Vacuum leak in brake area?

[leakyfaucet]

My idle surges from time to time from 750-1100, but very infrequently. It seems completely random as far as I can tell. I pumped the brakes when it happened last and the idle settled at 1100 (even though my idle is normally set at 750) and as soon as I stopped pumping it surged again. I've heard if pumping the brakes stops the surge, it means there's a vacuum leak.
My questions are as follows:

1. Even though it happens at random, does this still mean a vacuum leak?
2. Does this mean that there is a leak in the brake system, or could it be anywhere?
3. I know about checking the hose that runs from the vacuum tree to the master cylinder, but what other hoses could be affected based on what I've told you?

Thanks again!

 

[jerry beach]

I am guessing that you have a stock engine. Do you have a vacuum guage? You can get one for about $15. Hook it up to a spare port on the tree by the brake booster and see if you are getting 18-21 in. hg. The needle should be steady, or almost all the way steady. Check this when its not surging, then when it does. Do a visual inspection of all vacuum hoses first. Pull the codes and see if that tells you anything. Those are good places to start. If all seems well, then try cleaning the TB and MAF, then try clocking the MAF. That helps sometimes, and its quick and free to try it. Just think simple things first. Now is a good time to purchase the Charles Probst book on Ford EEC IV systems. Its available through Jegs or Summit. That book has helped me out alot.

 

[leakyfaucet]

Yes, stock engine.

Who sells vacuum gauges? Wal Mart, autozone? I've cleaned the MAF but what is clocking?

If I have a vacuum leak, the reading at the tree would be lower, right?
Thanks for your response. It's always good hearing new ideas. I forgot to mention: I've already cleaned out the EGR, IAC, put in and set a new TPS, checked TB.

Another quick question: I thought the big black thing that sits under the brake fluid resevoir was the master cylinder. Is it the same thing as the brake booster?

 

[jerry beach]

Clocking the MAF is simply rotating it relative to the air tube. It may not help you, but its something free to try. If its a 12 oclock, try 9:00, or 3:00. You can pick up a vacuum guage at the auto parts store, prolly not walmart, and they come with good instructions for use.

The big round thing behind you MC is the brake booster. The MC is bolted directly to it. Let the car sit for a 1/2 hour or so after you shut it off. Then push the brakes and see if you still hear the hissing, and feel the power assist. If not there is a leak, mine still has power assist the after sitting overnight.

 

[leakyfaucet]

Okay, I got the readings from the vacuum tree at idle. Is this the proper place to test? I got around 18 in. HG. It would go to a minumum of 17.5 and a maximum of 18.5.

I then took off the brake hose from the tree and tested there, and got the same results. If the brake booster hose was leaking, wouldn't testing on the spare port with the brake booster hose connected read a weaker vacuum than testing on the brake booster port?

I did the same thing for the A/C port, and the cruise control port. Testing with any of them plugged in or not yeilded the same vacuum reading. That means that nothing is leaking, right?

This is the first time I've ever used a vacuum gauge and was wondering if I'm even doing it right at all. Thanks for the help!

 

[jerry beach]

You are correct in assuming that if you disconnect something and hooking the guage in its place, there is no leak there. The guage came with instructions, right? Did you read them. 18in. hg. is in spec. Is the needle sweeping no more than 1 in. hg.? If so you have no vacuum leaks. The problem lies elsewhere. Wasnt that easier than spraying carb cleaner all over? Now you need to pull the codes. Do you have a Haynes manual? It gives good directions in there.

 

[leakyfaucet]

Yeah, that was easy. Honestly I never would have went out and bought a vacuum gauge if you hadn't recommended it. Thanks again.

No, the gauge doesn't seem to sweep more than 1 in. hg. I do have the haynes manual but being so inexperienced at electrical work, it doesn't seem to make sense to me. I've had someone do it before (sister's ex-boyfriend), he used the real diagnostic computer and it gave me not only the code numbers, but what they were. Very simple. However, I can't get a hold of the guy.

I almost never do any electrical work except for some minor soldering, and have only used a voltometer once, to set my TPS. Do I need a voltometer to do this? Without the diagnostic computer, I have to read pulses don't I? Sorry, it just doesn't make sense to me.

Perhaps you can hold my hand through this one too?

