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

[MattsTownCarSS]

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.

[slymer]

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: :suicide2:
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.

[turbo2256b]

Driving style can have a major effect. Terain can also be a cause its all up and down hills around here unlike flat Michigan or Ohio

[pstrbrc]

could a bad tps cause poor fuel milage?!



No. It just makes it surge really, REALLY bad off idle. The Spacer? Your car has the TV rod, not a Tv cable, and there's just not enough adjustment in the rod to lift the throttle body up an inch. Guess how I know! If you convert your tranny to the TV cable with these parts
http://www.summitracing.com/parts/LOK-KD2AODHT/
http://www.summitracing.com/parts/LOK-SRK-4000/
you can do it, but $100 is a lot to spend for what you're getting out of it unless you're planning other mods as well.

[86VickyLX]

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. Funny, opposite for the evil EEC-III CFI that lives on the 83 Grand Marquis twodoor.

[pstrbrc]

btw, if you are serious about the spacer idea, here's a couple of GMN posts you should read:

-interesting-CFI-performance-tidbit-i-found (http://www.grandmarq.net/vb/showthread.php?5854-interesting-CFI-performance-tidbit-i-found)

-New-CFI-Goodness&highlight=cfi+spacer (http://www.grandmarq.net/vb/showthread.php?22245-New-CFI-Goodness&highlight=cfi+spacer)

The second one is the most instructive. I'm working on modding a Trans-Dapt 2137 spacer and an aluminum cfi manifold to accomplish what the second post talks about. I'll take lots of pictures!

[ford man]

Hey the cfi injection does have an adjustable pressure regulator... Here is a copy and paste of what I wrote a while back on my readers rides page. I am now currently getting 17.1 average miles per gallon too!


Hey guys- little update for ya... The LTD is running really strong and smooth and I'm pulling down 16.8 miles to the gallon. That's driving on the 405 freeway under heavy traffic conditions from the valley to the westside about 30 miles a day over the hill. I was getting around 14 mpg before for the longest time.

A while back it needed a egr position sensor and I bought a new oxygen sensor and also got the 9mm ford racing wires. The egr sensor solved the driveability issue and it seemed to run better with the new wires. It did run obviously lean though- 5 degrees hotter than before on average and would run out of fuel on the top end and kind of fall on it's face wide open throttle. It wanted more gas! I knew the signs of a lean fuel mixture from working with carbuerators... but it's cfi what can I do? It always seemed run lean looking back at it now the new wires just made it more obvious...

I went online and happy discovered that the cfi fuel pressure regulator is adjustable!!! Adjustable from the factory.... but the factory dosen't want you to adjust it. It has a stanless steel cap blocking the adjusting screw... It took me forever to drill through! and it's pressed in so drilling was really the only option then I screwed a nail into it and pulled it out with pliers. Sure enough underneath was a allen key adjustment screw! Turn the screw clockwise to increase fuel pressure. The screw is a fine thread and the pressure increases slowly and linear.

When I started I had 44pph and now I have turned it up to around 46pph fuel pressure. I know stock is supposed to be 39pph so go figure... Noticeably more power and torque than before and the trip computer dosen't lie... every time I turned the fuel pressure up it liked it and responded with more mpg and smoothness. It dosen't stutter on the freeway anymore or under heavy part throttle. I have been checking my plugs and have turned the fuel pressure very gradually, over a period of a couple months making sure I didn't make it run rich; just dialing it in...

I hope this information can help Grand Marq members with cfi injection!

[gadget73]

I always thought it interesting when there is proof that more fuel can mean better economy. I understand why, a more efficiently running engine will actually need less fuel to make a certain amount of power, but its a concept that is difficult to explain to people sometimes. Of course its only true to a point. Once you go past the point of a properly tuned engine into a rich running motor, the economy will take a dive.

[flyb0t]

Sooo..timing chain is totally fine. Now the head scratching begins.

[gadget73]

you replaced it or checked it ? If its that single row thing with the plastic teeth on the cam gear, it really needs to be replaced.