Can't boost past 5psi

[fourgsixthree33]

Ok. No MBC or BCS.

Prior to this week, I ALWAYS maxed out at 10psi. The T25 had crazy...CRAZY...shaft play. Stll always boosted at 10psi.

Then one day, I got this misfire after swapping VC's. Acts exactly like the misfire I had before doing the Pot Mod (I have the 1G CAS on my 2Ga.).

Random misfire while cruising with low throttle. I went to the track friday. I made 9 passes, no issues with the misfire because I was always WOT.

So, I was thinking it was the turbo. Took off the T25 and installed my 14B. Just took it for a ride tonight, still boosting at only 5psi.

Now the other day I was looking over the car and found the plug on the knock sensor (on the knock sensor side) was broke and not making contact. So I cut both plugs off and wired the wires to eachother directly. No change in performance.

You guys have any ideas? Besides a BLT?

 

[BurrowZ]

I don't mean to be rude but why wouldn't you try a boost leak test first before even posting?

To help you out a little, I had a slow spooling problem with lower boost. BLT showed nothing and turns out the wastegate was sticking open a little.

 

[Riceburning101]

Agreed leak test and sounds like open wastegate

 

[fourgsixthree33]

I don't have access to one right now. Last time I did a BLT was a couple months back. Fixed a few small ones and haven't really messed with anything since.

It feels like timing is being pulled rather than a boost leak.

I would also like to add that I am reading normal vacuum. Around 20psi at idle.

I have not done this with the 14B yet, but in neutral when revving the car with the t25, it wouldn't go much past 5K RPMS's.

 

[boosting88]

I had that happened to me the downpipe was clogged with shit in it.

 

[blasterracer817]

http://www.dsmtuners.com/forums/articles-parts-fabrication/386650-how-build-boost-leak-tester.html
make your own boost leak tester and test that thing to see if thats what it is. Might as well see if its a leak rather than chasing something that might not be the problem. Good luck

 

[GSLENK]

I once blew an intercooler pipe coupler. I hit about 5psi under WOT/heavy load. MBC set at 17psi... It wasnt blown all the way off, just partially... hence only 5 psi.

Just do the BLT. If you dont have one, buy one now, or make one now. thats one of a few tools you should always have. and not have to borrow/rent.

 

[fourgsixthree33]

Thanks for the replies.

I am going to make a BLT.

Does the car always run bad with a boost leak?? My car seems to runs fairly smooth.

Hopefully it is just a small boost leak. I know there are a couple of small leaks.

 

[92AWDHX40]

my car ran ok with a boost leak but i dont like ok,i like it running its best.

 

[rlacasse1]

Does your engine bay seem unusually hot after you drive it for a bit?

 

[razrman8]

As many people have stated above, boost leak test is in order. A proper boost leak test is a good default to fall back on when your car is not running properly. To answer your question about it running smoothly, yes it can drive perfectly normal with a boost leak if you are just tooling around. My GSX has done something like that before, till you try to build boost, then it backfire and stutter. Please get that boost leak test properly performed and get back to us on it.

If and only if that boost leak test checks out, rlacasse1 made a point about it being hot under the bay. You may have an exhaust leak that you are unaware of. But check your boost leaks and get back to us. Good luck.

 

[fourgsixthree33]

Here is a pic of the wg arm. Does it look ok? Ill do the blt though. I am also running open downpipe.

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[GSTurbo1]

yea looks about right should be able to make the tension a little tighter. Might make you spool quicker

 

[NathanCarlK]

You can buy a boost leak tester in the marketplace for around $20 as well if you dont want to make one.

 

[rlacasse1]

I asked about the heat because you mentioned the knock sensor connector being jacked up.

If your knock sensor is bad, it will kill the timing and you will barely build boost. Additionally, it will retard the timing so badly that it will cause the exhaust manifold to heat up like a mother effer. Which is why I was asking if it was getting hot under the hood, at least hotter than usual.

 

[99boostedgst]

I can drive a mile all together come back and it feels like its on fire under the bay, magen manifold,and Garrett Turbo no heat sheilds. Even my VC is beyond hot.

 

[fourgsixthree33]

yea looks about right should be able to make the tension a little tighter. Might make you spool quicker

I was curious. Double checking that it looked alright.

You can buy a boost leak tester in the marketplace for around $20 as well if you dont want to make one.

I asked about the heat because you mentioned the knock sensor connector being jacked up.

If your knock sensor is bad, it will kill the timing and you will barely build boost. Additionally, it will retard the timing so badly that it will cause the exhaust manifold to heat up like a mother effer. Which is why I was asking if it was getting hot under the hood, at least hotter than usual.

I can drive a mile all together come back and it feels like its on fire under the bay, magen manifold,and Garrett Turbo no heat sheilds. Even my VC is beyond hot.

