302 cfi average mpg?

[Leo]

hey fellas, its been a while. good to see things changed for the better. i still got my 85 cv and the galaxies. good things.

my cfi is averaging about 14mpg. the car has already gotten a tune up. timing is at 11 degrees. still at 14mpg.

what do you guys think it might be?

[85crownHPP]

city or highway?

how new is the O2 sensor?

[Leo]

14mpg highway
o2 sensor 2 months old

[MattsLincoln]

it has to be running lean then my cfi gets 24MPG on the highway dont believe me ask 86VickyLX.

[85ltd]

Rebuilt motor, cfi, headers, dual exhaust, aftermarket air cleaner gets me 25 mpg on highway with 3.08 open gears. And about 19 in the city. But if I take off hard every time, its closer to 14-16.

My $0.02

Blane

[Leo]

how do i lean out the cfi?! is it that black knob that sits between the two sad little injectors.

[flyb0t]

Rebuilt motor, cfi, headers, dual exhaust, aftermarket air cleaner gets me 25 mpg on highway with 3.08 open gears. And about 19 in the city. But if I take off hard every time, its closer to 14-16.

My $0.02

Blane

Lucky bastard! My poor 84 gets 20, highway, maybe. 3.08 rear end, dual exhaust, new cap, rotor, wires, air filter (by cleaner do you mean the entire housing or..?), injectors, egr solenoid, egr valve. All that and she still gives me stumbling fits now and again. Cleaned out the system twice with Seafoam already. Meh, I'm of the opinion I need to work over the motor. How much of a rebuild did you do? I'll have to look into it, because those kinds of numbers are exactly what I need.

[sly]

heck... my 88 EFI gets 14. (gonna do a mileage run this weekend for highway)

I do tend to take off like a bat outta hell... the wide range gears in the trans makes the get up and go much nicer than it was originally... and this is on 2.73 gears. The low end torque would be epic with some 3.73 or better out back.

[85ltd]

Lucky bastard! My poor 84 gets 20, highway, maybe. 3.08 rear end, dual exhaust, new cap, rotor, wires, air filter (by cleaner do you mean the entire housing or..?), injectors, egr solenoid, egr valve. All that and she still gives me stumbling fits now and again. Cleaned out the system twice with Seafoam already. Meh, I'm of the opinion I need to work over the motor. How much of a rebuild did you do? I'll have to look into it, because those kinds of numbers are exactly what I need.

The rebuild was a stock master rebuild, whole thing costed me maybe $700, with all the extras. And I am using a Spectre air cleaner, the pancake thingy. Probably doesn't do much, but looks badass and sounds cool. I don't have catalytic converters or a smog system at all. The gas mileage is great for right now, but a lil Honda is still needed.

Blane

[gadget73]

The A/F is not adjustable on a CFI motor. If there are no vacuum leaks, the only other thing that usually makes it gobble fuel is a bad O2 sensor. they almost never set codes or exhibit any other running problems when the O2 fails. When one is right, 20+ mpg on the highway with stock gears is about right.


flyb0t: have you replaced the timing chain? The random stumble is a symptom of a worn out chain. They used crappy plastic cam gears on those year cars and the chain develops serious amounts of slop, both from age and wear. They are often shot before the 100k point. Conversely, with the double roller chain that most 86+ engines have, they're usually serviceable to 200k or better. I replaced one at 225k on my Mark VII and it really wasn't that bad.

[flyb0t]

flyb0t: have you replaced the timing chain? The random stumble is a symptom of a worn out chain. They used crappy plastic cam gears on those year cars and the chain develops serious amounts of slop, both from age and wear. They are often shot before the 100k point. Conversely, with the double roller chain that most 86+ engines have, they're usually serviceable to 200k or better. I replaced one at 225k on my Mark VII and it really wasn't that bad.

Hmm, haven't looked at the timing chain yet. Will have to check, if that's the case, it's something that got overlooked, because every other thing about the car had been replaced or verified working.

Also, 85ltd, I've gotta run emissions stuff on my car, do you think that has any part in your improved mileage? And $700 for a rebuild doesn't sound too bad.

[pstrbrc]

Haven't posted lately, but this interests me. '84 GM w/cfi. Was getting 18mpg/highway, but that's partly because of a set of 3.55's that came w/the car. But also...
I have several extra cfi units, so I pulled them all apart. Took one of the injector electrical connectors and wired it up to a wall wart set at 6v and a momentary switch I had laying around. Took the injectors, popped the screens out of the top of them, snapped on the pigtail, put gas line over the nose, poured in acetone, grabbed my air gun, pushed down the switch, and blew them out backwards. Nasty crap!! Repeat un til the acetone comes out clean. Then I grabbed an adjustable fuel pressure regulator ("They" say you can make your's adjustable, but I had a good one laying around, so...) and put the injectors and regulator in a cleaned-up tb, and bolted it on. Even before I put a 3.08 underneath it, I picked up 3 mpg. There's a schrader valve underneath a black cap on one side of the injector tops. A tire guage works, but you have to be careful not to spew gas spray all over the place. The stock regulator was having a hard time keeping pressure constant, and would fluctuate between 30-35#. I set the adjustable one to 42#, lost all stumble, and the O2 sensor adjusts to keep the mixture right. Haven't changed the timing chain yet, but that will come with a Summit 3600 cam and a bored-out TB, mustang shorties and an h-pipe.
Alll emission stuff is off, but I'm planning on putting an egr back on as soon as I find the right coolant switch in a JY. No point in paying $35 for that!Still have a 1st gen MegaSquirt box in the garage, and if the stock ecu can't deal with all of this, there's always that option.

[Leo]

could a bad tps cause poor fuel milage?!


dumb question:
would my tbi benefit any if i put 1 inch spacer under the cfi module ?!

[turbo2256b]

EGR system not working correctly can kill economy.

[85crownHPP]

I got 20-21 MPG highway (crap mileage around town) in mine when it was CFI, with no EGR hooked up. Of course I drove it like grandpa because it didn't like hard acceleration.