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Old 01-14-2011, 04:36 PM
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Misfire (cold weather?)

Another newbie question...

This last week's temps been about 20-25F out and I've been driving the Nova around. I let it warm up for about 5-10 minutes or so and it seems when I try to accelerate it misfires. Only when I do it fast though, like at stop sign trying to get across the street before the next car moves along. I noticed the sound coming from the passengers side of the engine bay while driving. It doesn't misfire when I'm at idle though, which I've tested by keeping it in N or P and quickly depressing the gas. Right now its about 40F out and it hasnt misfired, but once in while if I really get on it (keep in mind i live on a military base and "getting on it" means get up to 30mph as fast as I can haha) it hesitates slightly. Would the cold weather be the factor hear?
I checked all the hoses to see if there were any cracks (vacuum leaks) and everything looked good, also checked the plugs (which are new). Now number 6 plug worried me the most because when I took it out and placed it on the car it dripped out some oil about the size of a pea...dont know if that's significant or not, but a few of the plugs looked pretty bad. What would be the main cause of this? Here are pictures...







I'm very new to working on cars so thanks for any help!

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Old 01-14-2011, 05:43 PM
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Bye the looks of your old plugs you might want to just change them out for new ones and see if the miss goes away. They look rusty and fouled up anyway. Plugs are cheap and if the problem persists you might want to check out the rest of the ignition systems components(cap, rotor, plug wires, coil etc). If all else checks out ok then you have other problems like oil getting past the piston rings or through the valve seals. In the past I had a bad auto transmission was actually sucking trans fluid through the vacuum modulator, into the carb into the cylinders and fouling up plugs like every other couple of weeks or so.
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Old 01-14-2011, 06:27 PM
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Looks like either the choke is sticking part way closed or you have oil getting past the rings. Next time you get it warm, remove the air cleaner and check that the choke plate is fully open.
The plugs in your pic are fouled and won't be of any further use for you. It also seems that the two center plugs on both sides are the worst. If you have a chevy, that would probably rule out the engine sucking up tranny fluid as the modulator vacuum port on your manifold is on the #8 intake runner and would certainly foul out #8 plug first not to mention the tranny wouldn't shift properly.
Have you by any chance, over revved the engine lately? That would cause an engine with lots of miles on it to break either the top rings, or the ring lands on the pistons allowing oil to get passed the rings and foul plugs. The oil drip you mentioned is probably from a leaky valve cover that collects around the outside of the plug. If it came from the tip, it would have a steady miss and would only be running on 7 cyl.
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Old 01-14-2011, 07:30 PM
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does your heat cross over work on your intake ? and make sure your choke is working properly and check your feul filter and start by using AC DELCO spark plugs in your Chevy
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Old 01-14-2011, 07:33 PM
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Quote:
Originally Posted by dklong
does your heat cross over work on your intake ? and make sure your choke is working properly and check your feul filter and start by using AC DELCO spark plugs in your Chevy
What makes you think those plugs were in a chevy?
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Old 01-14-2011, 08:11 PM
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Its a 327 chevy engine to answer that question.

They are new plugs, the outside is rusted slightly I think because when I changed the thermostat the gasket I used didnt work and antifreeze spilled out over the engine. I thought I cleaned it all up but im sure it ran down the side onto the plugs.

I haven't over revved the engine, I dont think it's gone above 4500 rpm in a few months, certainly not lately... I live and work on the military base and the max speed it 30mph so i usually only get it to maybe 3000-3500 rpm, if i have to.
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Old 01-14-2011, 08:17 PM
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Quote:
Originally Posted by nastypurplenova
Its a 327 chevy engine to answer that question.

They are new plugs, the outside is rusted slightly I think because when I changed the thermostat the gasket I used didnt work and antifreeze spilled out over the engine. I thought I cleaned it all up but im sure it ran down the side onto the plugs.

I haven't over revved the engine, I dont think it's gone above 4500 rpm in a few months, certainly not lately... I live and work on the military base and the max speed it 30mph so i usually only get it to maybe 3000-3500 rpm, if i have to.
OMG! Ft. Lewis? I got 2 tickets in two days there by the same MP. I was fixing to ship out to Nam in 30 day's anyway. Asked him to put me in jail so I could get out of it.
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Old 01-14-2011, 08:31 PM
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Quote:
Originally Posted by dklong
does your heat cross over work on your intake ? and make sure your choke is working properly and check your feul filter and start by using AC DELCO spark plugs in your Chevy
This is an excellent guess. If the cross-over in the intake manifold is packed full of carbon deposit, then the choke box isn't going to heat up as fast as your engine warm-up, consequently, your choke will stay on longer than required and you'll get that dirty sooty plug appearance that you have there. The outer four corners is warming up normally.

