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Your MCSS MPG

Posted By: ILoveMyMonteCarloSS

Your MCSS MPG - 12/27/15 11:39 PM

Hey Montes,

I just calculated my MCSS' MPG, it's 12.5mpg. Seems a bit low, maybe 3 miles or so to me. Especially those of you who still have the stock 305 and stock carburetor, what MPG is your MCSS getting?
Posted By: tomh115

Re: Your MCSS MPG - 12/28/15 01:11 AM

15 to 20. Sometimes less when I drive it like I stole it
Posted By: ILoveMyMonteCarloSS

Re: Your MCSS MPG - 12/28/15 01:25 AM

15 to 20 is what I'm finding all other places, I think She's burning rich. Thoughts?
Posted By: mannblk

Re: Your MCSS MPG - 12/28/15 02:43 PM

Is your computer and all the engine/transmission still in stock form? The ccc 305 and 200R4 should easily get 17 city and 24 highway mpg. If the computer, distributor and carb have been changed and the proper lock-up installed for the torque converter, you should still be in that same range. HTH
Posted By: WPV

Re: Your MCSS MPG - 12/28/15 02:46 PM

I get 22mpg on the highway going between 75-77mph, now around key west, i get 12, but its ALWAYS stop and go traffic
Posted By: tomh115

Re: Your MCSS MPG - 12/28/15 03:16 PM

Wouldn't the 85 have the TH350C transmission (or whatever the 3 speed auto was that time)? So it would be lower than the 86-88s that had the 200 4R Transmission.
Posted By: WPV

Re: Your MCSS MPG - 12/28/15 03:57 PM

no the 85 was the first year of 3.73 gears standard and the 200-4r trans, so if its original it should have OD
Posted By: Buick Runner

Re: Your MCSS MPG - 12/28/15 07:23 PM

Very well could be a vacuum leak making the computer go rich. Have you checked the fuel mixture control solenoid dwell?
Posted By: upflying

Re: Your MCSS MPG - 12/28/15 10:01 PM

Originally Posted By: ILoveMyMonteCarloSS
Hey Montes,

I just calculated my MCSS' MPG, it's 12.5mpg.


How did you calculate mpg?
Since you just got the car, you may be suffering from skinny pedal right foot syndrome.
Drive the car for a month and check it again.
FWIW, I got about 18 on the highway.
Posted By: ILoveMyMonteCarloSS

Re: Your MCSS MPG - 12/29/15 02:06 AM

upflying, I filled up the tank then took a photo of the odometer, once I needed more gas I filled up again and had the exact amount of gas I used, then I divided the the miles driven by the gas I used.

BuickRunner, forgive my ignorance, but, there is a computer controlling the fuel mixture on the carb? I thought that was all mechanical.
Posted By: cj84ss

Re: Your MCSS MPG - 12/29/15 02:33 AM

You should be getting about 17 in town and up to 25 on the highway. Maybe you had some old gas in it. Check for some of the issues stated. I get the 15 in town and don't always drive it nice. Still have factory computer and running a 355 now.
Posted By: upflying

Re: Your MCSS MPG - 12/29/15 04:36 PM

Originally Posted By: ILoveMyMonteCarloSS

BuickRunner, forgive my ignorance, but, there is a computer controlling the fuel mixture on the carb? I thought that was all mechanical.

Yes, there is a mixture control solenoid in the Quadrajet. You can hear it clicking when you turn the key. It is controlled by the computer behind the right kick panel.
Posted By: Buick Runner

Re: Your MCSS MPG - 12/30/15 12:31 AM

Originally Posted By: upflying
Originally Posted By: ILoveMyMonteCarloSS

BuickRunner, forgive my ignorance, but, there is a computer controlling the fuel mixture on the carb? I thought that was all mechanical.

Yes, there is a mixture control solenoid in the Quadrajet. You can hear it clicking when you turn the key. It is controlled by the computer behind the right kick panel.


That is how it should be if your car is stock. The computer controls the fuel mixture on the primary side of the carb, timing advance, knock retard, torque converter lockup, etc. These cars are prone to having their various systems hacked up by their former owners who didn't know what they were doing.
Posted By: 86ttop

Re: Your MCSS MPG - 12/30/15 12:57 AM

I never really checked, but I could drive for 4 hours at highway speeds before I needed to get gas.
Posted By: ILoveMyMonteCarloSS

Re: Your MCSS MPG - 12/30/15 01:11 AM

I talked to some guys at my O'reilly's(the ones who know there stuff), I told them about how she idols high sometimes, they said that could be causing high MPG. I guess I might just need to turn her on and off until she idols correctly until I can look into it properly(under the hood), I'll see if that make a difference.
Posted By: Buick Runner

Re: Your MCSS MPG - 12/30/15 04:18 PM

The car has 3 idle speed adjustments, there is the fast idle where the engine idles faster when it is still cold. Then there is curb idle where the idle speed kicks down to a lower speed after warm up. Then there is the A/C kicker solenoid which raises the idle speed when the A/C is turned on. The fast idle should be set at 2,000 RPM while the curb idle should be 650 RPM, you check both with the transmission in Drive.
Posted By: 86ttop

Re: Your MCSS MPG - 12/31/15 12:14 AM

DO NOT CHECK THE CHOKE ON IDLE IN DRIVE only the curb idle after the engine is up to operating temperature!!!!!!!!!!!
Posted By: Buick Runner

Re: Your MCSS MPG - 01/01/16 12:59 AM

I have done it, but with a helper holding the brakes with wheel blocks.
Posted By: 86ttop

Re: Your MCSS MPG - 01/01/16 08:03 PM

Not the correct way,it's a no load setting.
Posted By: Buick Runner

Re: Your MCSS MPG - 01/02/16 11:08 PM

Well I won't argure with safety, still a good idea to have a helper when making these adjustments.
Posted By: NYmonteSS

Re: Your MCSS MPG - 01/15/16 05:34 PM

8 mpg! but its fun !!! hehe
Posted By: jmireles

Re: Your MCSS MPG - 01/30/16 09:45 PM

So what's happened, have you made any progress?
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