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Help needed on rough driving

A

Abel20

Guest
Well I am new to this forum as I just came back from a deployment. I have not messed with my car for about six months. My dad had the car and well problems started to happen. My car is a 1977 Corvette L-48.
When I start the car up and warms up it idles at about 13 RPM. When the car is put in reverse or drive it shakes and trembles. Once I get going the shaking stops but as I near or make a complete stop it keeps on trembling. What can be the probable cause and what can I check! Thanks Abel
 

Wayne robson

Well-known member
Joined
Feb 24, 2007
Messages
169
Location
australia
Corvette
sold my last corvette.
try and help

Hi Abel 20, did you mean 300 or 1300 revs, first thing i would check ismake your dad did not remove any spark plug wires, and placed them back wrong, then remove one spark plug on one side and another on the other side, choose essey accessable ones, take a good look at them to see if they have fouled up ,that i mean is black wet look, this i suspect could be the problem, because your dad may have started your car a few times while you were away with out giving it a proper warm up run,. then if thats not the problem alot of other checks are required,ill help you if its required,in a few days.Now this may seem strange to tell you, in your town there is a buick dealer named Avery Greene, they are very good on old gm cars, and have a classic gm show there every year, just incase you require proffessional help, regards wayne australia.
 
A

Abel20

Guest
The sperk plugs are all good. Somebody mentioned that it might be bad cylinders. Do bad cylinders cause shaking.
 
Joined
Jan 1, 2002
Messages
7,246
Location
Washington, Michigan
Corvette
'67 Marina Blue Convertible
Sounds like it needs a basic tune-up, with particular attention to the vacuum hoses and connections; lots of potential for vacuum leaks on a C3.

:beer
 

jdp6000

Well-known member
Joined
Aug 23, 2004
Messages
646
Location
Aurora, Ontario, Canada
Corvette
1982 CROSSFIRE
If it sat while you were gone and ran right before you left its probably the gas has gone bad.

Drain the gas and start with a fresh tank.

If there was water in the gas your filters may be fouled up.

Jim
 

kiwi vet

Well-known member
Joined
Jul 14, 2005
Messages
247
Location
New Zealand
Corvette
1981 Black/Camel T Top "RAC3R"
Dont know if this helps

Hey Abel20

Dont know if this helps but a buddy of mine had the exact same issue after the car had been in storage for a while (6 - 12 months).

Turned out in this case the transmission/convertor was clogged up with dirty old fluid (somehow seperated) and this was the cause, flushed it out, refilled it and it came right.

Have heard sometime convertor needs stripping/replacing if real bad.

Way to check if this might be your gremlin, once warmed up, with foot on brake select either reverse or drive, wait for shuddering to start then select neutral and see if it the shuddering stops. That isolates the transmission as the cause of the shuddering.

Hopefully just a flush & fill will solve it for you.

Good Luck
Ta Grant
 

whipperdecon

Member
Joined
Mar 12, 2007
Messages
6
Location
Canada
Corvette
1977 Bright Red Coupe
Hi Abel

[check your Dist Cap for cracks quote=Abel20;806713]Well I am new to this forum as I just came back from a deployment. I have not messed with my car for about six months. My dad had the car and well problems started to happen. My car is a 1977 Corvette L-48.
When I start the car up and warms up it idles at about 13 RPM. When the car is put in reverse or drive it shakes and trembles. Once I get going the shaking stops but as I near or make a complete stop it keeps on trembling. What can be the probable cause and what can I check! Thanks Abel[/quote]
 

Chiller

Well-known member
Joined
Mar 20, 2004
Messages
80
Location
N.Carolina
Corvette
1979 Black L-82
I just came back from a deployment. I have not messed with my car for about six months. My dad had the car and well problems started to happen. My car is a 1977 Corvette L-48.
When I start the car up and warms up it idles at about 13 RPM. When the car is put in reverse or drive it shakes and trembles. Once I get going the shaking stops but as I near or make a complete stop it keeps on trembling. What can be the probable cause and what can I check! Thanks Abel

From one Service member to another; Welcome home. As previously asked, what RPM is your Vette running at? How was it running before you left? Did your Dad just start it up occasionally or did he drive it around the "block" ? When I came back from deployment, I did a complete tune up and changed all of the fluids along with all filters. This would be a good place for you to start. This would eliminate the basic stuff. Just for clarification porposes, what type of tranny do you have? I see that previously kiwi vet said something about a converter. The seals in a Auto will dry up when it sets for a while with out being run through the gears.(So I have been told) Any ways, Start with a good good tune-up and a good "360" inspection of your vehicle.
Chiller
Chiller
 

zachh

Well-known member
Joined
Aug 1, 2005
Messages
221
Location
virginia beach, va
Corvette
1979 black 'n' silver L82 1978 Trans Am Y88
Check vacuum hoses. At idle, engines make a lot of vacuum (around 20 inches). A leak would lean out the engine which would cause a rough idle and make the car shake. At RPMS around 1500, there would only be about 5inches of vacuum which would makie any roughness in the engine unnoticable. Thats my guess in your problem. Spark plugs, a cracked distributor cap, bad wires, stale gas, clogged filters, etc would all make the engine run rough continuously and there would be ni times when the engine would smooth out. Im not sure about the transmission, usually a clogged converter would keep the transmission from shifting and there would be alot of slipping.
Best Wishes
zachh
 
A

Abel20

Guest
Thanks for your info Zachh. I had a quick question if you can answer it, will bad cylinders cause it to shake like I mentioned. Before I bought the car cylinders 7 and 8 were loosing compression.
 

Mr. Chuck

Well-known member
Joined
Jan 19, 2005
Messages
230
Location
Southern California
Corvette
1981 Two tone silver / dr grey
Thanks for your info Zachh. I had a quick question if you can answer it, will bad cylinders cause it to shake like I mentioned. Before I bought the car cylinders 7 and 8 were loosing compression.
If the compression is in question then a compression check will tell you the story. Be sure to check compression in all cylinders and write down the results. In older / high milage engines the real test of overall good/bad compression is to determine the spread from the highest to lowest reading. A wide spread will lead you to the bad cylinders, especially if 1 or 2 reading are low and the rest are higher and grouped together. The compression of higher milage engine will decrease as the cylinder walls wear, but as long as the spread is small the engine will still perform well enough for every day duty.
Two most common causes are with the valves (seating / burnt) or the piston rings (sticking / broken). A quick check to tell rings or valves; with plugs pulled, squirt a little light weight oil in the suspect plug hole and re-check the compression. Increased reading would suggest a ring problem. No change, then the valves are suspect. As suggested by others, fowled plugs in the lower reading cylinders are indicators of combustion problems,
Bad / broken engine mounts can also cause a lot of vibration, especially if engine isn't running well.
I also had an experience where mice had eaten through some vaccuum lines and spark plug wires, causing hard starting, rough idle & stalling on my 81 during a period it was idle for several weeks and this was in the garage.

I hope these ideas help, in addition to the other possibilities, like bad fuel, or the ignition causes by mis-connected spark plug wires, cracked dist cap. etc.

A word to wise or I'ved done that, been there before; when working on a long list of possible causes, always write down what was found as you go along. It is very easy to start jumping around and losing track of what was good or bad or what was un-clear at the time.

Good Luck!
 

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