MPG drop

ropadope · Post by **ropadope** » Tue Sep 05, 2006 8:45 pm

Hey-

just found this site and...kick butt! i'll sift through the forums to avoid asking redundant questions as much as possible. so:

last summer i got an 87 with, dig it, 98K miles on it (now at 114K). one owner, the stereotypical 'little old lady'. it's a 6 spd in very nice shape, but no sunroof dang it.

i took it to Colorado (i'm in Kansas) shortly thereafter and was impressed with its mpg in mixed highway/city/mountain driving -- 38 mpg at its highest, but averaging around 34 mpg.

since then, it has dropped off quite a bit. at first, i attributed the loss to cold winter weather. but it never came back this summer. now i average 24-26 mpg, no matter what kind of driving i do. doesn't change if i baby it on every shift or wrap it up to 4500 rpm on every shift for a full tank.

not much has been done to the car. i replaced the plugs, wires, fuel and air filters last year. oil and filter are changed roughly every 3K (synthetic oil, too...like it matters).

ideas?

thanks a ton. cool, cool site!

Typrus · Post by **Typrus** » Tue Sep 05, 2006 10:06 pm

How sudden was this drop? Anything different you do to it before the drop?
I'd personally try the Seafoam Treatment I wrote about in the repair guides. Might help you out.
25-ish is kind of the rule more than the exception around here. 30+ is coveted territory.

Carguylen · Post by **Carguylen** » Tue Sep 05, 2006 11:14 pm

My car must be running REAL good, then, I'm getting 23-25 out of an automatic!!

jdumars · Post by **jdumars** » Tue Sep 05, 2006 11:41 pm

tire pressure may be the culprit...

mine both get 30-32 mpg

Mickey_D · Post by **Mickey_D** » Wed Sep 06, 2006 1:00 am

A lot of these cars seem to have trouble with carby vacuum leaks all of a sudden. I hate the Hitachi carbs, mine is giving me so much trouble it's about to take a swim as soon as I can find a suitable Pinto to steal a Weber off of.

And yes. I only get 20-22mpg with most of it (75% + ) at 65mph.

Typrus · Post by **Typrus** » Wed Sep 06, 2006 1:02 am

I've dropped to around 23-24... But I've been really heavy on it recently.

Aisan makes our carbs?

Mickey_D · Post by **Mickey_D** » Wed Sep 06, 2006 1:38 am

I thought (just by looking at it, haven't pulled it for a difinitive look) that we had the Hitachi HH240D series carb on there, the same as Isuzu put on thier 1.8 and 2.0L I-4's that were in the Chevy LUV and Isuzu Impulse.

I could be entirely wrong, though.

But if they are even CLOSELY related to the Hitachi's, it's a wonder ANY of our cars make it past 50,000 miles with them. The Hitachi's are HORRIBLE carbs.

2wagons · Post by **2wagons** » Wed Sep 06, 2006 10:03 am

When I lived in Colorado, I got 35-40 mpg consistently in an '83 Deluxe. I now have an '87 in Virginia and get around 25-27 and jsut like you, it doesnt change much no matter how I drive it. My car has a rebuilt Aisan carb.

ropadope · Post by **ropadope** » Wed Sep 06, 2006 10:32 am

Is mountain fuel different? Also, I didn't go up very high into the mountains, but i was surprised that the car ran great without adjusting the carb. Which i thought might be an issue (i don't know jack about carbs), i've only ever had fuel injection before this Tercel.

I might try the Seafoam treatment. I've got a quart of Rislone that I was considering using, but because i'm on my way to pick up some kerosene, i'll look for Seafoam and keep the Rislone for the next oil change.

I did have the thermostat changed (no good reason), and the car's temp guage indicates that it's running slightly cooler than normal. That was well after the mileage drop, but i wonder if that might be a contributing factor. And although it says it running slightly cool, the oil dipstick is still too hot to touch after the car has been running for even short periods. Really, really hot! Does that matter?

takza · Post by **takza** » Thu Sep 07, 2006 6:03 am

This might tell you something:

http://www.aircarecolorado.com/repair/toyota.htm

"Since no customers responded to the mailing, DTEC contacted several of the Toyota Master Technicians in the area. Each technician identified the most likely causes of failure as the oxygen sensor, vacuum hose routing or degradation, vacuum switch operation, EBCV contamination, and carburetor overhaul. All of the technicians interviewed had attended EDGE training but commented that Toyota did not offer specific diagnostic information for the feedback-carbureted systems. Average repair costs were $275.00. Equipment used included a gas analyzer, labscope, and DVOM. Understanding of the specific operating strategies was viewed by the technicians as the most important skill required to properly repair these vehicles to pass the I/M 240 test."

"I have a 87 Tercel that was getting pretty crappy gas mileage and ran very rough, it would almost and sometimes would stall out at stop lights. I took it the Toyota dealer and they repaced two valves on the outside of the motor, the VSV and BSC valves. I never knew they existed before that. After that + a tune up and the car ran smooth as the day it was made, and I got back all the gas mileage (around 40 MPG). If you think you need them I still have the bill with the part numbers."

"If you want to really improve milage, make your automatic choke and fast idle so that they don't work. If you have a good battery and starter, you can still get it to start (it takes a while) and you will have to learn to use the clutch alot to compensate for the extreme jerking that goes on while the carb is cold. When I fixed my nonfunctional choke, the mileage went way down. 3AC Power""

http://www.maryngroup.com/Archives/Arti ... omemag.htm

Mickey_D · Post by **Mickey_D** » Thu Sep 07, 2006 12:54 pm

Heh, disabling the choke on my carr would make it completely undriveable for 4 - 6 months out of the year!!

You know how hard it is to start a car that's been sitting at -40 degrees for 12 hours?!?!?!?

Ogedei · Post by **Ogedei** » Thu Sep 07, 2006 2:16 pm

not 40 below but I know how hard it is to start after 12 hours in below freezing, I would not want to try in 40 below without an engine warmer.

What are these valves? the VSV and BSC valves
is the VSV the TVSV?

I would sure like to get my car back up to the 30's esp since I drive more highway and think the drop to 24 is a bit much

GTSSportCoupe · Post by **GTSSportCoupe** » Thu Sep 07, 2006 4:35 pm

I put a brand new weber on mine to try to get some decent fuel economy. It still sits around 25/28mpg (city/highway) no matter how I drive. Meanwhile my 87 MR2 with twice the horsepower gets 28/35mpg (city/highway), and has topped out around 38mpg before.

takza · Post by **takza** » Fri Sep 08, 2006 5:35 am

I have a manual choke I intend to install. Auto one works...but hey...I'm lookin' to find some trouble.

Chris · Post by **Chris** » Thu Sep 21, 2006 8:22 pm

Have you checked the mechanical and vacuum advance components of the ignition system?