2002 Ford Ranger Edge 3.0L with 66k original miles.

I have a rough idle immediately upon start up while cold or warm. I just bought the truck so I don't know what the gas mileage is suppose to look like yet. On the test drive there was no rough idle or anything unusual for a few days and then I noticed the rough idle. I give it gas or even while driving, the roughness seems to smooth out. No CEL or codes thrown except the one described below for the TPS that I fixed.

I replaced the cam synchronizer and cam sensor on day 1 of buying the truck simply for piece of mind and it did not improve or worsen the rough idle. While driving near my home, I got a CEL for P0122 for throttle position sensor circuit low input voltage so I bought another TPS at autozone and replaced it, but just as the cam synchronizer, it did not improve or worsen the idle. Since then I have replaced the fuel filter, plugs, plug wires, cleaned the IACV, and replaced the air filter. All with no effect on the rough idle.

I have searched high and low for a "visual" vacuum leak to no avail. I will buy a can of carb cleaner and try that route when I get home today.
Any help or suggesttions you guys could offer would be great!

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Of course by "visual" vacuum leak I mean broken or split hoses. None of which I could find. My coworker was telling me that since I have the 3.0 with the plastic manifold, it could be a gasket leak there too.

Is the PO122 code still present or was it cleared? Also did you try cold cranking to see how the engine sounds? Press the throttle all the way down and crank the engine, this will put it into clear flood mode mode and you can crank indefinitely. When doing this you wanna make sure you can hear every cylinder.

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Negative the code and check engine light both went away as soon as I started the truck after replacing the TPS.

I did not try cold cranking....What am I listening for exactly with the clear flood mode when you say "every cylinder"? is there a distinct sound im listening for?

Yeah. You're listening for a spot where you don't hear a noise. So you should hear every cylinder when it's under compression. Now if you if hear like pup pup pup pup pup ___ pup pup. Then you know it's a problem with compression.

The only reason I'm saying do this is because it's easy and I've seen a couple rangers with bad heads before, I don't think this is your problem. But it takes less 30 seconds.

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10-4 I will try this when I get home and will let you know the results.

And have you looked at the EGR yet or no?

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No EGR on my 3.0

Really? It has an EGR delete?

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For a rough idle, I would definitely check for vacuum leaks. That's the first thing I would do, and probably the least expensive too. Once you know there are none, you most likely will have fixed it.

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1996 Mazda B3000 V6, auto, 101,000 miles.

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