Question for you engine gurus, particularly if you're into the late model stuff:
Lynn had asked Bill the other day if he had a vacuum canister on his car, and that reminded me.........The 4.6 dohc in my car had a vacuumn canister on it when it was still in the Mark VIII. It was not something I transfered to my car, so I'm wondering if not having the canister could have anything to do with the idling issue I have. Mostly, the car idles fine for a few minutes at a stoplight, then it starts oscillating up and down.
Rich I wouldn't think so given most of the canisters had a one way valve in the supply side. They used them to provide a steady supply to things like the AC and other vacuum controlled items. It is worth a try to just put one in the system and see what the results might be.
AIC motor? New, old, replaced when the car went together? Pull it off and give it a good cleaning with NAPA brake cleaner, the 4800 stuff.
AIC ? don't know what that is unless you meant IAC (idle air motor), and I replaced that last summer, along with a thorough cleaning of throttle body, new gasket, new throttle position sensor.
That was my thought on the vacuum cannister..........needed with the A/C system door controls.
Gotta get me a vacuum gage.
Quote from: RICH MUISE on 2019-02-23 08:37
AIC ? don't know what that is unless you meant IAC (idle air motor), and I replaced that last summer, along with a thorough cleaning of throttle body, new gasket, new throttle position sensor.
That was my thought on the vacuum cannister..........needed with the A/C system door controls.
Gotta get me a vacuum gage.
You got it....
Old thread, but an update: I learnt lots more about how things work on my 4.6 having to basically take it apart to transfer stuff over to the replacement engine. I did have a vacuum canister. It's pretty small, so it wasn't what I was looking for. It's about a 1 1/4 x 3 cylinder, and it is right after a check valve as Bill mentioned. It is on the only vacuum supply line left coming off the intake.There are a total of 4 vacuum branch lines in use .......egr valve, fuel pressure regulator, and the 2 dashpots that control the intake runner ports. Vacuum for the fuel pressure is constant, but the egr and intake control vacuum lines run thru electronically controlled switches.
Rich I believe you may have found the idle problem with the EGR valve issue.
The heater control and ducting in the MKVIII were all electric actuators, the $34 each little pieces of junk that cost $1K to replace and are used industry wide.....so no vacuum inside the car like in the "old days"!