READ MY LOWER POST.... UPDATED PROBLEM LIST... NOW TO 12MPG OMG HELP ME$!$!$!$!$!

I have had my car for about 7 months now, and im puzzled about why my car only gets 20mpg.
I dont have any extra weight in the car, my tires are all at 30psi constantly, i don't do jackrabbit starts i just dont get it. I see people getting 45mpg highway, and i drive a mix of city and highway every day, and i get 20mpg. Something just doesn't seem right...

A few things that have me curious is the fact that when i start the car i get a decent sized puff of smoke from my exhaust, enough to be embarrassed by.
Any ideas on this problem? (The smoke smells like gasoline)
And im pretty sure my throttle position sensor is bad, but i dont know how to check it.
(see this topic for my description of the TPS problem https://www.fiero.nl/forum/Forum2/HTML/085322.html)
could you maybe tell me where it is and how to check it?

I dont know, i have several problems, all frustrating, W/e help u can give me is appreciated.

[This message has been edited by JZeFF (edited 09-09-2007).]

Crank the timing up a few degrees... you can get more if you use prem gas.
Replaace the O2 sensor.
Get a really good air filter.

Oh... Get a 5 speed manual.. 86 seems to have the best ratio for mpg.

And if you are going to do that get a performace cam.

The smoke could be one or two things, leaking head gasket or cracked head. and or valve guide seals.

[This message has been edited by 84Bill (edited 08-27-2007).]

And make sure you don't have 44psi tires. (not that I have done that...)

A new O2 sensor should help as 84Bill said.

If you have a computer (preferably an old laptop with serial cable) then get WINaldl (free software) and an aldl cable. Allows you to read the sensors the ECM uses and see what they are doing.

You can check the TPS with an analogue ohmmeter by placing the leads on the (very tiny) pins on the tps. Then open the throttle slowly and watch the ohmmeter for any big jumps or dips. The digital ohmmeters don't work as well with this test. The cool thing is a new TPS is about $20.

I really want to get that puff of smoke figured out. What could that be?
would the o2 sensor help that puff?
I buy the parts, my grandpa helps me install them, im still learning =)
And where is the TPS?

I was under the influence if it was a head gasket it would constantly smoke, i could be totally wrong tho.

[This message has been edited by JZeFF (edited 08-27-2007).]

Take off the air cleaner and watch the fuel injector. Turn the car off and watch if the fuel injector drips. It should not. Those injectors are pretty dang tough but they can get clogged or leak. Make sure there is no fuel escaping around the injector. There are 2 o-rings on it that seal it to the throttle body.

Does your exhaust smell rich after it warms up? Are there any codes?

quote Originally posted by JZeFF: I really want to get that puff of smoke figured out. What could that be?

More than likely if it's white smoke that lingers in the air, it is the valve guide seals.

If the smoke is black looking and smell like gas then sounds like your rich.

Could also be your CTS is bad or the wire is broke to it. If the ECM thinks the engine is very cold it is going to set the fuel very rich.

You can read the sensor with an Ohm meter and see if it read about right for the temp you believe it is at. (Room temp etc)


Also is your stat keeping the engine at 195* that will hurt your mpg also.

What color is the puff of smoke? How many miles are on your car? My guess is leaking valve guide seals without knowing any details.

Its a white puff of smoke that does linger, so valve guide seals will probably be checked as soon as i can.
The body of the car has 83k on it, but the engine has 60 something thousand on it. The old engine a piston broke through the side so i replaced it with this one. When we swapped this engine in it was in decent shape.

[This message has been edited by JZeFF (edited 08-27-2007).]

quote Originally posted by JZeFF: Its a white puff of smoke that does linger,

Usually happens after the engine idles for a while... at a light or at a drive thru right after you step on the gas?

No, it only happens when i first start the car, it seems like if it sits for more than an hour it puffs. Generally the longer the sit, the larger the puff.

quote Originally posted by JZeFF: No, it only happens when i first start the car, it seems like if it sits for more than an hour it puffs. Generally the longer the sit, the larger the puff.

I'd say valve guide seals. Mine does it every time I start mine after it sits awhile. I have a small oil consumption that goes with this. Does yours also?

[This message has been edited by ly41181 (edited 08-28-2007).]

quote Originally posted by ly41181: I'd say valve guide seals. Mine does it every time I start mine after it sits awhile. I have a small oil consumption that goes with this. Does yours also?

My duke does the same thing it's just old and the valve guide seals are worn no big deal, but back to your poor gas mileage. What temp are you running at, mine used to run way cool until I found out my thermostat was stuck wide open replaced it and gained back about 4-5mpg. Check your pcv valve, plugs, could be the catalytic converter.

