Car shakes when i turn it off
Thread Starter
Drifting
Joined: May 2008
Posts: 1,505
Likes: 7
From: Jacksonville FL
Car shakes when i turn it off
Ok so I just got my new starter installed and its been going pretty well. It usually turns over quick unless I give it too much gas but thats pretty normal. (80 Vette stock engine w/ sidepipes)
Anyways today I turned the engine off and sat for maybe 30 seconds... when I turned it off the whole car shook pretty bad. I tried to start it back up and it cranked and cranked but wouldnt start worth a damn. Finally after trying 3-4 times I got it to start up.
I turned it off later to test it out and it shook again but started fine with a slight push of the throttle. Turned it off again and it didnt shake and started fine.... anyone know what the problem could be?
Im planning a 900mi trip to Illinois and I need my car to make it
im about to leave for Japan for 6 months and I havent seen my family in quite some time. 
Anyways today I turned the engine off and sat for maybe 30 seconds... when I turned it off the whole car shook pretty bad. I tried to start it back up and it cranked and cranked but wouldnt start worth a damn. Finally after trying 3-4 times I got it to start up.
I turned it off later to test it out and it shook again but started fine with a slight push of the throttle. Turned it off again and it didnt shake and started fine.... anyone know what the problem could be?
Im planning a 900mi trip to Illinois and I need my car to make it
im about to leave for Japan for 6 months and I havent seen my family in quite some time.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
It sounds like the car is "dieseling" after you shut it off. That means that it's running on its own without any spark. The only way it can do that is with timing being retarded a bit too much and/or some carbon deposits in the firing chamber that are staying hot enough to fire the cylinders. When cars went to lower compression and retarded timing at idle (early 70's because of EPA regulations), they had trouble with this. The car companies came up with an assortment of ways to deal with it. But they basically fell into two groups. Completely shut off fuel supply so that there isn't any fuel in the cylinders after the ignition is turned "off"; or add an artificial load to the engine so that it will be 'forced' to shut down. You can simulate one of these approaches: Leave your car in gear (if an automatic) or apply parking break and let clutch out immediately after shutting off the ignition. Or turn on your A/C just before you want to shut the engine down (if you have one, of course). You should first see if you can advance timing just a couple of degrees, then reduces idles speed and lean it out a bit at idle. All of those will assist in limiting the "dieseling" problem. If you think the heads/pistons might be carboned-up, run some SeaFoam through it to clean the crud out. Good luck.
Thread Starter
Drifting
Joined: May 2008
Posts: 1,505
Likes: 7
From: Jacksonville FL
thanks it helped a lot. i adjusted the timing (via the distributor) and tightened down my ground on my battery since it was loose 
I did it in the parking lot before i left work. It wasn't as bad so I adjusted it a little more and it was perfect. My co-worker did say my car smelled really rich and its usually not bad unless I'm on the throttle so I figured it was the timing. Thank you for the help! 
I did it in the parking lot before i left work. It wasn't as bad so I adjusted it a little more and it was perfect. My co-worker did say my car smelled really rich and its usually not bad unless I'm on the throttle so I figured it was the timing. Thank you for the help!
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Glad it helped. You might also want to do a little 'tuning' on the carb idle settings. Doing so will not affect how the carb operates at normal operating speeds. You want the idle to be smooth and 'leaned down' [by slowly turning idle jets CW (inward)] until each one just starts to slow the idle speed of the car down...then back up 1/4 turn. Once you've set the idle jets, then you can re-adjust the idle speed (screw on left side near front of the Q-jet) to allow a smooth idle in neutral [manual trans] or Drive [auto trans].
