This is probably going to be a bit of a long post so I apologize but I want to give all the information I can to see if there's any reasonable solution to this. But I'll try to keep it as concise as possible.

The truck we're dealing with here is a 1999 Ford ranger XLT 3.0 💪 (flex fuel) automatic 4x4. If it matters it's an extended cab with a step side. Straight out of a 1997 episode of Baywatch.
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I bought the truck and as I was driving it back to my house the cam synchronizer I've decided to go the way of our federal government and stop working.

So in turn the oil pump didn't want to do its thing anymore and the whole engine ran drier than a nursing home gynecologist office.

I decided the best thing to do is to find a good source to used Ford ranger engine so I hopped online and checked out pricing, s*** myself, and then turned off my computer.

After I took a shower, I decided I would go the way of buying a Ford Taurus engine and throwing on all the conversion parts that are required.

Everything went swimmingly. I found a 60,000 mi motor. And because I overdo everything I put new rings, pistons, bearings, pushrods, lifters, valve job, new valves, had the block checked, everything looked good so we just honed it out and rock and roll.

So I throw that bad boy in, dump some dinosaur juice in there, fire it up and sure as s*** she runs good. While I was at it I replaced the power steering pump. I also did the plugs, wires.

I'm sure it has nothing to do with what's going on obviously, But I also replaced a butterload of suspension stuff.

So anyway, now that you've read the preface to war and Peace let me get to what's actually going on.

I got this stumbling idle b*******!!!!!!!

You can feel it in the cab, it's definitely missing or kicking over something.

It's only at idle, and it doesn't happen all the time. It really likes to do it when I rev up the motor to like 2500 3000 RPM and then bring it back down.

Oddly enough, it smooths out pretty well when the air conditioner is on or if it's in gear.

Might still have a couple of hiccups here and there.

So here's what I've looked at already you vultures!

Compression. Within 1 to 2 lb of 155 on all the cylinders.

I cleaned up the idle air control valve and it seems to be functioning because when it's disconnected the RPMs do drop.

I also cleaned the mass air flow sensor. With proper cleaner if you can believe it. I thought about just tossing it in the dishwasher, But there wasn't room with all my Tupperware.

I bought a smoke machine and did a smoke test to see about vacuum leaks.. after I got high af on baby oil vape, I could clearly see no vacuum leaks at all.

This was kind of backed up by the scanner that gave me live data. Because my fuel trims are all right in line. Nothing above 5% either direction on both banks.

So........

I checked out the coil pack just to make sure. Got a nice strong purple jumper coming to all the unplugged lines sometimes getting as far as an inch and a half away.

Seems strong. No orange lines..

I didn't switch out the fuel injectors. I cleaned them up and put on new seals and pintle caps. They were looking pretty darn good and they worked well on the old motor.

Also my fuel trims don't seem to be suggesting a clogged injector or one that is blowing its juice like a virgin on prom night.

So my build seems to be strong. I've done a couple. Screwed up more than a few. So I wasn't outside of thinking it was me.

But the numbers don't seem to be pointing to that.

I really don't know what the next step is.

Help me.



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Engine cold or up to operating temperature ?

How old are the O2 sensors?

 

Honestly both. It doesn't seem to really matter. But I would say maybe it gets a little bit worse after it's warm.

The O2 sensors were replaced when I did my rebuild.

Voltages are coming back good on them.