1985 5.0 gettin 14mpg what gives? +other probs

[91lxvert]

1985 5.0 gettin 14mpg what gives?

also no matter wether the vehicle is hot or cold when taking off it kinda stalls then it will finally go almost every single time unless i really ride the clutch,

and it has recently begun to have extreemly rough idle, bad enough to make the whole car shake, any ideas?

it also seems like when the car warms up it loses power

also the motor is completley stock other than a k&n and flowmasters.

any ideas are very much appreciated!

 

[oboeboy]

when was your last tune up?

Change Spark plugs, cap and rotor, fuel filter, check / replace wires, air filter

 

[jadedinpa]

how old is the carb? has it been tuned ever? it might need rebuilt.

 

[Blue Thunder]

My '85 GT/5-speed got 18-19 mpg highway with 4.10 gears in it.

From what you've stated, you have some serious tuning issues going on. First be sure all the ignition parts are functioning correctly, and time it. Then check for vac. leaks on the manifold and carb troubles.

On a side note, the intake manifolds on those cars have ports small enough to resemble coolant ports. If you replace the stocker with a Performer Intake you will notice a healthy power increase.

 

[91lxvert]

yeah im getting ready to do valve cover and intake gaskets on it, one problem though is im in cali,

what aftermarket manifolds are still smog legal,
and i remember hearing about somone that reworks the stock carb anyone know who that was and where i can find em?

thanks again

 

[85_SS_302_Coupe]

First off, NICE CAR! Looks as though we've got a couple distant cousin '85s...lol


Anyways, i'd do a SERIOUS tune up, from the fuel filter to the plugs and wires and all the typical tune up stuff. Then i'd check every vaccum line under the hood for cracks or disconnections. Then i'd run about 2 bottles of carb/fuel line cleaner with a full tank of the highest octane unleaded you can get your hands on, Sunoco is good for 94. If that doesnt do the trick, your carb is probably done for.

My car is a little chokey when it's first started if you dont let it warm up to driving temps, but if you just tap the gas a couple times, and give it plenty of throttle it's fine once it gets to about 20mph. After that and about 5 miles it's fine and doesnt choke at all.

As for the mpg, that could be any of the above check list items or a combination of any of'em. The stock carbs are there for fuel economy (they sure as hell dont have racing in mind...lol) I get about 16mpg with my 4.10 gears, but i can probably stretch it up to 17-18 if i stay under 25k RPM.

 

[sublime29]

It seems like your carb is in need of a rebuild.Don\t think it is hard.It is very easy and for the most part is a matter of taken it all apart and cleaning all the parts.There is a special cleaner you soak them in.Just remember there is a time limit to leave the parts in it.That stuff cam mess the surface up on the parts.Just make sure the rebuild kit has new floats and a power valve(may have to buy seperate).The hesitation when you 1st hit the pedal is most likely the power valve.It gives the carb a extra squirt of fuel when you 1st hit the gas.Just do it in a clean place and have a egg carton to keep screw and small parts sorted.A nice clean work bench or kitchen table(if wife allows).Just take your time and clean everything as clean as possible.The rebuild kit is around 20 bucs and has the directions.Also give it a complete tune up.The rough idle might just be the idle screw being set to low.You might want to get a can of carb cleaner and spray the hell out of it especially the idle circuits.

 

[91lxvert]

thanks for all the replies guys, ill be ordering the fms wires soon so when i get them in ill be startin on the tune up.

once off of idle and going the car runs amazing that is untill it warms completley up then its a dog.

85 ss 302 coupe: yeah when i saw your car and the replies you and a few of the others on here on one of my previous threads made me decide to buy it.

oh yeah, anyone got any ideas on the aftermarket manifold and possibly carb thats still california emissions legal?

 

[maverick0716]

Same symptoms happened with my car. There was a major vaccuum leak at the intake manifold....the gaskets were all screwed up.......I tried replacing wires, cap, rotor, and plugs to no avail.

 

[B.Matt]

i have the same problem I have tried new intake gasket, cap, roter, plugs, fuel and air filter, timing checked, pinched of all the vacum lines, no help. Driving me nuts. The plugs look like a perfect burn and i passed NJ emissions. Any other ideas