Idle problem, please help
Thread Starter
Racer
Joined: Dec 2005
Posts: 399
Likes: 0
From: Kearns UT
Idle problem, please help
My 78 has a zz502, MSD 6AL, Demon 850 carb, 4" K&N air filter, HEI ignition, New platinum plugs and MSD wires and an electric fuel pump pushing around 6 1/2 psi of fuel.
My problem is when I first start the car, it idles very very rough, I have to sit in the car and press the gas to keep it alive, my tach bonces all round and it smokes like crazy, but after about a minute of this, I can rev the engine without it cutting out, the smoke goes away and it idles just fine.
Any idea what is causing this, is it normal? The smoke and rough idle just don't seem normal, but then they go away.
My problem is when I first start the car, it idles very very rough, I have to sit in the car and press the gas to keep it alive, my tach bonces all round and it smokes like crazy, but after about a minute of this, I can rev the engine without it cutting out, the smoke goes away and it idles just fine.
Any idea what is causing this, is it normal? The smoke and rough idle just don't seem normal, but then they go away.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Blue smoke = oil. White smoke = water. What color is the smoke. If it's blue, you've got oil leak down somewhere. Usual suspect is valve stem seals. Oil leaks in to the cylinder, and it will idle rough and blow blue smoke until it burns off, then it'll be fine.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Blue smoke means you are getting oil in to the cylinder. The oil causes it to run rough until you burn it out of there, thus the blue smoke. When the blue smoke disappears, it runs fine, oils gone. Valve stem seals are usually the culprit in cases like this. When you shut it off, it takes some time for oil to leak down out of the head past the seals and into the cylinder. The longer it's off, the more will leak down. Once the engine burns it off, it's usually fine and shutting it off for a short time won't cause enough to leak down to cause the problem again. But shut it off long enough for it to cool down will. I had the problem on my Z28. If it was constant blue smoke, I might say rings or a gasket, but as it is only on start up, burns off and goes away, my bet's on valve stem seals.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Depends on what type they put in. There's all sorts of debates on what are the best, teflon, umbrella, etc. That's why I'm suprised nobody else has jumped in here with their two cents. I'm not saying for SURE this is your problem, but it is usually the culprit on things like this. And Yes, my Z28's brand new 383 did it, so it can happen on a relatively new engine
Le Mans Master
Joined: Jan 2004
Posts: 8,295
Likes: 30
From: one night in Bangkok you are never lonely
I had the same problem as you the kicker is the tach bonces all round. It was my Summit distributor. Ready my posts.
http://forums.corvetteforum.com/show....php?t=1289033
http://forums.corvetteforum.com/show....php?t=1289033
Last edited by Bangkok Dean; Apr 13, 2006 at 07:21 AM.
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Racer
Joined: Jan 2005
Posts: 492
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From: Birmingham AL
Also check your choke. You could be running too rich which can cause all sorts of smoke (unburnt fuel) and rough idle. Simple check would be to make sure the choke is wide open before you start it cold one day and see how it does.
Le Mans Master
Joined: Jan 2004
Posts: 8,295
Likes: 30
From: one night in Bangkok you are never lonely
Originally Posted by 79MakoL82
Bangkok Dean: For my own edification, would that cause blue smoke? I can understand the other symptoms, but the smoke would be a mystery to me. Did you have that also?
Thread Starter
Racer
Joined: Dec 2005
Posts: 399
Likes: 0
From: Kearns UT
I've been thinking of getting a new distributor anyway. I'm not quite sure what brand mine is, but it has a blue body. I've taken it apart before and can't find a name anywhere. It has an Accel HEI Supor Coil on top of it. What brand/make/model distributor do you think would go good with my application?
Race Director
Joined: Sep 2005
Posts: 18,640
Likes: 121
From: Farragut,TN
Sounds like the choke needs resetting to specifications. I've had leaking valve seals and unless the oil is pouring in haven't had the problem you have. check a spark plug or a few after a run. let the car sit crank it cold check the same plugs again and see what they look like. if there oily then its valve seals.
Melting Slicks
Joined: Nov 2000
Posts: 2,663
Likes: 3
From: Palm Harbor FL
Well, as I said, others would be jumping in and here they are, so I'll step out.
As I said Blue smoke = oil, white smoke = water, and black smoke = too rich (I added that one). I had the exact same problem as you with blue smoke, and it was seals. If it's truly blue, you have to find the source of the oil leak in to the cylinders and that could be seals. If the smoke is black, it's more likely too rich, and a carb adjustment is required.
I'm not telling you what your problem is, just giving you information to help try and diagnose. Look at everyone's suggestions and figure out which one makes the most sense for you. With smoke, I would think that it's unlikely the distributor, but I've been wrong before.
As I said Blue smoke = oil, white smoke = water, and black smoke = too rich (I added that one). I had the exact same problem as you with blue smoke, and it was seals. If it's truly blue, you have to find the source of the oil leak in to the cylinders and that could be seals. If the smoke is black, it's more likely too rich, and a carb adjustment is required.
I'm not telling you what your problem is, just giving you information to help try and diagnose. Look at everyone's suggestions and figure out which one makes the most sense for you. With smoke, I would think that it's unlikely the distributor, but I've been wrong before.
Last edited by 79MakoL82; Apr 13, 2006 at 07:46 PM.
Pro
Joined: Sep 2004
Posts: 595
Likes: 0
From: Boston MA
my guess is that you have no choke, right?
I would start with timing.
It sounds to me like you are running rich at idle.
What is your total timing set to?
Are you running vacuum advance?
Start with that and lets go from there?
I had/have a similiar problem and I think I can help you out.
Thanks,
Joe
I would start with timing.
It sounds to me like you are running rich at idle.
What is your total timing set to?
Are you running vacuum advance?
Start with that and lets go from there?
I had/have a similiar problem and I think I can help you out.
Thanks,
Joe
Thread Starter
Racer
Joined: Dec 2005
Posts: 399
Likes: 0
From: Kearns UT
Ok, I got bored today and called Barry Grant, the tech had me pull the carb off, adjust the primary and secondary butterflies to where I can just barely see the little mark on the inside of the carb, this is hard to explain, but he guaranteed me that this is the correct setting for my butterflies. I have an electric choke, so he explained how that works and helped me adjust it, so I'm pretty sure the carb is adjusted properly now as far as that goes. I checked my timing and at idle, without vacuum advance I have about 12 and the car idles at about 700-800 rpm. I'm not sure about the total timing, so I hope what I just gave helps.
After adjusting all of that stuff the car runs just fine, but when I hit about 3000 rpm's the motor cuts in and out very quickly, so I will shift to the next gear and it will run just fine, until about 3000 rpm again, does this shed some light on the problem or open up a whole new can of works?
After adjusting all of that stuff the car runs just fine, but when I hit about 3000 rpm's the motor cuts in and out very quickly, so I will shift to the next gear and it will run just fine, until about 3000 rpm again, does this shed some light on the problem or open up a whole new can of works?
Le Mans Master
Joined: Jan 2004
Posts: 8,295
Likes: 30
From: one night in Bangkok you are never lonely
as I said with the tach bouncing all over the place it sounds like your distributor is some of your problems. Mine ran all over the place but only some times. My fix was a new GM stock distributor.Good luck with finding your problem.
It looks like many here have given you some excelent options.
It looks like many here have given you some excelent options.