Rough idle and dying in park

[Homer Clifton]

94 Sierra rough idle and dies at times while in park. Drives fine and shifts fine only in park is there a issue. Replaced all plugs wires caps n button, and sensors. No help.

[riverbanks]

Sensors? including iac?

[Homer Clifton]

What he said 

[Mikebtte]

Sounds like a stuck EGR valve.

[dalejohnson2000]

Similar issue. 94 Sierra 5.7L.

Original problem was a Knock Sensor code and cracked head.

Replaced the head and the pig tail for the knock sensor.

Code gone, and running.

This is my Mother In-law's truck and it lives an hour away, so throwing parts at it may be the best answer.

When delivering it back running, the EGR code was thrown. 1 week ago. 

Last night replaced the EGR valve and solenoid and a cracked elbow on the PCV hose.

We cranked it up.

It spit an sputtered for about 10 or so seconds and smoothed out like silk.

Switched off and cranked up several times, same thing every time.

I noticed that while it was spitting and sputtering the Throttle Body was sounding like Darth Vader breathing.

Then it would go quiet and the truck would go to a smooth Idle.

So it had to be the IAC, ran to the parts store  before they closed and put it on.  Exactly the same thing....nuts.

Well we went on a test drive and the hesitation while driving was cured, and it ran strong.

Still have the 10-20 seconds of rough idle sounding like Darth Vader breathing.

 

While driving on the Test Drive the check engine light came on, no noticed difference driving. 

When we got to her house, I jumped the A-B terminals.

I could not get it to go into Diagnostics.  Several tries.

Even grounded B directly to other things.

When I cranked it back up, the light was off...

 

So, how to get rid of Darth Vader with out Luke? (could timing off a few degrees be the issue?)

And not going to diagnostics when jumped.

 

PS-temp sending sensor was checked by multimeter and different temperatures at the reassembly time.

MAP sensor unchecked

Vacuum Canister Solenoid unchecked

 

And a third issue.  There was a 2 wire female plug with Purple and Blue wires that should plug into something around the EGR valve, Can't find anything missing according to the wiring diagram.

 

Any help on any of the 3 will be helpful.

 

[Bigfutz]

That’s a fuel saving feature, not a bug. I recently rented a Malibu (work related travel) and the dang thing cut off every time I came to a full stop.

[Homer Clifton]

Also no check engine light until it starts to spudder n tries to die. And I get heat through my vents but doesn't register on my temp gauge it's not going above 120

[Homer Clifton]

Also did replace the EGR solenoid.coil pack and the PVC and tubing no vaccum leaks I've found.

[hiking_mike]

My 95 seems to have the same issues. Complete tune with a new coil and new EGR.Did you ever locate the issues.

[riverbanks]

Some,wear out the hole, the pintle for iac can't seal due to wear,worth looking at