Well I posted a question on the site a week or two ago about an engine swap and didn't get any results. So I went ahead with the swap and figured I would learn as I go and post post the results to help anyone else that I can. So it all started with my 1000 dollar Craigslist buy. Its an 87 4×4 short bed xlt with the 4.9. It didn't run so a buddy trailered it home for me.


My cheap craigslist buy.



Pretty ugly paint if you ask me
It only need a couple of things to make it drivable but the biggest problem was the missing vacuum line to the map sensor. So I got pretty lucky.but good enough is never good enough, it needed a new paint job.


Doing something about the ugly paint



New color
So after the paint and some more minor parts and interior pieces it was a reliable daily driver with good torque and decent mileage. But then a certain truck came up for sale that was special to me.


My truck I bought when I was 16. Sold it when I bought my house. Bought it back 3 years later.
I got it for just a couple hundred bucks. But what I really wanted was the 351w out of it. So I pulled the motor cleaned and put all new gaskets and some nice Ford blue engine paint.


Pulles the 351w out of my original truck. Cleaned it put new gaskets all around and paint.



Putting it in place of the 87 straight 6.
So thats where im at now. And the reason I put this in the engine swap section is because I had a lot of questions when I started the swap about compatability and whether or not it was even possibe. The only real problem I had it the dreaded wiring...Some time between 87 and 90 Ford changed the wiring harness quite a bit and integrated it in the truck a lot different. I ended up using the straight six wiring harness and splicing about half of the ecm wires to the correct locations. Wire connections for the most part are all the same types, but wire position within the connections are different. So hopefully this post will help someone out who wants to do this swap, I know every situation is different.

 

So I have an update, the new motor is in and everything is just about buttoned up all sensors test OK as far as I can tell. It starts and runs ok, but has a slight miss and a noticeable buck under any throttle. It was timed with a light to 12 btdc.new sparkplugs new cap and rotor. Good fuel pressure at idle or running.Does anyone have any ideas? It also start to hunt at idle between 800 and 1000rpm. Can someone please give some ideas?

 

Any codes? Are you using the 351 computer? Have you checked fuel pressure?

 

Yes im using the 351 computer. Can't get any codes from the thing. The check engine light does work koeo but goes out when started. The 351 computer is from an automatic truck. Fuel pressure was around 40 and jumped a few pounds when revved. It bled down fast when turned off but that could be my guage. I pulled a spark plug and it looks white and chalky like its running hot and lean. Also when I was checking and testing the wires and sensors I was getting 8.5 volts from the black and white wire from pin 46 of the computer. Thats the only thing so far that I've found that really seems wrong. That should be the common ground tps, ect, iat and evp. If someone electronically savvy could explain that?

 

Ok so heres another update. I took the truck out this morning and so far everything is good it ran perfect other than slightly retarded timing. It took 2 days of testing and a whole lot of cussing and racking my brain, but there were a few problems, i had pin 46 and pin 45 of the ecm harness backwards one is dark blue and the other is black, #1 spark plug was all but smashed shut, the ecm harness had some loose connections and when i did a shake test on the plug the truck revved and shut off.That was probably the biggest problem. So hopefully this will give someone else some things to check when their truck is missing and bucking.

 

Good work.. nice to hear you were successful. I was gonna say it sounded like you probably still had some wiring issues based on your previous reply. Can you pull codes now? It should give you the all clear code 11 if nothing else. And you may want to have another look at the fuel pressure bleed off.. just to make sure it's not bleeding into the motor through leaky injectors because that will cause running issues too. Check to see if the oil smells like gas and that that the crank case isn't filling up, if it isn't then the bleed off could be via the tank selector valve which isn't good but it's not as bad as leaky injectors.

 

Thank you Conanski. I was so excited it was running good I never even thought about checking codes. I'll do that and check the oil again tomorrow.