RickH

I have a '72 Cutlass with a 350 4BBL. It started missing a little so I brought it to Pep Boys for a tune up. They did plugs, plug wires, points, rotor, distributor cap and timed it. It still missed some so we decided to put in a new distributor. Still is missing. Anyone have any ideas as to what should be checked next?

coppercutlass

i had an issue like this turned out to be a fuel issue. make sure you did not get a bad batch of gas in the tank, check / replace fuel filter .

captjim

First thing I would check is a vacuum leak. Look at all the hoses and EGR if equipped.

pogo69

Second thing...your brave taking that nice car to pep boys

coppercutlass

Pogo pointed out the obvious. x2 with that

MDchanic

How would a new distributor have corrected a miss?

More importantly, can you tell us more about the miss?
Any particular times or conditions under which it happens?
Like cold or hot, full throttle, cruise, or idle, moving or standing still?

I agree that vacuum leaks are high on the list, as are dried out carburetor gaskets, a heavy float, or crud in a carburetor jet.

- Eric

RickH

Seems to have the miss most of the time. Under heavy acceleration, it doesn't seem to miss..Which vacumn hose would be the first one you would check?

oldcutlass

Could you tell us how the tune-up was performed, Spark plug gap, timing, dwell(if applicable depending on what dist was installed), was the carb adjusted, is the choke operating properly, does the advance work?

Frank3

Never hurts to run a compression test .
Matter of fact if I don't know a car , I do it before a tune-up .
If that is weak then a leak-down test .

My Cutlass was my Grandmothers , She bought it new , and I remember it missing sense I was little , nobody did a compression test till I did . Which lead me to pull a valve cover and find 2 broken valve springs .
You might find that , or bent push rod , cam losing a lobe , blown head gasket , stuck or burnt valve , cracked/worn rings , or you'll eliminate mechanical trouble .

MDchanic

What OldCutlass said. And Frank.

Also, I would say that a low-speed miss that smooths out under higher throttle / RPM conditions is less likely to be electrical (electrical problems tend to occur under conditions that demand higher spark voltage or coil current), and far more likely to be a vacuum leak.

There is no one hose that is usually the culprit, and you can have vacuum leaks at intake or carb gaskets, so that's not your key to success.
I would recommend first spraying around all gaskets, sealing surfaces, and hoses with the flammable substance of your choice (car-start ether, propane, carb cleaner, etc.) to try to find the leak, and if that fails, then disconnect ALL hoses and plug ALL barbs, see if that fixes it, and if it does, then reconnect them one at a time until you find the culprit.

- Eric

NDERISE

if its a dead miss on idle i would have someone put the car in gear while someone pulls the plug wires one at a time at the dist cap to locate which cyl. is missing buy the no change in eng rpm. if u can't find the missing cyl. then u may have a vacume leak, if u can determine the missing cyl. then ck comp.

jaunty75

Next thing you know, we'll see a photo of it on milk cartons.

ihengineer76

And if you do this, wear rubber gloves with leather ones over them. That is, unless you like a little electric shock to liven things up!

z11375ss

Keep pushing the gas. It's there somewhere!

redoldsman

Good point here. How long has the gas been in the car? This ethanol crap goes bad in a hurry.

NDERISE

YEP IHENGINEER76 That is y u pull the wires at the cap u r less likely to get zapped i do it all the time

captjim

The car does not need to be in gear and a vacuum leak can cause a cylinder to not fire. Once the cylinder is isolated, check for compression and look for leaks on that runner. Also, a long shot, but check wires #5 and #7, easy to mix them up.

fourtwenty

If they changed the wires they may have put them on backwards as oldsmobile is counter clockwise. Like Captjim said check 5 and 7
hope you get it figured out and if so please post the resolution cheerio

NDERISE

True it does not have to be in gear but it is more detected if it is

coppercutlass

Fwiw I have mixed 5 and 7 and in my case it popped out of the carb. Also when I had the fuel issue I mentioned it did not miss when in idled but once in gear it would act like a miss or almost a bog to some extent engine would shutter etc. We also used to run 87 we went to 93 . Still waiting to get good weather to see what it does. Just though I would mention that. I also think I had this issue when the car sat longer than a month. The simptoms always went away when we added fresh fuel.

yankees

Check plugs again and look for cracks where the ceramic base meets the metal. You never know. I put plugs in my racecar and it ran well 10.40's with a very slight miss, but thought I should have been running much faster. Pulled the plugs to find out the #3 was cracked around the ceramic base (very hard to see). Replaced the $2 plug and the race motor idle was perfect and the slight miss was gone. The following weekend car went 9.82 off of the trailer I dislike electrical/ignition problems. Ohm out the wires and add it to the list.