Rough, fluctuating idle

[MSTWNTD]

My friend and I are fixing and building his 2001 Ranger 3.0. We have most of the issues resolved, but still, a few remain. The real bugger right now is a rough, fluctuating idle that surges when it is cold. I suspect a vacuum leak, but I have tested with propane and brake cleaner and have found nothing. My best guess is leaking intake manifold gaskets. I hooked up a vacuum tester and it read 15 in mg (kinda low) that slowly rose to 20 after idling for about a minute. Does anyone suspect the same? I am wide open to feedback. I am tired of guessing.

 

[rusty ol ranger]

Hows the idle air control valve look?

 

[MSTWNTD]

Hows the idle air control valve look?

We cleaned it with throttle body and air intake cleaner and replaced the gasket after making sure the mating surfaces were clean. The idle is higher when it's cold and it raises when the AC kicks on so it appears to be functioning properly. We also cleaned the throttle body. Forgot to mention a few other things that we did- spark plugs, wires, coil, and pcv valve. We didn't document anything so I may be forgetting some others. There are also no codes and no check engine light. I wish I had a way to read live data so I could look a the fuel trims.

 

[rusty ol ranger]

Im not a 3.0 guru but does it have an EGR valve? I know the later 2.9s didnt so im not sure about the 3.0.

Also have you tried pulling any codes?

 

[MSTWNTD]

Im not a 3.0 guru but does it have an EGR valve? I know the later 2.9s didnt so im not sure about the 3.0.

Also have you tried pulling any codes?

We cleaned the valve, replaced the gasket, and unplugged the vacuum line from it with no change that I could notice. Refer back to my previous comment about the codes. I edited it but it probably didn't update while you were typing yours. Sorry, I'm new to the forum.

 

[MSTWNTD]

We also replaced the air filter and cleaned the MAF sensor.

 

[rusty ol ranger]

I wouldnt *think* itd be an intake gasket. Just based on the fact the vaccuum comes up to normal. I dont think a bad gasket would do that.


The low vaccuum is prolly due to the bad/low idle. Other then that bud im outta ideas. Someone better with EFI stuff should be along

 

[MSTWNTD]

I wouldnt *think* itd be an intake gasket. Just based on the fact the vaccuum comes up to normal. I dont think a bad gasket would do that.


The low vaccuum is prolly due to the bad/low idle. Other then that bud im outta ideas. Someone better with EFI stuff should be along

Okay, thanks for your input!