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Led Zeppelin and Fieros go well together.

fiero086 has valid idea cheap to check or replace ,auto duke should do 23 to 28 overall how far is foot from floor? speed kills kills gas mpg that is check cheap fixes first.check plug wires at nite to see if there is lite show cause by leaking electric,,make sure gas lines are not leakin hoses that go into tank split you must remove shield to check (not fun).proper plug gap only use cheap plugs,regular gap type,,incorect time of ignition is lead cause of bad mpg you will only achieve top mpg with 87 88 these have mods that produce excellent mpg,check all the normal suspects,an easy check is to remove one plug wire at a time,if one cylinder removal of wire makes no difference or less difference you have isolated problem,,SMOKE at start up 99% of time is seals fortunately duke head is easy to remove when remove hand lap valve seats unless valve job was done when you replace block..new seals will be tremendous help but old cars have loose valve shaft stems and the seals will not last as long but the new soft seal will be cure for a long time

Only 87 and up dukes regularly get better than 35mpg. Ya make sure you fill your tires to teh max PSI it says on the tire, 30 isn't 32, and 32 is the lowest max inflation I believe that exists. Automatics get worse mileage than manual trans.
Check all common things, tune it up if need be, air filter, spark plugs, wires, distrubutor cap/rotor. Make sure you have good gas, with a max of only 10% ethanol, no ethanol is best. Take it easy on the gas pedal. Maybe you have a sticky brake?

EDIT ( the jury is still out on filling to the max inflation, maybe check woth your auto mechanic / dealer for advice on that)

[This message has been edited by 2.5 (edited 08-29-2007).]

STRANGE delayed double post, sorry bout that

[This message has been edited by JZeFF (edited 08-28-2007).]

Talking about tire pressure is like opening a huge can of worms. I don't wish to step on anyones feet but for the sake of clarity, benefit and safety on my fellow members, I want to relay the information that I recieved from a tire manufacture after I got conflicting pressure info concerning my tire/ wheel purchase.

The correct tire pressure is on a sticker on the drivers door, I usually run at that PSI or maybe 2 extra pounds more if I am doing strictly highway driving. Inflating your tire to the max as listed on the side of the tire will give you better mileage however you will wear out the center of the tire tread in no time flat (no pun intended) and be subject to very adverse handling characteristics which can be extremely dangerous if the tire doesn't blow out first. The maximum tire pressure listed on the tire is the point of which if exceeded, a tire may burst, it is a safety rating. It is very easy to missunderstand this, matter of fact I had a tire manufacture correct Wheel-Max on this awhile back after I purchased wheel and tires. Always go by the vehicle manufactures recomendations on the sticker or owners manual for the correct tire pressure.

Better MPG, most has been covered, good tune up, air filter, gas filter, run a stock thermostat and drive moderately.

Editted for clarity and spelling.
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jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"

[This message has been edited by jetman (edited 08-28-2007).]

As Dodgerunner indicated I would suspect the the temp sensor for the ecm is not working. It is the one on the side of the thermostat housing.

Tire pressure is a good subject though especially with the rollovers Ford experienced when their OEM tires were under inflated. It seems there are 2 types of tires today, those rated at 35 psi max and those at 44 psi max. Now I have for 20 years had 35 psi max tires on my 1985 S10 Blazer. When heated from road friction, all tires will experience a pressure increase. 32 psi is used so that the increase won't put them over 35 psi. However, my last tire purchase had 44 psi tires. I did not notice this change and neither did the person installing them who inflated them to 32 psi. One tire tore itself apart in 6 months. Therefore my post above about watch out for 44 psi tires.....

Now newer cars have a recommended pressure for best ride versus best gas mileage. My 2001 S40 Volvo has both scales on the door jamb. It also uses 44 psi tires. It shows best ride quality at 39 psi front and 36 psi rear. Best fuel economy is 42 psi front and 40 psi rear.

On the tire it also says the max pressure at however many pounds of weight of vehicle on it. You'd want to figure that into it. These are low to the ground cars though, its the SUVs like Explorers that I'd worry more about. I thought if you were going by the vehicles door sticker inflation, you'd have to have stock size tires and maybe even the same brand as stock. (?)

[This message has been edited by 2.5 (edited 08-29-2007).]

If you mostly drive in the city you may be getting the best mileage you can expect with an automatic.
Give it a good tune up along with the other suggestions that have been mentioned.
It is also my belief that worn valve guide seals result in blue or blcak smoke, not white as you describe here.
Pay close attention to the injector and all temprature sensors.

Does your service engine light work and does it light up when you are driving?

Sorry yes my smoke at startup is blue, not white. The only thing I ever see smoke white is burning coolant right out the cylinders.

My service engine light comes on too, doesn't every Dukes? usually while I'm accellerating.

quote Originally posted by Indiana_resto_guy: If you mostly drive in the city you may be getting the best mileage you can expect with an automatic. Give it a good tune up along with the other suggestions that have been mentioned. It is also my belief that worn valve guide seals result in blue or blcak smoke, not white as you describe here. Pay close attention to the injector and all temprature sensors. Does your service engine light work and does it light up when you are driving?

My 86 duke , automatic gets 26-27 driving the 12 miles back and forth to work. That's a combination of semi rural and city. The worst I've ever gotten with it was 23 and that was because the injector O-ring let go and was pouring extra fuel into it.

For 2.5: if your service eng light is coming on while accelerating you need to run your codes. Something is amiss.... Mine only comes on at the bulb check or when there is a problem.

