Loud hissing noise, wont stay running

[BP_93explorer]

It was running fine when I parked it. Now it will start when I give it gas and dies if I let off. There is a hissing associated with it so I assumed a vacuum line. There appears to be two lines missing. The one pictured and there is one directly on the other side. Anybody know what goes there? I can't find any hoses just laying there waiting to be plugged back in. Any help is appreciated.

 

[shamaal]

If you can't find the hose, for the moment cap it; the end of a bic pen will work in a pinch. Vacuum leaks play havoc with the engine's operation. I've attached a picture from a 91 which is reasonably close. There is an EGR on yours and perhaps an automatic transmission line.

There should be an EPA sticker next to the hood latch in the engine bay showing the engine control vacuum system.

Respond if there are questions

 

[Willard]

those may have been just capped off, some of mine are, in which case just go by a cap and put it on

 

[shamaal]

Looking at your pic, as a minimum the FPR line is missing. The attached pic shows the location of the FPR follow the vacuum line back and see if it's connected.

 

[CDW6212R]

That leakage is very common with the 4.0 OHV V6. The slightest backfire(not loud), just a cough backwards through the intake, will blow off one or more of the vacuum plugs or hoses. I carried a few spare plugs in my 93 Explorer, it would do that at start up about once a month. I always was able to find the missing plug, except once. Good luck,

 

[cgriffin_5139]

Looking at your pic, as a minimum the FPR line is missing. The attached pic shows the location of the FPR follow the vacuum line back and see if it's connected.

In his pic the :bsnicker: FPR line is right there under the upper intake manafold.

 

[BP_93explorer]

that diagram? I don't understand it. I'll plug 'em up and see what happens. I wish I could find my old pictures of the engine so I can compare them.

 

[BP_93explorer]

i put tape around the holes just to see if that would help. it did. it started up and sounded just like normal. luckily there is another vehicle here until i can get a more permanent plug. i searched all around an couldn't find anything unplugged.

 

[shamaal]

The picture isn't clear, but what you want is the gizmo with the two dark lines and single dashed line going into it. That's the vacuum tree from your first pic. Not shown on the diagram because it isn't technically part of the emission control system is a vacuum line off the tree that goes to the vacuum reservoir. That's the plasic globe thing under the air filter. It provides the vacuum for the air recirculation damper when you switch to MAX A/C.

Then there's a hose that goes to the vacuum modulator if you have an automatic transmission, I can't tell from the diagram if it's shown. The rest are capped off.

 

[LXNavajo_94]

I found on mine the reason the hoses and plugs were blowing off is because the transmission vaccum modulator was bad and the lines were sucking trans fluid into the intake

 

[millerman753]

i just had the same problem with mine. going to fix it tonight. change the modulator and replug the vacuum leak. wish me luck.

 

[millerman753]

ok.. just went to change the part. could not find it for nothing.. found one on the top left front of the motor.. but hte line was gas... i found a hose off that and 2 others on the back of the one in the pic he shows.. caped hte one in front and ran great.. had to add 3 quarts of atf to shift and drive. now runs fine.. gonna check it betta in the am while the sun is out.

 

[BP_93explorer]

Ok, this just happened again. There was more of a pop noise this time though. Blueish white smoke started coming from under the hood. I thought something really bad happened. I plugged the lines again since the same two were missing and it fired right up and runs fine. I noticed a lot of oil this time though. The plugs and other lines slip off with ease. Does that mean I need to change that modulator or is this a sign of something else?

 

[shamaal]

For clarity, the FPR shown in #4 is the fuel pressure regulator, the vacuum line for it is black and underneath.

The vacuum modulator is on the automatic transmission. A bad vacuum modulator is famous for popping the hoses off the tree and spilling ATF on the engine. That would explain the blue smoke.

BP_93, this sounds like your problem. Try a search on replace vacuum modulator for information and respond back here if there are questions.

http://www.explorerforum.com/forums...129&page=2&highlight=replace+vacuum+modulator

 

[BP_93explorer]

Well that was a pain in the ass. Taking out the seats and console was the easy part. I couldn't get a light in there to see the part while I was working on it. Finally got a 10mm socket on there and it worked great. I wish they would round off the corners of all that metal though, I'm all cut up. I wore gloves after the first major cut but I couldn't feel what I was doing.

Pics of the destruction

This is the right part, isn't it?

 

[mikeinri]

I'm with you on that, I wasted the better part of a weekend on that job. Transmission is much better, but I really wish I'd just brought it to a shop...

Mike

 

[CDW6212R]

I wonder how long that takes from above. I did both my 91 and 93 from underneath. I removed the modulator on each to replace the pin behind them, with a 1/8" longer pin. My 1-2 shifts are firmer this way. Regards,

 

[BP_93explorer]

Well it was raining off and on but I got it all done in 6 hours. That time includes the rain delay and going to get the parts.

If I was able to tackle this job, would I be able to do the compressor? Its about to get real hot here.

 

[CDW6212R]

The AC compressor, that's basic stuff, the freon is the only issue there. If you haven't had freon for a long time, you may need a new dryer also. If you have the old freon, and it's full, you should have it recovered by a pro, that stuff is high dollar, well over $100 to fill. Good luck,

 

[BP_93explorer]

I haven't driven this much since replacing that modulator but I've noticed a problem. It started shifting hard when coming to a stop. I thought it might be something else but I let it coast to a stop and noticed the same hard shift. What oversight might I have made when doing this job? Or is this just one of the signs of a tranny going bad?