LsTurbo91

ok, today i was enlarging the wastegate port on my drag manifold a bit to see if my boost creep problem would go away. I started the car, I noticed my boost gauge was reading 14-16inhg at idle. Normally it would be 18-20. I went on my way thinking it might be a small leak on my vacuum hoses. I made a 3rd gear run on the freeway and 2nd gear. I went home to try to find the leak. I disconnected the brake booster vacuum and pcv and plugged it temporarily to see if it was leaking from the hoses. After that it dropped back to 18 then a 1 min or 2 you start hearing knocking noise coming from the engine. I stopped the engine and reconnected the hoses back and I still hear the knocking noise. After I heard the knocking noise I see the boost guage reading 10ingh at idle. It feels like im running on 3 cylinders. All 4 plugs are firing. What could this be ? Spun Rod bearing?


[Modified by 9psiLsT, 3:53 PM 7/18/2001]

redline

I would look at valves. Bearing are not going to affect vaccuum reading but valves will.

k

LsTurbo91

ok, I went through each cylinder and they all seem fine except for one which was fairly loose. I didn't get a chance to tighten it because I had to go back to work. Do you think that is the cause?

Liltrix

How did U do the enlargement? are U sure a piece of material or debris didnt get blown into the enging for the mods U were doing?

LsTurbo91

nah I doubt it. I took measures to prevent that. Plus it would be very little to none debris going into the turbine which would just go right out of the exhaust. Well I readjusted it and I still have a low vacuum 16. When I started it, it wouldnt start until the 5th try. Once it started it stumbled and you can hear it knocking. I revved it to 1500. You can hear the knocking but slowly start to fade away. After that it was fine. Then when idling. the vacuum would start on 18 then slowly drop to 16 or so. At least its not knocking anymore.

GSRwBOOST

do a compression test... just to be safe. Believe me when I tell you the feeling you get will either be a relief or complete dissapointment...

if the knocking returns or is even audible.. take it in and have it looked at.. if it's a spun rod bearing.. you dont want it to compound into a much larger problem...

VaporTrail

agreed. Do yourself a favor and drain your oil, and if you can, use a very fine strainer for it. If you see brass shavings in the oil, that's a spun bearing. Ran into that a little while ago with a friends motor. It was because he allowed a valve lash retainer nut get loose, which got into his oil pan, and wreaked havoc.