Member

Registered: Jan 2002
Location: fla
Posts: 43 vapor lock & new exhaust

Hi

i had a new cat back exhaust installed on a 92 rs w/ 305 tbi 150 k miles about 1 month or so ago.

its not performance just stock replacement.

i began having/noticing stall problems and rough idle lately.

incident 1; out from work, car sat 8 hrs, started right up, rough idle kinda stalled but didnt. turned it off, could not restart for 10 min. battery goor got goos crank no turn over.

incident 2 driving home same night, about 30 miles high speed on i95 70 mph + /- for about 1/2 hour get to exit ramp, uphill, car runs rough at stop light, stalls cannot start for 10 min. good crank as above.


incident 3 get home, park in drive, return to move car wont start . repeat above.

i csan smell gas outside car.

take to dealer in am, techie says vapor lock after running car 2 hour in lot, it will not start, when it does its rough.

he says the new exhaust is boiling the gas in tank or lines causing vapor lock which is the problem.


ok, any one have same problem ?

if this sounds right any suggestions?

i will take it back to exhaust shop, i would just like some info to tell them.

dealer said runn exhaust closer to factory spec, i thought it looked rather close to original route.

help is appreciated

thanks john


sorry for the novel

 

vapor lock? I doubt that with an electric f/p in the tank. Only the old fashoned cars get that whith the old block mounted mechanical fuel pumps.

 

if you dont have any heat sheilding between the gas tank and the muffler thats a different story. All the fuel will back up into the vapor canister if the gas is forced to boil. If its getting hot enough to boil from the muffler, then your in serious risk of causing a fire. Make sure the stock sheet metal heat sheild is in place to protect teh tank from the heat of the exaust. The fuel pump raises the pressure of the gas to almost around one atmosphere or so so that should stop the fuel from boiling unless its really HOT.

 

the stock shield is in place.

i felt the filler neck just under the cap, the fender wont let me get lower, and it was hot/warm.

could the 3 inch tail pipes cause it as opposed to the 2 in stock tail pipes/

john

 

if all the heat shilding is in place, then your problem is something else. Dont know what it is off the top of my head but i doubt its vapor lock. The fuel would have to be really, really hot to boil under pressure. All the fuel lines run opposite to the exaust routing so its not the lines gettign to hot. It coudl be the egr. If the car just idles rough and is hard to start but runs good under throttle, then the valve could be sticking.

 

Sounds like the problem is also happening when the car is cold, as you stated in you first incident. Try checking for a vacuum leak or disconnected vacuum line or something like that. At least it's a place to start.

Steve

 

...Sorry double post.