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2.8 V-6 Fuel economy...not what it should be by Rich Truett
Started on: 03-29-2015 04:34 PM
Replies: 26 (558 views)
Last post by: Gall757 on 04-07-2015 05:02 PM
Rich Truett
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Report this Post03-29-2015 04:34 PM Click Here to See the Profile for Rich TruettClick Here to Email Rich TruettSend a Private Message to Rich TruettEdit/Delete MessageReply w/QuoteDirect Link to This Post
Although my '88 Formula automatic is running well, the fuel economy seems very low.
I used 5.9 gallons over the last 83 miles. That's just over 14 mpg in combined city/highway driving.
There are no trouble codes.
The only mechanical issue I know of is the catalytic converter. The internal parts are loose and it rattles over bumps, and a small exhaust leak.

Question: What kind of fuel economy should an '88 Formula automatic get that is driven normally?

Thanks,

Rich Truett

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Gall757
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Report this Post03-29-2015 05:02 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
http://www.fiero.nl/forum/Forum1/HTML/094226.html

Do you have a thermostat?

[This message has been edited by Gall757 (edited 03-29-2015).]

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hiwil88formula
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Report this Post03-29-2015 05:03 PM Click Here to See the Profile for hiwil88formulaClick Here to Email hiwil88formulaSend a Private Message to hiwil88formulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
20-25 is about normal. Have you changed the O2 sensor? If not I would start there. It could be bad and not throw a code.
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cmechmann
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Report this Post03-29-2015 05:24 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
When i had the 2.8/3sp auto in the 85, I got 14-17 city, 20-23 highway. In city with many short trips, the cold start injector causes it to use a lot.
With the 3800 and 4sp auto, I got 14-18 city and 26-29 highway. But I couldn't help myself from getting into the SC. Did get close to 32 on a long trip and that was during cooler weather. I could only imagine if I had a 2.8/3.1 with the 4sp/overdrive transmission, I could get close to 36-38.
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Patrick
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Report this Post03-29-2015 05:27 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Rich Truett:

...and a small exhaust leak.


Before the O2 sensor? If so, I've read here numerous times that this will fool the sensor and result in the engine running richer than it should.

[This message has been edited by Patrick (edited 03-29-2015).]

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Rich Truett
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Report this Post03-29-2015 07:22 PM Click Here to See the Profile for Rich TruettClick Here to Email Rich TruettSend a Private Message to Rich TruettEdit/Delete MessageReply w/QuoteDirect Link to This Post
The following has been replaced on my engine:
02 sensor
MAP sensor
Coolant Temp Sensor
IAC
Cap, rotor, wires
ICM
plugs
And yes, it does have a T-Stat. but...the gage barely budges off cold. I may need to look into that.

I have not checked the timing.
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Gall757
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Report this Post03-29-2015 08:31 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
You may find that the thermostat is bent....The Ogre has a write-up about thermostats for the Fiero.....it's required reading....
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Rich Truett
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Report this Post03-29-2015 09:17 PM Click Here to See the Profile for Rich TruettClick Here to Email Rich TruettSend a Private Message to Rich TruettEdit/Delete MessageReply w/QuoteDirect Link to This Post
For the last 30 years, I have been dealing with British Leyland vehicles, Triumphs mostly, and some Rovers.

Good god. The Fiero seems to have British Leyland era quality issues.

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Gall757
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Report this Post03-29-2015 09:23 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
.....The Fiero has it's issues, but I wouldn't go THAT far!
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Csjag
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Report this Post03-29-2015 09:39 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:

.....The Fiero has it's issues, but I wouldn't go THAT far!


I agree, I have had MG's and Jaguars and compared to them the Fiero is bulletproof.
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f85gtron
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Report this Post03-30-2015 09:13 AM Click Here to See the Profile for f85gtronSend a Private Message to f85gtronEdit/Delete MessageReply w/QuoteDirect Link to This Post
Think "Lucas" ha ha
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css9450
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Report this Post03-30-2015 10:17 AM Click Here to See the Profile for css9450Click Here to Email css9450Send a Private Message to css9450Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by f85gtron:

Think "Lucas" ha ha


The "Prince of Darkness"!!

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Lou6t4gto
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Report this Post04-01-2015 02:00 PM Click Here to See the Profile for Lou6t4gtoClick Here to Email Lou6t4gtoSend a Private Message to Lou6t4gtoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Lucas "prince of Darkness" was always a corrosion problem. I've Had Many Triumphs, MGs, Healey's. Fiero's are Light years ahead of all the British cars.
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Report this Post04-02-2015 03:54 AM Click Here to See the Profile for SlammedClick Here to Email SlammedSend a Private Message to SlammedEdit/Delete MessageReply w/QuoteDirect Link to This Post
Leak before the o2 and that cat would certainly do it. The pieces of the core could be blocking it up and I'm sure there are chunks stuck inside your muffler
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sardonyx247
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Report this Post04-02-2015 04:17 AM Click Here to See the Profile for sardonyx247Click Here to visit sardonyx247's HomePageClick Here to Email sardonyx247Send a Private Message to sardonyx247Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Rich Truett:
...the gage barely budges off cold.


