Before anyone asks, I did to a search and found a few related threads, but mostly they turned into a "post your mileage" instead of fix the problem posts.

Okay, the car is an 85 GT V6 (4speed since that's all the V6's got in 85). I've just driven the car for the first full tank of gas and the guage is sitting just off 'E'. The trip odometer is reading about 115 miles. It seems to me that it should be getting better mileage, and I'm pretty sure it's running rich. I figure that to be in the ballpark of 12-13mpg, I'll know for sure when I fill up.

Mods:
Hot ignition including Accel coil and ignition module (the one in the distributer).
Recently replaced sparkplugs and wires and changed the oil.
No cat
160 thermostat, 176 fan switch.
No water separater in the airbox.
Broken fuel evap canister, replacement coming soon (main line plugged at the moment)

Symptoms:
Sooty exhaust on startup, and when revved.
Visible exhaust sometimes when revved. (Looks blackish, but thin so hard to tell.)
Unburnt gas smell sometimes when revved/accelerated hard and then stopped quickly.
Gas gauge goes down too fast.

Gauges:
Temp - never gets above halfway between 100 and 220 lines.
Oil - 50 to 60psi at idle, just under 80 above 3000rpm.
No warning lights including Check Engine.

I drive her harder than I need to, do my best to keep the tach out of the yellow, but I do enjoy running hard to 50mph or so at the lights. Maybe 1 out of 10 lights I go fast. I also try to let her warm up a bit before I go driving, but only have the time to do this maybe 40% of the time.

I'm almost certain it's running too rich, my question is what's the first things to check? What's the full list of possible culprits? Is my mileage do entirely to my cold thermo and fan switch and my somewhat heavy right foot?

Thanks in advance for the help.

------------------
85 GT (to be modified...)
--Um, no the paint isn't oxidized, that's the ultra-rare Whirlpool White textured finish... yeah.
89 Lincoln Town Car (has Fiero Envy)
--Hey! Can I have an anti-sway bar too?

Yup, 160 thermostat may be keeping the ECM in open loop...

Oxygen sensor may be toast or may be coked over by the rich condition.

Also be sure timing is at specs.

18-20 MPG should be attainable. Try a 180 thermostat and Rodney Dickman has a 192 fan switch. Also take a look at the O2 sensor to see if it's carboned up.

Hey, that sounds just like my car's problems, exactly! I have tried everything. Timeing is absoultly perfect, new coil, module, distributor, plugs, wires, gaskets from heads up, o2 sensor, thermostat, rebuilt injectors, Rodney's vacuum lines, probally more that I can't think of. (No, I didn't do this ALL just to solve gas milage problems, this is just everything that has been done to the car) My car kinda sputters on start up for about 10 seconds, has a slightly noticeable gas odor when reved, "sooty" exhaust, gas gauge fall faster then a brick.

Now, my car has a 195 deg. thermostat, and it still only runs about 165-175 degrees. The upper end was rebuilt, so that might yeild an increased cooling efficiency. When I go out and cruise on the weekends and race pretty hard off lights, it will get up to the 220 mark and the fan will kick on, but it cools down real quick once the fan comes on. I do have a cat, water separater, and working fuel evap canister. When I fire the car in the morning it puts out some white smoke, but its real quick and doesn't last for more then 5 seconds.

My car is the same way! I was getting a MAP sensor error, but I took it off to replace it, and the parts store gave me the wrong one, so when I put the old on back on with the ECM reset the MAP sensor code went away, but now I am getting OX sensor rich code (with a new OX sensor).

I metered the MAP sensor as outline onthe online service guide, and the voltage is high at idle, so I think the sensor is still bad. Also I tried checking the MAT sensor, but it doenst seem to match the decsription onthe online service guide - mine has 4 termals, the top two and the bottom two read 49 ohms to each other, so I dont know that that means.

I am going after a new MAP sensor, will let you know what happens. Last check I was getting 15mpg, and a sooty exhaust.

Okay, well my gas gauge is off. When the needle is just barely off the 'E', it takes a tiny bit more than 7 gallons to fill it. Did the math and I'm getting 16.5 mpg, which isn't too bad, but still not quite enough.

BTW, I thought the sensor with only one wire that is next to the thermostat was the fan switch sensor. It's the one I replaced with the 176 degree fan switch... Unless I'm mistaken the ECM engine temperature sensor is on the other side of the motor (back or 'non belt' side).

