1995 Camaro Z28 LT1, first the car started to run bad, stuttering, loss of power, etc... at first it only did it when you would slightly try to speed up it would stumble. than that got worse and did it all the time. so i changed the opti, wires, plugs. ran great for 2 days, than it lost vacuum the air will only blow out heater vents, and the stumble is back. i have changed the opti 2 more times no change, looked everywhere for a vacuum leak with no luck. i sprayed carb cleaner to look and i also traced as much of the lines as i could. now im thinking maybe it wore out a cam lobe, bad lifter, i looked for a broke valve spring. any ideas? maybe it is the intake?
thanks
chris
also new coil, iac, water pump

 

sounds like your vacuum for the heater controls is leaking. you can unhook it at the motor and plug to see if thats it, its a hose coming out of the wiring harness on the passenger side of the motor. towards the back. http://shbox.com/1/vac_check_valve.jpg

 

someone has to have an idea of what i can look at next. im still thinking intake leak even tho i could not find it with the spray. but i dont want to put it back together and find that once again its not fixed.

 

Craby,
i tried that i thought the same thing. that was where i started.

 

try opening the exhaust before the cat and see what that does. pick up or rent a vacuum tester and see if you can find leak that way. when was the last time the intake gaskets have been changed. mine was so lose it was sucking oil in from the motor. when i took it apart it had oil on both sides of the intake gasket. front and rear intake seals were leakin bad. thing is it ran fine. so it ran good right after you changed plugs and such,,, that would sorta point to that area but if your vacuum is so bad the heater controls wont work thats bad. have you tested the vacuum pressure?

 

Vaccum leaks normally result in High RPMs on a EFI car. Vacuum gage would tell you if it was a valve train issue. How is the conncetor to the Opti?

 

i just changed the intake gasket a few minutes ago, not fixed. the harness for the opti was broke so i got another 1 off ebay, it had a little piece of plastic inside i had to cut off. i have tried with both harnesses tho.
also i did not try the exhaust yet. think it could be the cat?

Is it possible that they gave me another bad opti, maybe its off a little, it only goes on there 1 way. It has good vacuum with a Gage im at about 18-19# and it stays steady so its not in the valve train. And everytime i try something it seems to get a little better. Map sensor, knock sensor?

 

I brought it in and got it scanned at the dealer. They say everything electrical checks out. They say its internal, like a stuck valve or cracked compression ring, head gasket. What do you all think, i still have to do a compression test to find the cylinder. Thanks