New to the site. I have some questions. I own a 91 F150 with 420,000 miles on it. Yes that is the accurate mileage. The truck is in overall good shape. A 96 5.0 has been installed last year that had 68,000 miles on it. Its tight, it does not use any oil and runs smooth. It has the AOD trans in it that was installed with the motor, mileage unknown. I picked it up this past weekend and drove it home. 400 miles at 9 miles to the gallon, dang that was expensive. I plan on doing a full tune up, plugs, oil, air filter, check timing... It has alot of new parts on it, distributor, starter, alternator, wires, hoses... pretty much the whole nine yards. My question is what else do I need to check on the truck, as far as motor wise. Looking for better gas mileage. I also plan on changing the cat converter, cause it has been cut up, along with a cat back exhaust system. I also noticed that the 96 motor has oxygen sensors at both headers and the y pipe. Only one of these is hooked up, the y pipe sensor. Could this screw up the ECU as far as fuel mixture? It does not smell of gas when it is running. It did sit for close to 6 months before I got it. Also the trans shifts kinda hard, low speed is the worst, and it has a shudder around 35 to 40mph sometimes. It also seems to be hunting for gears, it kicks out of overdrive very easily going up just a slight grade. What do I need to look at? I plan adjusting the linkage and changing the fluid in it.Just looking for some help in any other area's that I might look at. I would like to get this running really good cause its my commuter for the winter, and my dirtbike hauler for my son and I. Any help would be great. Thanks.

 

The '91 and the '96 are two very different animals. The '91 is OBD I, is Speed Density, and is fairly simple to dial-in. The '96 is OBD II, has Mass Air, and has much finer ECM controlled fuel trim adjustments. It's really going to depend on exactly how much of the '96 you installed. You mentioned the engine, tranny and exhaust, did you also install the ECM from the '96? What about the air intake tube (with the Mass Air unit)? If you left either one of those behind, you're gonna have some trouble. The O2 sensors are critical as far as having an efficiently running engine is concerned, but if you don't have the correct ECM installed, it's gonna be bad anyway.

Try and be as specific as you can, and tell us everything that was included in the swap.

 

I will check with the PO this weekend to find out the details of how much was swapped over with the motor. Thanks for the info. I will post what I find out.

 

I looked over the truck this weekend while I was tuning it up and installing the new exhuast system.

It looks like the 91 ECU is being used in the truck. There is no Mass Air sensor in the intake tubes from the filter box. There is only wiring for one Oxy sensor that I can find, its located in the y pipe. I installed a new one with the exhuast. I looked for the connector for the driver side header sensor and could not find one. Where out of the wiring harness does this connector come out at?

What I found during the tune up was crazy, it's a wonder the truck ran at all. The air filter was covered in burnt oil from the oil breather tube. I doubt very little air was making it through. I think the burnt oil was from the original motor when it blew up. I also found the oil vent tube busted at the fitting, so that will be replaced soon. The plugs looked blackened and wet from fuel, so it was running rich. I did not get the timing finished. Does anybody know the firing order for a 96 302? The info I have is very non specific. Also the suggested timing?

Changed out the converter. Dang it was hacked up. When I installed the new one I did not hook the smog gear back up. I need to make up an adapter to stretch the tube down to the new location. The check engine light is on now, so I suppose its from that. Going to fix that as well in the near future. The Eddelbrock RPM exhaust went on like a champ. I would suggest this exhaust system to any one wanting to put a new system on their truck. A little pricey but the fit and quality are top notch. It also sounds great, very mellow tone.

After all this was done took it out for a test drive and boy what a diference. Still not as much snap as I want but its getting better. I am going to check the mileage this week to see if its any better. It has to be considering what I found.

One question about the tranny. It seems very soft, alot of slip in it. I was screwing around and tried to power brake it, it just slipped in the tranny. The truck would not spin the wheels. Is this normal? I don't know if I have a posi in the rear end or not, would that make a difference? Any input on this would be great. It seems the motor is running fairly good, its just loosing some power in the tranny. Any way to fix that short of a rebuild? I am not looking for a drag truck, just some more gid up and go than it has right now.

Sorry for the long post but got alot of work done this weekend. Thanks for your input.

Kilroy1

 

You do not need or want the downstream O2 sensor on a 91. It will not properly control the fuel air ratio. You need to be connected to the sensor closest to the engine, which is either in one of your exhaust manifolds or in the y-pipe immediately below them

 

It sounds like they just swapped in the engine itself, which is good. As mentioned, you only need to use the O2 sensor closest to the engine. Plug the other holes. You do need to finish the pipe to the convertor, as it relies on it to get it up to temp, and prevent it from premature clogging.
Firing order is 1-5-4-2-6-3-7-8.
I agree with your choice of exhaust.
As far as your rear end goes, there should be a decal on the inner door jamb (drivers side) that lists a code for it. Post the code, and we'll tell you what the rear end originally was.

Can't help you much with the tranny. Sorry.

 

Just posting an update. Did some more service to the truck this past weekend. Changed the oil, checked the timing, and a few other things. Found that the timing was over 10 deg's out, it was set at about 20 deg's BTDC. I adjusted it to 10 deg's BTDC as suggested some where else in this board. I also flushed and changed the oil init. The oil looked like tar pouring out of the drain plug. Had a real bad burnt smell too. Took it out for a drive after the work, man this is what I am talking about. I pulled out of my drive way and accelerated up the hill as usual. Bout smoked the tires off of the thing. All my neighbors came out to see what was going on. This is the way a 302 should feel. I have not checked the mileage yet this week but it shoud be better. I barely have to give it any throttle at all to run 55-65mph on the way into work. The tranny is shifting better as well. Not hunting for gears nearly as bad. It shifts a little hard every once in a while but I can live with that. I still have what sounds like a spark plug wire ticking. I noticed when I put plugs in that not all of the connectors looked that good, its also missing just a little. I think thats the cause. Going to get new wires this weekend to see if it helps. Thanks for the info from everybody. Now I need to work on those door locks so I can put a radio back in it... and interior could use a little TLC too....mmm I guess this is going to a work in progress for a while. My wife won't like the sound of that. I hope everybody has a good holiday.

Kilroy1

 

That is some good mileage on that old classic truck and should have many more miles left in it I hope my 05 will have that many miles on it someday.