Hey all,
I recently did a tune up on my 86 V6 fiero SE, which included an O2 sensor replacement, and I'm still getting terrible gas mileage.
The only code my car is throwing is a Vehicle Speed Sensor code.... which I wouldn't think would have anything to do with poor mileage? I was just wondering what common causes were and what some of you are getting gas mileage wise?
Thanks a lot.

A VSS code would effect your mileage. Fix the VSS, and your mileage will go up.
You may not have needed to swap the O2 sensor at all.

-Dave

A heavy right foot.

Bad or missing thermostat
Bad CTS
Leaking injector

VSS is used by ECM.
Any DTC stored in ECM can cut MPG.

If speedo works then VSS works means speedo board is bad, wire problem or ECM problem.

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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)

The Ogre's Fiero Cave (It's also at the top and bottom of every forum page...)

Dirty IAC might hurt mileage. I recently cleaned mine and my mileage seemed to go up a bit.

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Jonathan

'68-69 GTO Nose - The Project has Begun!
My '85 L67 Build Thread

Anybody know where the VSS is located? Maybe even the thermostat? I can't seem to find the housing.

quote Originally posted by shaneg: Anybody know where the VSS is located? Maybe even the thermostat? I can't seem to find the housing.

I tried to take a pic of the VSS. It is difficult to shoot because of all the wires, tubes, heat shields, etc in that area. Can't get a clear view and the camera doesn't know what to focus on. Anyway to find the VSS just look between the engine and the trunk right below the spark plug on the passenger side. Plug #1 or #2. Can't remember which way they are numbered. Just go straight down from there and you'll see the unit sitting there on the trans. It has a wiring connector on it and it is held in place by one 10mm bolt. It pulls straight out when the bolt and the "holder" is removed.

The thermostat is under the yellow cap.

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Jonathan

'68-69 GTO Nose - The Project has Begun!
My '85 L67 Build Thread

quote Originally posted by Boostdreamer: I tried to take a pic of the VSS. It is difficult to shoot because of all the wires, tubes, heat shields, etc in that area. Can't get a clear view and the camera doesn't know what to focus on. Anyway to find the VSS just look between the engine and the trunk right below the spark plug on the passenger side. Plug #1 or #2. Can't remember which way they are numbered. Just go straight down from there and you'll see the unit sitting there on the trans. It has a wiring connector on it and it is held in place by one 10mm bolt. It pulls straight out when the bolt and the "holder" is removed. The thermostat is under the yellow cap.

Drivers side under plug # 5, do not remove the 10mm bolt all the way, loosen it, and spin the little retaining tab out of the way, I learned this the hard way when my little tab fell into the tranny.

[This message has been edited by zkhennings (edited 06-17-2013).]

It seems like my VSS is loose. The bolt is tight, but it seems to turn and wiggle a substantial amount. Also, there are red and yellow wires coming off of it. These look like they have been cut, and then spliced back together at one point. My car is throwing the code, but the speedo works, it seems to be off, but it works a decent amount. Cruise control doesn't seem to work.

quote Originally posted by zkhennings: Drivers side under plug # 5, do not remove the 10mm bolt all the way, loosen it, and spin the little retaining tab out of the way, I learned this the hard way when my little tab fell into the tranny.

You're thinking 5-speed. He has an automatic. I was thinking 5-speed when I said it was held on by a 10mm bolt. The VSS in the automatic is held on by a clip.


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Jonathan

'68-69 GTO Nose - The Project has Begun!
My '85 L67 Build Thread

[This message has been edited by Boostdreamer (edited 06-17-2013).]