MPFI 3.1 V-6
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Joined: Jul 1999
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From: Adrian, Mi, USA
Car: 1988 Pontiac Firebird Formula
Engine: 5.7 TPI
Transmission: 700R4
Re: MPFI 3.1 V-6
You should get at LEAST 15, and as high as 27 or so on the freeway. When is the last time you had a tuneup? Is the check engine lite on? Have you ever replaced the O2 sensor?
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Re: MPFI 3.1 V-6
Ploegi.Thanks! i just purcased this 1992 firebird. MPFI V6. it had been garaged for 6 years. So, no recent tune up. 12 MPG. You referenced the O2 sensor. Is this something I can replace with out a scan tool of scope? Also, what about the other sensors (temp etc.) that feed info to the ECM? To the left/front of the engine is a module fed/hooked-up to the eshaust manifold. Is the O2 sensor located there? Or should I take it in to a shop and have them hook-up a scope to check things out. New spark plugs? Oh, the check ingine light is not on. Thanks! Andrew
Last edited by andwied; Nov 30, 2009 at 03:15 PM. Reason: Additional info.
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Re: MPFI 3.1 V-6
ploegi: Poor MPG; 12. Can I replace the O2 sensor? Or, should I take it into a shop and have them hook it up tp the a scan or scope tool? Also, will replacing the spark plugs improve the MPG. I just bought this '92 firebird. It had been garaged for 6 years, thus no recent tune-up. Thanks for your help! Andrew
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From: Oklahoma City
Car: 1991 Firebird
Engine: 3.1L +bolt ons
Transmission: 700R4
Axle/Gears: Moser forged, 3.73, SLP posi
Re: MPFI 3.1 V-6
Holy crap, that's & BMW 7 series V12 kinda mileage.
O2 sensor is in your exhaust, passenger side, by the cat. Just get one at Autozone/Pepboys/Whatever (about $25) and take a wrench to it. It's probably really stuck on there, I had to put body weight on the wrench to get mine off. Plug in the new one, screw it back on, done.
Yes, new plugs, wires, cap, rotor, oil and filters. I'd also run seafoam.
Crap, why am I typing all this? Just do this:
I would also add: try to find gas without ethanol. That junk takes 4 mpg off my average.
O2 sensor is in your exhaust, passenger side, by the cat. Just get one at Autozone/Pepboys/Whatever (about $25) and take a wrench to it. It's probably really stuck on there, I had to put body weight on the wrench to get mine off. Plug in the new one, screw it back on, done.
Yes, new plugs, wires, cap, rotor, oil and filters. I'd also run seafoam.
Crap, why am I typing all this? Just do this:
Originally Posted by Tom P
Tom P's Major Tuneup Info: 3rd gen (82-92) F-body series
Here's the Major Tuneup stuff- this covers alot more than a garage would do for you, and it'll wind up to be cheaper (or at least the same price)! First, buy a Haynes 82-92 Firebird (or 82-92 Camaro) manual.. they're about $15 from any auto parts store. I like them alot better than the Chilton's manuals (which aren't what they used to be 25 years ago). And of course, the ultimate manual is the GM Service Manual, available from http://www.helminc.com - I paid about $60 for mine back in 1994.
Replace: Distributor cap/rotor, spark plug wires (use aftermarket), spark plugs, air filter (use K&N replacements), PCV valve, fuel filter, engine oil/filter, auto trans fluid/filter (or manual trans gear lube), and rear axle gear lube (use limited slip additive if required). Check and reset the timing to stock specs (in Haynes manual). Check and reset the TV cable if you have an automagic (in Haynes manual). Do a lube job and get an alignment done- the car will go faster "easier" if the front wheels are straight. Buy a can of "Intake and Throttle Body Cleaner for Fuel Injected Engines" by Gumout (yellow or gray can, with a red cap), and follow the can's instructions to clean out your intake. DO NOT USE CARB/CHOKE CLEANER- this removes the protective coating fuel injected engines have. Put a bottle of injector cleaner or my "red magic" (STP Gas Treatment) into a full tank of good gas.
It's also a good idea to replace your coolant, check your brake fluid level and p/s fluid level, check the belts, and check your brakes while you're at it.
Call Summit Racing at 800-230-3030 for a free catalog, then you can pick and choose a spark plug wire set and get your K&N air filter(s). (You can also find this stuff through their website, at http://www.summitracing.com , but it's not as thorough as the catalog.) When you leaf thru the catalog, you WON'T SEE any parts listed for a 2.8l v6 - you need to call them and ask them for part #'s/availablility. (Same goes with exhaust, etc.) If you're like me, and can't want to wait for the catalog in the mail, call them and order one anyway! Then, go to their website, at http://www.summitracing.com , look up their ignition wires, decide on a brand, and give them a call for a part # and price.
But definately do a tuneup first... you'll see the best improvment from the "fun" parts when your car is in good running condition.
Here's the Major Tuneup stuff- this covers alot more than a garage would do for you, and it'll wind up to be cheaper (or at least the same price)! First, buy a Haynes 82-92 Firebird (or 82-92 Camaro) manual.. they're about $15 from any auto parts store. I like them alot better than the Chilton's manuals (which aren't what they used to be 25 years ago). And of course, the ultimate manual is the GM Service Manual, available from http://www.helminc.com - I paid about $60 for mine back in 1994.
Replace: Distributor cap/rotor, spark plug wires (use aftermarket), spark plugs, air filter (use K&N replacements), PCV valve, fuel filter, engine oil/filter, auto trans fluid/filter (or manual trans gear lube), and rear axle gear lube (use limited slip additive if required). Check and reset the timing to stock specs (in Haynes manual). Check and reset the TV cable if you have an automagic (in Haynes manual). Do a lube job and get an alignment done- the car will go faster "easier" if the front wheels are straight. Buy a can of "Intake and Throttle Body Cleaner for Fuel Injected Engines" by Gumout (yellow or gray can, with a red cap), and follow the can's instructions to clean out your intake. DO NOT USE CARB/CHOKE CLEANER- this removes the protective coating fuel injected engines have. Put a bottle of injector cleaner or my "red magic" (STP Gas Treatment) into a full tank of good gas.
It's also a good idea to replace your coolant, check your brake fluid level and p/s fluid level, check the belts, and check your brakes while you're at it.
Call Summit Racing at 800-230-3030 for a free catalog, then you can pick and choose a spark plug wire set and get your K&N air filter(s). (You can also find this stuff through their website, at http://www.summitracing.com , but it's not as thorough as the catalog.) When you leaf thru the catalog, you WON'T SEE any parts listed for a 2.8l v6 - you need to call them and ask them for part #'s/availablility. (Same goes with exhaust, etc.) If you're like me, and can't want to wait for the catalog in the mail, call them and order one anyway! Then, go to their website, at http://www.summitracing.com , look up their ignition wires, decide on a brand, and give them a call for a part # and price.
But definately do a tuneup first... you'll see the best improvment from the "fun" parts when your car is in good running condition.
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Re: MPFI 3.1 V-6
tune her up man! mine sat for 4 years and ive replaced the whole ignition system and had the fuel system cleaned, my 3.1L gets 33 on the highway now 
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Re: MPFI 3.1 V-6
Everyone has given you great ideas, and after a 6yr rest it's all probaly neccesary. I had the exact same problem and after all the usual tuneup stuff, my problem was a plugged catalytic converter! I am now getting about 16/city and 27/hwy. Good Luck!
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