Running rough

Picked my car up from the body shop today after some touch ups. It shook all over and rough. I'm not sure what happened during the time it was gone. It ran like a top when I dropped it off.

It is a 302, Edlebrock carb, and a petronix module.

https://vimeo.com/124574642

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Check the idle circuit on the carb or maybe a plug wire got pulled loose. I've had some debris blocking a passage in the idle circuit and it ran like total garbage.

It looks like you aren't running on all eight cylinders.

Mikes73's suggestion is a good one but before you start taking stuff apart you might want to perform some simple checks to see if it is in fact a misfire and if it is which cylinder is affected.

With the engine running you can carefully (don't get zapped) pull one spark plug wire at a time. If there is a noticeable change for the worse in how the engine runs you know that cylinder is firing. Reconnect the wire and move to the next one. If you remove a wire and there is no change in how it runs you have found the affected cylinder.

You can then use a spark tester on that wire to see if the issue is ignition related.

Thanks guys. After I stopped cussing, got home, and thought about it, I had come to the same conclusion. When I dropped the car off last week I had said to the shop guy "It ran better today that it ever has". Words that I guess I will now eat...

pull the air filter off and see if it is clogged up with body shop dust and paint.

good chance something is clogging up the carb.

check all the ignition wires are seated.

check vacuum hoses.

does the engine smooth out if you press the pedal a little?

It's idles better this evening but put any power to it and it runs like crap. I checked all the vacuum lines and found nothing. Next it's time to pull plugs wires.

I have no luck with electrical. I usually shock the crap out of myself.

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It may have been moved several times very short distances at the body shop without the engine ever warming up and opening the choke. This could cause the plugs to become gas fouled. Just a thought. Chuck

It may have been moved several times very short distances at the body shop without the engine ever warming up and opening the choke. This could cause the plugs to become gas fouled. Just a thought. Chuck

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That is what the shop guy said. He said usually opening it up will fix it but sometimes they need to be cleaned.

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I would pull the plug and clean first, then take it out on the highway

No one else has suggested and I may be well off-base but what kind of fuel are you running? Ethanol E10/E15? How long has it been in the tank? You also really don't know how long the station had it in their tank prior to you gassing up. Just a thought. Good luck!

The gas had crossed my mind. I would say it is 3 weeks old and I'm not sure of the grade.

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That's just way too rough. I too believe you are missing at least 1 cylinder.

I'd get my timing light and hook it to the battery, then go around clamping each spark wire. Once clamped, pull the trigger and point it at anything so you can see the flashes. If you get regular bright flashes, that cylinder has good spark. Do it on each wire. I'll be shocked (no pun intended) if you are getting good spark at all cylinders. If the spark is good, I would replace plugs - perhaps one has been broken somehow, or one fouled.

But if you have good spark, there is a possibility that a vacuum line got knocked loose. To check that, I would hook up a vacuum gauge to the engine manifold (on top of intake back near firewall). If you're getting anything less than 16 to 18 (inches of mercury - and it should be a relatively steady reading) you probably have a vac line knocked off.

I think spark, plugs, and vacuum are top 3 potential issues. What you're looking at is not normal and you really need to chase it down..

Thanks everyone. I checked plugs, spark, and vacuum lines the best I could without all the extra diagnostic tools (I just don't have them). I've found a shop that has a good reputation for working on classic cars. I have an appointment with them in the morning. Hopefully it's easy.

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look like coil failure or module failure to me.

Look at the crank damper to see if the outer ring is gone or showing signs of having moved. Now that I watched the video again it looks familiar. Chuck

yeah, you're right Chuck, maybe harmonic balancer blew it's ring... something is outa whack.

Look at the crank damper to see if the outer ring is gone or showing signs of having moved. Now that I watched the video again it looks familiar. Chuck

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I noticed an oil drip under the car last night. Would this be something I would see with this issue?

Anytime your engine runs that rough, the harmonic vibrations can be enough to cause minor leaks at the seals. So while yes it would potentially occur-it would also occur with swapped plug wires, an ignition problem etc.

Look at the crank damper to see if the outer ring is gone or showing signs of having moved. Now that I watched the video again it looks familiar. Chuck

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We have a winner. It was cracked.

Their going to replace and I'll get it back tomorrow.

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