It would be pretty hard to get the sensor/switches wrong as they have different connectors. And I suppose the new ones looked just like the old ones you removed. I would agree with deceler8: the low temp stat and fan switch are probably the culprit. My 87 GT is un-tampered with (195 stat, 235 fan), runs out great at 166k miles, and gets around 20 mpg in traffic and 27 on the road to Toney, AL. The gas odor would be a combo of the EFE system (charcoal cannister) being disconnected and the rich exhaust.

on the V6 the 1 wire sensor next to the thermostat is the fan switch?! Are you sure about that?

Then is the one next to it is the gauge sender (2 wires)?

then where is the ECM temp sensor and what does it look like - how many wires? the online sevice guide says its next to the thermostat and the Chilton manual says nothing?

I guess if i gound it and the fan comes on then its the fan switch.

I got a new MAP sensor at NAPA over lunch. The color of the connector is black, and the wire on the car is green (and the old one was a green connector) but this one is keyed correctly, so I put it in. My idle dropped from about 850 to 650-700, and it doenst stumble from a red lite nearly as often now (still does once in a while). But most of the time I do get smooth acceleration for 0 right up to 75 now.

I know my plugs are carboned up so I have to pull them and clean them and see what this new MAP sensor does for me.

OK who knows where the ECM temp sensor is on an 85 V6???

Ken - check out this post: https://www.fiero.nl/forum/Forum2/HTML/010013.html

Im making some progress!

thanks for the tip on the ECM temp sensor being horizontal - i will check mine tonight.

I looked through the ogres cave and found some tips. Teh engine grounds are important for the ECM to work properly, esp the OX sensor. I started cleaning up the ground connections on my engine and battery. The small wire that drops right off the battery to the wheel well was corroded at the end. Dremil tool with a small grindstone is perfect for this.

I thought I had found the engine ground, but turns out it is the engine lid ground, guess I will have to jack the car up and crawl under tonight to find the real strap.

also I pulled the vacuum lines off both ends of the metal tubes that run along the back of the engine space to the evap canister, put my finger over one end and sucked on the other - bingo! leaking vacuum line- stuck golf tees in the flexible tubes for now until i can replace the metal sections.

I am up to 130 miles on a half tank of gas (according to the gauge - I dont trust it though). I know my plugs are fouled, will clean them with I pull the engine cover to do a compression test.

anyone know a better way to clean fouled plugs? I use a fine wire wheel on the dremil tool. Ive heard this is not the best idea because small bits of the wire wheel can get stuck in the plug, and then fall into the engine. Is there a solvant that takes carbon off plugs?

One thing I forgot to mention: my cold idle is about 1500, and my warm idle is just over 1000rpm. Is 650 really the number to shoot for? That seems kinda slow to me, but I have no real idea what it should be.

spektyr have you check the AB jumper thing to see if you are running open loop? that is one of the signs, a really fast idle.

I have had my test connector cover off so many times I keep the torqx 15 bit and 1/4" socket to hold it with in the 'coverted' ashtray (chisled the butt snuffers out and painted them black - good for holding change now and the bent paperclip).

last time it took the cover off I was seriously thinking a wiring a test switch to it.

Im still running rich - still looking for the magic bullet - still getting a code 45 and flashing check engine light every 7 miles or so.

There is no way I was gonna pull the connector off that ECM temp switch last night, I think you have to remove the EGR valve to even see it down there.

I plan on pulling the conector off the ECM itself and metering the sensors to see if any of them are open or shorted at that end of the wireing harness. It doesnt do any good to replace a sensor if the signal doesnt makeit to the ECM module, so I think I will go after it that way. Then if I find a bad one I can chase it down to the sensor and see if its that or the wires.

I psudo-tanked up this morning, stopped the pump after it kicked off, and I estimate I am up to 20mpg city driving. I pulled my plugs and only one is really carboned up, so I think I may only have one leaky injector that is causing the OX rich sensor code.

I put a rear brake caliper on last night (stupid #40 torx screw onthe parking brake bracket cost me a trip to Sears & Sawbucks). My brakes are still really soft. There must be a trapped bubble inthe system somewhere, so Im gonna see howmuch a vacuum bleeder cost.

Does anyone know? should an 85 with vacuum assist brakes have a hard pedal when running? It seems like the pedal is hard with the engine off when I bled the lines last night, but when I started it up this morning I can push the pedal all the way to the floor. No leaks anywhere. I think either there is a bubble stuck in the system somewhere, or Im gonna need a new master cylinder.

