engine keeps running

A

Arthur Brown

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it runs for another second or two after turning off the ignition. Timing or a carburetor problem ??
 
Arthur Brown said:
it runs for another second or two after turning off the ignition. Timing or a carburetor problem ??
Click to expand...

Usually idle too high. Early Vettes had an idle solenoid that closed the throttle plates when turned off.
 
Arthur Brown said:
it runs for another second or two after turning off the ignition. Timing or a carburetor problem ??
Click to expand...

With the ignition off, it doesn't seem like it could be due to a timing problem. As I recall, engine run-on, was a problem with the mid-1970 cars due to smog provisions. I't think that the engine run-on is due to a too lean condition. At any rate the engine continues to run since it is essentially running like a Diesel engine. The early smog controls would soot up the spark plugs, so I think glowing carbon was the culprit behind run-on. I can remember using a tactic to kill an engine that continued to run after turning off the ignition: put the brake on, put the car in Drive, and step on the gas....that'd kill the engine. The reason I mentioned "in Drive" was that this run-on condition, as I recall, was worse with an automatic transmissions. With a manual, putting the brake on and shifting to first gear would quickly kill the engine.
 
I have a buddy that had a similar problem with a car of his one time. He had a good tune done to the engine including timing, tuning the distributor and setting up the carb all of which helped a lot but did not completely eliminate the problem. On the advice of a mechanic he started running a higher octane gas and that took care of any remaining problem. So, you might be looking at solving multiple issues to get things right.

Hope this helps.

DC
 
Thanks a lot for your replies, much appreciated. I'll try 93 octane gas and a slightly lower idle first. If that does not help I'll pull the spark plugs. When I pull the plugs, what am I looking for?
 
funny that mine does it too sometimes... not everytime though .... my idle is at 1000rpm, no emission stuff.... manual trans.... guess I should lower the idle a little...
 
BBShark said:
Arthur Brown said:
Thanks a lot for your replies, much appreciated. I'll try 93 octane gas and a slightly lower idle first. If that does not help I'll pull the spark plugs. When I pull the plugs, what am I looking for?
Click to expand...



This article has a chart for reading plugs.
http://www.aa1car.com/library/sprkplg2.htm
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This is damn usefull, if not already, this should be in the tech section. Will definitely help me troubleshoot this greasy exhaust port problem I'm having.
 
68/70Vette said:
Arthur Brown said:
it runs for another second or two after turning off the ignition. Timing or a carburetor problem ??
Click to expand...

With the ignition off, it doesn't seem like it could be due to a timing problem. As I recall, engine run-on, was a problem with the mid-1970 cars due to smog provisions. I't think that the engine run-on is due to a too lean condition. At any rate the engine continues to run since it is essentially running like a Diesel engine. The early smog controls would soot up the spark plugs, so I think glowing carbon was the culprit behind run-on. I can remember using a tactic to kill an engine that continued to run after turning off the ignition: put the brake on, put the car in Drive, and step on the gas....that'd kill the engine. The reason I mentioned "in Drive" was that this run-on condition, as I recall, was worse with an automatic transmissions. With a manual, putting the brake on and shifting to first gear would quickly kill the engine.
Click to expand...

I think you'll find this to be a timing problem. Have you checked it? Alot of times the "diesling" effect you mention was after the inginition was shut off, the engine would just about stop, then give a turn or two and blow back through the carb, sometimes running backwards a few revolutions. This was typically timing, I'm not sure it had anything to do with emissions. I'd look there first :drink:
 
hehe....one of the lovely things about FI,

but the way I wound up fixing all them old Pontiacs in the 60-70's was to get as much advance as I could looking for 36 as I recall, then connecting the vac advance to full mani vac directly....no krazy emissions plumbing crap....this would increase the idle pretty good, and so to close the primaries on the Qj.....set the mix screws for max vac plus out 1 turn,

but this was back in the daze before the Qj's were all worn throttle shafts and other faults from just plain age and 40 years of mechanics....and these were typically 389+++ Poncho engines...not SBC....

the Qj on my 350 chebby Camper here was toast from many angles, but I had a 'new' one on the garage wall hanging there for the last 20++ years, unused and ignored.....but it found love again.....

:yahoo::censored:
 
69427: vacuum is hooked to the manifold

damoroso: if it's timing related would it be too far advanced or too far retarded ?

"give it a turn or two" - that's exactly what it sounds and feels like :)

thanks for taking the time to reply , your help is really appreciated.
 
From an old thread.







Here's a response that Lars gave on another forum:

Re: Deiseling at shut-off, lots of smoke at start-up...Need Help... (Double_0_7)

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Dieseling at shut-down is most commonly caused by idle speed too high. Drop your idle speed down just a tad, and it will solve the problem. If your car is equipped with the idle-up solenoid, be sure the idle speed is set with the solenoid, and that the idle speed screw on the carb is set to the lowest possible idle speed (about 400 rpm). This will solve the run-on problem.


Timing won't cause run-on, since the timing is off when the problem occurs. Just set your idle speed down to the lowest comfortable level, and make sure your idle mixture is not too rich. Run-on was a common problem in the mid-70's, and GM actually issued a Service Bulletin telling the dealers to lower the idle speed...
 
SmokinBBC said:
From an old thread.







Here's a response that Lars gave on another forum:

Re: Deiseling at shut-off, lots of smoke at start-up...Need Help... (Double_0_7)

--------------------------------------------------------------------------------
Dieseling at shut-down is most commonly caused by idle speed too high. Drop your idle speed down just a tad, and it will solve the problem. If your car is equipped with the idle-up solenoid, be sure the idle speed is set with the solenoid, and that the idle speed screw on the carb is set to the lowest possible idle speed (about 400 rpm). This will solve the run-on problem.


Timing won't cause run-on, since the timing is off when the problem occurs. Just set your idle speed down to the lowest comfortable level, and make sure your idle mixture is not too rich. Run-on was a common problem in the mid-70's, and GM actually issued a Service Bulletin telling the dealers to lower the idle speed...
Click to expand...

Yep.:goodnight:
 
Carbon buildup with an overly hot engine can cause it too, even with somewhat normal idle speeds.
 
SmokinBBC said:
From an old thread.







Here's a response that Lars gave on another forum:

Re: Deiseling at shut-off, lots of smoke at start-up...Need Help... (Double_0_7)

--------------------------------------------------------------------------------
Dieseling at shut-down is most commonly caused by idle speed too high. Drop your idle speed down just a tad, and it will solve the problem. If your car is equipped with the idle-up solenoid, be sure the idle speed is set with the solenoid, and that the idle speed screw on the carb is set to the lowest possible idle speed (about 400 rpm). This will solve the run-on problem.


Timing won't cause run-on, since the timing is off when the problem occurs. Just set your idle speed down to the lowest comfortable level, and make sure your idle mixture is not too rich. Run-on was a common problem in the mid-70's, and GM actually issued a Service Bulletin telling the dealers to lower the idle speed...
Click to expand...


That makes sense, see today wasn't a complete waist, I learned something!! :D
 
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