ok here's the problem guys, a few days ago I was driving on the interstate and all of a sudden when i stepped on the gas, the boost gauge reads to about 4psi and then drops and it feels like my car is chocking. I looked for a pinched vacuum line but didnt find any. and the funny thing is, sometimes it lets me boost all the way to 6.5 or whatever the stock boost is on the BB DET without a problem but most times it won't. so what could it be or what should i look for?
Please help,
TIA, Nick

bad turbo...clogged converter..maybe?

Are all your gaskets before the Turbo O.K.?

Originally posted by unlucky
bad turbo...clogged converter..maybe?

I don't think my turbo is bad because i *** did the engine swap a few months ago with Jason G. Young and it was in good condition then (and I haven't abused it at all :o ) but I have no clue what a converter is if someone can help elaborate? (sorry I'm a turbo dummy :()
Originally posted by Jackson Diamond
Are all your gaskets before the Turbo O.K.?
How should i check for bad gaskets? (again sorry for the dumb question)

BTW, I have been having idle issues since the install( rpm needle is never stable and idle gets worse the longer i drive the car:confused: ) so I have adjusted TPS, reground the MAF, replaced O2 sensor, replace plugs and wires, and also exchanged the AAC valve with my DE unit.

Turbos die all the time, and it may have nothing to due with age or abuse. Have a pro check it out. A catalytic converter is a big brick that goes between the downpipe and the rest of the exhaust system, and if it's cracked, molten, or clogged, your performance would indeed suck. Cats, by the way, are on all cars, not just turbo ones. You find leaks by listening for them or by forcing smoke through the system and looking for exit points.

Nick, tell us about your exhaust piping, please. What diameter is it. That could be critical to your troubles, too.

The catalytic converter is suspect as well, as that cowboy guy said. :)

wow, I had no idea the Cat can be connected to a problem like this. So if the catalytic convertor is shot, shouldn't I be able to smell that awful scent?


I have a 2.5in downpipe connected to my stock cat which by the way has 150k miles on it, and the rest of the cat-back is stock (2.25in??) and I have one of those performance mufflers which is also the same size as the rest if the cat-back(2.25in). I've been meaning to upgrade to a 3" cat-back this summer since i didnt have the money after my swap.

You might see what happens when you pull the cat out. It'll be loud as hell, so do it in an unpopulated area. If I were you, I'd want a test pipe for the track anyway; you don't have one of those to try? :) It may or may not smell, though it often does.

Nick, if you have stock piping from the cat back, it is 1 and 7/8" diameter, IIRC. Which is choking the daylights out of your turbo.

I had my stock piping in there for a brief period of time after installing my T28.


Here were my symptoms. Tell me if they are not identical to yours:

-Short bursts of boost are fine. One-gear pulls are no problem at all.
-Multiple gear pulls under boost are not fine. In fact, the engine/turbo falls flat on its face probably about the middle of second gear. It almost feels like you're NA again.

If that is what you're going through, then (barring any other major problems), your cat is probably clogged up and that exhaust pipe is choking your car (and turbo) to death.

That turbo will not last long under those conditions, btw. The solution is a new catalytic converter and 2.5" or 3" (best) exhaust all the way back.

Hope this helps.

-GP-

you guys are making a great point. but I was told by a few reliable people that it would be ok to run with a stock cat-back IF I STAY WITH STOCK BOOST, AND DONT RUN THE TURBO MORE THAN 20-30 SECONDS AT A TIME, and thats what I've been doing for the past 4 months (3k miles).
but anyways, right now about 90% of the time when I boost at any gear, i can see about 4psi of boost (maybe a bit higher sometimes) before I feel a serious choke and a drop of boost. And the other 10% of the time, it feels okay and holds boost with no problem at all.
I'll try to take time to take off the cat tomorrow and run with the DP to see what it does:rolleyes:

ok I just took off the catalytic convertor but the problem is still there:mad: now I dont know what to look for anymore. I think i should start looking at every vacuum line. can anyone tell me the easiest way to check for leaks? I heard of people spraying some solution on the vacuum lines :confused: can someone clarify the procedure for a dummy like me please??

pull your intake pipe off of the turbo and check the shaft for play. Sounds like you fried it... Also check your grounds..
Travis

ok, I *** checked my ecu and its showing the knock sensor code, and my spark plugs are a little dark and the electrodes are gray(I think that means I'm running lean ??) A friend suggested that boost isn't holding because the ECU is getting a knock sensor signal which means the car is detonating from running lean so therefore, the ecu is cutting off boost to avoid harm to the engine. Does this sound like a possible explanation??

He also suggested that I unplug the knock sensor to see if the boost will hold.
please let me know your thoughts on this guys,
thanks

The ECU cannot just shut off boost. You will have boost whether you want it or not.

I'm surprised that no one has suggested this, but could it be the wastegate? I know its internal...but, couldn't it be messed up? Or could the seal between the wastegate and the turbo be messed up(I know this would usually cause it to boost out the ass...but, who knows):confused:

Originally posted by SENTRASER
I'm surprised that no one has suggested this, but could it be the wastegate? I know its internal...but, couldn't it be messed up? Or could the seal between the wastegate and the turbo be messed up(I know this would usually cause it to boost out the ass...but, who knows):confused:

Yeah I thought about that too Ryan, but I'm gonna disconnect the knock sensor and see if its bad first before I start taking apart the turbo:mad:

Originally posted by 1BAD_NX
ok, I *** checked my ecu and its showing the knock sensor code, and my spark plugs are a little dark and the electrodes are gray(I think that means I'm running lean ??) A friend suggested that boost isn't holding because the ECU is getting a knock sensor signal which means the car is detonating from running lean so therefore, the ecu is cutting off boost to avoid harm to the engine. Does this sound like a possible explanation??

He also suggested that I unplug the knock sensor to see if the boost will hold.
please let me know your thoughts on this guys,
thanks
Your plugs sound normal to me... it's when they're all shiny with little specs of metal on them that you want to worry... and look to see if the porcelin has little pepper-looking specs on it. If so...then that's a good indication that it's lean..
Travis

if your knock sensor shows up faulty, the computer automatically takes 5 degrees out of your timing. increasing cylinder temps and exhaust volume, which makes the computer take more timing out...and so on. but it wouldnt cause you to lose boost. just make you slower.

check wastegate function, make sure it isnt stuck open or something, or that your turbine still has blades on it.

ok I've been driving around with the knock sensor disconnected for a whole day and the car feels no different, is that unusual?
This weekend I'll start tearing out the turbo and check the wastegate. Thanks for all your advise guys, I'll be sure to let you know the results.
-Nick-

well, if the MIL light is already on, it wont feel any different

good luck with the removal process, it is failry easy