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Username Post: Help diagnosing a possible misfire        (Topic#348514)
loco 
Member
Posts: 109

Reg: 01-12-03
12-02-17 11:52 AM - Post#2716642    

I'm looking for a little advice diagnosing a possible misfire.

I have a 63 Impala with a stock 350 motor. It has a basic Acell ignition and edelbrock carb. For years the car has run great. Last week I took her for a spin and stopped into a store. When I came back out and started it up, it felt like it would barely run. Felt like a solid misfire. I drove her home and started inspecting. I found a burnt plug wire, so I replaced it. I also for the heck of it, replaced all 8 plugs.

Its still misfiring. At idle, I can barely feel it, but when I put it in gear, I can really feel it. At this point, I'm not sure if its fuel or spark related.

Today I took it for another drive and I can really feel it at the pedal. Sort of like, when I depress the gas pedal, it sputters, then instantly takes off.... Obviously it feels rather rough during that short sputter period.

The car has no issue starting. When I turn the key, it fires right up.

Where should I begin ??



 
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BG64SS409 
Contributor
Posts: 639
BG64SS409
Loc: Edmonton,Alberta Canada
Reg: 05-03-08
12-02-17 12:09 PM - Post#2716643    
    In response to loco

How did the plug on the burnt wire cylinder look?


Brett

64SS Impala,Original documented numbers matching 1 of 36 Canadian made SS409 340hp/PG
2013 Callaway Suburban, supercharged 450hp


 
loco 
Member
Posts: 109

Reg: 01-12-03
12-02-17 12:38 PM - Post#2716644    
    In response to BG64SS409

all 8 plugs looked pretty good. id say in color they were brownish. i generally change plugs in the car every 2 years. i always consider this a maintenance item and do it weather they need it or not.



 
junky 
Frequent Contributor
Posts: 2299

Loc: Northeast CT
Reg: 06-27-10
12-02-17 01:49 PM - Post#2716656    
    In response to BG64SS409

might you put the wrong wire on the plug by mistake? Also, check for a cracked distributor cap. Open the hood on a dark night, with no lights on, and see if you can see any sparks jumping from the plug wires to ground. What condition are the points??

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
loco 
Member
Posts: 109

Reg: 01-12-03
12-02-17 03:27 PM - Post#2716665    
    In response to junky

Thanks for the reply. I'm leaning toward plug wires. But really no sure. It was missing before I did the plugs, plus I did them 1 at a time.

It's electronic ignition so no points.

It's dark now, gonna head out into the garage and look for jumping spark... I'll report back.



Edited by loco on 12-02-17 03:35 PM. Reason for edit: No reason given.

 
loco 
Member
Posts: 109

Reg: 01-12-03
12-02-17 04:10 PM - Post#2716671    
    In response to loco

Well, no spark jumping around. Turned the key and it fired right up. I turned the lights out and it was dark as you could imagine. I would have seen the slightest flicker. Looked all over and nothing. Just for good measure I checked the timing. The mark on the balancer is signed up exactly at the end of the tab. Can't read what it says but it exactly at the edge of the tab.

Just for grins, I threw it in reverse and sure enough, it's a solid miss. hmmmm just don't know.



 
Shepherd 
Contributor
Posts: 978

Loc: Lake George, NY
Reg: 11-11-15
12-02-17 04:15 PM - Post#2716672    
    In response to loco

When in gear under load,have someone look around under the hood for arcing, especially around the coil, cap and wires near the exh. manifolds.



 
raycow 
Honored Member
Posts: 26948
raycow
Loc: San Francisco, CA
Reg: 11-26-02
12-02-17 04:18 PM - Post#2716673    
    In response to loco

If you have a solid miss, see if you can pin it down to a single cylinder by pulling the plug wires one at a time. If you can, you might have a valve issue on that one cylinder. This can occur spontaneously, just as you described. Your next move should be a compression check.

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
junky 
Frequent Contributor
Posts: 2299

Loc: Northeast CT
Reg: 06-27-10
12-02-17 05:48 PM - Post#2716680    
    In response to Shepherd

Mist around the plug wires, and see if it gets worse. I had a miss in my engine, and found that it was time to have it rebuilt. I wasn't happy about spending the money on it, but sometimes you have to do what is necessary if you want to continue to drive your dream car.

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
DonSSDD 
Silver Supporting Member
Posts: 6639
DonSSDD
Loc: Nova Scotia, Canada
Reg: 08-21-01
12-03-17 05:18 AM - Post#2716711    
    In response to junky

What octane fuel are you running?

How many miles a year do you drive the car?

How much of it is highway driving at say 60 MPH or above?

Ever run Sea Foam in the gas?

It could be a lot of low speed city type driving on ethanol fuel has created crap in your valves and carb, you may have a valve that is not seating cleanly. If this is possible, a nice long hot ride with a dose of Sea Foam would be my next option.

