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I have a 2000 Ranger 4x4 4.0L and it started running very rough. My local shop replaced the plugs, plug wires, and ignition coils and it would fine for a while. I tested it beforehand with my OBD2 reader and it definitely has a vacuum leak.
Few months later it's back and I told the shop to look for a vacuum leak. Low and behold they found one in the lower intake manifold gasket. I replaced it all myself and when I turned it on it's running above 2000 RPMs and if I leave it on it creeps up to 3k.
I figured I did it wrong so I just gave up and brought it to a different shop. They call me 2 days later saying they replaced the gaskets again and it still has the issue. They cant figure it out. Awesome.
There is no CEL and no codes. I go it back and unplugged the IAC with no change. Did the same with the MAF and idle went down for about a minute then right back up.
Could his be a bad IAC or PCV? Bad MAF? I thought unplugging the IAC and MAF would've ruled them out as problems. Could the throttle body not be closing all the way? I'm at a loss and need some guidance. I'm pretty sure the issue is mechanical and not electrical but I'm a well known idiot and am often wrong.