85 running bad

[kmanracing24]

I have a 1985 Caprice Classic with a 305. It used to idle at about 1000 rpm in drive and now it only idles at about 500 or so in drive. When I am stopped at a stop sign or light, I hit the gas to go and sometimes the car almost dies or does die. It also shakes sometimes at stop lights and signs while Im in drive. Does anyone have any idea what I should do? Thanks in advance.

[caffeineaholic]

I have the same year caprice and engine and I also have this problem (but I'm pretty sure it is due to me trying to adjust the carb on it). How long have you had this problem? Have the vacuum lines been replaced recently or has it been a long time? Has the fuel filter in the carb been replaced? Do you take good care of it and maintain it? How many miles on it?

A little more info would help out.

-Take care.

[kmanracing24]

I have had this problem for maybe 4ish months. The vacuum lines haven't been replaced since I have had the car. Same with the fuel filter. It has 127000 miles. I keep up with maintenance pretty well. Thanks

[caffeineaholic]

But for how long have you had the car and do you know if the prior owner did any maintenance on it? Replacing the fuel filter on the carb is cheap and fairly easy to do; in my opinion it should be replaced if you are not sure. Also, I forgot to ask, does the car run fine once it's up to some speed (maybe more than 15mph or so?)

[kmanracing24]

Yeah I could change the fuel filter. The guy that had it before me kept up on regular maintenance. I have had the car for just over 2 years and it runs fine after 15 except that it seems to be running a higher rpm than it did before.

[caffeineaholic]

I'm not a mechanic or expert but some of the many things I think it could be are bad engine vacuum (vacuum leaks), bad/poor/dying fuel pump (mechanical), fuel filter on the carb, carb issues (or improperly adjusted), failing o2 sensor, failing misc. emissions-related sensors, bad spark plugs & wires, and maybe even distributor issues possibly.

I would probably start with simple stuff, I would suggest checking all of the vacuum lines for wear. Also, purchasing a vacuum/pressure gauge can be a good investment and it will help to see if your engine vacuum is where it should be (I think it should be above 15, mine is ~18mmHg I believe). Also, since the fuel filter for the carb is so cheap and fairly simple to replace I would replace it (just be careful not to damage the fuel line by twisting it too much).

Some vacuum lines may look okay, but if you bend them a bit you may notice major wear on them. Just this year I've been starting to learn about carburated cars and I had no idea how important engine vacuum was; it's worth the time to take a detailed look in my opinion.