Engine wants to die - possible vacuum leak?

[200ci66]

Details of my car are down below. Lately, my car has been idleing very rough and wants to die (especially when cold, but will once in a while die out of nowhere while hot). I've played with the timing have I have it set comfortably at 14* btdc which is two degrees more advanced than recommended. Finally, I have played around with the carb, but I can't find a comfortable idle. Either my car is idling way too fast, or it idles too low and wants to die (and it does this around the recommended rpm of around 550-600 in drive). In order to get my car to idle smoother and die less often (still dies) I have to get the idle up there around 700 in gear, but this is way too fast of an idle to live with because it shifts into reverse EXTREMELY hard and even sounds like it's idling too fast in park.

Something else I'll add - whenever it dies, I just hit in neutral and flip the key and it starts right up. It's almost become habit. Also, it only dies when rpms are dropping - such as when I am slowing down to turn onto a side street or coming to an extremely sudden stop (yellow stoplights).

I suspect a vacuum leak, but don't even know where to begin looking for one. Does anyone have any opinions on what this sounds like to them?

 

[First Fox]

If you suspect a vacuum leak a quick test is to let the engine idle, and spray some carb cleaner or brake cleaner around any likely vacuum leak locations like the carb mounting flange, vacuum tees, core plugs in the log etc. If there is a leak it will draw the flammable fluid into the engine and will increase the idle speed slightly. Work slowly and try to isolate it. If you come up empty there, disconnect and plug any vacuum operated accessories; heater controls, brake booster etc. and start it up again and see if the idle is improved. Be sure to check the condition of any and all vacuum accessories. If a rubber hose to anything vacuum operated has deteriorated or come loose, well, that'll do it. 8)

You can check for an overly rich condition by idling the engine, and introducing a vacuum leak by slowly removing a vacuum line while it is still idling. If the idle improves it is likely you have a fuel problem likely a blown power-valve or a sinking float.

 

[200ci66]

I don't have any carb cleaner or brake cleaner at the moment, but on a whim I pulled the vacuum line on my distributor and it didn't seem to run any different. However I believe that vacuum line only has to do with advance - correct? (It is a 68 distributor, not a 66)

And thank you for the reply FirstFox

 

[First Fox]

Yes, that line controls the VACUUM advance only. The mechanical advance is controlled from weights and springs inside the distributor, and it is a possibility that there may be a problem there also. Gotta check one thing at a time though. If your distributor advance was connected to ported vacuum, then you would have noticed little if any change in idle speed and the only change would have been from a small vacuum leak when you disconnected the line.

You can check the vacuum advance by pulling that distributor vacuum line off at the carb and either connect it to full manifold vacuum temporarily, or put the line in your mouth and suck 'till you turn blue. If you notice no change in idle, it is likely that something is wrong inside the distributor. that very thing happened to me once and the idle suddenly went to hell. Turns out the vacuum advance arm had come loose where it attached to the advance plate and was preventing the advance plate from returning to where it should have been. If you inspect the inside of your distributor you will probably see what I am saying. Either way, applying vacuum to that advance can should change the idle, even if it is running rich or lean.

BTW, No carb or brake cleaner on hand? Shame on you. :nono:

 

[mugsy]

My car had an issue with idle and it ended up being the float was too high. It sounds very similar to your problem. Fro your car's issues, I'd start the car and get it up to operating temp. Then look down the carb throat and see if fuel is coming from the booster or other areas. Fuel at idle should be metered thru the idle circuit below the throttle plate only. In my case, because the carb was supplying too much fuel it would idle but only when the throttle plate was slightly open so that there was enough air to mix with all the fuel that was spilling over/thru/under the carb!! It is got progressively worse until it started dieing at traffic lights.

By all means do check for vac leaks while troubleshooting as well, very simple to do and worth your time and effort. But it's possible that the engine is stalling due to either not enough OR way too much fuel!

 

[vssman]

While you're checking those things above, also check your PCV valve. I'd pull the hose off it and plug the line with a bolt to see if it helped the idle.

 

[tri-power 250]

I had the same problem. I just rebuilt my alternator and replaced my regulator. The car now idles very smoothly.
Ken

 

[ludwig]

Isolate one problem at a time. Don't just go changing a bunch of stuff. Start with the easy stuff like the spray and the hoses.

 

[200ci66]

Sprayed carb cleaner everywhere. No leaks. Advance on distributor is also working.

Pcv valve has suction when I put my finger over it after pulling it out of the valve cover. Is this a sign that it is good or could it still need replaced? It's making a little bit of noise (high pitched whine) but I thought this was normal. Could this little 2 dollar part need replacing? I may just go ahead and replace it anyway to try it and see.

 

[ludwig]

That one won't kill you financially and you can believe that you ruled it out as a problem.

We have to wait for more answers now from guys that know more than me. And that would be a LOT of guys here.

 

[JackFish]

My experience with a vacuum leak is that the car wants to rev up, not down.

 

[200ci66]

I think I may have had the engine running too rich at idle. Re-tuning the carb and limiting myself to only 2 turns on the mixture screw then setting proper idle helped a lot. Idles at 1100 rpms in park and 650 in drive. Still a little fact but it's definitely smoother and easier to deal with.