Idle

1968ElectraLimited

1968ElectraLimited

Team Member
I have a few old V8:s and one of them is my 1968 Electra. According to the service manual, the idle should be 550 rpm when car is in drive. I find it hard to get my engines running smooth and not stall at such a low rpm. My Electra wont idle smooth below 700 rpm. Engines has around 78 k miles on it, card has been rebuilt. Is this a common issue? Otherwise car runs great and smooth on the road and is quite responsive.

/Gustav
 
I believe that car has the SP400. You should make sure the transmission is in high stall when adjusting the idle.
 
You are describing two concerns smoothness at idle and stalling under load.
Bob makes a good point for checking the correct setting under load.

For improved idle. On my car I have had issues with water contamination collecting in the carburetor's bowl and bottom of pump chamber and check ball where it causes white buildup/corrosion like mess.
Fuel idle mixture can be done with the addition of an oxygen sensor and an air fuel meter, otherwise it's the turning the mixture in to bog and back out respective of number mixture screws. Keep in mind that the carburetor has an idle circuit and off idle. The idle circuit does not function at highway speeds. I'd look to settings as it was pointed out.
 
Sorry, it runs great and does not stall under load! Its peppy and the tires spin if i step on it. Its just that it doesnt runt smooth under 700 rpm. Carburator cleaned last winter.

I have the TH 400, but in 1968 the switch pitch is gone.
 
get some carb cleaner and start spraying around carb area and listen for rpm change. where it changes is a good starting point that you may find a leaking gasket.
 
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How does a vacuum leak affect the engine? Is it a difference between a vacuum leak from a bad base gasket and a vacuum leak from the heater vacuum hose or the vacuum door lock system?

I also wonder it its a good idea to connect the distributor vacuum advance to manifold vacuum, instead carburetor manifold vacuum? My car has the controlled combustion system and the distributor is connected to the carburator, except when engine is really hot. If I understand this right, manifold vacuum makes the car run cooler at idle.
 
Thanks @suncoupe72 !

There is a lot of vacuum hoses! One thick one goes from the front of the carb to the engine block just behind the carb (if I stand in front of car) What is that? Cant find a vacuum diagram. Rest of the vacuum is for the CCS (on the air cleaner), vacuum accessories and brake booster.
 
you really need to get yourself the factory buick manual for your car. it will have all the vacuum diagrams and testing procedures you need.
 
Electra225CustomLimited said:
Thanks @suncoupe72 !

There is a lot of vacuum hoses! One thick one goes from the front of the carb to the engine block just behind the carb (if I stand in front of car) What is that? Cant find a vacuum diagram. Rest of the vacuum is for the CCS (on the air cleaner), vacuum accessories and brake booster.
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The orientation of the engine bay and the suspension, brakes, etc. is in most part the convention is that you are sitting inside of the car when you describe the position. On a front wheel drive car, where the engine is perpendicular to the driver it definitely makes it confusing if you don't know how to describe the location?

The workshop manual you will need to read it more than once to grasp. On my 1963 manual when it doesn't have a diagram it will explain where parts go and do. You would need to be able to identify the parts and locations. Sometimes they are in another area or not on the same page.
 
I had some vacuum leaks in the PCV system. The hose from the carb to the PCV valve and the hose from the valve cover to the air cleaner. The latter one is harder to replace, have to wait a few weeks to get one.

I have a digital tool for setting the timing. It shows engine rpm too. When engine drops in rpm and doesn't run smooth, it doesn't show a correct value or a value at all. Does anybody know why, is it always so, or could it be something wrong with my tool`?
 
electronics are designed many ways. Im guessing it is the delay of the digital tool and or it has minimum rpm to function. In some cases analog meter is better. Usually with electronics most common is capacitors go bad. They leak. ESR meter is used to test capacitors most effectively. DMM can be used too. I wouldnt chase timing light right now.

Are u familiar with setting timing with vacuum gauge?
 
Thanks! The strobe light/timing tool is new so I suppose capacitor is OK. I have some experience with old tube radios. Have been repairing a lot, but very few transistor radios.

No, never tried setting timing with vacuum.
 
Hey, been replacing some bad vacuum lines in the PVC circuit. I also plugged all vacuum hoses to find out if the car runs smoother. But it didnt.

The car usually dies below 700 rpm. So it dies when stop the car in drive. Can bad timin or points cause this problem?
 
What are you setting your initial timing to, looking at one tune up chart it appears GM recommendation is 2-1/2 degrees. I wouldn't be afraid of trying at least 6-7 and maybe even 10.
Points shouldn't be an issue as long as they are working.
Get a vacuum gauge and do a compression test on the engine. All cylinders should produce within 10% of the high and low. Record your results.
Check your vacuum at idle.
 
try spraying carb cleaner around carb/ intake area see if idle changes if so then you found your leak. may have an internal vacuum leak in the carb as well. good luck
 
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