Vacuum issue with 89 Ranger 2.9l

[Mylesp30]

I recently changed the PCV valve and grommet and now it is idling very high. I didn’t change the breather yet because it has not come in yet but I did change the grommet. I did not change the lines. I read that the PCV valve could be stuck open. However I put my old one back in it and it is still idling high where it wasn’t before. Any ideas or suggestions?

 

[86_FX4]

Its been awhile since I've been in a vehicle of that year, but sounds to me like moving things around cracked a vaccum line somewhere or popped one off. Sometimes you can confirm this by if your AC blend doors stop working, hot/cold seems off, or if your truck is equipped with a cruise and it stopped working as well. Many older cars use vaccum to control AC blend doors, heater valve and cruise control. Also a small crack usually will introduce more air to TB and increase idle.

Edit: In the past when I've had that issue, go to autozone, get a pack of vac hose adpaters, and some vac hose in the same size you see on your car. Will be cheap and is sold by the foot. Generally its mostly all one size and a few bigger ones coming off throttle body. The line and adapters are cheap, replace everything you can see and touch easily, if you've got some stubborn ones or ones that disappear behind firewall or in hard to reach places you can splice with the adapters, but would avoid if possible and would only do if you obviously found a crack and see no easy way to replace the entire line. Some old head car guys will use starting fluid and spray around vac lines. Idle will increase more when you're spraying in the area of the leak as it sucks the starting fluid into TB.

 

[Mylesp30]

Do you know of any other lines that are near the pcv valve and breather on the opposite of pcv valve? Those are the only ones I messed with and lines seem fine

 

[RonD]

Cold engines idle high, 1,000rpms or so
700rpm after warm up
I assume that's not it?

Engine warm and idling
Pull off the PCV hose and plug that port with your finger, if RPMs drop it's leaking
Do the same with any vacuum hose connected to intake, pull it off and block that port


Yes, PCV valve has a weighted valve inside
When throttle is closed, intake vacuum is high and the weighted valve is pulled up by vacuum and closes off the hose to intake
As throttle opens vacuum drops and so does the weighted valve, pulling in "air" from valve cover and crank case

The "air" in the valve cover and crank case areas is Blow-by, basically exhaust gases
When a cylinder fires some of that explosive pressure "blows by" the piston and rings, hence the name blow-by, and its made up of exhaust gases, it ends up in the crank case which is connected to valve cover areas by the oil drains in the head(s)

PCV system was added to suck out the blow-by and re-burn it in the engine
So its an emissions system

Just FYI, blow-by gases are hot enough to Vaporize oil, and they do vaporize some of the oil coating cylinder walls and piston/rings
That's the only place in an engine hot enough to vaporize oil
So the oil vapor can also be sucked into the PCV Valve and intake
As any engine gets older blow-by increases and so will oil vapor,many add Catch Cans to reduce the oil vapor being sucked into the intake

The Breather hose is to let in filtered outside cooler air to try and condense some of the oil vapor inside the engine, but also serves as an Overflow device if PCV Valve isn't working
Blow-by(and oil vapor) can exit thru the Breather and into the air plenum and be sucked into the intake via throttle body
If throttle plate has a oil coating that is whats happening or there is way too much blow-by

 

[Mylesp30]

Also, where can I get a new vacuum line for the pcv valve? I can’t find it online at any parts store

 

[86_FX4]

Also, where can I get a new vacuum line for the pcv valve? I can’t find it online at any parts store

If you can measure the diameter or take it off, autozone/oreilly/pepboys will have it in the back by the foot.

 

[86_FX4]

Look close at the PCV valve line, is it possible you split it when reinstalling? Maybe you'll get lucky and you can trim off enough to get around the split and reuse same line.

 

[Mylesp30]

Update: I went a got a new vacuum line and put it on and it’s not idling as high. It was idling at about 3500 rpms now it’s more like 2200-2500 rpms. Is it possible it’s the vacuum hose for the breather on the opposite valve cover? Those are the only two things I’ve touched since it started doing it

 

[RonD]

No, the breather is not a vacuum line
(well technically it is a "ported vacuum", but won't effect idle RPMs)

Remove the air plenum(big air tube) from upper intake
Look at the throttle plate
Manually move it to make sure its closing all the way
Start engine
Use a piece of thicker cardboard to cover the intake's opening slowly cutting off air flow into the engine
You will often hear air being sucked in from a vacuum leak point as intake's opening is covered
Engine should, of course, stall with full blockage of intake opening

 

[Mylesp30]

I the throttle is opening and closing fine but I put cardboard over it and it didn’t stall and engine idle didn’t go down at all so I couldn’t hear any vacuum leaks. Any other suggestions?

 

[RonD]

Well that is impossible, lol

Engine can not run without air

 

[Mylesp30]

I’m not saying it’s impossible I just can’t hear anything bc the engine is idling so loud