Gas mileage report [4.9L / manual OD]

[Gary Lewis]

Yes, 94 was the last year of the IDI. In fact 1994 is a horrible, confusing year for diesels. Ford offered 3 different 7.3L options at once. The 7.3 IDI (naturally aspirated), 7.3 IDIT (factory turbo) and the 7.3 DI Powerstroke. Sheesh.

You have a nice list except I would comment that Big Blue and a diesel F250/F350 would be a little redundant as far as purpose. Maybe a diesel swapped Bronco?

Wow, that is confusing. So if you say "I have a '94 Ford diesel" there will be lots of questions following.

As for my list, yes a Bronco would be a good addition. Perhaps replacing the F350, as you suggested.

[vjsimone]

Same bore and stroke, but 33% more cylinders. And the one with 1/3 more cylinders spun about 1/3 more revs per mile. Hmmmm, I'm getting a faint, fuzzy picture here.

Wonder how much oil he used?

Since ye mention it, I have a theory on Idle Screws; the very end of those screws seems to be mostly a rough cut. As noticed, turn the screw a little, not much difference in the idle rpm. Another time turn the screw barely and a big difference in the idle change. For the most part, the angle of the screw in relation to the idle screw stop are not aligned. Not an ideal match do those two metals make.

So, a lower rpm may have nothing to do with the previous Idle Mixture Adjustment, maybe the metals have burnished a small amount from the taping and the vibration, actually closing the throttle slightly, lowering the idle rpm. The solution may be to bump up the idle to the correct rpm.

An improvement to this is when the screw is accessible, remove it, grind or file the tip of the screw to resemble my future bald head. The smother the surface area, the less erratic the adjustment will be.

In Chris’s case, there was some talk of readjusting F/A mix to his altitude, so maybe a combination of the two going on here...

 

[Gary Lewis]

Since ye mention it, I have a theory on Idle Screws; the very end of those screws seems to be mostly a rough cut. As noticed, turn the screw a little, not much difference in the idle rpm. Another time turn the screw barely and a big difference in the idle change. For the most part, the angle of the screw in relation to the idle screw stop are not aligned. Not an ideal match do those two metals make.

So, a lower rpm may have nothing to do with the previous Idle Mixture Adjustment, maybe the metals have burnished a small amount from the taping and the vibration, actually closing the throttle slightly, lowering the idle rpm. The solution may be to bump up the idle to the correct rpm.

An improvement to this is when the screw is accessible, remove it, grind or file the tip of the screw to resemble my future bald head. The smother the surface area, the less erratic the adjustment will be.

In Chris’s case, there was some talk of readjusting F/A mix to his altitude, so maybe a combination of the two going on here...

Interesting observation, and one of which I'd not thought. Yes, maybe Chris' throttle stop screw had a rough spot on the end and it was burnished or otherwise smoothed by hitting the stop. Might easily do it.

And, he was supposed to adjust the idle mix when he got to elevation. A 5000' change can certainly impact the idle mix.

[ctubutis]

Interesting observation, and one of which I'd not thought. Yes, maybe Chris' throttle stop screw had a rough spot on the end and it was burnished or otherwise smoothed by hitting the stop. Might easily do it.

And, he was supposed to adjust the idle mix when he got to elevation. A 5000' change can certainly impact the idle mix.

Which I did, after retarding the timing to ~7 BTDC. It seems to run OK and I haven't gotten it to ping during a short test drive but more driving will tell more.

I also replaced the glass fuel filter with a larger, plastic one, we'll see how that affects the fuel delivery problem.

[Gary Lewis]

Which I did, after retarding the timing to ~7 BTDC. It seems to run OK and I haven't gotten it to ping during a short test drive but more driving will tell more.

I also replaced the glass fuel filter with a larger, plastic one, we'll see how that affects the fuel delivery problem.

I hope it doesn't ping. The altitude will help, as will the timing change.

How's it idling? And still shutting off correctly?

[ctubutis]

I hope it doesn't ping. The altitude will help, as will the timing change.

How's it idling? And still shutting off correctly?

Yes, the idling & shutting off are real good!

The one thing I noticed ONCE - directly after having adjusted things - is a hard warm restart; I like it when I can just turn the key and have it start up pretty instantly, but it didn't want to do that after initial readjustment. But that symptom went away after a ~2 mile drive, so I'll monitor it and see what happens.

I never made painted timing marks on the balancer that delineate 0-10, all I have is painted lines at 0 & 10. So, my best guess is it's at somewhere around 7 but I really don't know for certain.

Vacuum is at ~14 at idle speed, it goes up to 17 with a bit of throttle.

[1986F150Six]

Yes, the idling & shutting off are real good!

The one thing I noticed ONCE - directly after having adjusted things - is a hard warm restart; I like it when I can just turn the key and have it start up pretty instantly, but it didn't want to do that after initial readjustment. But that symptom went away after a ~2 mile drive, so I'll monitor it and see what happens.

I never made painted timing marks on the balancer that delineate 0-10, all I have is painted lines at 0 & 10. So, my best guess is it's at somewhere around 7 but I really don't know for certain.

Vacuum is at ~14 at idle speed, it goes up to 17 with a bit of throttle.

At this point, I would try advancing the static timing slightly. If still no ping, try a little more. Once pinging is noted, retard just slightly.

[Gary Lewis]

At this point, I would try advancing the static timing slightly. If still no ping, try a little more. Once pinging is noted, retard just slightly.

Idle vacuum is said to reduce about 1" for every 1000' of elevation. We were at about 700' here when we adjusted things, and you are about 5,830 in Centennial. So we should be able to add 5 to your vacuum reading giving us 19", and that is a good reading for an engine with a moderate cam.

And David is right - you may be able to run just a bit more advance, but that'll require painting more lines so you can tell more precisely where you are. My approach would be to just loosen the clamp bolt slightly, and then use a wooden or rubber mallet on the vacuum advance to move the distributor. But remember that the vacuum advance is held in by two little screws, so go easy on the tapping.