79 vette stuttering

Reply Subscribe

Thread Tools

Search this Thread

Apr 10, 2006 | 06:05 PM

Frankie too

Thread Starter

4th Gear

Joined: Mar 2006

Posts: 4

Likes: 0

79 vette stuttering

A mechanic has the idle fairly high (the tach in car says 850). the carburater is a rodchester quadra jet. when in gear it boggs down and runs rough. it has new distributer, fuel filter, plugs, wires. It is L82 engine. car has 9500 miles on it. I am 56 years old and know nothing about cars. this is my first vette.. Help

Last edited by Frankie too; Apr 10, 2006 at 06:07 PM.

Apr 10, 2006 | 08:47 PM

cmac72

Instructor

Joined: Sep 2004

Posts: 193

Likes: 0

Welcome to the club - I'm 55 and my 79 is my first Vette (mine is a gift from my wife); although, it has the same engine as my very first car and I've owned various GM cars so most of the mechanics are familiar. I'd start with the basics - make sure all the plug wires are going to the right place and that they are secure and not broken somewhere. Disconnect the vacuum to the distributor and plug the EGR valve and check the timing. Check your choke to make sure it actually pulls down when warm. Your air cleaner clean? If you still have the cat in the car make sure you have a good stream of exhaust coming out - a partially plugged cat can really mess things up (like they say, don't ask how I know). Make sure you don't have any vacuum leaks in any of the vacuum hoses or around the base of the carb. I've had occasions where the bolts holding the quadrajet in place are a little lose. Check you snorkel to ensure that when the engine is warm, the door opens so you aren't still getting the air warmed by the exhaust manifold. I'm not an expert - but you might as well start with the easy stuff and if that doesn't help there are a lot of experts on this forum. Lots of luck.

Apr 10, 2006 | 08:58 PM

79MakoL82

Melting Slicks

Joined: Nov 2000

Posts: 2,663

Likes: 3

From: Palm Harbor FL

Quote:

Originally Posted by Frankie too

A mechanic has the idle fairly high (the tach in car says 850). the carburater is a rochester quadra jet. when in gear it boggs down and runs rough. it has new distributer, fuel filter, plugs, wires. It is L82 engine. car has 9500 miles on it. I am 56 years old and know nothing about cars. this is my first vette.. Help

I assume it's an auto. 850's not all that high. A manual's idle speed is supposed to be abut 900 in Neutral. I believe an auto's should be set so that it is at 700 in drive. Mine's a 4-speed manual. If it's running fine at 850 in neutral, and bogging down in Drive, it sounds like more of a tranny problem than an engine problem. What is the RPM in Drive? Maybe it needs to be adjusted up? Like I said, it should be at 700 in Drive. Any lower, adjust it up. You may need an additional 50-100 rpm's in neutral to keep it above 700 in Drive.

Remember, these cars weren't built for fuel conservation.

PS cmac72: Nice car. Mine was also a gift from my wife! Aren't wives GREAT

Last edited by 79MakoL82; Apr 10, 2006 at 09:01 PM.

Apr 11, 2006 | 07:15 AM

Eric79-L48

Instructor

Joined: Jan 2006

Posts: 223

Likes: 14

From: South Florida

Quote:

Originally Posted by Frankie too

You say 9500 miles. Is that original miles? Rebuilt Original Motor? Rebuilt Carb? How does it run off idle? When you say "bogs down" what do you mean exactly? Do you mean you punch the gas and the car craps out? What's the timing situation? Vacuum leak? More details please.

Apr 12, 2006 | 02:09 AM

CarlR

Instructor

Joined: Mar 2006

Posts: 108

Likes: 0

From: Lansing MI

Well let me try to help my uncle out by filling in some details on this one.

Timing is hopefully going to be checked today.
Can't find any leaks, and any questionable hoses that have been found have been replaced.
Everything is completely original in the car.
The car will idle in park around 950-1000 RPM (at least was tonight) Then when shifted into drive, it goes to about 550 RPM and sometimes stalls out. If it doesn't stall, it makes it's way back up to about 1300 or so RPM. I haven't personally done it, but I don't believe there are any problems when you just stomp on it in drive.
I'd like for him to get this car running smooth.
Thanks for the suggestions mentioned so far.

Apr 12, 2006 | 01:47 PM

79MakoL82

Melting Slicks

Joined: Nov 2000

Posts: 2,663

Likes: 3

From: Palm Harbor FL

So it sounds like when it is in neutral, it idles fine, and only stutters and stalls when you are trying to idle in drive. Then when you are driving normally (not idling at a stop) it is fine. 550 is too low to idle on these cars, so I'm guessing that is why it gets rough and stalls. I'm not an automatic tranny guy, but it sounds tranny related. The book just shows that idle in drive should be 700, but I don't think it should have to be at 1,500 in Neutral to achieve that. Maybe a stall converter problem. I don't know. I'd be guessing there.

Last edited by 79MakoL82; Apr 12, 2006 at 04:22 PM.

Apr 13, 2006 | 11:15 AM

rrhodes4

Instructor

Joined: Sep 2005

Posts: 144

Likes: 1

From: Collierville TN

I have a 1980 L-48 A/T. In drive it is supposed to idle at 500 rpm, 600 in nuetral/park and 1850 at fast idle. That is where mine is set and it runs out great. Sounds to me like either a vacuum leak or the Q-jet is in need of a rebuild. One other thing to look at is whether the vacuum advance on the distibuter was properly disconnected when the timing was checked/set.