Are stock Fiero brakes really that bad? Shouldnt I be able to lock up at least two of the wheels in a panic stop? Should the pedal be going all the way to the floor?

Ken, it sounds like you've got some brake problems. My Fiero doesn't stop well enough to please me, but with some moderate/heavy effort I can get the tires screaming on a stop. The pedal is too heavy for my taste, but I can stop the car pretty quickly. My Lincoln Town Car stops much, MUCH faster, which is why I think my sports car Fiero should have better brakes.

Another question on the mileage... A lot of chip manufacturers have an upgrade chip that 'requires' the use of the 160 thermo and 176 fan switch. They are supposed to 'retune' the motor to run at the cooler temps. Would they lean out my motor a bit, or are they just a waste of cash?

Also, I've heard that the ADS chips are the best, but what's the difference between the street and strip chips? Is it just that the strip chips aren't designed to be used with Cats?

Ken, if the brakes always build and hold a hard pedal with the engine off, but not with it on, you probably need a booster.

------------------
85 2M4(Lil' Bit)

Bump... still hoping for an answer on the chips.

I'm really interested in this brake problem. My car doesn't really have good brakes, nothing like any of my other cars. But, I noticed that with the engine off, the brake pedal can be pressed down 2-3 times before it becomes so hard it can't be pushed down any more times. When I start the engine it relieves the pressure and I have normal braking. With the engine running, the brake pedal doesn't "hold" the pressure like when it is not running. Whats the deal? All my cars, including a 90 Lincoln TownCar with awesome brakes that will throw you thru the window if you slam them, and locks up all 4 wheels with hardly any effort. Thanks

I dont understand how a faulty booster can make a pedal that is hard with the engine off go to the floor with the engine running.

I thought the booster adds to the pressure you are applying to the brake pedal.

My brake pedal is about 6" off the floor with the engine off, with it running I can push it right to the floor.

I bled a whole quart of brake fluid through the system, stating by emptying the resevoir, wiping it clean, and then bleeding the rr wheel first with a vacuum bleeder pump and working LR, FR, FL.

I didnt open the lines by the master cylinder, I figured the vacuum bleeder pump would pull any air out that was in there anywhere, and I bled all the lines till I got clean fluid at each wheel and no bubbles.

The pedal is hard with the engine off, and feels spongy with the engine running, and I cant lockup the tires, not even if I pump the brakes, while driving.

I am thinking the master cylinder needs rebuilding. I would think the only problem with the booster would be if it leaks vacuum, But if someone can explain how a bad booster can make the pedal go the floor (if there is a logical explaination) I would rather learn from your experience that to have to figure it out from trail and error.

How do you guys drive???? I've gotten just over 9 MPG somedays and around 18 MPG other times. What is the difference? How I drive. when I go through a tank without a lot of hard driving I get 18 If I'm racing a lot I get around 9. BTW I have an 85 GT with 160000 on the engine and 130000 on the body.

Just my 2¢ on a different track to solve the problems...

Start over and put everything together with stock components first and get everything completely kosher. I know I sound like an ol fart but bear with me Sometimes the shortcuts and guessing cost you more time & frustration than they're worth.

Once you're running in OEM condition with good performance and no warning lights THEN start doing the performance mods ONE AT A TIME. That way you have the benefit of all systems known to be working and be able to blame your new problems on the last modification. Right now you're "fishing" and there is a little doubt thrown in with respect to the low temp stat & switch and performance chip.

Also: there is a big fat ground that attaches to the lowest, front tranny-to-engine bolt. I forgot to hook mine up after installing the trans and it caused rich running and poor idle quality. It's pretty easy to get to from underneath.

quote Originally posted by RacinRob: How do you guys drive???? I've gotten just over 9 MPG somedays and around 18 MPG other times. What is the difference? How I drive. when I go through a tank without a lot of hard driving I get 18 If I'm racing a lot I get around 9. BTW I have an 85 GT with 160000 on the engine and 130000 on the body.

Well Preimum gas and a bumped up timing help, I change my oil every 3000 miles, keep all my airfilters fresh and clean, A really good set of plugs helps I use splitfire myself. I Keep the tires at 35 (high side) check it every week and get it aligned every so often to keep her from dragging the wheels. Also When I do my brakes I grease the pins with synthetic grease to keep the calipers from sticking and causing the pads to rub against the disk, Hardly anyone does this anymore because every Fiero I'v owned (4) the pins were all frozen. I also repack the wheel bearings when I do the brakes.

