant on boost pressure and (not anymore) dependant on temperature.

its an EXTREMELY annoying problem and i dont have the money right now to just start throwing sensors at it.

any insight?
thanks
-Alex

The ecu temp sensor is only $20 at the dealership. Did you check all your hose clamps and make sure they are tight??

You might check the hoses that go to and from the boost control solenoid. My car ran really bad when one of those was off.

Just a word of caution.. I wouldn't run any boost until the car is up to normal operating temps. Oil doesn't warm up as fast as the coolant and cold oil doesn't flow and lube as well as it should. I have an oil temp gauge on mine and take it easy until the needle starts to budge.

Jeff

i'm sure all my hoses/clamps are tight and leak free.
i'm using an mbc so the boost solenoid is unhooked from the system (although still plugged in).
and being an apprentice i've seen my fair share of engines ruined because of too much flooring it when cold so i know to wait until the engine is warmed up before being aggressive. heck i dont even move the car until the needle has started to move up when its cold enough outside.
and i guess i'm going to have to swap the coolant sensor i just hate to see 20$ wasted... money doesnt grow on trees. 20$ is enough for me, and plus change one 20$ sensor here and another there and before you know it you've changed 10 and then you're down 200$.

i just wanted to see if anyone had a similar problem that had been solved.
maybe i'll just try and unplug the sensor after the car is warm and see what happens...

thanks
-Alex

alright well i guess the fact that it was so boost related is what clouded my judgement.
it was the coolant temp sensor. i switched it out this morning and immediate improvements were obvious including an extremely smooth idle that i thought would have been impossible out of my car and quicker starting (sounds like it only cranks over once).
and the bogging is gone!!!!

although the sensor was 44$ my cost, list price was 88$ so yeah not 20$ over here... and the install was a pita! i had to move my turbo coolant tank 3 different vac hoses and then squish my hand into a spot about half its size, i'm a bit cut up now but the cold numbed my hand enough that i didnt feel it in the moment .
it might have been easier to move the intercooler but its always impossible to get back on so it would have taken at least an hour as opposed to the half hour it took.

when i went to unplug it half of it came off with the plug so it was for sure done.

anyways i'm happy now
thanks all
-Alex

alright so i thought the coolant temp sensor fixed it but it didnt.
so i went around testing sensors and i didnt like what i was seeing from the tps. so i changed it with a new one and it just so happened that it was fairly warm for the past 3-4 days so my car was running perfect and i was sure i'd found it!

but last night it got pretty cold and right now its -19 and my car's started bogging again. it seems to be related mostly to the temperature outside not engine temperature. is it possible that the air is so cold its freezing my maf? i've neveer herd of anyone having any problems like this and there are lots of people on here that live in places as cold if not colder than me.

on another note the other day when my car was running ok before i changed my tps, at one point when i almost floored it my check eng light blinked at me. the car was running fine at that point cuz it was a warm day and i was well over 5 psi when it happened.
it was the code for the maf again... why? i dont know... it hasnt happened since.

so the things i've done:
swapped maf with used known good one
new tps
new coolant temp sensor
new o2 sensor in summer
pulled plugs and were still all fine and gapped ok
plug wires and coil are fairly new.

any ideas would be great!

thanks
-Alex

omg! i'm so sure i found the problem!!!
my bpv was stuck open! constantly until a fair amount of pressure is applied to the vac nipple!!!! so at low boost its bypassing some of the pressure back into the intake! which makes sense cuz i was having a bit more turbo lag than i should have.
i'm about to stick my spare slightly cracked but ok one on and i'll report back tomorrow on how it went!

just out of curosity how does our bpv work? open or closed at idle? and what causes it to open when the throttle is let off? sudden vacuum?

thanks
-Alex

interesting. I need to look at mine. I wonder if you can lube it up. Like spray some wd40 or dump seafoam through it. My car seems fine though, just never hurts to have a bit more boost response.

ok so the problem isnt really gone but i'm fairly sure its just that the computer has to relearn the fueling parameters.
how long does this usually take? according to mitchell on demand it can take up to 40 start ups which would equal like 15-20 days maybe.
i tried doing an ecu reset and then starting up without touching the throttle and all that stuff... but i'm pretty sure for some reason my ecu just doesnt reset.
any ideas?

the old bpv was open all the time i put 15 psi on it and it stayed open and then 15 in. hg and it was still open no matter what

the one i swapped it with is closed from 0psi up to 15 psi (and over i just didnt go over that) and then opens under any vacuum, is the bpv supposed to be open at idle? my car seems to idle better with the vac hose off of the bpv (aka with it closed at idle)

anyone have any reccomendations on an aftermarket replacement that is 100% recirculating and not 300$? cuz i wanna change it anyways.

thanks
-Alex

It is supposed to be open at idle.
The one I have is a bosch-style replacement for a VW 1.8t, or something like that. Its all aluminum and was ~30USD on ebay. Its been working well for about 2.5 years now.

