Run On When Key Off....Help.
Thread Starter
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Run On When Key Off....Help.
My car has just started this recently. When I turn the key off the car wants to run on one or two cycles. Doesn't do it always. But should never do it. Anyone have any pointers? I am thinking timing. Any help would be greatly appreciated.
Thread Starter
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Re: Run On When Key Off....Help. (Ak. Mal)
Would the timing be too much or not enough?
Melting Slicks
Joined: Feb 2001
Posts: 2,115
Likes: 0
From: VA
Re: Run On When Key Off....Help. (Eddie 70)
Would the timing be too much or not enough?
Ron
Drifting
Joined: Aug 2003
Posts: 1,327
Likes: 16
From: Fl
Re: Run On When Key Off....Help. (Eddie 70)
how long has it been since you changed the spark plugs??
if they are carbonized badly, the carbon wil glow red hot after ignition is turned off. this will lead to run-on ....
also ... may want to do the ... mist water into the carb at 2000 RPM thingy ...
this will remove every bit of carbon buildup in the combustion chamber and clean the plugs too.
WARNING !!!! be really !!!!! carefull when doing the misting trick .. water must be misted into carb and only for very short bursts ... DO NOT pour water from a glass or stream it from a water spray bottle. water does not to compress and it could bend a valve if not done with care ...
my 2 cents ....
Bill
if they are carbonized badly, the carbon wil glow red hot after ignition is turned off. this will lead to run-on ....
also ... may want to do the ... mist water into the carb at 2000 RPM thingy ...
this will remove every bit of carbon buildup in the combustion chamber and clean the plugs too.
WARNING !!!! be really !!!!! carefull when doing the misting trick .. water must be misted into carb and only for very short bursts ... DO NOT pour water from a glass or stream it from a water spray bottle. water does not to compress and it could bend a valve if not done with care ...
my 2 cents ....
Bill
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Run On When Key Off....Help. (72ls5fla)
Somtimes the timing gets a little retarded and when that happens the idle will go down so we compensate by turning the idle adjustment up, now you have the dieseling problem :D
Safety Car
Joined: Feb 1999
Posts: 3,631
Likes: 14
From: Fountain Hills AZ
Re: Run On When Key Off....Help. (Eddie 70)
Would the timing be too much or not enough?
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Race Director
Joined: Feb 1999
Posts: 16,978
Likes: 7
From: In Dreams There Is Truth Ohio
Re: Run On When Key Off....Help. (e3pres)
Pre-ignition. I would suspect a high idle, and /or hot spots, carbon build up on the piston tops, valves. Run some premium gas with a engine top cleaner. If you had a carb, you drip some atf in your carb, that always worked and cleaned the piston tops.
Racer
Joined: Mar 2001
Posts: 438
Likes: 0
From: Houston, Texas
Re: Run On When Key Off....Help. (GDaina)
It also could be the butterflys not closing - which could also cause a high idle. Since fuel is always present, all that is needed to diesel is a hot spot and air. I had some warn throttle plates that didnt exactly center in the bores, They would jam open just a littl ebit and cause a run on.
Instructor
Joined: Feb 2003
Posts: 238
Likes: 0
From: Tee Tops off all year FL
Re: Run On When Key Off....Help. (Eddie 70)
Some carbs are equiped with an idle stop solenoid. When properly adjusted it's purpose is to prevent run-on/dieseling. You set your idle by turning the plunger. Then disconnect the wire to de-energize the solenoid, and set the idle speed screw in the carb to the lowest rpm that will keep the engine running. On an 80 like mine, the idle stop has a different function, it is an idle up that only comes on with the AC selected. Not sure which one yours has.
Melting Slicks
Joined: Feb 2003
Posts: 3,053
Likes: 4
St. Jude Donor '03,'11
Re: Run On When Key Off....Help. (GDaina)
Ignition timing shouldn't matter after the key is off.
My suburban does that a lot with winter gas. I guess winter gas has less octane.
cleaning the combustion chamber and going to a colder plug should do it.
are you running premium gas?
My suburban does that a lot with winter gas. I guess winter gas has less octane.
cleaning the combustion chamber and going to a colder plug should do it.
are you running premium gas?
Safety Car
Joined: Aug 2001
Posts: 3,685
Likes: 202
From: Waterford Mi
Re: Run On When Key Off....Help. (turtlevette)
Run-on is usually caused by air/fuel being sucked in after the engine has been running for a while and is hot. As stated above, high idel can cuase it. What RPM's are you running when in nuetral just be fore you shut it off? If it is higher than 850 then try to lower it a little.
Instructor
Joined: Oct 2003
Posts: 186
Likes: 0
Re: Run On When Key Off....Help. (Eddie 70)
idle air/fuel mixture, and vaccum leaks is another place to look. sometimes a vac leak starts out small, and with a tune-up idle mixture is changed to compensate. then leak gets worse, more adjustment, bam **** poor idle and run-on result. unfortunately C3's are very prone to vaccum leaks with all the vac accs. you can pull and cap all vac lines, that should take care of that issue in your troubleshooting. rich mixture is detectable in the exhaust, you'll smell raw fuel if it is bad. check condition of base gasket under carb. Brian
Thread Starter
Race Director
Joined: Feb 1999
Posts: 19,659
Likes: 34
From: Lenoir City Tennessee
Ci 6, 8 & 10 Veteran
St. Jude Donor '05-'06-'07-'08-'09-'10-'11-'12-'13-'14-'15
Re: Run On When Key Off....Help. (AKRAY4PLAY)
Idle speed is around 650 RPM so I don't think that is the problem. The plugs have only been installed for about 200 miles. Could be running rich. Thanks for all of the responses so far, it gives me things to check tomorrow.
Instructor
Joined: Oct 2003
Posts: 186
Likes: 0
Re: Run On When Key Off....Help. (Eddie 70)
pull a couple plugs, they should tell you the tune by color. heavily creamed coffee color is perfect! dark is rich. perfectly clean is lean or still to new to tell. Brian
Race Director
Joined: Apr 2000
Posts: 17,676
Likes: 201
From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Re: Run On When Key Off....Help. (turtlevette)
Ignition timing shouldn't matter after the key is off.
My suburban does that a lot with winter gas. I guess winter gas has less octane.
cleaning the combustion chamber and going to a colder plug should do it.
are you running premium gas?
My suburban does that a lot with winter gas. I guess winter gas has less octane.
cleaning the combustion chamber and going to a colder plug should do it.
are you running premium gas?
That is really strange, I kinda put my car away a few weeks ago and now it is nice out so I have been driving it around. I have a dieseling problem now that I did not have before in the summer /fall . Hmmmm
Melting Slicks
Joined: Dec 1999
Posts: 2,116
Likes: 156
From: Mid West
Cruise-In III Veteran
Re: Run On When Key Off....Help. (MotorHead)
Somtimes the timing gets a little retarded and when that happens the idle will go down so we compensate by turning the idle adjustment up, now you have the dieseling problem :D
Had my ZZ4 turned up to 1000rpm idle and had terrible dieseling problems. Reset the idle to 650 rpm, shuts off great now.
