Unable to boos above 11 - 14 psi

[mrslow]

Problem just started recently, I was on 21psi no problems and then it started maxing out around 11 - 14 psi with a stutter or misfire type of feeling, I thought it was a leaky BOV so I replaced it and the problem still persists. BLT comes up with no leaks and it feels like when the wastegate opens up it starts acting like this.

I've checked vacuum lines so far and haven't found any leaks. Should I check if there's fouling on the plugs or a bad plug wire? Or am I heading the wrong direction to try and chase this problem down?

 

[TAMA_player]

Are you really sure there are no leaks?
How are your AFR's when the stuttering occurs? if they comes 1 or 2 degree rich, is time to check transistor and coil connections. This happens to me once, also refuses to build boost.
But think your problem are more related to leaks, i recommend to do a comprehensive leak check.

 

[T is for TURBO]

How high did you take your boost leak? how long did it take to leak down?
It's rare, but it does happen, sometimes the flex section in the downpipe will collapse and cause boost issues.
Any CEL codes?

 

[talon3394]

Does the engine lose power? If the engine is revving fine it should build boost until your wastegate opens, Is it an external wastegate? if so check the spring and make sure its not broken or weak.

 

[T is for TURBO]

Hi bro, are you really sure there are no leaks?
How are you AFR's when the stuttering occurs? if they comes 1 or 2 degree rich, is time to check transistor and coil connections, spark plugs, and cables.
I am more biased on the leaks if you ask. And isn't easy to see them because you are on SD. When this happens to me, it ends being a bad intake gasket or bad injector orings. My car likes to blow both....

Where did he say he was running speed density?

 

[Dude McGee]

Even with minor boost leaks and a loose WG flapper, it should still eventually build boost, just not efficiently. A major boost leak on SD could cause similar issues. If your car is tuned for higher psi, you might have fouled your plugs. But Id check for shaftplay or messed up fins. It will only take a minute and you can eliminate the turbo as your problem that way quickly.

I think the SD thought is an assumption based off the 3 bar map in mods list. For 20psi, I think youd need a 4 bar though...

 

[T is for TURBO]

If he had an IAT along with a map sensor, then it would be safe to assume he's running SD. Plenty of people run map sensors with the stock MAF.

 

[Dude McGee]

True enough, although some people run SD without an IAT (I dont understand why, its a cheap easy to install sensor). Usually when people go through the trouble of chamging over to SD they list it though.

 

[mrslow]

It's running speed density, I didn't do the tune myself but have been meaning to get in there and make changes to it. BLT was up to 25psi. I will check everything afte work and post an update.

 

[TAMA_player]

Where did he say he was running speed density?

Ohh you are right, i misread that, i just read ECM V3 and map, and my brain assumes SD, sorry....

 

[mrslow]

Ok so I managed to go through and replace a couple of vacuum lines and now the BOV definitely opens up, previously it would just flutter, however it only opens under a certain PSI and then afterwards it still misfires and will flutter if higher than roughly 5 - 10PSI.

 

[Dsmkauai]

Have you checked the turbo for shaft play yet? Also you could have a pre-turbo exhaust leak id inspect those areas as well.

 

[mrslow]

I'm waiting on the car to cool down and then I'll check it out. Probably in an hour or two I'll get back to you and let you know how that looks.

 

[YzRacer119]

Could also be your boost controller sticking or wastegate sticking rather than being lose. My car did something pretty similar once when some tephlon tape got into the ball/spring mechanism. Cleaned out the BC and was good to go. It may not be your problem but It's something to check while you're waiting for it to cool off.

 

[mrslow]

Could also be your boost controller sticking or wastegate sticking rather than being lose. My car did something pretty similar once when some tephlon tape got into the ball/spring mechanism. Cleaned out the BC and was good to go. It may not be your problem but It's something to check while you're waiting for it to cool off.

There was a GReddy Profec hooked up, I removed that since it's external wastegate and it did fix the BOV not opening but it's still got a misfire. As for the wastegate I know it's opening because I can smell it before the car begins to stutter/misfire/whathaveyou.

 

[AWDtalontsi96]

check your spark plug gap could be getting spark blow out. your coils can weaken over time. I run like a .25 spark plug gap on 22psi

 

[jayson427]

I would test your coils if it keeps misfiring like that. Could be bad/old spark plug wires too.

 

[mrslow]

I don't have access to any tools to check the plugs themselves right now (I know I know, I have very few tools at home unfortunately), how would I go about testing the coils?

Also I have noticed I get knock in first gear sometimes, enough to trigger a CEL until I left off or shift. No other gear has this issue. I believe it's set to throw a CEL at 7* with knock, I have a replacement OEM sensor that I'll be putting in this weekend.

 

[TAMA_player]

I don't have access to any tools to check the plugs themselves right now (I know I know, I have very few tools at home unfortunately), how would I go about testing the coils?

When i had this no boost issue, the car misfires when trying to get on boost, it ended being the terminals (coils) getting vibration from the engine and cutting spark randomly .

Is easy to test this condition just get the car in idle and move the terminals with your hand trying to move them and looking for an odd engine misfire. This only will take you 4 minutes, just to be sure.
Both coil and transistor terminals.

 

[mrslow]

When i had this no boost issue, the car misfires when trying to get on boost, it ended being the terminals (coils) getting vibration from the engine and cutting spark randomly .

Is easy to test this condition just get the car in idle and move the terminals with your hand trying to move them and looking for an odd engine misfire. This only will take you 4 minutes, just to be sure.
Both coil and transistor terminals.

I've checked that and no change, although I do suspect either a bad coil/plug/wire or vacuum leak still.

Ok so I checked the turbo and there is some up and down and in and out shaft play, not a huge amount but there is definitely some there.

 

[mrslow]

Bit of a thread revive. I fixed all vacuum leaks in the system, BLT again and have now come to the conclusion that it's hitting fuel cut. I've gotten a knock sensor and coolant temp sensor to replace the ones on the car, is there anything else I should check or replace?