What happened?
03-30-2018, 03:37 PM
#1
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Thread Starter
What happened?
Went to get gas, and after fill up on the way home, I did some spirited driving. Accelerator got stuck at 3k rpm. Pulled into a parking lot and shut the engine. I checked the carb linkage and gas pedal and both seem fine. As I was checking around the linkage again, I heard a click like something had loosened up. Started the car and no more high rpm; however, the engine now idles very rough like missing cylinders, all not firing. Oil pressure, water temp, and battery showed normal on the gauges. Limped home about a 1 1/2 mile, hoped didn’t damage anything more by that. No oil leaks. Forgot: 73, 350, 4spd. Any thoughts what direction I should go from here? Any comments/advise will be appreciated. One more question for the Tampa folks: Any recommended good mechanic for older Vettes in the Tampa Bay Area? I’m new here.
03-30-2018, 03:54 PM
#3
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Thread Starter
03-30-2018, 04:27 PM
#4
Just another Corvette guy
Check that the throttle cable plastic covering hasn't deteriorated to the point where the sleeve hangs up on it. Also, are you certain a floor mat didn't get caught up in the pedal linkage. I know, sounds stupid, but it happens. Good Luck!
(Post a couple pics of your car!)
(Post a couple pics of your car!)
03-30-2018, 08:45 PM
#6
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Thread Starter
Checked that, its ok. The problem i'm having now is the engine idling rough barely. I went out and bought new plugs and installed them in the hope that because the other ones were fowled, the engine would fire and run right. That didn't work, it still runs rough. I have a bad feeling that something else is going on. These old cars are fun while they run right. Unfortunately, I bought without really knowing the history. Hard with old cars. Hoping that its not that bad. The car had 47K miles original documented in Florida. Now I dispute that. Its not a numbers matching car. Everything is, except for the block. If the engine is toast, then ill go and do a crate.
03-30-2018, 08:51 PM
#7
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Thread Starter
03-30-2018, 09:03 PM
#8
Race Director
Could, if they are stuck a tiny bit open.
03-30-2018, 09:05 PM
#9
Race Director
Reset the mixture screws, turn each one in / out until you get the highest RPM on that side, do both - then open both up 1/4 to 1/2 turn.
If the secondary was partially open when the mixture was set - then it's off.
Check all vacuum hoses for a leak. If you have a leak the car will idle poorly and idle faster.
Also make sure the secondary's close and open freely - no binding.
If the secondary was partially open when the mixture was set - then it's off.
Check all vacuum hoses for a leak. If you have a leak the car will idle poorly and idle faster.
Also make sure the secondary's close and open freely - no binding.
Last edited by BLUE1972; 03-30-2018 at 09:08 PM.
03-31-2018, 07:41 AM
#13
Burning Brakes
As part of your checking for vacuum leaks, make sure the carb gaskets are good and it is sitting tight on the manifold.
Check vacuum lines to headlights and power brake booster (if applicable).
Fran
Check vacuum lines to headlights and power brake booster (if applicable).
Fran
03-31-2018, 07:56 AM
#14
Burning Brakes
The secondary throttle plates may not be all the way closed which is why it will not idle correctly. I had this happen years ago. I used K&W carb cleaner to get everything clean and moving properly again. I sprayed the shaft,plates and all the linkages to free everything up.
Last edited by 76strokervette; 03-31-2018 at 01:06 PM.
03-31-2018, 08:51 AM
#15
Grab the distributor cap and try to twist it. Are you sure it wasn't just the hold-down coming loose, and the "stuck" throttle not just the timing being turned temporarily advanced? If it is loose and now retarded, that could explain the lack of an idle and missing.
Could also be something odd in the distributor, such as a condenser wire rubbed through insulation and arching.
Could also be something odd in the distributor, such as a condenser wire rubbed through insulation and arching.
Last edited by JoeMinnesota; 03-31-2018 at 08:55 AM.