63 Pontiac Parisienne Sport Coupe(CDN Chev mechanically (409, 4 speed),62 Bel Air SC (sold), 59 El Camino (sold), 62 Bel Air SC(sold), 63 SWC Vette (sold),
Member #2194


 
loco 
Member
Posts: 109

Reg: 01-12-03
12-05-17 07:54 AM - Post#2716941    
    In response to DonSSDD

I am acutally running seafoam in the tank right now. I usually drive the car about a dozen times a year. About once a month for about an hour each time.

I'm going to start with the very basics. Replace all plug wires (which I have wanted to do anyway) cap & rotor. I also plan to syphon the fuel, because it has been in the tank for a good while, change the fuel filter. Hopefully one of these will fix my issue.

I'm sure you guys know, chasing a miss or hesitation can just make you bang your head against the wall.



 
omarine 
Contributor
Posts: 128

Loc: San Diego
Reg: 06-29-15
12-05-17 09:04 AM - Post#2716949    
    In response to loco

Don't overlook the simple. If it's firing OK, but stumbles when you hit the gas, and then recovers, then it sounds like a bad accelerator pump not squirting fuel as it should when giving it gas.

Also when rinsing a gas tank, don't ignore the 3 rubber hoses that go from sending unit to the carb, happened to me when car was in the shop for 3 mos being painted. Car was started daily while there but ran horribly when it was done. I did everything and it was the 3 cheap hoses from tank to carb.

that's cheap too, barley $10 to fix

cheers
oscar

61 Impala bubbletop, 283, 2bbl Rochester, generator, points and drum brakes- daily driver
'49 Harley Davidson FL - Panhead


Edited by omarine on 12-05-17 09:06 AM. Reason for edit: No reason given.

 
junky 
Frequent Contributor
Posts: 2299

Loc: Northeast CT
Reg: 06-27-10
12-05-17 07:01 PM - Post#2717000    
    In response to loco

A friend just took a car out of storage, that hasn't been started in over 10 years. Put in a new battery, turned the key, and after a few cranks, it started. Said that it runs as well now, as when his dad last drove it. If it starts on the old gas, then that gas is still volatile enough for the engine. Do one thing at a time, such as changing plugs. Run the engine, and see if the problem goes away. If not, then move onto the wires. Over 60 years of experience dealing with problems.

Never argue with an idiot. He'll drag you down to his level, then beat you with experience.


 
bruno 
Senior Member
Posts: 3208
bruno
Loc: Curitiba, PR, Brazil
Reg: 10-04-04
12-06-17 07:53 AM - Post#2717055    
    In response to loco

I had very similar issues, apart from the burnt sparkplug, with both my 235 and with the current 261. It ended up being the diaphram of the vaccuum advance wich was torn.

Changed the whole vaccum advance thingy and smooth acceleration.

Dunno if you're running any ignition system that doesn't use vaccum advance, but if so, do the simple test of sucking the little pipe and sticking with your tongue to see if it holds up the vacuum.

Bruno Leite Two tons of steel, one hundred miles an hour. No looking back, grooving on the power. http://community.webshots.com/user/realenemy


 
DonSSDD 
Silver Supporting Member
Posts: 6639
DonSSDD
Loc: Nova Scotia, Canada
Reg: 08-21-01
12-06-17 04:27 PM - Post#2717107    
    In response to bruno

"I am acutally running seafoam in the tank right now. I usually drive the car about a dozen times a year. About once a month for about an hour each time."

Do you run it at highway speed for an hour- it needs to get nice and hot for an hour, not loping around in the city at low speed.

63 Pontiac Parisienne Sport Coupe(CDN Chev mechanically (409, 4 speed),62 Bel Air SC (sold), 59 El Camino (sold), 62 Bel Air SC(sold), 63 SWC Vette (sold),
Member #2194


 
0utlaw 
Very Senior Member
Posts: 2777
0utlaw
Loc: US East Coast
Reg: 09-10-02
12-06-17 04:51 PM - Post#2717112    
    In response to loco

By any chance, do you have dual exhaust? If so, from what I understand, it skips when you put it in reverse. With the parking brake on or heavy blocks behind the rear wheels or both, put it in reverse and walk back to the rear and listen at the pipes. You might be at least to determine which side is missing. If you start pulling one wire at a time as it's running (using a heavy glove), when you find one that doesn't change rpm, you isolated the cylinder. What I found is that when you start pulling wires, sometimes the clips pull away from the wire under the boot and you would never know it unless you measure with an ohmmeter. They can come apart fairly easy and just need to be re-crimped. Even brand new wires. Jim



 
raycow 
Honored Member
Posts: 26948
raycow
Loc: San Francisco, CA
Reg: 11-26-02
12-06-17 09:05 PM - Post#2717147    
    In response to 0utlaw

It is safer to pull wires at the distributor instead of the plugs. This is because once you break contact the wire will be dead and you won't get a shock.