+1 on that. My car always puts off a lot of heat. Especially since it is already 90* out outside.

My friend texted me and said he still had his boost leak tester. So after work, I went over to his place, picked him up, and went to the nearest gas station with an air compressor.

Put about 20-25lbs into the system. Right away we seen some leaks after using the soapy water. Fixed a clamp on the upper IC pipe, fixed a couple zip ties on vacuum lines, and cut a section of the line for the WG because there was a small tear in it. Pressurized it again, no leaks except for a VERY small leak coming from the vacuum line for the boost gauge. Couldn't get it to completely stop leaking, but it is very small.

I also had bought a new Potentiometer on the way to his place. So I unplugged the ECU and quickly wired up the new Pot.

Took it for a drive, no real noticeable difference. I don't start boosting until 4K. After 5K, she pulls pretty good. But anything under 4000RPMS SUCKSSS. I can barely spin the tires in first gear.

Any more suggestions? Still leaning towards to knock sensor? Would it work how I have it wired up??

 

[everydaydriven]

Check your actual timing bro. I once had a tensioner give and it aloud the intake to jump a tooth when in a pull. Next pull ran like shit. Bet that's it. All else is been check. Set for TDC and make sure the cams base lines line up. Bet they don't.

 

[Rsawd95dsm]

Try gauging where the WG flapper is right now then take the arm of the wastegate and manually move the flapper to c how far it goes until its completely shut. Sounds like to me the WG isnt fully sealing

 

[fourgsixthree33]

Try gauging where the WG flapper is right now then take the arm of the wastegate and manually move the flapper to c how far it goes until its completely shut. Sounds like to me the WG isnt fully sealing

Will do, but IMO, the chances of two different WG's on two different turbos having the same exact problem is slim to none.

It does sound like a WG problem though. So I checked it. Pulled the pin out, and it moves back and forth as it should.

Also checked the mechanical timing- dead on.
Inspected the FMIC- no holes or anything.
Checked the exhaust manifold studs/nuts- tight.

Could it very well be my knock sensor? A friend checked my codes with a code reader BEFORE I got rid of the plugs and wired the KS directly to the harness. It said "Knock Sensor Circuit Malfunction" and something about no TDC signal.

 

[LandSpeed-DSM]

Drop the downpipe and check the inside of your flex section.

Provided you have performed the following:

BLT
Tested you WG actuator
Made sure the gate isnt stuck
No pre turbine leaks

 

[fourgsixthree33]

Drop the downpipe and check the inside of your flex section.

Provided you have performed the following:

BLT
Tested you WG actuator
Made sure the gate isnt stuck
No pre turbine leaks

Ok so get this guys. I zip tied the vacuum line for the WG so that it was kinked. I hit 12+ boost!? This means the actuator is bad??

I run open downpipe btw LandSpeed. More like open O2 housing I guess.

 

[SBstar]

Could be an issue, did you check the turbine housing for cracks through the wastegate hole? This could/would keep you from building boost, maybe possible with both turbo's but unlikely My guess is that the wastegate is fine, with it forced shut you should've hit 20+ psi easily, you simply forced everything you could through the system which obviously has a clog. . As said, check your downpipe/cat to see if they're clogged as that's a pretty good possibility. If all else fails unbolt your downpipe and go for a ride, after you put the wastegate stuff back to normal. Also check all your piping for a rag or anything you may have left behind in the system, it happens.

 

[everydaydriven]

O I'm sure it could of went more I just told him to see if that would fix the issue. Don't wanna just jump on it an blow seals. Sounds like a old 14b wastegate to me that has loads of miles WOT on it. Swap it out. Simple task an u have a spare on hand.

Let us know then

 

[fourgsixthree33]

Could be an issue, did you check the turbine housing for cracks through the wastegate hole? This could/would keep you from building boost, maybe possible with both turbo's but unlikely My guess is that the wastegate is fine, with it forced shut you should've hit 20+ psi easily, you simply forced everything you could through the system which obviously has a clog. . As said, check your downpipe/cat to see if they're clogged as that's a pretty good possibility. If all else fails unbolt your downpipe and go for a ride, after you put the wastegate stuff back to normal. Also check all your piping for a rag or anything you may have left behind in the system, it happens.

Again, for the 3rd time, I am ALREADY running open downpipe.

Thanks for the advice though. Great info.

O I'm sure it could of went more I just told him to see if that would fix the issue. Don't wanna just jump on it an blow seals. Sounds like a old 14b wastegate to me that has loads of miles WOT on it. Swap it out. Simple task an u have a spare on hand.

Let us know then

Yea, with the line pinched I boosted 15psi, then hit fuel cut . Swapping the WG actuator tomorrow.

I inspected the 14B thouroghly when I got it. No cracks. It was in known good condition when it was pulled off the last DSM it was on. No issues.