I think thats about it, not much more than routine stuff

I probably could get more out of it but doing 75mph every day at 4500 rpm kinda kills the MPG a bit.

Damn foot!

I'm not going back to OEM.

Ignition system: I'd have to buy another one, the original one is shot.
Cooling system: The only thing I've replaced that can affect the ECM is the thermo. I can't replace the thermo with the original without replacing the fan switch, and I don't have a plug that would fit it (since the new one has a different plug).
Air Intake: I can't replace the water separator, and I'm not putting anything but K&N filters in it for the rest of it's life.
Catalytic Converter: If the old one is still in the trash can I guess I could put it on, but it's full of holes so I think I'll skip that.

I will be checking the various engine sensors. My question was, and remains, 'Do any of the aftermarket performance chips designed to work with lower temperature thermostats and fanswitches actually lean out the mixture to compensate for the lower operating temperature?'

I am not going to spend a great deal of time or money making the 2.8 run absolutely perfect. I'd like it to run well, but since I'm going to replace it (hopefully this winter) it would be silly for me to spend a lot of money making it perfect, just so it can sit in a corner of my garage.

ok PLEASE dont hate me but........

Ive got an 87 gt with a 2.8 bored and stroked out to a 3.4
its got
mustang injectors (19#)
big bore throttle body
accel moduel and coil
a hypertech chip (thermomaster)
160 thermostat
ive got rodney's metal vacuume lines
I use stock AC delco spark plugs
and accel 8.8 wires

I tend to drive my car hard and my milage is.............
please dont hate me 23.3 MPG

I just figured this out the other day on a road trip. This was on a 2 lane road where my speed varied from 40 to 90. Im guessing my average speed was around 60. Now this is a new motor and I barely have 1000 miles on it. However I think the power and mileage and excellent.

I havent had much time to work on mine this weekend, but I did look all over the engine and tranny and didnt see a ground strap anywhere, so I put one on.

the best place I could find is on the top of the transmission, just to the left of the EGR muffin (there was a big bolt hole there with nothing in it) and over to the frame - there is a little L braket on the frame there that isnt being used for anything.

So I get the ground strap put in and start it up, and within a few seconds I get a MAP sensor error (with my new map sensor?!) i cleared the error and restarted it, and babied it for a while.

I still get O2 rich errors now, but the exhaust smells really different. Before it had a rich sooty smell, now it has a heavy sulfer / rotten egg smell - which I think might be a good thing, i think it might be buring off all the carbon in the cat and running closer to where it should be.

will give it a week like this and see how the mileage turns out. It was up to 20mpg before I added the ground strap. I still suspect I have a stuck-on injector, which is driving the ECM nuts.

Guys please

Can you clear up the ground strap essue.

Is this valid for all V6? Auto or Manual?

Where exactly the strap should be by default?

How its absence can affect gas mileage?

Can I go ahead and just add one?

THanks and waiting for answers.....

As an electronics tech I can answer one question. You can add as many grounds as you like. Virtually any metal part of the car is 'ground', the only parts that aren't would be those that aren't used by a component as the ground. Electrically speaking the only issue with the wiring for ground is it must be able to handle the load. Bigger wire handles more load, and adding extra wires is like using a bigger wire. The actual current delivered to a component is dictated by the 'hot' wire, not the ground, so extra grounds won't hurt.

If you're so inclined, you could add a hundred grounds, it wouldn't hurt anything (except the appearance of your engine compartment.) Now that you mention it, I might just do that and see if it has any effect on my car. I haven't gotten around to crawling under it to see what my motor ground looks like.

As for affecting mileage... well all (or most) of the sensors use the engine block as ground, so if there isn't a solid ground wire to flow electricity back to the battery, the sensors wouldn't function properly, hence the ECM wouldn't be controlling the motor properly. Bingo, bad performance.

Given the bad ground connection I seem to have in the front of my car, it's probably a good idea for me to check all the grounds I can find.

While I'm posting, I'll refresh the question that's burning in my mind. Does anyone know if there is an aftermarket chip designed to run with the lower temp thermo and fan switch that actually affects the fuel/air mixture? I've seen some posts that suggest that most of them do almost nothing, and if I can plug in a chip that will lean my car out, I'd like to know which one(s) will do it.

Thanks

[This message has been edited by Spektyr (edited 05-13-2001).]