Ray

Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.


 
0utlaw 
Very Senior Member
Posts: 2777
0utlaw
Loc: US East Coast
Reg: 09-10-02
12-07-17 02:29 AM - Post#2717155    
    In response to raycow

Good point! Jim




 
loco 
Member
Posts: 109

Reg: 01-12-03
12-07-17 12:06 PM - Post#2717202    
    In response to 0utlaw

Excellent advice gentleman. I appreciate you.

In theory, if I attach my timing light to each of the plug wires, and the light pulses, that wire should be good....right ?



 
bruno 
Senior Member
Posts: 3208
bruno
Loc: Curitiba, PR, Brazil
Reg: 10-04-04
12-07-17 12:17 PM - Post#2717203    
    In response to loco

Well, if you pull the wire off the sparkplug, the spark still jumps from the wire to the sparplug in a short distance. You can hear the noise and also see it, specially if it's somewhat dark.

Bruno Leite Two tons of steel, one hundred miles an hour. No looking back, grooving on the power. http://community.webshots.com/user/realenemy


 
rrausch 
"13th Year" Silver Supporting Member
Posts: 13531
rrausch
Loc: L.A, Cal. & St. Louis...
Reg: 04-07-03
12-07-17 03:59 PM - Post#2717222    
    In response to bruno

Just don't do that if you have a gas leak.

When I was 19 I worked as an asst. manager in a small Western Auto store in Kansas City. I had keys to the store and we were closed on Sundays, so there were times I went into the service dept. on Sunday afternoon with the '58 Corvette in my avatar, and worked on it. It was nice being in the shop with no one around. So I was blissfully fiddling away on my car one Sunday... I had changed the oil and the old oil was sitting in a pan under the engine, and I had done... something to the carb, don't remember now exactly what, but a small amount of gas had dripped down into the pan of used oil. And I got ready to leave, fired the engine up and flames shot up from the engine. The pan of oil under the car was on fire. I grabbed the fire extinguisher--it was the old soda/acid type that you had to turn upside down for it to work, I flipped it upside down and sprayed it under the car, into the pan of old oil and put the fire out. I was shaken up and didn't notice that I'd covered the entire wall next to the car in a mixture of old motor oil and fire extinguisher juice... but the shop manager sure let me know that Monday morning when I came in to work. It's amazing what a well placed boot can do to educate a young man's mind.

1953 210 Convertible, 261 with dual Carter YF 966S carbs, P.S., Remote Bendix P.B. Booster... shade-tree restoration about done.




 
toro455 
"3rd Year" Silver Supporting Member
Posts: 342
toro455
Loc: Western NY
Reg: 06-15-02
12-07-17 08:15 PM - Post#2717252    
    In response to loco

I had a vehicle with a miss and decided to use my timing light which displays RPM to figure out which wire was bad.

Normally you place the pick-up on only number one but if you instead go wire by wire, only looking at the tach/RPM reading, you will see how many pulses per minute each cylinder is seeing. That way you don't pull wires and you don't disturb anything which might be causing the issue. I found I had one wire reading about half the RPM of the other 7. I changed only that wire and corrected the issue.



 
loco 
Member
Posts: 109

Reg: 01-12-03
12-08-17 08:29 AM - Post#2717308    
    In response to toro455

  • toro455 Said:
I had a vehicle with a miss and decided to use my timing light which displays RPM to figure out which wire was bad.

Normally you place the pick-up on only number one but if you instead go wire by wire, only looking at the tach/RPM reading, you will see how many pulses per minute each cylinder is seeing. That way you don't pull wires and you don't disturb anything which might be causing the issue. I found I had one wire reading about half the RPM of the other 7. I changed only that wire and corrected the issue.



Bingo, this is what i was thinking. Thanks. I'll give this a shot this weekend and report back.

Thanks all !




 
Verne_Frantz 
61-64 Subject Matter Expert
Posts: 5233
Verne_Frantz
Loc: Hightstown,NJ USA
Reg: 08-22-00
12-08-17 02:38 PM - Post#2717332    
    In response to toro455

  • toro455 Said:
I had a vehicle with a miss and decided to use my timing light which displays RPM to figure out which wire was bad.

Normally you place the pick-up on only number one but if you instead go wire by wire, only looking at the tach/RPM reading, you will see how many pulses per minute each cylinder is seeing. That way you don't pull wires and you don't disturb anything which might be causing the issue. I found I had one wire reading about half the RPM of the other 7. I changed only that wire and corrected the issue.




Excellent troubleshooting technique!
Verne



 
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