Vacuum Lines


SawyerRanger

SawyerRanger

15+ Year Member

Joined
Aug 3, 2008
Messages
108
Points
3,101
City
Southeastern MA
Vehicle Year
1999
Transmission
Automatic
Vacuum Lines cause mysterious shaking? (SOLVED!)

How do I find and check the vacuum lines of a 99 OHV 4.0? I think a leaking vacuum line has been causing some recent misfiring, but I really have no idea where to find these things. I've looked at the emissions label and in my Chilton, but I don't know how to distinguish between radiator, coolant, vacuum hoses etc.

Thanks for any help guys
 
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Coolant lines are going to be pretty big like an inch or two in diameter but vacuum lines usually run like 1/2" or smaller. The way that I check vacuum lines is to get a propane torch and don't ignite it. Run the engine and start working the propane torch around the engine spraying the propane. Work the torch around where you see the thinner lines. When you hit a line that is broken the idle will change fairly noticeably.
 
On 98-2000 rangers(I've had a few) the most common vacumn leak is the line that runs from the engine to the body on the passengers side of the engine. Behind the altenator you should find a small hard plastic line, follow it and you will probably find it has melted to the exhaust or has been pinched or cracked somehow. I don't think it would leak enough to casue misfire though. Its probably a bigger leak like the line going to the brake booster or an intake gasket
 
I'll go out and check for those lines right now. The strange thing is, the misfire is only on cylinder #3, so I will most likely pull the plug and wire and check those as well.

Then it started shaking and the CEL came on, went to Autozone and they pulled codes, it got P0303 (misfire on cylinder #3) caused by vacuum leak, injector, plug, wire, etc.

So I changed the air filter and cleaned the MAF when I got home and the shaking went away nearly 90-100% I would say. Driven it roughly 25 miles since cleaning the MAF, had to unplug the negative battery cable so I could get the MAF out, and I knew the CEL would turn off, but it has not come on yet, so does that mean I fixed it? haha

However I'd still like to check the vacuum lines and plugs just to make sure. It almost still feels like there may be a slight misfire (it's possible that I'm being a truck-hypochondriac), so could a vacuum leak cause a misfire only on 1 cylinder?

EDIT: Went out and checked for some of those lines, and I saw this:
Vacuum Lines


Something told me that the wire belonged plugged into that cylinder, so I attached it:
Vacuum Lines


Can anyone tell me what that is? (Located on the passenger side)
 
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That would be the 4 port heater control valve as Ford calls it. It regulates the coolant flow to and from your heater core.
 
Yeh another that wouldnt hurt, is you can get vaccume line at any autoparts store for a couple bucks for 4 ft. Then you can just replace them all with new lines. But remember to do one at a time so you do not get them mixed up.
 
I hope these are the vacuum lines:
I've highlighted them all in the pics so we know which lines I'm talking about.
Vacuum Lines

The red circled hose is coming off the brake booster

The blue circled hose is coming from a tank (the A/C control?) to the A/C pump on the belt line

Here is a close up picture of the yellow line:
Vacuum Lines

I think it may have to do something with the PCV, but I'm no mechanic :bawling: yet, anyway.

Larger pics are here:
http://i40.photobucket.com/albums/e233/ConquistadorJake/brake-1.jpg?t=1230666041
http://i40.photobucket.com/albums/e233/ConquistadorJake/pcv-1.jpg?t=1230666043

This is on a 4.0 OHV. I have yet to pull the plug and wire, that's my next step I think. Does anyone know how to test them to see if they're working besides physical examination?

Again, appreciate all your help guys so much, I may ask all the stupid questions but they're helping me :headbang:
 
Okay your on the right track. the red circle is a vaccume line, but it is larger than the rest. The Yellow is the PCV vaccume line, that can be replaced. The blue one is not a vaccume line. I wouldnt touch that. Now there are three other lines that I can think of that should be replaced. I tried searching and could not find a good picture online so I will do my best to explain it. in the first of the larger pics you posted, it would be on the left where it cannot be seen. I believe it is the IAC valve and there are two lines coming from the bottom of that that attach onto a metal tube that runs along side the exhaust header. One like like 10" the other is 8".

The 3rd one can be seen from right behind the drivers side head lamp, right by the battery. There is a small canister with a vaccume line going to underneath the throttle body. It is hard to see with the air intake tube on. Also it can be easier to replace if you remove the belt.

Hope that helps.
 
Ok, took a few more pics.. The link to the larger version will be underneath each one.

This is the line I saw coming out of the IAC (right underneath it):
Vacuum Lines

http://i40.photobucket.com/albums/e233/ConquistadorJake/iacvalve-1.jpg?t=1230673780

It went around the A/C pump and joined up with a pump right behind the battery:
Vacuum Lines

http://i40.photobucket.com/albums/e233/ConquistadorJake/iacvalvevacuumpump-1.jpg?t=1230673780
I know that's not the exhaust header, but that's all I could see coming out of the IAC

Didn't see the line coming from the headlight area, although I do think I saw the metal canister you were talking about, not too sure. I did see a line coming from the power steering pump that went to underneath the truck, but I think it may have been a coolant line or something, took a pic of it anyway.
http://i40.photobucket.com/albums/e233/ConquistadorJake/pspumptounderneath-1.jpg?t=1230673781

And I figured this may be good to post up, here is the vacuum diagram that I found ON the truck.. However in my Chilton, I can't find the same one, only different ones.
Vacuum Lines

http://i40.photobucket.com/albums/e233/ConquistadorJake/vacuumhosediagram-1.jpg?t=1230673781

EDIT: CEL came back on, started to get pissed with this misfiring, and I'm pretty sure it's not a vacuum line, I've checked nearly every line in there, vacuum or not. Firestone better fix this (3rd try so far..) and I better not have to pay a cent.. Just so I know for the future, is there any really BAD things that can occur from consistent misfiring? Like cracked cylinder heads or something? Because I'd really hate to see my 4.0 crap the bed at 55k cause Firestone can't install plugs correctly -_-
 
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solved!

Just an update, so in case anyone else having this issue, this could help them.

Took it back to Firestone after the CEL came on again (cylinder #3). They ran their computer on it for us the night before to help reassure us that they would fix the issue, and the guy saw that bank 1 was running lean.

So we dropped it off in the morning, and they called a few hours later, turns out the cylinder #3 plug was LOOSE.. So it wasn't firing at all, explaining my 12mpg, shaking, and bank 1 lean.

They were kind enough to run to the nearest parts store (it was sunday, so everything else was closed) and buy 6 new plugs of a different brand, and installed all of them.

The shaking is gone, and my 4.0 is healthy again! :headbang: Bank 1 is now reading correctly, so the O2 sensor is working and the plug is as well.

Hopefully this will help someone who is having the same problem.
 
I've had a similar problem for the past 2 moths...this thread could be of great Help.
I'll keep you posted !!!
Thanks
 
Thanks for the Detective Work!

Mine's definitely Vacuum leak.
Thanks for the work & Pix of the AC vacuum lines!
AC/Heater flaps go back & forth on Accel/Decel and the only lines on the Sticker are the Emissions lines.

Off I Go!:icon_confused:
 
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