Hello, So as my luck would have it I have a weird ordeal. Let me rewind and give a bit of history on the rig. 2003 Ford Ranger 3.0L Vulcan V6 Flex fuel with around 120K on the clock. The engine was neglected and retired early. The last shop it went to said it needed an engine. It initially went in for a Check engine light staying on Cylinder 1 Misfire. So that said it has had an engine replacement. I installed new coil, plugs, wires, cam syncronizer and IAC all motorcraft parts. I broke the engine in and on the rigs first road test I am stuck again with the same check engine light cylinder 1 misfire. The engine ran a little rough on initial start up I got the cam syncronizer dialed in at 38* as the service literature says it smoothed out a little bit. The test drive went fair but the check engine light was really discerning. I dont know if that running rough is part of the relearn process or what. Now I made sure the plug wires were on the right coil tower and going to the right plugs. I am kinda lost with this one. Literally all that money spent on the engine and it runs the same as the old one did. Fuel system has been kept up new fuel, new filter and fuel dampener. I am curious as to what any thoughts on this might be...? Could it be the PCM...? That is the only variable left I think. Any insight from the Ford Ranger gurus would be greatly appreciated. Thank you for your time.

 

Welcome to the forum

Who installed the "new" engine?
And is it a "new" engine or a rebuild or a used one?

And didn't "they" put in new coil, plugs and injectors?

There is not really a way for a computer to disable 1 cylinder on an engine, could be bad injector wire back to computer

2004-2006 3.0ls did have valve seat issues, which could also effected 2003s, but I assume the heads were new

Compression test should be done FIRST
Then you can start guessing after that

 

^^^^^
I agree on the compression check first. This will give you a much better idea of what is happening inside and get you in the right (Hopefully) direction. Otherwise you're throwing good money on top of good money with no results!

 

Okay so had some time this afternoon before the overnight shift to run a compression test to check the engine. I have the pending fault for misfire cylinder #1. All plugs out, accelerator to the floorboard, coil pack disconnected cranked engine for 6 seconds I had an average compression of 145 psi dry...the cylinders are within 5 psi of each other. The highest was 147psi on one hole and the lowest was 143 psi on #1. With plugs back in double checking spark plug wires again the engine still runs rough. The scan tool is showing an increase in detected misfires. Just like it was before on the old engine. The engine running has a solid needle @ 18"/Hg at idle. No indications show any internal engine issues. I guess bring the smoke machine out and check the integrity of the intake...? Work up from the basics I guess...Again I am always welcoming insight from others. Thank you for your time.

 

Numbers are low but as long as they are equal, that's the only point of a compression test

3.0l Vulcan runs 9.3:1 compression ratio(CR), general rule of thumb on expected compression PSI on cold dry compression test is CR x 18 = expected psi
9.3 x 18 = 167psi
18 is from air pressure at sea level, 15psi, and 3psi from mechanical compression of that air

But as said, 140-150psi is just fine for any cylinder to ignite a gasoline air/fuel mix

So its a spark or fuel issue
If its a vacuum leak then it would have to be on #1 intake runner to just effect #1

Spark or fuel injector can be cylinder specific
On the coil pack reverse spark plug wires #1 and #5 they share a coil in the pack, but one is reverse spark

Not much you can check on fuel injector, should read 11-18 OHMs if you want to test it
Only other thing is to swap it with say #3 injector and see if P0301 goes away and P0303 comes up instead