I apologize if this question has already been asked before, but I recently tuned up my 68 Fleetwood 472 and it runs fine, but it has a slightly rough idle. I suspect that somewhere in the vast tangle of vacuum hoses that there is a leak. Could that cause a lumpy idle? I notice that the vacuum operated trunk release is not working as well.

I love this car but it sure has lots of vacuum lines!

Yes, a vacuum leak could cause a bad idle. You should get a vacuum guage, hook it up to one of your vacuum ports, and see what it reads. Don't know what it should be for your car - my '76 pulls just under 20 lbs. at idle, but most cars I've seen don't pull that much. A service manual would probably have the ratings if no one else here can provide them.

I'm not familiar with '68s, but I think the trunk release and pulldown motors electric? If you have the automatic parking brake release, it is vacuum though.

Thanks Joe:

I will try that out and regarding the trunk release, it has what looks like
vacuum lines going to the switch, maybe they are just heavy gauge electrcial wires.

Dave

Mr. Bailey, you could also try spraying ether in a suspected area of a vacuumn leak and if your engine revs up then you have a vacuumn leak. Also, are your vacuumn lines a bit chalky, or have tiny cracks in them? If so, I'd strongly recommend spending a couple of bucks and replacing ALL of your vacuumn lines as this can be done for very cheap and will prevent problems diagnosing your car both now and in the future.

If you replace all your vacuum lines get a 25 or 50 ft roll. check prices. Around $15 online. Pepboys wanted around $50!

I apologize if this question has already been asked before, but I recently tuned up my 68 Fleetwood 472 and it runs fine, but it has a slightly rough idle. I suspect that somewhere in the vast tangle of vacuum hoses that there is a leak. Could that cause a lumpy idle? I notice that the vacuum operated trunk release is not working as well.

I love this car but it sure has lots of vacuum lines!

Feel lucky, we dont have to deal with emission lines.

Anyway, a rough idle could be cause by a number of things. Check the check valve on the brake booster and that line all the way to the intake. Check PCV line and grommet and where it connects to the carb. Your cam could be unevenly worn down. You could have uneven pressure throughout the cylinders (check them). Your timing could be off... points worn out... plugs/wires shot. Carb could need some tuning/cleaning... those are some of the major things.

Thank you guys, this is a great running car with low miles and the idle is only
slightly rough, but you can feel it.

It also does not seem as fast as a 472 ought to be. I had a 390 in a 66 Sixty Special that felt faster.

When you park, all of the vacuum pressure drains off pretty fast, and then you can't use the power locks until you restart the car.

There's so many vacumm hoses under the dash, I'm not sure how you can get at some of them, but I will give it a shot.

Thanks again for the tips.

It also does not seem as fast as a 472 ought to be. I had a 390 in a 66 Sixty Special that felt faster.

A '66 with a 390? Was it a transplanted engine? A '66 should have a 429. :confused:

Could you get a vacuum pump to take on the load?

HEY THERE! I am in the same boat....er, I mean car. I have a 69 Deville and some of my hoses are disconnected. Is there anyone out there who has a vacuum hose location diagram for this engine? I have one hose in particular that connects at the bottom of the carb, right under the distributer vacuum hose, that I can not find where it goes. All the googles tell me is that it should attach to a purge canister, which my car is missing??? Any help as to where all these vacuum hoses should go, PLEASE let me know. Thats so much,
Wit:confused:

no i don't but i also am looking for a digram of vacuum lines for a 1971 Cadillac so if you find one could you let me know by email oclev01@yahoo.com i would appreciate it.

I got one for 75 Eldo' not sure if same? I'll email you. I'll see if I can figure out how to scan it but it's huge . It folds out from 9 1/2 by 11 to about six times that I think

Hit Ebay for a factory shop manual / factory service manual. I got mine for around $25 and I'm never going back to anything else! Get one for your year car, it has everything you'll need.

double post