so i replaced my fuel cap on my 91 camaro rs because when i went around a corner with a full tank i would leak fuel from it. went to an auto parts store got the correct on for my car, put it on and now my tank pressurizes, my check engine light comes on and my car has a dramatic loss of power, put the old cap back on and it got worse any ideas? its a 6cyl

 

go under your car on the gas tank theres a tube with a weird little white thing hanging, pull it apart and clean it out. then unhook the battery cable for 5min and youll bee good

 

ok cleaned out the breather (lil white thingy) checked all the lines and vacuum lines still no change. i checked the new cap and its creating a negative pressure ie vacuum in the tank so i put the old back on. no more neg pressure but no change to the rest of the car

 

my old rs did the same thing actually both of my old rs 91 and 92 did that. they both hissed for like 3 seconds after taking the cap off. just change the oring on the old cap

 

Some pressure is normal--and you'll hear a hiss when you remove the cap.

JamesC

 

there is a little bit of pressure with the old one but the new one is creating what was described to me as a vapor lock. my car runs a lil bit better now that i put the old cap back on for a couple days, but still not the way it was

 

Since you have a 91, you might check the following link:

https://www.thirdgen.org/forums/body...call-read.html

JamesC

 

okay ive checked all my lines the maf and my ignition (plugs wires distributer, ect) still nothin any other ideas would be much appreciated... should also mention my car sounds great no misses or sputtering nothing like that it just has the loss of power and the checkengine light

 

Read codes and let us know what codes you find. To read codes, do the following:

Jump terminals a&b in the ALDL(the black 12 pin connector below and just to the right of the streeing column). A&B are the two rightmost terminals in the top row. Turn the key on and count flashes. Long flashes are tens, quick flashes are ones.

There are many things that can cause power loss. Knowing what failure(s) is turning on the MIL might help us find that cause.