Bad blt test..

[talonsteve25]

My car has been acting a bit strange. When its hot and i shut it off and let it sit for about half an hour and try to start it again in runs around 20's on my wb and slowly comes back down to normal. Other wise it runs fine cruises at 14.1 and under boost runs 10.3.

So i did a blt today and found it cant hold over 2 psi for more then a few seconds.. i know its suppost to be able to hold 20 psi for 30 sec so i have some issues. But the thing is it runs fine under boost and off boost and i dont get why? Im replacing all the injector seals today to because they are hard as plastic. But it doesnt make sence that it only runs lean warm and at idle for 30 sec or so? Any input appreatiated!

 

[kenamond]

My car has been acting a bit strange. When its hot and i shut it off and let it sit for about half an hour and try to start it again in runs around 20's on my wb and slowly comes back down to normal. Other wise it runs fine cruises at 14.1 and under boost runs 10.3.

So i did a blt today and found it cant hold over 2 psi for more then a few seconds.. i know its suppost to be able to hold 20 psi for 30 sec so i have some issues. But the thing is it runs fine under boost and off boost and i dont get why? Im replacing all the injector seals today to because they are hard as plastic. But it doesnt make sence that it only runs lean warm and at idle for 30 sec or so? Any input appreatiated!

Could be a vaccuum leak. If that's the case, you'd run lean at idle/cruise, but your fuel trims might be compensating. Take a look at your LTFT values. The rule of thumb I've heard is that you want them to be within +/-4%. If they seem high at idle, then that indicates that you're running abnormally lean and extra fuel is being added via the LTFT-Lo trim.

It could also be a leak that leaks in under vaccuum and out under boost. In this case, it isn't always as obvious under load as it is at idle. There's less airflow at idle than under load, so a leak makes more of an impact at idle than under load (the air doesn't have enough time to leak out as much air as it would at idle). If your BLT came back at a 2psi max, you've got to fix that. Otherwise, you have no idea if there are other problems. I assume you're using compressed air to do this and not a bike pump. Get a 2nd pair of ears and eyes to help you. If it's a 2psi max, that's probably something you'd be able to hear (hissing). Check your PCV valve during a boost leak test; unscrew it from the VC and see if air comes out the brass nipple of the valve during the test. If so, put your thumb firmly over it and repeat the test and see how much that helps. Also, remove the oil cap and see if you hear hissing inside the VC. That might be leaks through the intake valve stem seals (they separate the intake ports from the head, so if you pressurize the intake, it can leak up above the head by the cams) and it might be worn rings (blowby) that you're hearing. Make sure the motor's warmed up so that the rings have expanded, or the ring blowby will fool you into thinking it's a boost leak.

You just have to find the leaks...they're somewhere.

 

[talonsteve25]

I found an air leak in each injector seal and the biss screw to. The lean idle only happens for a little bit then it slowly goes away and idles fine. The biggest thing i think i did wrong was check the engine after it sat over night, and like you said kenamond it could be ring blow by becuase the motor is cold. And i was using a compressor not a bike pump.

And the motor was just rebuilt 2k ago with weisco/ eagle combo and built head and stock cams so i dont think my valves would leak but will check just to make sure. Ill fix the seals right now warm it up and try again and if im not back complaining its fixed