 

[jerry beach]

All you need is a test light, [unless you have a check engine light in your car] and a jumper wire[just a piece of wire]. Here is how you hook it up, the diagram is in your book, along with step by step instructions for hooking it up and reading the flashes.

Oh, you hook the test light up in place of the volt meter. Or just use the jumper only and read the CE light in the car.

 

[leakyfaucet]

So I just hook it up exactly light that in the picture? It would work with a digital voltmeter, right?

I don't understand what you mean by needing a test light unless I have a check engine light. Also, I don't understand why it says I don't need a voltmeter if my car has a check engine light. What am I missing?

-edit: Hold on, I think I'm getting it. The check engine light in the dash will blink a certain number of times to tell me the code number? If so, what do I need the voltmeter for? Just to give power to the test connector?

 

[leakyfaucet]

Okay, let me start all over. I have a working check engine light in my dash. (I know this because it comes on almost every time I drive it ) So all I need to do is attach that jumper wire and I can get the codes by counting the number of times the check engine light flashes?

 

[jerry beach]

Just install the jumper as pictured, then get out a pen a paper. Turn on your key and watch the CE light, that is if it works. Otherwise, hook up the test light in place of the volt meter, and read the flashes of the test light after you turn on the key. You cant really use a digital one, unless it has analog capability.

Then after you get all the two digit codes[they will repeat twice for each code so you dont get mixed up] Start the engine and record the ER codes[engine running].

Just follow the instructions in the book, and make the substitutions I told you about. You will get the hang of it after a few tries, it was a pain for me at first too.

 

[leakyfaucet]

Great, that's another thing I wouldn't have tried without your advice. I'll try it tomorrow. Thanks yet again!

 

[jrichker]

Here's some additional info to go along with the good stuff Jerry has already given you...

Here's the link to dump the computer codes with only a jumper wire or paper clip and the check engine light, or test light or voltmeter. I’ve used it for years, and it works great.

See http://www.troublecodes.net/Ford/
OR
See http://www.dalidesign.com/hbook/eectest.html for more descriptive help
OR
See http://www.mustangworks.com/articles/electronics/eec-iv_codes.html

Trouble codes are either 2 digit or 3 digit, there are no cars that use both 2 digit codes and 3 digit codes. Codes have different answers if the engine is running from the answers that it has when the engine isn't running. It helps a lot to know if you had the engine running when you ran the test.

 

[leakyfaucet]

Okay, I checked the engine codes with KOEO and with engine running. I got 41, 81, and 91. According to Haynes, the 41 and 81 are both oxygen sensor problems. I can verify this with the inside of my tailpipes being black and when I scanned the code with the real computer I got some codes about oxygen sensors not switching on. The 91 code is supposed to be the thermactor air circuit. I took out my smog pump and plugged the vacuum lines, but I didn't know it would cause a check engine light. Has anybody else that's removed their smog pump got this code? I'm not sure if it triggers the check engine light, or just puts out a code. I hope it's just a properly functioning circuit that can tell that there's nothing flowing down there, and doesn't really affect the way the engine runs.

Since I have just recently put in oxygen sensors (about 3 months ago), I plan on replacing the 02 sensor harness, even though it appears to be in decent shape. There are a few places where it looks like it got burned, but I see no broken or exposed metal in the wires.

Do you think that the oxygen sensors not turning on could trigger an idle surge? That's about the only thing left to fix I'd say!

 

[leakyfaucet]

Just to bump, and reiterate:

Does removing the smog pump and plugging the vacuum lines create any trouble codes? I did a search and found another post about a guy who had a bad TAB and TAD solenoid, and he also had the codes 41 and 91, and replacing the TAB and TAD solenoid supposedly fixed it.

 

[jerry beach]

Is your car a 5-speed or auto? There are 3 types of codes ( fine time to mention that huh?) Its not a big deal, but read your book carefully and it will explain the different types of codes. They are KOEO, KOER. And Continuous Memory. Designated by O, R, and C in the Probst book. Code 41 R, and C are O2 probs, right side. Code 81 KOEO is secondary air injection diverter, emissions crap. Code 91 KOER is O2 indicates system lean, left side. Code 91 in contiuous memory is No O2 switching detected, left side. So you need to know which test the code is coming up in to properly read it. I know its a pain, thats why you get some good books and follow the instructions.