5.96 mpg....

[Efibroncoman]

This sounds bad... I wonder what I can do to improve it... My bronco has the factory 1975 302 with World Product heads, Lunati Voodoo cam, 1991 EFI with RJM harness, headers and 2 into 1 exhaust. I think my main problem is my compression ratio is around 8 or 8.5:1. Engine runs good and only has like 30k miles on it. Any ideas?

I think it's time to build a new motor....

[trash]

Re: 5.96 mpg....

I agree.I built my 393 with windsor sr heads 9.5-1cr zf 5.13s 37 km2s .last time I drove to loon lake I got 13.5mpg and I was loaded down and hauling ass.Well like 75 -80 it felt like I was haulin ass with 8 " lift and 37s.Still 13.5mpg Oh yeah I only had about 1000 miles on the motor

[bent70]

Re: 5.96 mpg....

Throw a turbo on it.....perfect compression.

Check you aic sensor i think. The one next to the front driver injector. I've read that if it doenst read corectly it will never go to closed loop and stay running ritch. What temp does the motor get to. You want around 180* to enter closed loop.
Hopefully this is the right direction on your issue.

[Efibroncoman]

Re: 5.96 mpg....

It runs all day at about 180. I have a little testing to do on some sensors. All of my sensors and injectors are basically junk yard parts. I did buy new O2 sensors but there's a few others that could be causing it to run rich. I know 4500+ lbs is a lot for a 302 to push down the road, but I would expect at least 9-10 mpg.

[Sillyneck]

Re: 5.96 mpg....

something is wrong. your airfuel is jacked. could be as stupid as your oxygen sensor. I'd get a dyno tune with computer work. My 5.0 in my jeep back in 2000 got about 8mpg and I had to carry 3 gerry cans for a long trip. Two oxygen sensors and maybe the tps? I don't remember but it was 19mpg on the next trip and 13 years later it still runs like a champ for the current owner.

My jeep now has a nasty 350 in it w/ commander 950 injection. Before I understood how to tune it I went on a trip w/ target airfuel of 10:1....entire rubicon trail took 30gals in and back out. Learned about it... found that adjustment in the program.. made it 14.7 target across the board and now you can BREATHE around it and it gets amazing economy.

[Viperwolf1]

Re: 5.96 mpg....

180 thermostat is making it run richer. ECM thinks it's always in warm up mode. Get a 195.

[Efibroncoman]

Re: 5.96 mpg....

I tested the TPS and AIS and both are showing ohm readings that they are supposed to. I used to have a 192 thermostat in it and it seemed to get too hot(over210). The excessive heat could have been because of a bad radiator. I now have a 180 degree thermostat, because I thought the temp to meet was 170. But after re-checking oldfuelinjection.com it looks like it is 185. Maybe I'll try putting a 192 back in and seeing how it runs then. My new radiator is much better than the old one... Hopefully it will run right and not too hot.

[bent70]

Re: 5.96 mpg....

I need to get an air/fuel gauge. My mustang has simaler problems and it would be nice to have when i inject the bronco.

[Spaceburger]

Re: 5.96 mpg....

what firing order is your cam? Is it the HO or is it the old 289/302 firing order?

[Efibroncoman]

Re: 5.96 mpg....

It's the H.O./351W firing order. I had to go with a flat tappet cam because it's a 75 block. But the cam has 112 degree lobe separation and leaves a little to be desired.... I'm not real happy with it.

[Broncrick]

Re: 5.96 mpg....

180 thermostat is making it run richer. ECM thinks it's always in warm up mode. Get a 195.

X2 , cured my prob

[welndmn]

Re: 5.96 mpg....

You sure you're reading the miles correctly, are you checking it over a GPS?
With as many mods as you have, your speedo is not true.

[slvregl]

Re: 5.96 mpg....

Yeah something is not right...My stock 91' 5.0 was getting 17mpg with 35's running 65-70 everywhere! And it was running a little rich..but the temp stayed at 202 F...I think maybe a combo of the Thermostat and O2 sensors??

[Efibroncoman]

Re: 5.96 mpg....

I have an Autometer electronic speedo that uses the VSS. No speedo cable, really easy to adjust, and you don't have to change the speedo gear...

[Sillyneck]

Re: 5.96 mpg....

X2 , cured my prob

X3...that was the other thing I couldn't remember. I think I had something stupid like 160 degree.