finding vacumn lines.

[digitaldrifter91]

i have a 99 mercury villager and it doesnt idle correctly. it flutuates between 800 rpm and 700 rpm. im guessing its a vacumn line. i looked inside and i see no vacumn lines loose but i do see this one vacumn tube comming from the bottom somewhere with an opend end (metal fitting). i dont see anything that can possibly connect to it.

is there a way i can narrow down my search and find out which vacumn line is causing my idle to be irradict? is there a way i can tell if its really my vacumn lines? i heard of vacumn pressure testing but im not sure.

thanks guys for any input.

 

[Rick]

What you might want to check is your IAT censor.
It's a little black peace that has about 4 wires going to it. It controls the air entering your throttle body when your not on the gas. If that is cloged with carbon you will have an uneven idle. So what you will want to do is remove that, it's held in by 2 hex screws. Clean it up with Carb cleaner. Then you will also want to get a rag and open your throttle plate, try and clean up your throttle plate to with the carb cleaner.

 

[digitaldrifter91]

ok cool thanks. im going to buy the book for the car today so i can find it. would it be my mass air flow sensor as well?

 

[Rick]

It can but even if it was a bit dirty it wouldn't make a big different, the mass air flow would effect your fuel consumption. Eg if dirty you would use more gas just like if your air filter was clogged.
If you are going to clean the MAF be very very carefull. They are like thin strands of hair.

 

[digitaldrifter91]

thanks. i havent checked it out. all this idle started after i saw the check engine light on and the filter was super clogged. after i changed it, the car was never the same. gas consumption on the 20 17 gallon tank is at 246-290 miles to the tank. kinda low i think

 

[billman]

If you have access to a hand vacuum gauge, you can at least take some readings to try to isolate a few things. Being careful, most people will use small blasts of carb cleaner near your suspected leaks, if it is a leak, the idle will change. A safer way is to spray some soapy water.

Good luck.

 

[BOBISTHEOILGUY]

Another little trick I'll use to isolate vacumm lines is to squeeze the line shut. Usually with a pair of needle nose or regular pliers will do the trick. This too can cause the idle to shift if you run on the same circuit of the leak.

One other thing is if you suspect or hear a slight hiss, take a rag, lay across the engine and it will "cover" the sound, giving you an idea of the suspected area of the leak as well.

 

[digitaldrifter91]

i do hear a hiss from this device called the UPR...it sounds like HiSssssssssssssssssssssssssssssssssssssss. like air comming out of a air compressors line. nto loud seems normal.

thanks dudes.