My 69 is "dieseling" after the switch is turned off. It's not that bad, only does it for about a second but I don't want it getting worse. I drove it last night for about 40 miles round trip then shut it off and it stumbled a time or two after shut off. I then realized I didn't pull up far enought in the garage so I cranked it to ease forward and it didn't do it when I shut it back off. It just started the last couple times I have driven it. Any ideas? Thanks,

Auto or manual? Either way, you can shut it off in gear.

Some configurations used an idle stop solenoid, which is energized with the ignition on and is used to set idle speed; when ignition is off, the plunger retracts and the throttle blades close completely, stopping the engine.

Heat, fuel volatility can cause seasonal issues. If it continues, you'll want to find the cause. Any spark plug or carburetor changes or timing changes lately?

Dieseling is caused by the throttle blades not closeing enough.

what are you ideling at?

Mine does it sometimes when I shut it off while the fast idle is still engaged.

Car is an auto, no changes have been made to the engine. I am working on burning the fuel out of it so I can fill up with fresh gas. The fuel in it is 8 months old. I have a new temp gauge and it only warms up to 190. I've only been driving it late in the day when it's cool.


I have my tach disconnected, but I will reconnect it. It seems to be about normal though.

Thanks,

Untill you get new gas in it do as vikki said and turn it off in gear.With new gas you can adjust the carb mixture screws and idle stop to get the throttle blades to close enough to stop deseling.

It's around a half tank now, dang thing seems to be getting good gas mileage so I may siphon it out and use it in the mower.



Motor warmed up to 190, in park about 1200 rpm, in drive 800 rpm.
Is it idling to fast? Also if the carb is out of adjustment would it make the exhaust smell really bad? Thanks,

Having the timing to far advanced will also contribute to after running.

get gasoline instead of diesel....

sorry , couldnt resist!

Yes, idle is to high.
Stock type cams sould be about 800 in park/650 in drive.

My cam is not stock, supposable it's a ram air spec cam. What do you think my idle should be with this cam? How do I adjust it? Thanks,

Click on the picture below to see a video of it running.

Lower octane fuel will deisel in higher compression engines...

I bet he has weak springs in the distibutor, so at those idle speeds the centrifugal ignition advance is already coming in, resulting in too much timing for his combination of compression, camshaft, and gasoline quality. Or the initial is acidently too far advanced.

Definitely verify what your timing is at idle, and get some fresh 93 octane in that car.

I drove it tonight but it was cut short due to rain. I shut it off a few times and it only stumbled once so it maybe getting better. I'm just below half a tank now so I will have fresh gas in it this weekend even if I have to siphon it out. Also the engine only has a little over 2k maybe 2.5k on it since the rebuild and was also converted to HEI. I've never checked timing before. Should I leave it to a pro or could I be walked through it if I buy a light? Thanks,

First warm up your engine and adjust your idle in park to around 800 using the idle adjustment screw located on the front driverside of the Quadrajet carb.

After you have done that, here are step by step instructions on checking timing. http://www.hotrodder.com/kwkride/timing.html
It is very easy to do. The old Sears Craftsman Model 2134 is supposed to be very accurate (can find them on ebay if you want to wait 2 weeks for shipping!) , but any cheap auto parts store timing light will do for the basics.

1st you need to check timing.
Only go to someone familiar with old Pontiac's.
Otherwise learn how yourself(you should anyway).

Just get a cheap timing light. No need for a dial-back one.
Find out what initial is by removing vacuum hose from carb(plug port at carb).
With RAIV cam you'll need 16-18 initial.
Total about 34-36. Maybe 38.
RAIII cams will be alittle less, but not much.

You may have to adjust carb some during timing adjustment depending on how far off everything is.

Final carb adjustment is made after timing is set.
RA cams like about 900 in park, and 700 in drive.
You may get by with less rpm's though.

I will pickup a light and get this thing adjusted hopefully before the weekend is up. Thanks,

Almost forgot, what spark plugs are you running. It could be that for your combo they are too "hot" which could also cause dieseling. Find out your timing and let us know what plugs you run.