I recently got my 85 conversion back. having never put over 50 miles on it but now driving 50 miles per week or so I am curious. It seems that it gets horrible gas mileage, runs like a top, sounds great, goes like stink but I feel like i need a fuel truck to follow me around. Ill bet its since I race it around but anyone can comment?

What are you getting per gallon?

quote Originally posted by VFR182: Ill bet its since I race it around but anyone can comment?

Yes - had a local fellow to me say the same thing. Was absoulty convinced there was something wrong with the car, but when he took it on a road trip and kept his foot out of it the gas milage went up.

Of course, this assumes everything is working on the car (O2 sensor, no vac leaks, etc). Try taking it easy for a tank of gas and see what happens...

thats what i figured. I am getting about 12 mpg. the old duke that was in there averaged about 36mpg and even more on the highway without ac running. My guess is each hole shot from the stop light consumes a gallon or so..

Yea, my wife's 4.9 gets about 15 around town but 27mpg on the highway. It's FI with Ed's harness.
It's too hard to stay out of the pedal.

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Proud Member of the North Florida Fiero club

4T60E Parks harness/ Rockcrawl chip-- more to come--

quote Originally posted by VFR182: runs like a top, sounds great, goes like stink but I feel like i need a fuel truck to follow me around. Ill bet its since I race it around but anyone can comment?

Ah Steve, I think we've got your first clue.

My 4.9 gets in the vicinity of 27 and up. I also believe the vast majority of your miles are driven in town. Check it on a trip to somewhere beside the local pub.

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Ron

Never, never do anything or wear things that you don't want to have to explain to Paramedics, it can get very embarrassing. They talk!

<- 24 w/ the 5spd

Stick or auto? I got 22 MPG with the 4 speed. 30MPG with the 6 speed on the highway, half that in town.

Jack

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If you can not run with the big dogs, stay on the porch!

I'm getting about 16-17 around town. I haven't taken it on a long trip yet, but I did spend one day with just freeway speed cruising and it was around 24.

The funny thing is the car smells rich, but there's no visible exhaust smoke, and after 2000 miles since the swap, the oil is still very clean. I'm not running a catalytic converter, which may account for the smell. The car is so quick stoplight to stoplight, I have a seriously hard time keeping my foot out of it.

With only 12 mpg, something is either amiss or you're having some serious fun with the car. Like the others said, first thing to check is for a vacuum leak. Next is for a dead O2 sensor.

Its an automatic. Funny you mentioned the rich smell. Mine also has no converter but I too smell fuel like a rich running condition, no smoke no drips from the pipes. most likely unburned exhaust contributing to global warming, death of a penguine somewhere and ice cap failure. I will check on the other suggestions. Incidentally I killed a few polar bears this morning ont he way to work..

I got 24-26 up and down the coast of oregon. Some city some highway. But oh, what a fun drive.

quote Originally posted by VFR182: I recently got my 85 conversion back. having never put over 50 miles on it but now driving 50 miles per week or so I am curious. It seems that it gets horrible gas mileage, runs like a top, sounds great, goes like stink but I feel like i need a fuel truck to follow me around. Ill bet its since I race it around but anyone can comment?

Two things right off the bat:

1) if you dont have a catalytic converter, you NEED to install an extra relay and run heated O2 sensors, otherwise your car will just not run efficiently and you will get horrible gas mileage. sure the o2 sensors will check out to the computer and give a reading, but they wont heat up enough to give the PROPER readings.

2) make sure the power steering inputon the ECM is recieving a straight +12 volts from an ignition source, otherwise you will load up rich all the time because it will think that the power steering is cramping and it will enrich the fuel mixture. ive seen this drop people's economy with the 4.9L as much as 8-10 mpg, no joke...

[This message has been edited by aaronrus (edited 10-20-2007).]

quote Originally posted by RONT4.9: I got 24-26 up and down the coast of oregon. Some city some highway. But oh, what a fun drive.

That is a nice drive. Also up Mt Hood and into the gorge. Lots of nice roads with lots if curves.

I get around 15-18mpg around town. Not sure what I get on the highway, havent been on any long trips with it yet. I'm sure my mileage would be better if my right foot was lighter.

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88 Coupe: Modded 4.9L V8 5 speed
87 Coupe: 4 Cyl 5 Speed
84 Coupe: 4 Cyl 4 speed
01 BMW 525i
www.geocities.com/fast88fiero

Any time gas milage is poor and the car runs great check out the ground connections,this is for coolant temperature sensor,especially if car has 2 wire sensor,the ground wire may run to ecm..if 1 wire cts ground to block you are O.K. it is possible for tape to prevent good ground if you use to much but this is rare occurrence. some time in swap there is not proper engine to frame ground

quote Originally posted by aaronrus: Two things right off the bat: 1) if you dont have a catalytic converter, you NEED to install an extra relay and run heated O2 sensors, otherwise your car will just not run efficiently and you will get horrible gas mileage. sure the o2 sensors will check out to the computer and give a reading, but they wont heat up enough to give the PROPER readings. 2) make sure the power steering inputon the ECM is recieving a straight +12 volts from an ignition source, otherwise you will load up rich all the time because it will think that the power steering is cramping and it will enrich the fuel mixture. ive seen this drop people's economy with the 4.9L as much as 8-10 mpg, no joke...

Hmmmm....interesting. The heated O2 sensor sounds like a good idea. I didn't realize the lack of a cat would have that effect. I'll give it a shot when I get a chance and report back with the results. I'm using an Injection Technology harness.....that should supply the needed 12 volts to the ECM for the power steering input, correct? I was under the impression that without that input, the ECM would disable fuel trim completely and the car wouldn't run at all.