poor gas mileage = vaccum lines?

[edt77]

Since my terc sat for 6 months over last winter i have been getting shitty gas mileage (ie 20ish) i have replaced the fuel filter, looked at the carb, which was recently rebuilt, my buddie told me that the vacuum lines could be the problem? i have searched for vacuum line in the forum but have come up short with a good answer. I go have the Chilton repair guide
(should i use that to troubleshoot?) is it something that i can do myself or should i use my mechanic...
just asking
thanks guys

[Petros]

tracing a vac line leaking is pretty easy, search this board for topics about looking for a vac leak. |t should have other vac leak symptoms, fast or hunting idle, weak acceleration, flat spot off of idle, etc.

You might see if any of the brakes are dragging, jack up the car and see if the wheels turn (trans in neutral and brakes off). Check the air cleaner for rats nest, that is always a problem around here for cars that sit.

Good luck.

[xirdneh]

Low tire pressure?

[Darkelf]

Check your plugs... If it sat for that long the gas was more than likely pretty bad, that will foul plugs really quick. dump a can of Seafoam into the gas tank, it'll help clean out the lines and carb too.

[deejay1272]

Hey edt,

You should probably try spraying some carb cleaner on critical vacuum connections to check for leaks. If there's a vacuum leak, then you'll know it because the RPMs will temporarily increase when the carb cleaner is sucked into the lines. I'm also told that liquefied propane is a good approach as well, but I find that the carb cleaner works quite well as an alternative. Just peep the Factory Service Manual for more information about the vacuum characteristics that pertain to your model of Tercel. It'll take you some time to figure things out since it's a mess of vacuum lines (I'm struggling with this same challenge myself), but you're a smart dude so you'll be fine. Good luck!

[ARCHINSTL]

There is a color-coded vac diagram for Federal cars as a sticky in Repair Guides...
Tom M.

[garyfish]

If the problem is fuel-related from a vehicle sitting for extended periods, there's a new product out that may work (but I haven't tried it)... called Start Your Engines! Fuel System Revitalizer

http://www.baileysonline.com/itemdetail ... catID=9928

anybody here heard of it, or tried it?

[Typrus]

Check all your dashpots. A mityvac will help. A cracked diaphragm can be a source of much headache.
Ole' silver was doing 40+ mpg on my Colo Springs trek's. With a non-functioning vacuum advance and a "modified" vacuum routing.

New gas will gum up carbs quick if allowed to sit. BG44k your tank and Sea-Foam your intake. You might try BG 109 "CPR" treating your oil. In case your ring lands are sticky.

Check all lubricants (diff, tranny, etc) and check as mentioned for dragging brakes. Check your wheel bearings (3ACPower had a rear bearing fail resulting in an axle shaft coming out while corning)

Check your wires for shorts (a squirt bottle of water and a dark garage will help... squirt some water on and watch for arcs)

May not hurt to check your accessory bearings as well. Slack up the belts and spin the pulleys. Shouldn't be hard to rotate.

Have your battery tested. And alternator. A weak battery resulting in the alternator full-fielding more often will drag down the engine. Not to mention decreased voltage will make for weaker spark.

Make sure your PCV valve isn't stuck.

Tire pressures.

Hmmmm....

Sure theres more just can't think of it.

[edt77]

Thanks for all the good info I will be going through it this week during my leisurely free time. I was with my mechanic buddie and we were looking at the carb and noticed a big vac hose what was disconnected. After we were dont tinkering around we plugged the hose back in to its respected spots and low and behold the car idled much better! To my disgust after about 15 min of driving the car around town. I smelled a rubber burnning noise and the car got louder as if there were an exaust leak coming from the the headers!? I checked it out and there is no visible exsust leak. The smell seemed to be coming from one of the vaccum hoses that run by the radiaror. I have a california model with all the emissions bs still installed. I am worried now. This is not what I wanted to happen.

Any ideas!?

[takza]

I've got the Cali model...it has a feature that puts intake air into the exhaust under certain conditions,,,when you take that big tube off...you will hear the exhaust. There is a metal reed valve in it that can get bugs/crap in it and stop working...might check that. See the FSM for the details. I had to use a section of duct tape to make it it got only filtered air into the opening in the bottom front of the air cleaner.

You might have the hoses routed wong.

There is a graphic of the Cali vac hose routing on this forum somewhere.

[sdoan]

There is a color-coded vac diagram for Federal cars as a sticky in Repair Guides...
Tom M.

Check the vacuum diagram under the hood of your car and if it is different than your engine check the diagram in the factory service manual. I have a 1984 with California emission system and the vacuum diagram is wrong under the hood, but the vacuum diagram in the 1983 FSM is correct. The quickest way to see the difference is that my car has a single vacuum port on the "gas filter" (on the intake manifold in front of the carb) whereas the sticker under the hood shows 2 vacuum ports. There are other differences that make the under-hood vacuum diagram totally wrong on my car.

Good Luck

[edt77]

I've got the Cali model...it has a feature that puts intake air into the exhaust under certain conditions,,,when you take that big tube off...you will hear the exhaust. There is a metal reed valve in it that can get bugs/crap in it and stop working...might check that. See the FSM for the details. I had to use a section of duct tape to make it it got only filtered air into the opening in the bottom front of the air cleaner.

You might have the hoses routed wong.

There is a graphic of the Cali vac hose routing on this forum somewhere.

Yep hoses are set up wrong. It had a new engine put in in 2003 with 30k on in since. I cant imagine it has been set wrong this hole time. It was running alot quieter before I connected the hose but the idle was waining... I am going to buy all new hoses this week and set it up correctly. This thing is becoming more and more of a endeavor for me to get this Terc back into tip top shape.