Help with knock in 4th gear
10-19-2014, 04:17 PM
#1
Instructor
Thread Starter
Help with knock in 4th gear
I have 04 C5 with a Procharger P1SC, AR 1 7/8" long tube headers, Corsa cat backs, Alky methanol system, Innovator West 10% overdrive harmonic balancer.
I switch out my SC pulley to raise my boost level from 7 psi to 12 psi and was having it dyno tuned. The engine did great up through 3rd gear all the way to 6200 rpm. The motor sounded like a beast. I was having a problem with my PCV air flow because it blew the oil dip stick out near WOT. That worried my a lot thinking I was getting a lot of blow by, but I went grabbed a couple pieces of 3/8" hose 4' in length from the parts store and hooked them up to my PCV points and ran the line off the side of the car with some a couple of shop cloths wrapped around them. Then check it randomly after WOT revs for blowby oil and I even kept my hand over it a couple of time to feel for any blowby and their almost nothing, so the blowby wasn't the problem. Which was good news, but it did appear that the small oil catch can I'm using wasn't letting any air pass through it. So I'm ordering a new one soon as soon as I can figure where to mount it on my 04 because there is no room anywhere that I can find and that's why I was using the small one in the first place.
Now when the tuner tries to do the 4th gear run we got a knock about 3600 to 3800 rpm. So the computer did it's thing and started pulling timing. the tuner even pulled timing all the way down to 4 deg and it was still showing a small knock on his computer.
Does anybody have an idea of what might be going on and how I can fix this problem. any help on this would be greatly appreciated. Thanks in advance
Forgot to mention that I installed new plugs and wires, larger air filter dongle , and air filter a couple of days before the dyno session.
I have had the SC on the car about a year and the first tuner told me that the motor seemed solid because it wouldn't knock and that he had to make it knock, which I didn't understand, but I also don't know that much about custom tuning a car either.
I switch out my SC pulley to raise my boost level from 7 psi to 12 psi and was having it dyno tuned. The engine did great up through 3rd gear all the way to 6200 rpm. The motor sounded like a beast. I was having a problem with my PCV air flow because it blew the oil dip stick out near WOT. That worried my a lot thinking I was getting a lot of blow by, but I went grabbed a couple pieces of 3/8" hose 4' in length from the parts store and hooked them up to my PCV points and ran the line off the side of the car with some a couple of shop cloths wrapped around them. Then check it randomly after WOT revs for blowby oil and I even kept my hand over it a couple of time to feel for any blowby and their almost nothing, so the blowby wasn't the problem. Which was good news, but it did appear that the small oil catch can I'm using wasn't letting any air pass through it. So I'm ordering a new one soon as soon as I can figure where to mount it on my 04 because there is no room anywhere that I can find and that's why I was using the small one in the first place.
Now when the tuner tries to do the 4th gear run we got a knock about 3600 to 3800 rpm. So the computer did it's thing and started pulling timing. the tuner even pulled timing all the way down to 4 deg and it was still showing a small knock on his computer.
Does anybody have an idea of what might be going on and how I can fix this problem. any help on this would be greatly appreciated. Thanks in advance
Forgot to mention that I installed new plugs and wires, larger air filter dongle , and air filter a couple of days before the dyno session.
I have had the SC on the car about a year and the first tuner told me that the motor seemed solid because it wouldn't knock and that he had to make it knock, which I didn't understand, but I also don't know that much about custom tuning a car either.
10-19-2014, 10:55 PM
#2
Drifting
Member Since: Sep 2009
Location: cinnaminson n.j.
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St. Jude Donor '14
Do you hear a knock? If so start killing cylinders one at a time by disconnecting the injector. See if there is a significant change in the knocking sound on one cylinder. That's the problem cylinder. You might have a broken ring land on a piston. If you can't here a knock, you may have pushed boost pressure past the pcv and pressurized the crankcase. That will blow out the dipstick.
10-20-2014, 08:10 PM
#3
Instructor
Thread Starter
I will definitely try the injector trick, but I definitely couldn't hear the engine knock when it was happening. If I can't hear it knock will the injector trick still work.
If I have pushed the boost pressure past the PCV how can I correct this problem because when it happened I had already run 2 hoses straight from the PCV connections off the valve cover and the one under the throttle body area off the side of the car, so I know there was know restriction from a clogged hose or oil catch can.
the engine has been running a little rich for the past 6 months, but only if I really opened it up. I would get the DIC codes for bank 1 & 2 running rich and because of this I haven't been really opening it up very often.
I was planning to take the intake off to check for excessive oil build up and then remove the heads to check for excessive carbon build up, but I hate to do all that if it isn't really necessary because of the $200+ cost of new gaskets and bolts, but if I need to I will.
If I have pushed the boost pressure past the PCV how can I correct this problem because when it happened I had already run 2 hoses straight from the PCV connections off the valve cover and the one under the throttle body area off the side of the car, so I know there was know restriction from a clogged hose or oil catch can.
the engine has been running a little rich for the past 6 months, but only if I really opened it up. I would get the DIC codes for bank 1 & 2 running rich and because of this I haven't been really opening it up very often.
I was planning to take the intake off to check for excessive oil build up and then remove the heads to check for excessive carbon build up, but I hate to do all that if it isn't really necessary because of the $200+ cost of new gaskets and bolts, but if I need to I will.