Here not too long ago I installed a CC503 cam and it cranked fine and runs fine in the upper rpms but down low I have a surge issue almost like a miss. When I described the problem in a earlier thread someone mentioned cam surge. So I started looking up cam surges and that sounds just like my issue. But the more I drive it the more I fill that this little cam can’t be this bad. I started to look up stuttering and so a lot of folks mentioned O2 sensors. Well I know I haven’t replaced mine in 8 years so tonight I unplugged them and drove the car and I didn’t have any more stuttering at all it was all smooth. My question is when disconnecting the O2 sensors what all does that do? Do you think my O2's are shot? Here is a link to the post that i started about the surge when i installed the cam. http://www.camaroz28.com/forums/showthread.php?t=631681
Thanks in advance and sorry for the long post

 

When you unplug your cars o2's the car switches back to open loop. Which means the cars fueling is running off of default settings programmed into the pcm. Also known as speed density. Try replacing the o2's first, but most likely you have a header gasket leakin. Or you might have a leak at the collector(s). Also vacuum leaks will cause this. I have been battling this same issue. When you hold the throttle steady while cruisin the car bucks a lil. Step in the gas a bit, pulls steady! I bet if you scan your car's fuel trims they are way out from 0 at cruise/idle.

 

well i have sprayed starter fluid around the top of the engine and vaccume lines and I dont hear an exhaust leak. I will double check for exhaust leaks. Thanks

 

my little hotcam has cam surge. with the stock a4 trans it would surge bad if i went from park to "Drive" and kept the car sitting still. once i started rolling it would go away. when the converter would lock up at 47mph it would buck a little. since the rpms are so low like 1500rpms. it wasnt alot but i noticed it. my mail order tune was crap!


might be the tune or its normal? does the surge go away if you cruise at a higher rpm?

 

Yea it does go away at higher rpms. Why would it be smooth when i unplug the 02 sensors though?

 

Basically by unplugging the o2's, your pcm switches back to open loop. The pcm in open loop commands more fuel at low rpms/idle. This is why you have no surge in open loop. When the pcm switches to closed loop, it uses the o2 sensors to maintain stoich 14.7:1 afr. This is sometimes to lean for some cams and causes surge. It also can be a exhaust leak lettin air enter the exhaust, which hinders the o2's readings, which will cause surge. A hands on tune might eliminate most of the surge, being there are no exhaust leaks.

 

That makes since but I can’t believe that cam surge would be this bad with this cam. When I have the 02s unplugged I can feel very very little surge something I would call normal. Anyone in the memphis area that can ride with me and tell me if this is normal?

 

Can someone take a look at my datamaster log file for me?
http://gh94z28.diinoweb.com/files/
It is the 092208.csv Thanks in advance

 

After driving it more since the new O2s it fills a lot better but i notice that in any gear at any rpm the stutter is when you very lightly apply throttle.

 

This seems to be a throttle position issue to me now. It doesn’t seem to be anything with a certain rpm. This happens when the throttle is at a certain throttle position which is very light acceleration in any rpm or speed. Does anyone have any suggestion? Thanks

 

I would check your rocker adjustment. That is usually a cause for many problems after a cam install. Just throwing it out there.
Did you get new o2's yet?

 

Yes i did and that helped. I will look into the rocker adjustment. It runs great after you get past that throttle position.

 

When I first got my car back it had some cam surge, but that went away after driving a bit. Also you could get the tune touched up wich should help alot as long as there is not another problem causing the same symtoms.

 

I had surge with my old 224/224 cam on a tight lsa, but only at that light throttle position you are describing, after a few weeks of driving I learned to not have the throttle at that position and had no problems with it.

 

Krill,
Would yours do it at any rpm and speed?

 

If its surging at any speed or rpm, then its not just cam surge. Either the tune needs work, or you got somethin else goin on!

 

My **** does the same thing, with the CC306. It will do it under a real light acceleration, or if I try and hold a steady RPM like 4000 while driving. As soon as you get in it, it goes away. I do have a minor header gasket leak at the moment, but it has always done it since the cam was put in, and I didn't have an exhaust leak then. I also put new o2 sensors in immediately after the cam. And I still have it. The only thing I haven't tried is unhooking the o2's. I would really like to get rid of this if it is possible. If it is cam surge so be it...otherwise, I want it gone.

D

 

it just seems like it happens as soon as i hit that point on the accelerator pedal which is about a half inch. I hope that make sense.

 

I dont really remember but 1st and 2nd gear was the worst (M6). I didnt have any problem cruising at 1500rpms in 6th gear though..

 

That sounds like typical cam surge. A good speed density tune will cure that.