That will do it right there.
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f85gtron
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Report this Post04-02-2015 07:01 AM Click Here to See the Profile for f85gtronSend a Private Message to f85gtronEdit/Delete MessageReply w/QuoteDirect Link to This Post
Check thermostat first. If it's bent or stick open, the engine will never warm up and more fuel will keep being injected into the motor than normal. (Assuming your cooling temp sender is accurate ha ha)
The second thing, since you had a cat fall apart, is to hook a screw in type compression tester in where the o2 sensor is and look for high pressure in the exhaust. I think your looking for over 4 lbs at 2800 rpms? (Somebody correct me if I'm wrong). Anything above that would indicate a blockage.
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FrugalFiero
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Report this Post04-02-2015 09:42 AM Click Here to See the Profile for FrugalFieroEdit/Delete MessageReply w/QuoteDirect Link to This Post
Something's up if your temp gauge barely moves - my Formula has a 180 degree stat installed and the temp gauge goes up about a third of the way.

If you want to drive your Formula up to Genesee county, we could hook it up to my tech1 which might help in diagnosis.

[This message has been edited by FrugalFiero (edited 04-02-2015).]

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2.5
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Report this Post04-02-2015 04:43 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by sardonyx247:

That will do it right there.


Ya it would. I was also thinking, its still been chilly at times in March, hes in detroit. Has the car been idling to warm up, killing your mileage?
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Ancient Mariner
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Report this Post04-02-2015 05:23 PM Click Here to See the Profile for Ancient MarinerClick Here to Email Ancient MarinerSend a Private Message to Ancient MarinerEdit/Delete MessageReply w/QuoteDirect Link to This Post
I've got an '86 SE, 187,000 miles (original engine and 4-speed), 185* thermostat, that consistently gives 31-32 on the Interstate, and 23-24 in town. Completely stock, don't run the A/C, and occasionally hot-dog it . It was originally engineered to use the 185* thermostat, so that's what I use.
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Rich Truett
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Report this Post04-02-2015 06:12 PM Click Here to See the Profile for Rich TruettClick Here to Email Rich TruettSend a Private Message to Rich TruettEdit/Delete MessageReply w/QuoteDirect Link to This Post
I have the dreaded exhaust leak at the inner or window side exhaust manifold. I think it is just a blow gasket, so my plan is get in there fix that leak and while the exhaust system is partially apart, either install a new converter or else the bypass pipe the Fiero Factory sells. And while that is going on, replace the thermostat. The exhaust leak is a small one, just a tick-tick-tick you can hear under acceleration, but I understand that could also be affecting things.
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Gall757
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Report this Post04-02-2015 06:18 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ancient Mariner:
It was originally engineered to use the 185* thermostat, so that's what I use.


Technical housekeeping........original thermostat was 195*
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Ancient Mariner
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Report this Post04-03-2015 07:11 AM Click Here to See the Profile for Ancient MarinerClick Here to Email Ancient MarinerSend a Private Message to Ancient MarinerEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Gall757:


Technical housekeeping........original thermostat was 195*


Correct - My bad

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Rich Truett
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Report this Post04-04-2015 08:34 PM Click Here to See the Profile for Rich TruettClick Here to Email Rich TruettSend a Private Message to Rich TruettEdit/Delete MessageReply w/QuoteDirect Link to This Post
I pulled the original AC Delco 195f thermostat out today.
I needed pliers to get it out.
It looked OK, not stuck open.

I have not fired up the car yet to see where the temp gage will go, but with the old t-stat, the gage barely budged off cold.

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Report this Post04-04-2015 09:41 PM Click Here to See the Profile for tsharkSend a Private Message to tsharkEdit/Delete MessageReply w/QuoteDirect Link to This Post
..

[This message has been edited by tshark (edited 09-08-2018).]

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Rich Truett
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Report this Post04-04-2015 10:40 PM Click Here to See the Profile for Rich TruettClick Here to Email Rich TruettSend a Private Message to Rich TruettEdit/Delete MessageReply w/QuoteDirect Link to This Post
The new one pressed right in.

I noticed the O-Ring on the original thermostat was slightly deformed, but that likely is due to it being removed.

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coltonandrew
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Report this Post04-05-2015 09:59 AM Click Here to See the Profile for coltonandrewClick Here to Email coltonandrewSend a Private Message to coltonandrewEdit/Delete MessageReply w/QuoteDirect Link to This Post
A few thoughts, I'm not good at diagnosing but I can give you some ideas.

The fuel pump isn't working correctly
The fuel filter is gunked up
There might be debris in the fuel lines which might cause a lot more problems
Small vacuum leaks (spray around the engine bay with carb cleaner or ether starter fluid and listen)
gunked up engine internals. I personally use seafoam in the brake booster line in the front hood of the car. This might get some of the gunk out
clogged cat. The gases cant go anywhere and are creating backpressure.

You might just be running too rich. Have you pulled the spark plugs and diagnosed those? White/grey clouded tips = too rich. Black/ grimey = dirty internals or very old plugs. Also, the plug gaps may have stretched from use causing a weak spark and forcing your car to pump in more gas. I've have the best luck with Bosche +4 iridium plugs.

Those are just a few ideas, I could be way off
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Gall757
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Report this Post04-07-2015 05:02 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
This thread wraps up here......

http://www.fiero.nl/forum/Forum2/HTML/135096.html

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