I picked up a nice 4cyl ranger for $300. The only issue is it has a very rough idle and won’t rev right sometimes. The previous owner said a mechanic though it was a stuck intake manifold runner valve, even though I can’t get it to throw a code.

I tried replacing the IAC and cleaning the MAF, no change. Looked for vacuum leaks. When the IAC is unplugged when the engine is warm it dies right away, suggesting no vacuum leak.

Could the IMRC valve be the issue without throwing a code? Any way to test this?

TIA

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2003 Ford Ranger Extended Cab w/ Value Package
4.0 SOHC, 4x4, Stick Shift, 146xxx mi, Some Mods...

Build Thread >>> http://www.fordrangerforum.com/proje...ml#post2172639

Valves & sensors usually throw codes but not always. If no codes though you should try simpler cheaper options first though.

Change the fuel filter. Get some gasoline treatment, injector cleaner maybe too. Buy the better stuff, it works better. Check your fuel pressure. Clean the throttle body & intake. Check the air filter & make sure the intake tube has a good seal. If you're still having issues maybe do the intake gasket set, it's a cheap fix & a relatively easy job on the 2.3. While you're there clean the injectors & replace the o-rings. Might as well do the valve covers too.

It probably wouldn't hurt to replace the imrc as well, they're fairly inexpensive. If you're still having issues after that consider the maf, it should trip a code but possibly isn't. Also consider plugs & wires.

If you got it that cheap chances are you'll need to put some wrench time in to get it running decent. But if there's no codes chances are it's all routine maintenance stuff that's fairly cheap & on the 2.3 mostly easy to do.

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Thanks for the ideas. I started tearing off the intake manifold today and found that one of the plugs at the end of the manifold runner butterfly valves had fallen off, causing a huge vacuum leak. Put it back in and it runs great. I am going to be installing a threaded brass plug instead for a more permanent fix.

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2003 Ford Ranger Extended Cab w/ Value Package
4.0 SOHC, 4x4, Stick Shift, 146xxx mi, Some Mods...

Build Thread >>> http://www.fordrangerforum.com/proje...ml#post2172639

Vacuum leaks will definitely cause issues. I'm surprised you didn't have an engine light. But yea, lots of times things like that are an easy fix.

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This is actually a well documented issue, and there are a few write ups surrounding this problem.

If you hadn't seen it, I was going to suggest it.

FWIW, the IMRC essentially does nothing, so, even when functioning, you won't notice a difference (I never did, in either working/failed states)

A lot of people pull the runner rod and drop out the butterflies, but thats up to you.

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2001.5 2.3 213xxx and counting
M501-HD L154 Manual
Don't bother looking for 1st gear synchros, I bought the last one