Engine running rough at idle need help??????
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Engine running rough at idle need help??????
OK people I have a fine 79 that's been worked on and totally restored. The only problem is my engine (L48 w/4spd) runs rough at idle. I mean she jumps around alot. Like I had a race cam in it and I don't. Everyone that looks at the car gives me a different reason why it jumps and I tried everything they suggested to fix/and quiet the idle. Adjusted carb, played w/idle (I have it at 1100) anything below that and the engine whats to jump out of the car? Here are some spec's she runs like a bear, starts w/1st turn of the key and has a lot of power. I can light up the big 255/60/15's on the back and go from 60 to 100 in 4gear in no time? Ok I changed the stock Quadrajet to a new 600 Edelbrock Carb and Edel Intake manifold. I also put on headers and true dual exhaust. My next step is to pull out the motor and rip it down and rebuilt it myself. I need help and I need to stop spending money, help me.
Let me know what you think, its driving me crazy!!!!!
Let me know what you think, its driving me crazy!!!!!
Last edited by Jims79; May 13, 2005 at 01:21 PM. Reason: Re-write
Team Owner
Joined: Mar 2004
Posts: 24,202
Likes: 17
Try to suffocate the engine with your hands over the carb. Check for a vacuum leak this way! It sounds like a vacuum leak since you did a manifold job on it. You also need to really check the timing as well, since you pulled the distributer.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Rough Idle
Speaking of the timing my buddie and I found that my balancer shifted 30* south but the car still runs good. However we can't check the timing. So my first plan is to replace the balancer then check timing and I'll check for a vacuum leak. I hope that's it. Maybe I'll get a new set of vacuum hoses too. I'll let u know after I get the new parts.
Thanks
Jims79
Thanks
Jims79
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Changed Balancer
Well just to keep you guys up to date I changed my H-balancer (needed to be changed) next I'll try the vac leak. If that doesn't quite the engine down I'll replace the plugs and then the plug wires. I can't wait to drive my vette w/out spending $$$ and my weekends fixing it. Oh forgot I need to replace the clutch fan also. I'm thinking of replacing the unit w/a light weight alum fan. Any thoughts on the swap? Somebody stop me........................
Last edited by Jims79; May 10, 2005 at 10:58 AM.
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
Naturally, it could be lots of things. So, I'll only focus on a potential vacuum leak. To rule out vacuum, take a can of ether (starting fluid) and spray it around the outside perimeter where the intake manifold joins the heads, along with around the base of the carb. If the engine speeds up and smooths out temporarily, you found the source of a vacuum leak. If it doesn't make any difference, then you could have any number of problems, which are beyond the scope of this reply.
Good luck. You'll find it. It just takes perseverance.
Good luck. You'll find it. It just takes perseverance.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Still running rough but ruled out
OK I changed the balancer, (needed to be done to set timing) I checked for vaccuum leaks, No leaks. Next I'm going to change the plugs (only 1000 miles on them but someone suggested it) then maybe the plug wires. Wires are 5 years old yellow Accel from pep-boys.
One buddie suggested the ignition module in the distributor. What do you think of that?
Maybe I should buy a new HEI distributor from Mid America $199.
I'm still running the factory 79 distributor.
One buddie suggested the ignition module in the distributor. What do you think of that?
Maybe I should buy a new HEI distributor from Mid America $199.
I'm still running the factory 79 distributor.
Melting Slicks
Joined: May 2005
Posts: 2,143
Likes: 0
From: San Diego California
mine has the same problem it idles rough sometimes not all the times its a DD, somedays it idles OK but someday's it idles relly rough I had to raise the idle to help it idle better
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Originally Posted by Jims79
One buddie suggested the ignition module in the distributor. What do you think of that?
Maybe I should buy a new HEI distributor from Mid America $199.
I'm still running the factory 79 distributor.
Maybe I should buy a new HEI distributor from Mid America $199.
I'm still running the factory 79 distributor.
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Melting Slicks
Joined: May 2005
Posts: 2,143
Likes: 0
From: San Diego California
Originally Posted by Gordonm
Don't go spending money that is not needed. The module will usually either work or not work. A new dist. is not needed. Find out what the problem is before you start. Just throwing parts at it is not a good idea. You might hit the right part but you might spend a lot of money on stuff that is not needed.
I bought a new carb, plugs, wires, and distributor but it didnt help I'm gessing it could be a vacum problem but dont know 
Racer
Joined: Feb 2001
Posts: 405
Likes: 15
From: Minneapolis
I agree with Gordonm, don't go "shotgunning" hoping to stumble on a fix. Might be useful to re-trace your steps, as to what you did to the motor before it began missing. If you replaced the intake and carb, then you should focus your trouble shooting efforts on vacuum/fuel systems first. If the timing is set right, the distrtibutor shouldn't be the cause. Make sure the intake manifold bolts are tight.
If you don't have a troubleshooting manual to go by, then I suggest you let a pro have at it. Probably would be cheaper for you in the long run, rather than replacing parts at will.
If you don't have a troubleshooting manual to go by, then I suggest you let a pro have at it. Probably would be cheaper for you in the long run, rather than replacing parts at will.
Le Mans Master
Joined: Mar 2002
Posts: 7,456
Likes: 2
From: Coming home from Luckenbach Texas
If an L48 goes from 60-100 in 3 seconds, you may not be dealing with a stock engine. It's possible a previous owner has stuck a lumpy cam in there...at the very least.
BTW: Make sure your vacuum advance can is hooked up to a manifold vacuum source, not a ported vacuum source. It sounds like you need the can to be engaged at idle.
BTW: Make sure your vacuum advance can is hooked up to a manifold vacuum source, not a ported vacuum source. It sounds like you need the can to be engaged at idle.
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
The owner I got the car from told me the engine was rebuilt and it looks sounds and runs like it has. But who knows, I was told the same story about my old 68 400/4 spd Conv Firebird. I was driving it one day w/the top down feeling fine and pull up to a stop light. When I heard a terrible noise coming from this piece of sh-t sitting next to me. When the light changed and the junk pile left the noise was coming from my piece of crap. Sold it after replacing the engine and got my vette. I double check the vaccumm. Thanks
Melting Slicks
Joined: Aug 2004
Posts: 2,165
Likes: 950
From: Keizer Oregon
60 to 100 mph in 3 seconds 
definitely not a stock L48.....my 440 hp 383 stroker w/<3100lbs weight won't even do that......we are talking 11 sec@130mph 1/4 mile times here.....Count yourself lucky that your car even idles 
definitely not a stock L48.....my 440 hp 383 stroker w/<3100lbs weight won't even do that......we are talking 11 sec@130mph 1/4 mile times here.....Count yourself lucky that your car even idles
Thread Starter
Safety Car
Joined: Dec 2004
Posts: 4,876
Likes: 1
From: Jersey Shore Exit 98
Its not that fast and its not stock but I wouldn't compare it to your 383 440 or say its a 11 sec car, 14, 15 sec maybe. If I'm lucky and don't blowup my 25yr old motor.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by Jims79
Its not that fast and its not stock but I wouldn't compare it to your 383 440 or say its a 11 sec car, 14, 15 sec maybe. If I'm lucky and don't blowup my 25yr old motor.
16 sec,17 sec ,18 sec, 19 sec.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
Originally Posted by Jims79
when am I going to get some garage time. 
