Im still having trouble with boost on my car. I own a 1999 2.4 with the GM SC and for some reason I cant go pass 3psi of boost. I made a post before but the problem isnt solved. Im wandering...
*if I had bad tuning, say i was running pig rich would that cause my boost to go down?
*If I had an exhaust leak?
*I do hear air gushing out when I approach boost (0 on the gauge), could that mean my bypass valve is really bad (cant really hear it once it starts whining though)?
I only want 2 more pounds of boost, it pisses me off to only see three. Any suggestions are helpful, seriously this needs to be fixed. I checked all the hoses and kinks, couldnt find any problems at all.
my first guess would be a boost leak in one of your lines and if not you have something hooked up wrong i would go and make sure you everything is hooked up and clamped down and connect right
also try the search button
You take a women and X her by PSI devide the legs and you can then juice the car......LOL
Tuning (or your complete lack thereof) has nothing do with how much boost you're making. Boost is generated before fuel comes into play.
Exhaust leak affects turbos, not superchargers.
Get a vacuum tester/pump and check the bypass. If it holds vac, it's fine. If it doesn't, it's fooked.
Have you tried a different gauge? The calibration may be off.
14.330 @ 96.37mph
Sam,
I had a similar problem once and tried solving by guess work, this wasted a lot of time and money. Now I solve problems systematically. So my advice will be based on looking at related systems and finding the cause in progressive steps.
This is my opinion;
Problem as I understand it; The SC does not appear to be generating proper amounts of boost.
Based on what you have said, I would focus on the related area from the intake manifold portion of the S/C to the air intake. The S/C is a big air pump;
1. Rule out an possible air restriction prior to the super charger. (air intake/air box/air filter/throttle body)
2. Next is the waste gate diaphragm and waste gate valve, If operation properly it should vent near idle and not vent as RPM rise.
a. Check the waste gate diaphragm to see if it has wiggled free of it's mounting bracket. There are three plastics pins that hold the waste gate diaphragm to the mounting bracket. (
Mine came free during operation and I got a simsimilarsult, very little boost due to the waste gate stuck in the open position. The diaphragm is located on the underneath of the S/C so it was hard to see until I removed the S/C. Loctite epoxy reattached the diaphragm frame to the mounting bracket.
b. The diaphragm itself could be bad, does it travel to open and closed positions?
3. Next work your way through the S/C, Pulley working? S/C frame cracked? S/C intake manifold cracked?
4. Intake gasket leak? There are four separate o-ring type gaskets for the S/C intake manifold flange that run about $40 each.
5. Is it time to get the S/C rebuilt? There is a place named in other JBO posts that will rebuild the S/C and ship it back to you.
Good Luck,
Don
Don thanks for taking the time to write that. I dont think its the SC but it is a possibility. This has been happening ever since I put it on. Im thinking of looking into the bypass, but couldnt I tell if that was the case by looking at my boostgauge. At idle, normal operating temperature it runs at 19HG, is that normal? By the way, you can manually open and close the wastegate? Im afraid to break it, but if the SC is on the car can it be done to check? and how?
Thanks,
Sam
Remember I don't know everything you can see or have experience, but;
First, if you are going to read the boost gauge for information concerning the problem ok, but now you must ensure it is working properly and not part of the problem. Double check your guage line/sensor/gauge for kinks and such just to be sure your readings are trustworthy. (FYI-I had wierd readings once on my auto meter gauge, it turned out to be a kink in the line as it entered the fire wall.)
Second, not sure there is much you can check on the waste gate diaphram while the S/C is installed, not much room. Once off, yes I could carefully move the waste gate push rod. It was very clear that the gate was in the open position. I would atleast try to check and see if the diaphram frame is free of the mounting bracket like the pic above.
Thrid, I am simplely suggesting you ensure the S/C and boost gauge are working properly before you start digging into tuning. Or you may have an ugly story to tell us in the future.
FYI - my 2000 LD9 GM S/C is giving upto 8-10 psi. You can ask others what they normally see.
