'85 4.9 WITH ALL emissions equip vac routing RESOLVED (mostly)

Everything hand tightened only with a star driver, wrenches, etc...

Gary, I would be delighted to leave the alternator as is for now.

It still has a noticeable, quite irregular stumble at speed although it idles MUCH better and is up to 12.5mpg (I have a heavy steel shell on, but I was only getting 10 before).  The dieseling is much better as well.  Computer, maybe? I am willing to replace it but I am nervous about remanufactured parts (RockAuto does have one for my truck, Cardone reman)   Or open mine up and see if it could be rebuilt...?

I am honestly pretty unsure as to the 3 different screws and how best to set them.  I adjusted the fast idle so that it was touching the top step on the step plate, and that seemed to allow the choke plate to close all the way when I depressed the gas pedal.  Mixture screw only changed the vac a little bit...I turned it counterclockwise until it sounded a bit better, then backed it down just until it slowed a bit, and then a tiny bit out again.

The curb idle (which I am not supposed to mess with??--driver's side, closest to front of vehicle) was way far away from the carb body.  Bringing it in to where it was touching the carb body deepened the vacuum significantly.  

I have to go back and re-read all the carb tuning stuff after my head empties out a bit

My relatively new spark plugs are probably fouled though after having the vacuum leak at the manifold so I will change those as well.  I was running Autolite coppers but maybe I should try the Motorcraft?  Currently gapped at .044, I might try .042 and see if that helps mpg.   I could splurge and upgrade the wires too, I suppose.  

I've actually come a long ways on this truck in a year, considering how little knowledge I started with and how much more I will never, ever, know.  

it sounds like the results are getting good. the only reason to adjust the curb idle screw is to set the engine run speed at idle and that does not change the tune.
 setting the fast idle cam screw only changes idle speed while the choke is in use and not yet pulled off. and does not change the tune.
 the idle air mixture screw at the base actually tunes the amount of emulsified fuel allowed to be drawn into the air stream of air getting by the "closed" throttle plate.
the only tuning you have done so far is "idle tuning"
the carb rebuilder did the range of operation tuning.
 the repairs to vacuum leaks are range of operation tuning.
 and plugs, wires, cap, rotor and timing properly set are all range of operation tuning also.
the mpg sounds very normal as much as i hate to say it. these rarely get better but I'm usually at fault in my case. i have been able to get 17-19mpg from my v10 excursion a few times by really minding my business and i just know these 300/6 have better available and I intend to build one for that.

Learned a few things from this thread thanks fellas

TheGeneral wrote

Everything hand tightened only with a star driver, wrenches, etc...

Gary, I would be delighted to leave the alternator as is for now.

It still has a noticeable, quite irregular stumble at speed although it idles MUCH better and is up to 12.5mpg (I have a heavy steel shell on, but I was only getting 10 before).  The dieseling is much better as well.  Computer, maybe? I am willing to replace it but I am nervous about remanufactured parts (RockAuto does have one for my truck, Cardone reman)   Or open mine up and see if it could be rebuilt...?

Late to the party... but I do have a 1984/1985 Ford Reman'd ECU for a Manual 4.9 in my drawer of spare ECUs. Bought for my truck off eBay (still in the Ford Service box!), ran it for several months (no more than a year) but swapped for an AOD one I found at a salvage yard last fall (my original one had a burned out O2 analog input, not repairable). Other than some idle speed differences, they behaved the same; I'm 99.5% sure it's a good unit. If you want it, let me know... Edit- It's not quite the right one for your application, but was used on some similar applications (Cali manual 4x4's in 1984, for example). Yours is probably an E4FZ-12A650-ACB (what's called out on parts list 392), this one is an E4FZ-12A650-NB.


A1 Cardone reman ECUs suck. All they do is rattle can them silver. I tried one but all it did was exhibit a different set of problems than my original (which I proved were ECU faults). At least they gave me a refund!

Hey there, just saw your post.  Well now I have a different can of worms, starting to get too hot and almost overheat...  

anyhow, The main issue with lining up an ECU that's almost but not quite identical would be all the smog stuff and how all of  it interacts with the ECU.  I am willing to give it a try though!  How much do you want for it--and do you need a tailgate haha, I have one.  Also a side rail kit.

don't let it overheat! "when" it gets warm is a strong clue to why. pay close attention to conditions and driving style along with temp. full of coolant of course and half of the reservoir too