Idle issues and running slightly rough

[SHObogdan1]

Hi everyone, I recently opened a thread about a coolant leak in the throttle body area. I took the intake manifold off my 93 ATX to get a better look at all the coolant and heater hoses. I tightened them all up and put the intake and everything else back together. The leaks are all taken care of but now it seems to idle a bit rough. It seems to gallop between 500-900rpm after start up. It does the same thing when the engine is warmed up to operating temperature but only at idle. The short runners do open up as usual when stepping on it and it doesn't seem to lack any power and there is no hesitation. So I know this sounds like the typical "vacuum leak" problem but I'm not exactly sure. I have no check engine light on so when I run the diagnostic everything turns out fine. I suspected maybe the MAF sensor so I pulled that out and it seemed to gain revs but didn't really change the issue. I pulled the IAC valve off and tested it by turning the ignition on while plugged in and it does stick a little. I don't think it's from the intake manifold itself, I cleaned both mating surfaces really well and I used new gaskets, and some loctite gasket sealant to make sure everything there is sealed and tightened the intake bolts really well. Other than that the EGR valve, DPFE and O2 sensors are new as well as the spark plugs and wires so I don't think those failed on me yet. Anyone else have this problem from the IAC valve or MAF sensor? Like I said, no CEL appears so I can't really tell the issue from there.

 

[rubydist]

1. after disconnecting the battery (which I assume you did to remove / reinstall the intake) you need to perform the idle reset procedure. Otherwise, the idle will act stupid for a few weeks till it figures out what to do.
2. a sticky iac will cause the lopey idle speed as you describe. it might have been okay before you r/r the intake, but the movement and orientation changes resulting from that process could have resulted in some carbon getting in the iac such that it now sticks.

if the idle reset procedure does not fix it, then look for a different iac. btw, in my experience, the new ones are no better than the junk yard ones, and pretty much all Taurus of the 86-95 vintage used the same iac, so you should be able to score one at the jy. just make sure the connector is the same and the same orientation - some of them point the wiring harness toward the hood on the SHO, which does not fit.

 

[SHOtimer]

Get a can of carb cleaner and spray it down on the connections for the intake manifold to the head, i bet you have a leak.

Doug