Clogged fuel filter caused a SES light on acceleration for me. Let off the gas pedal and the light went out. No codes were ever stored.

Change all filters, clean the Throttle Body, basic tune up, advance timeing 9 degrees, replace or pull off the Catalytic converter, replace thermostat, and check all sensors. The Duke should get 36+ MPG and if you want more MPG I have a first gen guke that has a RWD bolt pattern a weber carb and gets 45-51 MPG depending on season and thats city but it will be for sale soon.

quote Originally posted by Hudini: If you have a computer (preferably an old laptop with serial cable) then get WINaldl (free software) and an aldl cable. Allows you to read the sensors the ECM uses and see what they are doing.

In the past the WINaldl software would not work on a L4 has a L4 software been writen?. If so I want it.

Hager

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1987 Pontiac Fiero Coupe (Notchback) 2.5L L4 Automatic

My understanding is that WINaldl has always worked for 84-86 2.5L Dukes with a distributor. It does not work for the 87-88 Dukes with DIS. I suggested it because his is an '85. Someone correct me if I'm wrong.

[This message has been edited by Hudini (edited 08-30-2007).]

I had an 88 duke in my pontiac 6000. I managed to get it to 10mpg. that's definantly bad. and the manifold was glowing cherry red at the oxy sensor

How much city & how much highway. I can get 33+mpg on commutes over 35 miles cruising at 66mph w/ my black 86 2.5 auto.

[This message has been edited by 30+mpg (edited 08-30-2007).]

Ok finally had time to try and work on this problem. Its getting worse
Recently i have been getting close to 12mpg... (GAS IS KILLING ME IM 17!!!!)
when i first start the car acceleration is rough, it putts along. Sometimes the car goes REALLY slow, takes a second to start going normal speed.
Along with that has come the added joy of the transmission shifting really late, i will have the engine hitting 4k rpm for a good 3 seconds before it decides to shift into 2nd gear.
I checked the TPS and its fine, i took apart the throttle body and noticed that it was gargling gas, possibly the cause of the white smoke. So we replaced a bad o-ring, we checked the injector to make sure it was good and clean. But after doing that the car still runs rough.
I still have the problem of the engine chugging along when trying to stay a constant speed. (tachometer jumps up and down)
Another thing i have noticed is a really loud sucking (sounds like a compressed can of air, but 500x louder)noise on acceleration, and the engine doesnt seem to want to go over 3500rpm no matter how much gas i give it.
getting the car to go 50mph was also a task, it just doesnt want to do it.

Any ideas?

[This message has been edited by JZeFF (edited 09-09-2007).]

Clogged catalytic converter would do that. Try removing the O2 sensor and driving it a bit. See if the power picks up.

Ok, i just went and unscrewed the o2 sensor. TADAA my power problem i think is solved. Me and my grandpa are going to remove the catalytic converter on Tuesday and put in a straight pipe until i can afford a new cat. And luckily i have a parts car at his house with a possibly good o2 sensor that we can replace too. Any idea how much a new o2 sensor costs?

One problem down, many more to go.
Now how about that problem where i cant maintain a constant speed, the tach jumps and so does the car... any ideas?

[This message has been edited by JZeFF (edited 09-09-2007).]

New Bosch O2 is about $22 and AC Delco about $32 from Rock Auto. These have the OEM type connector. If you go with the $20 universal type Bosch you have to cut and splice the OEM connector from your current O2 sensor.

www.rockauto.com


EDIT: If the jumping occurs at the same speed every time, I would guess Throttle Position Sensor. Mine only happened at 45mph. Any slower or faster and everything was fine. You can test the resistance across 2 pins with an analogue ohmmeter, not the digital multimeters. The old pointer type ones where you can watch the pointer sweep across the dial as you turn the TPS. The pins are very small and it's somewhat difficult to setup. You watch the dial for a smooth sweep of the pointer with no sudden jerks or dead spots. The '85 TPS runs $25 to $85 depending on brand.

[This message has been edited by Hudini (edited 09-09-2007).]

See we used a digital ohmmeter today to check thats a good idea. But i dont really know what 2 pins you are talking about. I know the my grandpa used the 2 pins on top of the Throttle body, i believe one was red and one was black... and he also stuck the ohm meter in where the TPS plugs in. Which is the correct one to check? We did it with the car turned off, does the car need to be running?

This is where pictures would be nice.

[This message has been edited by JZeFF (edited 09-09-2007).]

The TPS has a 3 pin connector. (A) 5v reference, (B) TPS signal, and (C) ground. The pins to test (IIRC) are B and C on the TPS itself. This is all I have for pics. My '87 Duke uses a different style TPS with very small pins on the TPS. Hopefully yours are easier to work with. The TPS is unplugged and the car is off for the test. With the analogue ohmmeter connected you open the throttle to full slowly as you watch the needle sweep.

[This message has been edited by Hudini (edited 09-09-2007).]

Ok awesome, Huge help, plus for you =)

Im going back to his house tomorrow, we will recheck that with an analog meter. I will let you all know what happens.