Another reason is that the valve seals can be leaking down in these mid-cylinders and the engine heat can't burn of the oil leak down that takes place when the motor is turned off.

Going up a heat range on the center plugs may give some relief. If this is a stock 327 manifold, they were prone to coking up the cross-over passage in the intake.
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Old 01-14-2011, 08:36 PM
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Quote:
Originally Posted by sqzbox
What makes you think those plugs were in a chevy?
What would you put in a Nova?

Autolite plugs don't give work well with Chevys, stick with the AC's.
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Old 01-14-2011, 08:56 PM
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Quote:
Originally Posted by alittle1
What would you put in a Nova?.
Dam! I read that 1st post three times and didn't see the name Nova till now much less put 2+2 together with the name like nastypurplenova.
I drove through a snow storm in Alabama monday and moved 120 trailers from a whse. to Toyota production plant tues. through today. I'm tired.
Just trying to keep awake till the wife get's home from work at 1 in the morning.

Time to get off this thing as I'm going down hill fast!
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Old 01-15-2011, 01:20 PM
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nastypurplenova is this a stock 327 or a modified 327, what type of ignition system are you using points or hei or a performance electronic distributor, if you are using points they are a weak ignition system, and every time you adjust the point gap or ( adjust the dwell ) you have to adjust your timing,
give us some more info on your Nova
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Old 01-15-2011, 03:50 PM
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OMG! Ft. Lewis? I got 2 tickets in two days there by the same MP. I was fixing to ship out to Nam in 30 day's anyway. Asked him to put me in jail so I could get out of it.
haha.. no I'm on the colder side of the state... Fairchild AFB(Spokane).

Quote:
This is an excellent guess. If the cross-over in the intake manifold is packed full of carbon deposit, then the choke box isn't going to heat up as fast as your engine warm-up, consequently, your choke will stay on longer than required and you'll get that dirty sooty plug appearance that you have there. The outer four corners is warming up normally. Another reason is that the valve seals can be leaking down in these mid-cylinders and the engine heat can't burn of the oil leak down that takes place when the motor is turned off. Going up a heat range on the center plugs may give some relief. If this is a stock 327 manifold, they were prone to coking up the cross-over passage in the intake.
These ideas make sense. I'll try to just keep an extra set of plugs in the car just in case it doesnt want to start up on me haha
I don't know a lot about this stuff and im trying to read through the tech section here but how would I know which ports are for the cross over? I'm sure if there are some carbon deposits inside the intake manifold i'd probably see it...
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Old 01-15-2011, 04:07 PM
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Quote:
Originally Posted by dklong
nastypurplenova is this a stock 327 or a modified 327, what type of ignition system are you using points or hei or a performance electronic distributor, if you are using points they are a weak ignition system, and every time you adjust the point gap or ( adjust the dwell ) you have to adjust your timing,
give us some more info on your Nova

It is setup with HEI, from what I was told it has 64cc heads, looks like a high rise intake but not sure... again, im new to all of this. Other than that, not sure what kind of cam, type of heads, any specs or ect...
this is the most recent pic of it (minus the air filter of course)
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Old 01-15-2011, 06:30 PM
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No headers? Can't see them. Sure would be a shame not to have them as you would be missing power and torque. Nice clean engine bay! You need to get off that base and blow her out.
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Old 01-15-2011, 08:35 PM
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what year is your Nova ? what temperature of thermostat are you using , try a 195 thermostat for winter. for the heat riser to work there should be a valve in the right exhaust manifold , where the y pipe or exhaust bolts on, what type of air cleaner are you using , an open after market is not good for cold temps,it can cause the carb to ice up. use a stock air cleaner for the winter time , they have a pipe on them that takes hot air off the exhaust manifold to make them work better in colder weather your carb maybe running a bit on the rich side fouling the spark plugs, you have an electric choke , try adjusting it a little rich , this will make the choke stay on abit longer
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