Hey all, I got my SS back in October. It was my Mamaw's car until she died, and she wanted me to have it. I was driving something else at the time, so it sat up for about two years, only getting cranked and driven around a little bit when I visited my Papaw, which was every other month at best.

After a few small alternator problems in November and December, she ran great for about two good months.

One night, on my way home from class, my car suddenly struggled to go anywhere. I'd hit the gas, but nothing would happen. I could get up to speed eventually, but it took a very long time.

Everyone told me it was a problem with my cat, so I took it in to get a new one. Well imagine my surprise when the man told me that my cat had been cut off. I asked my Papaw and he said the same. He's never liked the things.

So after a new O2 sensor, fuel pump, thermostat, and a laundry list of other things that I needed, I got my car back and it ran just as poorly as the day I dropped it off.

I took it somewhere else and they found that I needed a new vacuum head on the carburator. They replaced and while it does run better, now when I hit my accelerator my car revs up and there's a burst, but then the RPMs drop back down and the car slows down as well.

I'm lost, gang. Has anyone else had this problem?

It's an '85 Monte SS with the original 305 and tranny in it, if it helps. Anything you can tell me would be great.

 

if it still has the cam driven fuel pump get a block off plate and wire up an electric pump inline in the fuel delivery line. it actually sucks the gas from the tank so make sure that the line is not leaking fuel or sucking air. the fact that it sat this is my best guess at it and change the filter in the carb inlet. if you need to replace the fuel line i recommend running nylon lines they last forever and are much easier to work with. just don't put them too close to something too hot obviously.
a good carb cleaner spray will keep the engine running at idle and allow you to rev it up and determine whether its getting enough fuel if it runs better on carb spray + gas its likely not getting enough fuel.
older engines are easier sometimes to figure out that new. all you need is air+fuel+spark and then all the varying combinations of it. i had an 87 ls with a 305 also and that car had an electric pump wired in with a kill switch. and that car would run and drive hard on donkey ****, i swear it ran on 4 year old gas at 130 km/h it just made a lot of black smoke.

 

There is not a whole to go wrong with these old cars. VERY easy to work on. If it’s not the cat then I suspect it’s something with the exhaust being clogged or as simple as your gas cap not venting. But without being right there to see for oneself it will be hit and miss. One way to tell if your exhaust it to drop the pipes from the manifold and see if it runs better or worse. DO NOT drive very far. Also check the flapper valve that closes on the passenger side to see if it opens and closes or it is stuck shut. Even with a bad fuel pump you should get to run normal at first then drop off but that could be a float level problem with the car. You can always take to a dealer and the can diagnose it for around $85 then you can fix it yourself. BTW I still have my original fuel pump and alternator on mine, just about everything else has been replaced. If it still has the old q-jet check the fuel filter too.

 

Thanks everyone for your suggestions. The problem is going to surprise some of you.

I had water in my gas tank. A crap ton I guess.

I guess as it sat up, it condensed a ton and was making it run really rough until I was down to about 1/4 of a tank.

I threw some Heet in there yesterday, put 25 bucks in it tonight (Got me about half a tank) and cruised comfortably.