2001 4.2L for 1997 4.2L Swap Problems - Ford Truck Enthusiasts Forums


2001 4.2L for 1997 4.2L Swap Problems

Old 03-04-2004, 04:11 PM
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2001 4.2L for 1997 4.2L Swap Problems

Well, I have a 1997 F150 with a 4.2L V6 with a 5-speed manual, and it recently bombed at 80k because of the gasket problem. I paid over $10,000 for this truck in mid-2001 when it only had 35,000 miles on it, and I have loved it until the engine went in it about a month ago. I decided because of the money I had invested in this truck, the best decision was just to replace the engine.

I was able to obtain a complete brand new generation 2001 model 4.2L engine with wiring harness, and I installed it into my 1997 F150 this weekend. The swap went very smoothly, the motor mounts bolted up exactly along with the transmission input shaft and bellhousing. The wiring harness even mated to my PCM perfectly, and all of my serpentine belt components bolted on to the new engine just fine.

Note: The 2001-04 "new generation" 4.2L is quite different than the 1997-00 "old generation" 4.2L. The intakes are the most noticable difference. But there are also electrical differences, the vacuum ports are totally different, and the throttle cables are different.

When the swap was complete, I encountered my first major problem... The vehicle will turn over, but it will not start-up. I suspect that this may be due in part to one small electrical connection coming off the main wiring harness that did not mate up. This is the ONLY other electrical connection that mates directly to the PCM other than the main big square headed wiring harness. The connection is located right behind where the main engine wiring harness plugs into the PCU. The one on my 1997 F150 is round and 4 male pins inside it with 4 wires going to it, but this connection on my new 2001 engine wiring harness is square and has 5 active female terminals with 5 wires coming out of it.

I have examined the wires in these harnesses very carefully and 3 of the wires on each harness have an identical color scheme. The 1 different colored wire on my 1997 terminal is gray/blue stripe, and the other 2 wires on my 2001 terminal is all gray and gray with a yellow strip.

I have checked with the local Ford dealer's parts department and they have no clue what these wiring harness operates and they do not have an adapter to mates these two harnesses together. I suspect that the engine is either not getting fuel or the spark plugs are not firing. Either way, both problems are electrical.

Does anyone know what this part of the wiring harness operates on the engine and if it must be plugged up in order to start-up?
Old 03-04-2004, 04:23 PM
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A friend of mine has a Ford Escort GT and had ordered a Jap spec turbo engine from japan. When the engine arrived we swapped the motors. The mechanical swap was simple, but the wiring was a mess. First off, the jap spec motor was from an all wheel drive car and a turbo motor. Well, we have the turbo, but no all wheel drive. So the computer could not sense the all wheel drive and all the wire colors were different.

He called a jap dealer and had them mail the schematics for the wiring harness. this told him exactly where every wire went and what it was for. I know nothing about electronics, but by using the schematics, he was able to resolve the problem and the car kicks butt big time.

Perhaps you can locate the schematics for this computer?
Old 03-04-2004, 05:56 PM
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Am I missing something here? Why cant you use the 2001 engine and just bolt your 97 intake and accessories onto it? Or,are you trying to use the 2001 componants on your 97?
Old 03-04-2004, 06:53 PM
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I could swap the intakes, but mine is very dirty with grime inside (common with gasket failures) and much more cumbersome and I would like to use the new intake that came with my new engine. I already have a K&N Cold Ari Intake on it and plan on putting a true dual exhaust system on it once I get the engine running. Besides, it will probably be more trouble to switch wiring harnesses and intakes on the two engines than it will be to solve this seemingly simple wiring problem. I need to find out what this smaller PCM to engine wiring harness operates and go from there. And to answer your question, I have not ruled out the possibility of swapping intakes and wiring harnesses, but it will only be before I have tried everything else and is my last resort to get the engine to run.
Old 03-09-2004, 06:18 PM
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why didn't you keep the 97 wire harness in place? I believe that their is in fact differences in the wiring patterns comparing the 2001 to the 97. I was trying to swap out my 97 PCM with a 2000 PCM and my engine just turns like yours. My next move would be to examine the 2 wire harnesses and follow each wire from each sensor to see what pin(s) on the PCM they connect to and make your comparisons. It may just be a matter of relocating a few wire connections.

I now have to get me a wireharness for the 2000 f-150 so I can do the same. ( I was just actually swapping the PCMs last week and realized that there is difference)
Getting the schematic is a great idea, and I do know how to read one, just dont know where to get one....

I would really like to see if anyone out there knows about PCMs and why we just can't "plug -n- play"..

97 F-150, MT 5-speed, 4.2L, 4x2 (I really wish I had a V8)
Old 04-07-2004, 12:19 AM
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do you still have the 97 pcm ?
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