Previous owner botched 4.0 Swap, help me save it!

[neggen32]

So this is kind of a long story but basically I bought a 1987 Ranger a little over a month ago that the previous owner did a 1991 4.0 swap on. I had been without a reliable vehicle for over a year due to my terrible luck with vehicles breaking down and was stoked because I finally thought I got a reliable one (haha). It ran amazingly at first until three weeks ago when it died all of a sudden on the freeway, and I had to get it towed home. It had spark, compression, fuel pressure, and would crank, it just wouldn't start. After checking everything I could think of and giving up, I let my mechanic friend look at it. He figured out the injectors weren't opening, but couldn't figure out why and he also gave up. I finally took it to a supposedly really good shop, they spent a week and a half checking everything, and got so frustrated with it that they almost actually gave it back to me. They said their only guess was that it needed a new computer, which I bought, and that didn't work. Then they finally figured out that the "PIP signal to ECU is grounded with the key off."

They ran a wire outside of this harness to bypass this problem, and finally got the truck to start. But it sounds terrible, dies when it gets any gas, and is un-drivable. The problem is, the previous owner used everything from the 1991 except the wiring harness that goes from the engine to the computer and the ignition control module and all that. For some reason this is still the 1987 harness with a mess of splicing and mismatched wires. Because of this, the 1991 computer is having a hard time reading incoming info from sensors, and it's impossible to pull codes from. It doesn't even have a mass airflow sensor on it and it's basically just running in the failsafe mode.

Anyways, sorry for the novel but does anyone out there have any advice on what to do next? The mechanics said that if I can source a 1991 4.0 engine to computer harness, an MAF sensor, and the intake that can accept the sensor, it will officially run like a complete 91 4.0. I'm pretty lost on what years/models are compatible with this, so I figured you guys might have an idea or where the heck to find them. Thank you so much!

 

[bobbywalter]

not a novel.


where are you located?



the reason for the splicing is the generational change of the wiring. the early style is totally different in concerns to the interface connectors.



your best solution is a donor harness and pcm to your needs wired stand alone.



this is a robust system, but the variance of the wiring year over year and some times even mid year, post 92 is astounding in my experience.

so pick a complete donor for the wiring from one single unit.

over lay it and be done.

 

[neggen32]

Hey Bobby, thanks for the reply!

After reading your response, I went to the local pull apart and checked out a bunch of potential donors for the intake w/ MAF port and the harness. A lot of them were either missing the parts, automatic, or had the 2.9L engine. I was finally able to find the intake off a 1991 Ranger with 4.0, and the harness off a 1991 Explorer. It's the same year as my engine, it was 4x4, with 5 speed, and it was the 4.0L so I'm really hoping it has the same harness and will work with the 91 Ranger computer and all the plugs! It was a pain in the ass to get out but I was able to unplug everything and pull it out whole without cutting.

I also read your response to my other post, unfortunately I'm in Seattle Washington! I appreciate the offer though, wish I lived closer, I could use the help. I'll let you know how it all goes. Thanks again.