My car is not boosting correctly.  Car has power up to about 2500 rpm and then nothing.  MPG is normal.  I can't hear boost leaking like it does from an IC pipe.  I checked the hoses on the TB and they're fine.  Also checked the IC piping and it's all tight.  Air filter is new, K&N RU-1390.

If I accelerate very slowly I can get it to 3000 rpm.  If you get on the gas it doesn't move.  I read the post about how to check your turbo.  I think the problem has something to do with the wastegate.

I don't think it's a bad cat cause this happened suddenly.  And before this problem the car had great power.  I have the TG chip.  Spark plugs and wires are 10 months old.  AC Delco's.

I found a cracked line going to the turbo, to the wastegate.  I routed the turbo outlet hose to the wastegate directly to bypass the solenoid, no change.  I unhooked the turbo outlet hose altogether and the car boosts, only upon slow acceleration but I can get it to about 5000 rpm.

I'm thinking maybe the wastegate spring?  Or what else can I check?  I want my boost back!  :?

Have you checked the solenoid operation? Does it get voltage to actuate the wastegate?  Does the SES lite come on?

The cat can become clogged suddenly.  My dads did, thats why I didn't think the problem was a bad cat for a while, but it did in fact end up being the cat.  It went from overboosting one day, to not boosting at all the next.  It would boost to about 2psi if we pulled the vacuum line off the wastegate and power would fall way off at around 5k or so.  With the vacuum line on correctly it wouldn't get any boost.  Drop the exhaust and see if it fixes the problem, if so its the cat.  If not, I'm thinking the wastegate spring, but that is even easier to check, zip-tie the wastegate shut and go out and drive it.  If it boosts (which it should do very quickly and easily so be careful not to overboost) then thats the problem.

Shawn

There is no SES light.  How do you check the solenoid operation?  Can I pull the connector at idle and check for voltage?  I routed the turbo outlet vacuum line directly to the wastegate to bypass the solenoid, no change.

I will try to zip tie the wastegate shut.  If that is the problem, the spring is in the wastegate itself?  Would it be easier just to get a new wastegate at that point?

If neither helps, I guess the next thing will be the exhaust.  I was thinking of getting rid of the cat, I guess I will have an excuse to do it.

Thanks for the responses, and sorry for all the questions!   :oops:

Quote from: no1kickerThere is no SES light.  How do you check the solenoid operation?  Can I pull the connector at idle and check for voltage?  I routed the turbo outlet vacuum line directly to the wastegate to bypass the solenoid, no change.

I will try to zip tie the wastegate shut.  If that is the problem, the spring is in the wastegate itself?  Would it be easier just to get a new wastegate at that point?

If neither helps, I guess the next thing will be the exhaust.  I was thinking of getting rid of the cat, I guess I will have an excuse to do it.

Thanks for the responses, and sorry for all the questions!   :oops:

Yes the spring that goes bad is inside the wastegate, however Jud showed me pics of how to fix that problem when you're spring wears out or breaks.  You can put a spring on it externally, and if that is the problem I will send you the pics of mine so you know what you have to do.  

Shawn

If you bypass the actuator solenoid you will only get 4.5 lbs of boost. That is what the wastegate actuator diaphram preload is set at.

Putting a spring external to the wastegate actuator is not a very wise thing to do as you have no idea what the preload will be set at.

You said it will boost if you remove the charge pipe from the turbo outlet?? You need to go through all the pieces and parts from the charge pipe inlet all the way through to the throttle body. You most likely have serious crude build-up in your intercooler, something has collapsed in there somehow, or you have a SEVERE LEAK that you are just not hearing... 8)

Sorry, I think I wrote that wrong.  I get boost if I remove the vacuum line that goes to the bottom of the turbo (between the lower IC pipe and air filter).

Quote from: no1kickerSorry, I think I wrote that wrong.  I get boost if I remove the vacuum line that goes to the bottom of the turbo (between the lower IC pipe and air filter).

This is because the wastegate isn't being opened by the solenoid, because there is no vacuum to the solenoid.  So, this makes me think the wastegate is functioning normally.  If it is, there should be no change if you zip-tie it shut because it should be staying shut already.  

Shawn

Yea go with dbtk and Kenny!!!  And just to help out more than anything!!!!...the wastegate spring is not the thing its the rubber diaphragm that takes a leak when things fail in there 8)   And like Kenny said, wooohhh, you can run uncontrolled boost with another spring added on, this will defeat the computer from controlling boost and one other main benefit and that is when you knock and have spark knock timing retard for a length of time, the computer will bring down the boost if knock retard timing is not helping, a very good safety feature to keep!!!

Good luck!!!

Jeff M

Bypassing the actuator I get boost.  Feels like it's around the 4.5lbs, but I don't have a pressure gauge.  I'm just going by sound and feel.  I tied the wastegate shut and took it for a ride with the vacuum hoses in the right spots.  Builds boost very quickly but dies quickly at around 3500 rpm, stutters and won't go above that.

I read in the service manual that it is recommended to check exhaust backpressure.  It shows what looks like a pressure gauge in the O2 sensor spot, and what the max psi can be, otherwise there is a big restriction.  Of course the people at pep boys and autozone had no idea about this.  So I was going to put a fitting in and hook a pressure gauge to it.  Anyone know the thread size of an O2 sensor, is it a standard size?  Or am I just wasting my time with this.

How do you check solenoid operation to rule it out?  And I don't think it's fuel related, cause I can accelerate slowly and get to almost 5000 rpm.

I wouldn't even mess with trying to test the backpressure, just drop the exhaust and drive it around the block, if the exhaust is blocked somewhere, this should definately tell you that.  It is sounding pretty much EXACTLY like what my dads TGP did with a clogged cat.  Its worth the 15-20 min. job of taking it off.  

When you tie it closed, does it die quickly like this at any throttle position, or just WOT?  

Does you car still have the stock cat?

Shawn

With the wastegate tied shut, it will die quickly.  If you hit the gas it dies quicker than in you slowly accelerate.  I'm pretty sure my car has the stock cat.  I'll drop the exhaust and hopefully that will help.  Thanks again.

Well I got rid of the cat today.  Car has more power.  There is still hesitation at boost.  When it starts to make boost, it hesitates, then boosts slowly after that.  Any more suggestions, I have no idea what it could be.

I'd check the spark plugs again to see the condition they are in. Fuel pressure test it. If you grab the WG actuator rod and pull it towarts the DP it should feel tight and should snap back into place. Blow on the actuator port and it should hold pressure. Remove the WG selinoid hoses and pressure test them..they might be cracked. Check the TB (throttle body) to upper charge pipe hose. It might look like its clamped on right..but I had mine come loose from the bottom of the TB. Remove and check all IC hoses. And while your at it..flush the IC. It needs it after what..100K miles?

Thanks for the suggestions.  Last night I pulled and reconnected the ECM fuse, and it helped a lot.  Now it feels like the car is about 75% at boost.  There is still the hesitation right when the car starts to make boost.  Car is 100% below boost and idle is normal.

I only pulled one plug today (the easiest, right front).  It looked normal but it had build up, here's a pic:



The WG rod seems normal.  It takes a good pull to move it, and when you let go it goes right back into place.  I checked the upper IC to TB pipe and it's on tight, as well as all the other hoses and lines.

I also cleaned the TPS connector today and pulled the ECM fuse again, maybe that will help a bit.  I didn't check the solenoid, I'll do that tomorrow.  Next weekend I'll remove the IC piping to make sure nothings blocking it.  I'm going to run some fuel system cleaner too.  Also going to try swapping MAP sensors with another TGP.

I really appreciate the help so far.