I've had this nagging problem now for a while and I'm trying to figure it out. I think I have a vac leak, and now I'm trying to chase it. I have an adapter with a schrader valve on it that i want to put in the intake tube to the blower. Then I want to hit it with maybe 10-15 psi from a regulated compressor and see if I can hear or feel any leaks.

What makes me think I have a vac leak is the truck stumbles off idle and doesn't feel that snappy at all. I get up to 6deg of knock at either throttle tip in or when going under load. At idle, warm, and in gear I am only -15 in vac, that seams low to me.

Also with the maggie. when you git -2in vac shouldn't the bypas close and you should get instant boost right? I can go progressivly from vacume right into boost and back again and hold it where I want. Going from memory it seems I have to give it more pedal to get into boost now.

 

Your idea of trying to pressurize the intake will only work if you remove some intake rockers so that all of the intake valves are shut.

 

That would be ideal. My buddy actually came up with that idea when trying to find a leak on his turbo miata. It does leak through those open valves, but atleast on his we were still able to find the leak in his intake. I figure it can't hurt. If I have to I can pop the valve covers off and pull the needed rockers. I could also try the ole meathod of spraying starter fluid to try to find the leak.

 

With your cam you should be pulling more vac then that, I idle at like -14 to -15 with my cam and It is larger with more overlap. Are you still using your 02's or are you OLSD? If you have 02s are you getting any odd fuel trims?

 

I'm still using the 02's. My LTFT are all over the place. I don't have any logs, just watching a scan gauge as I drive, but it goes +/- 10 in some cases. Also as the mornings are getting cold, the truck will run much better first off then as I drive it get worse That makes me think as things heat up the leak gets worse.

 

when I was geting tuned by nelson I had some issues and thought we had a vac leak. He had a rubber boot that fit over the throttle body and he pumped in pressurised smoke and wherever the smoke comes out is your leak

 

Dont hit it with pressure, get a smoker if you think you have vacuum leaks. The smoke will seap thru in an instant.

 

Pumping smoke through won't hurt anything as it settles out?

 

I don't mean to highjack this thread but what do you use for a smoker?

 

No the smoke cant hurt it is petro based.They are a small unit that uses a light oil and heats it and you regulate the pressure and volume of smoke that goes in. These are on the tool trucks and go for around 250 ish. If you think your leak is in the intake sys you may want to pull the rockers to shut the valves this will fill the intake and all parts or systems that use vacuum ie brake booster, evap solenoid and dont forget to plug the tb. Hope this kinda clears things up.