car dies when disengaging clutch after cam install

[rnstphns]

I did a cam swap on a buddys car the other day and seem to be having some issues. The only mods to the car are the following; 1g CAS, all emissions deleted, 16g, intake, exhaust, bc 272's, and adjustable cam gears. The car ran perfect on the way over to my house and everyother thread i find havent been resolved or havent been responded to since it was resolved. The car fires right up and idles perfect, but as soon as the clutch pedal is pushed down the car boggs and tries to stall. If the car is reved while the pedal is pressed it will stall. We've boost leak checked it and fixed all of those. Checked for vaccum leaks and haven't found any. Changed the TPS and ISC and it hasnt effected the problem at all. I halfway think it could be a clutch problem but the fact it drove over here just fine and the fact the clutch doesnt have to be depressed all of the way to make it act up makes me think otherwise. Is there a sensor or vaccum that allows the motor to maintain idle when the clutch is depressed similar to the one on the power steering? any help would be appreciated.

 

[delta448]

From the way you describe it, it really sounds like it's a problem with the clutch system, but I think it's possible the car is just running really rich or getting a bad/choppy airflow signal. Changing cams really has a pronounced effect on the vacuum at idle and can cause big problems with the MAS readings. It's time for you to find all the boost leaks.

When you press the clutch, does it start bogging even before you use up all of the clutch pedal free play or does it start only once there's actually fluid being pushed out of the master cylinder?

Maybe when you tightened the cam caps you pulled the trans and block out of alignment there Mr. Hercules.

 

[jrohner]

You'll most likely have to turn the BISS out a bit after putting in more aggressive cams.

 

[constant_proj21]

^^agreed, turn the idle up a bit before searching for clutch issues.

 

[delta448]

I completely agree. I think that the problem is 100% the now lower idle vacuum. Just curious, what's the CR on your 6 bolt Mahles?

Moving the idle rpm a little higher with the BISS will definitely help, it'll increase vacuum and smooth out the MAS signal for sure, the only question is how high you will have to raise idle speed in order to stabilize it. Not that it matters, but I like the lumpy idle, so I'd try to keep it a little lower than some.

I still think you should boost leak test too.

 

[rnstphns]

The biss screw has been adjusted. I can have it idleing at 1500 rpms or 900 rpms and it still does the same thing. It boggs as soon as you start to push down on the clutch pedal.

Just curious, what's the CR on your 6 bolt Mahles?

Their 8.5:1.

 

[wazzelby]

Any chance you installed the 1G cas 180 degrees out? Just something else to check..

 

[delta448]

It boggs as soon as you start to push down on the clutch pedal.

Try this: hold the clutch switch down with a finger and push the clutch pedal in with the other hand. Still bogging?

 

[rnstphns]

Any chance you installed the 1G cas 180 degrees out? Just something else to check..

checked it and its all correct.

Try this: hold the clutch switch down with a finger and push the clutch pedal in with the other hand. Still bogging?

Sure does. Drove it today, and the drivetrain seems to be working perfectly fine. The clutch engages and disengages as it should. If I'm decelerating and just put it in nuetral without pushing in the clutch it drops back down to around 1000 rpms and doesnt try to stahl. If i push in the clutch in the same scenario it stahls out. Any more ideas?

 

[delta448]

When you depress the pedal with the engine running, is there any abnormal noise, like metal on metal grinding?

I think you may have a problem with either the TOB or possibly some loose flywheel bolts, assuming the crank endplay is within spec.

 

[rnstphns]

I checked for crank endplay when I was down there doing the timing belt and it all checked out. For some reason the biss screw isnt functioning correctly either. It only makes a minimal difference from being all the way in, to all the way out. What could cause that. I scanned for codes and it had a random misfire code and an o2 sensor code. I was expecting a isc malfunction code but there was none.

 

[delta448]

Did you use a scan tool to enter idle adjustment mode?
On a 2G you have to do that in order to command the ECU to hold the ISC in the center of it's travel and keep it from offsetting any changes to idle speed. Otherwise when you move the BISS one way the ISC will automatically move the other way to attempt to maintain the same idle speed.

 

[byebyev8]

Maybe your throw out bearing is bad. Do you have a lightweight flywheel?

 

[rnstphns]

Did you use a scan tool to enter idle adjustment mode?
On a 2G you have to do that in order to command the ECU to hold the ISC in the center of it's travel and keep it from offsetting any changes to idle speed. Otherwise when you move the BISS one way the ISC will automatically move the other way to attempt to maintain the same idle speed.

we did not do that.

Do you have a lightweight flywheel?

yes it does.