03-31-2018, 09:01 AM
#16
Dementer sole survivor
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Do as others have suggested. Start with a basic tuneup. check that all your plugs are firing, make sure you have no vacuum leaks, recheck your timing. Check that all your plug wires are connected and that you havent burned through one. Rough running with no loud knocking is actually a good sign, if you blew up your motor you would hear some bad mechanical noises. Old engines are really easy to work on as they dont rely on computers to run and sensors to tell the computer whats going on. Get a can of carb cleaner or starting fluid and spray quick spurts on youvacuum connections and the base of your carb. If the rpms change you found a vaccum leak.
keep us posted
keep us posted
03-31-2018, 02:57 PM
#17
Le Mans Master
Motor mounts
Check your motor mounts. If the mounts are bad, the engine could shift and lock the linkage. When you turn the engine off, the engine goes back to the correct position. Also, if you need an old school mechanic, PM me. I have referred more than a few members to my buddy in Tampa. He has a wicked 70 LT1 and a beautiful 58. Small shop, killer work. Jerry
04-01-2018, 08:54 PM
#18
Ages ago when my throttle got stuck it was a frayed cable within the sleeve. Replaced it.
You may want to consider disconnecting the throttle cable from the carb just to eliminate that from the potential problem list.
A question though: Did you over-rev the engine? If you did not over-rev, and it was running well before, then I would just suspect something at the carb and or linkage connection(s).
You may want to consider disconnecting the throttle cable from the carb just to eliminate that from the potential problem list.
A question though: Did you over-rev the engine? If you did not over-rev, and it was running well before, then I would just suspect something at the carb and or linkage connection(s).
04-09-2018, 08:53 AM
#19
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Thread Starter
Thanks to all for the help. Haven’t been able to follow through on this and respond, but eventually I got to it. With the help of a friend, we started to check things from the block on up:
Compression check= good
Pulled valve covers off= good, oil getting up to rockers and flowing, everything nice and tight and all moving the same.
Ignition= distributor good, cap is good, rotor was good but installed new one while there, checked ohms on all wires and spark getting to plugs all were good, coil was good, had previously installed new plugs and rechecked gap which were good.
Checked vacuum lines= good
That left the carb= checked linkage, choke, looked good. Peeked down at the secondary plates and appeared to be closed. We then fired up the engine and she still stumbled and warmed her up a bit. Brought up the rpms and held it there. Heavy fuel smell, but little by little seemed to run better. Left it idling for a bit and idle became good.
For those that said carb and secondaries getting stuck, I believe that was the case. As it was suggested by a couple here, the secondaries got stuck opened then shut at some point. Don’t know if the float was also messing up. Seems a good reason to send the carb out to be sorted out by the experts. Hopes this helps others with same issues. Thanks to all for the guidance.
Compression check= good
Pulled valve covers off= good, oil getting up to rockers and flowing, everything nice and tight and all moving the same.
Ignition= distributor good, cap is good, rotor was good but installed new one while there, checked ohms on all wires and spark getting to plugs all were good, coil was good, had previously installed new plugs and rechecked gap which were good.
Checked vacuum lines= good
That left the carb= checked linkage, choke, looked good. Peeked down at the secondary plates and appeared to be closed. We then fired up the engine and she still stumbled and warmed her up a bit. Brought up the rpms and held it there. Heavy fuel smell, but little by little seemed to run better. Left it idling for a bit and idle became good.
For those that said carb and secondaries getting stuck, I believe that was the case. As it was suggested by a couple here, the secondaries got stuck opened then shut at some point. Don’t know if the float was also messing up. Seems a good reason to send the carb out to be sorted out by the experts. Hopes this helps others with same issues. Thanks to all for the guidance.
04-09-2018, 08:55 AM
#20
Advanced
Thread Starter
Check your motor mounts. If the mounts are bad, the engine could shift and lock the linkage. When you turn the engine off, the engine goes back to the correct position. Also, if you need an old school mechanic, PM me. I have referred more than a few members to my buddy in Tampa. He has a wicked 70 LT1 and a beautiful 58. Small shop, killer work. Jerry
