scott2683

I'm trying to get my 880 ready to cruise, and she drives great except I have a miss in the engine under constant throttle. If the car is idling, or if I am accelerating the engine is very smooth, as soon as I hold the pedal steady, it starts missing. there is no pattern to the miss. In the past week I've put in new plugs, wires, cap, points, condenser, adjusted the timing, and tuned the (original) carb. Any advice on what the issue might be would be greatly appreciated. Could it be the condenser in the coil? Possibly the carb needs rebuilt?

1966sportfury

worn. distributor shaft? if you pop the cap go back n forth with it (side to side) not (rotational that will have play thats normal) but side to should have no play

sweeperking

Your miss could actully be a few differnt things, I recommend putting it on a scope. Probably not what you want to here but this would be the quickest and easiest diagnosis. I would also check compression (do compression test first unless you own a scope)

Polaradude

I am curious as to the "scope" you speak of ?

Distributor shaft may have the wobble as Bob mentioned
Do you have Vacuum advance on the car ?

340SIXPACK

hello if you have changed the points, you used a dwell meter?? if you run the car with the meter hooked up watch the needle on the meter if it bounces around and will not hold steady the distributor shaft is worn out. also check the vacum advance ,by using a vacume pump with the cap off aplay vacume to the pod and watch the plate in the distrbutor if it move and holds vacume its good ,if it dos not move or hold vacume its bad, i would also check the engine with a vacume gauge,hook it up to ported vacume and see what the gauge needle is doing it should hold a steady 15 to 20 inch depending on what typy of cam you have,i if the needle moves fast back and fouth you have a problem in vavle train ,like worn cam lobe or what i might be susspecting a bad lifter or cracked valve spring ,i hope i was alittle helpful .let me know .how it turns out . Anthony

sweeperking

[quote=Polaradude;44383]I am curious as to the "scope" you speak of ?

Its call an automotive oscilloscope used in engine diagnosis. Most shops that work on older cars still use them. Very helpfull in troubleshooting

scott2683

Thanks for all the advice, As soon as I can get a little extra time, I am going to start digging in and trying to diagnose the problem. I hope it is nothing severe, The engine is a 361 and has under 60,000 miles on it. It had been sitting for a couple years before I bought it this winter. At first I thought maybe old gas, but I've filled it up and drove over 100 miles, so I know all the old gas is out, I will keep you guys updated on what I find out. Thanks again!

67 GTX

i would check all of those points above, as well as make sure that all the wires going into the wiring harness are where they are supposed to be

scott2683

I think I have found the solution to my miss. The carburetor is not creating enough suction for the vacuum advance to work, The vacuum advance hose was cracked, I replaced it and still no change at all. I have a rebuild kit for the carb ordered, its a stromberg 2bbl, so needless to say, no one had it in stock. My dad took the carb off, there is a decent amount of carbon on the bottom. So hopefully this corrects my missfire at steady speed, and I'm ready to cruise.

Polaradude

Interesting...lol

sweeperking

Your non functioning vacuum advance will give you a hesitation on acceleration and the vacuum leak will give you a rough idle (miss at idle) although if your running rich it would probably smooth out, something dont make sense here there has to be other issues

6fury4

[quote=scott2683;44354]I'm trying to get my 880 ready to cruise, and she drives great except I have a miss in the engine under constant throttle. If the car is idling, or if I am accelerating the engine is very smooth, as soon as I hold the pedal steady, it starts missing.

The fuel pump cam lobe may be worn enough that constant fuel pressure may be a problem. If pressure drops momentarily, fuel bowls will be left with only enough to 'siphon', then creating dead spots in fuel delivery. When accelerating, the accelerator pump will make up for lack of fuel temporarily, allowing the pump to then, over-deliver for fuel needs while revving, and at idle, fuel need is low. This is a stab in the dark, but temporarily putting an electric pump in line with the mechanical would eliminate the problem if it were the problem.

scott2683

it appears the vacuum advance wasn't the issue of my miss at steady speeds. After reading your posts, and having my carburetor rebuilt with the same issue reappearing , I knew I had overlooked something. I was inside my car the other night, under the dash installing new bulbs and trying to tear out a wiring harness the previous owner had installed for a cd player, for some reason I decided to fire up the engine while under there, and thats when I heard a huge vacuum leak coming from near my brake pedal. I shut off the engine, popped the hood, and plugged the vacuum hose going to the brake booster, and BAM! WhenI started the car back up the engine got smootherand my noise from under the dash was gone. my dad took the car down the road and no miss. He pulled the booster out and the seal was rotted, in fact the booster looked to be in really bad shape. I should have noticed this or felt it in the brakes, but the brakes worked alright, I'm not used to 4 wheel disc, and I wasn't sure what the "proper" feel was supposed to be. So thats the good news, now for the bad news, they don't make my brake booster anymore, so I have to ship mine out and they will rebuild it and ship it back, which means I'm out of a car to cruise in this weekend. The price is gonna be around $200 to get it fixed. I called every auto parts store in a 100 mile radius and most people laughed at me when I told them what I was looking for. O'Reilly auto parts which is one of the larger stores in my area said I would be looking at roughly a month for them to send it out, repair it, and ship it back. Napa, had a 7-10 day return policy, so they definitely earned my business. I just wanted to share this news with everyone. Thanks for all the suggestions and help! Like I said I am still pretty new to all of this old car jazz, and while I really enjoy learning as I go, I sometimes overlook the obvious

Sgt. Veteran

At least you found it without a crash being involved due to sudden loss of all brakes, hope ya get it back up and running soon

scott2683

Thanks everyone for all your help. I got my brake booster back the other day, it took a little longer than I thought, but it was also cheaper than I thought, by almost $50 which is always a good thing. When I went to install the booster the pedal rod was about 3/4 of an inch too short, which was really weird since it was the same one I had prior just rebuilt. My dad took it to work and fabricated a new pedal rod for me. I'm very satisfied with the way the car runs now. It runs and drives like new!