Don
yep, do exactly what these guys said.
s/c itself i know is fine(i have a feeling it is a boost line / guage issue).
i was seeing 5-5.5 psi everytime.
keep us updated.
if all else fails, check the coupler in the snout attatched to the pulley...
my buddies m62 with alot of miles on it, the coupler went out and there was a ton of play in the pulley before the rotors would turn, and he didn't see anywhere near as much boost as he used to..replaced the coupler and now its back to where it used to be
Sam, replace your throttle cable first. I can almost garuntee that your TB isnt opening all the way with it like it is now, then work from there...
RyZ96 wrote:if all else fails, check the coupler in the snout attatched to the pulley...
my buddies m62 with alot of miles on it, the coupler went out and there was a ton of play in the pulley before the rotors would turn, and he didn't see anywhere near as much boost as he used to..replaced the coupler and now its back to where it used to be
I got that same problem on my GTP. It still makes full boost though. Just makes an annoying rattling noise at idle.
Darren, I would say your right, but we hooked up a vacum line from the throttle before the sc, and saw 0psi at WOT. I doubt thats it, but its worth a shot since where only dealing with 2 more pounds of boost. Im going to go pick a cable up tommorow. By the way, where you been man. You lost the motor lol But hopefully, I can swing by show you the car...
Good luck Sam,
When you find and fix the problem, let us know what all happened. Sharing our different troubles and repairs may help someone having a similar problem in the future.
Don
The guy called me to do the engine swap, i gave him the price to do it which was a killer price btw and he never called me again...
You might want to double check and make sure you have the bolts that hold the SC to the head tight.
FORGET GIRLS GONE WILD WE HAVE GOVERNMENT SPENDING GONE WILD!
^ i have seen people do that, and i almost did that myself.
any updates sam?
Gonna do most of the things you guys suggested tommorow:
* change all vacum hoses and put clamps
* retourque the sc bolts
*buy a new throttle cable
i used some windshield washer tubing for my vaccum hoses. worked well. comes in like 6 foot sections and any parts store has it.
Okay, Make sure you DO NOT have this,
Underdrive Pulley
LOL, this is what i had on my car and come to think about it, a smaller pulley in the belt rotation will make your charger pin slower, this was my problem, so i bought a stock sized lightened crank and a 2.6" charger pulley...
NEW SIG COMING SOON FOR 07'!!!
Just a few thing's I want to add...
When his car is in boost it sustains a constant amount of psi It does not decrease with the higher RPM's which is not normal. The boost is suppose to decrease as the engine increases it's speed since more and more air is being drawn into the engine. I have a feeling the problem lies either in the wastegate acuator or throttle cable.
The boost guage seems to be operating fine aswell. We orginally thought that the line was krinked but we replaced it and got the same result.
BTW he doesn't have an aftermarket underdrive pulley....just stock.
Markseco wrote:
When his car is in boost it sustains a constant amount of psi It does not decrease with the higher RPM's which is not normal. The boost is suppose to decrease as the engine increases it's speed since more and more air is being drawn into the engine.
Sorry to say, but my GM charger maintained the same psi throughout the RPM band, and if anything it went up near redline a little bit. Don't know where you got the idea above, but I see nothing wrong with his car doing such.
My charger did the same thing though, showed 3 psi, ended up being the bypass valve broke off the bracket like the one above, as they did a great job mounting it (not!).
mine went up as well , ive seen close to 9psi from 6000 up in 2nd gear
Joe, was it hard to change the bypass? I have the part number and im ready to buy. Since you had the same problem, well I have a hunch thats it. How do I tell its broken with the sc mounted on the car?
Joe Schulte wrote:Markseco wrote:
When his car is in boost it sustains a constant amount of psi It does not decrease with the higher RPM's which is not normal. The boost is suppose to decrease as the engine increases it's speed since more and more air is being drawn into the engine.
Sorry to say, but my GM charger maintained the same psi throughout the RPM band, and if anything it went up near redline a little bit. Don't know where you got the idea above, but I see nothing wrong with his car doing such.
My charger did the same thing though, showed 3 psi, ended up being the bypass valve broke off the bracket like the one above, as they did a great job mounting it (not!).
Maybe it's different for you guys with the superchargered cars. I know my car won't sustain a certian amount of boost for the entire RPM band...it starts to fall.
Sam, first thing you do is replace the throttle cable, that NEEDS to be replaced, so do that first and see, then move onto the bypass valve.
