Morning and sitting for about 5 hours. Cold start up rough idle and loss of vacuum from brake booster. Assumed vacuum leak so I replaced the intake gaskets, quick-connect bushing assembly in intake and tested vacuum valve at the booster. All OK. Went ahead and did spark plugs while i was in there. Still no change. If this were a carburetor, I'd blame the choke for the idle problem. Typical misfire codes on all cylinders 1 thru 6. That's it, no more specific data. Drives normal and runs normal warmed up. I'd imagine if it were a vacuum leak it would be happening all of time but it isn't. Could it be the TPS or is there a specific code if it were? Thanks

 

I went through same thing with my 3.0 X Type. I got some spray carb cleaner and sprayed it around various intake manifold areas where there are gaskets and hoses. When theengine speed changes you have found a leak. Mine was around the motor that drives the intake manifold runner length veins. Good luck.

 

Have you tested for codes?

 

Misfire codes for all cylinders 1 thru 6 1316 (misfire) and 1000

 

The P1316 indicates multiple misfires and could be a number of things causing it but the first place I would be looking at is your fuel delivery. It is possible that many of your injectors are fouling. I would suggest adding a fuel treatment BG44K to your fuel and see if it clears up. I recommend it because it is the best on the market and can be found at most good repair shops. Give that a try first and see how it goes.

Link to codes. http://jagrepair.com/images/AutoRepairPhotos/P20003.PDF

 

Reading the fuel trims will tell you if you have an air (vacuum) leak.