I have narrowed down the rough idle problem

[89LincolnTWNcar]

....To A vacuum leak of some kind. I bought a vacuum tester and it reads around 7-9 (psi??) when it should read 17-22 as the book says. The needle also bounces with each rythmic surge of the idle. I think all my vacuum lines are ok, but i could be wrong. Could this be injectors??? I mean the car starts right up no prob..........

[Grand Marquis GT]

Shit dude, that IS a bad vac leak!!!

Does the cruise work?

Also, unplug your power brake booster line from the booster, stick something big in there to block it, and see if that fixes the idle.

If so, you got aleaky power brake booster.

Also, try spraying every inch of vac line and conncetion (including the areas around the intake where parts go together) with carb cleaner while running.

If the idle changes when you do this, BINGO! You found a vac leak!!

[89LincolnTWNcar]

WAIT it might be the booster, because the brakes dont work at all when the idle gets really low and i can feel the brake pedal shake.

[Grand Marquis GT]

Yes!!!

[gadget73]

The booster should hold vacuum and be mostly unaffected by the idle. If you don't have power assist for one or two pedal pumps after shutting the engine down its toast. 7-9" (vacuum is measured in inches of mercury) is horrible. Pull that line and plug it. Other major vac connections are the PCV valve and the feed to the vacuum tree on the firewall. How did you hook up the PCV valve? The HO uppers have an extra 'tee' thingy under the edge of the intake. I ran my line from the hose barb under the upper intake, to the T, then to the PCV. Thats how HO engines are plumbed. lopo motors don't have that extra T but its not a big deal.

[89LincolnTWNcar]

It's not the brake booster, I pulled the line and plugged it and it ran the same, so it must be elsewhere. I have the PCV set up in a wierd way, you know there is a front and a rear drainplug on the bottom of the upper intake. Well the rear one has a frozen plug in it, the threads are completely stripped and i cant get it out. SO I ran the PCV from the "T" in the front hole on the upper intake, all the way back to the pcv screen. (PCV valve rattles and is good, PCV screen is new, PCV vacuum line is new) When I pull the upper there is a good amount of oil in the rear intake runner. Why??

[gadget73]

About the oil in the intake runner, no clue. The exact PCV hose plumbing I don't think is super critical just so long as anything that has a vacuum hose connection is either plumbed to something or capped off. If you removed the smog pump, make sure the fat vac line to it is plugged off. Its a main line off the cruise servo. You can remove the T and run vaccuum direct to the servo without making any stupid problems. There is also a line off the cruise servo in through the firewall for the parking brake release. Might be a good idea to check on that to make sure its not leaking. Cap if in doubt. I would honestly hook a vac guage to it and take a pair of needle nose pliers and start pinching off the lines off the upper intake. Whichever line you choke off that makes the vacuum jump, start tracing it and anything that branches off it. Keep in mind one of those hoses feeds to that vacuum tree on the firewall, and there are a lot of lines tied to that. Make sure they're all connected and no caps are missing.

[nfldfordltd]

How about your intake gaskets?

If there is a leak between your upper and lower intake, or the lower and the heads then that may be the source of your vacuum leak. I had a 351W with the 7200VV carb and the gasket between the carb and intake was leaking, and I had the same problems as you describe.

[gadget73]

If SEFI engines have a leak there, they idle really really high. When I did my rocker swap with the screwed up spacer, it idled at 4000 rpm when I first started it up.

[89LincolnTWNcar]

I just re-did the lower intake to head seals with Feltpro printoseals, so its not leaking from there, lol. I'm thinking I just forgot 1 little vacuum line or in my work I busted one loose or it tore off its nipple.