The BPV is a normally closed valve. If you take it out, and try blowing into it, you should not have any seapage out the other side. Only when vacuum is applied should the valve start to open.

So under engine vacuum conditions the BPV should be open to some degree.

yeah the replacement one is working properly then
my car is progressively getting better every couple of starts its a bit better.
the intake noise is alot quieter too since there isnt all this boost rushing by all the time.
right after changing it i immediately noticed a change in the exhaust note and my interpretation from cars i've heard before it went from rich (bacause boost was being bypassed back to the intake and not entering the cylinders) to lean (because now there was no boost going back to the intake and it is all entering the engine and so the computer is slowly adjusting and changing its parameters to meet the new demands but since it was so used to the leak its sort of confused about the new air so its taking time to adjust.)

anyways my throttle response has gone through the roof my part throttle and part boost response and performance has gone up alot and is still going up and my full boost performance seems alot better too but i havent tested it much in case my enigne is running lean i dont want to blow it up.

so i hope one day this helps someone out with similar problems.
in any case if anyone has any bogging take your bpv out and you should not be able to blow through it with no vac on the nipple.

so thanks to you guys who have helped i'm just happy its over.

-Alex

Were you experiencing sometimes when you gave it more gas the revs would fall a bit or stay where they were and take a long time before it would start gaining rpm's? I still believe I am experiencing the same issue, as well I hear my turbo ALOT. Like at 2500+ always hear the turbo.

the vf11 mostly with the stock plumbing is barely audible the td-04 is louder but still very quiet in comparison to a lot of other cars i've been in. if you can really hear it theres something fishy like a boost leak or possibly failing bearings in the turbo. when my vf11 went on me the whine was so loud it would make me cringe and i just couldnt bear going past 5 psi cuz it was so loud.

yes when my car was bogging the rpms would drop at worst of times up to 500 rpms
and going up hills they would then sometimes barely rise and hold around 2000 rpms unless i went past half throttle or so.
it was like my car would accelerate until i hit about 1 psi then the rpms would drop and the car would sortof "hit a brick wall" then i would give it more gas and the boost would rise to 12psi and then the rpms would fly up and the car would jolt forward.

what setup are you running? stock? and is the noise a woosh or a whine? i had a fairly loud woosh sound with the leaking bpv but not really any difference in the whine. and hows your tubo lag?

-Alex

I would call it more of a whine. The car is 100% stock. Everything SEEMS fine, but I still think there is more the car can give power wise.

well check the plastic pipe between the turbo and throttle body
make sure there are no cracks and the clamps are tight make sure the bpv is sealing properly on it and the tubing from it to the intake is leak free and see if theres much oil residue in the big plastic pipe. then make sure you cant blow through the bpv with no vacuum on it.
although often times a pcv valve leaves oil residue a failing turbo will too.
if theres oil in the pipe after the turbo check the one before it if its dry then its definitely the turbo going.
if theres any air getting in between the maf and the turbo it will cause problems like that too so make sure the rubber elbows arent cracked, the resonator isnt cracked and the clamps are tight on everything.

either way its a 15 year old turbo so it wont be at the top of its game.

for the hell of it clean your mass air flow sensor and throttle bore and give your car a tune up if it needs one.(plugs wires air and fuel filter)

So far did plugs, filter, pcv, seafoamed it and all. Soon going to pull apart ALL of the intake and PCV hoses and make sure they are clean. Didn't see anything visually that was damaged and I snugged up my clamps. I did notice alot of oil resisdue on the pipes around the intake. After I cleaned the engine, nothing has appeared. I did notice one turbo line doesn't have a clamp or maybe it did? Either was wasn't making a good seal. Need to go over a few little things. Will pickup ignition wires and a fuel filter once I start working.

All parts I used are OEM btw.

good to hear youre taking care of her
clean your maf for sure with some intake cleaner or equivalent cuz when they get dirty the readings can be all messed up
check the operation of you bpv too
but if you said everything seems fine then it might just be the age of the turbo but it may be working well still
when exactly are you experiencing this lack of power and falling or not rapid rising rpms?
part throttle? full throttle? up hills?

-Alex

More like inclines at part throttle. Full throttle or in power light mode it obviously downshifts though and seems to pull more. Ordered alot of parts going to inspect everything on the car including the intake and pcv system. Going to replace all my fluids with synthetic. Driving my 93 wagon again until I know everything is 100% on the sedan. It kept overheating. Water pump is leaking so no point killing the motor.

yeah it does sound like the problem i was having so check everything and we'll go from there

as for synthetic fluids just be careful they're known to clean out the system too much some times. when seals get old dirt is sometimes what's actually doing all the sealing because it begins to accumulate on the edges of seals, when you put synthetic in it may attack this dirt and remove it causing leaks.

personally i wouldnt put sunthetic fluid in a 16 year old car that hasnt had it for the past 16 years but i know many people have without any real problems. just keep an eye out.


-ALex