EVAP Solenoid problem?

[WhiteMonteZZZ]

The monte did something odd the last couple days.

 

At random while driving at light throttle (maybe 40-50 mph) the car starts to "jerk" very lightly. Very light though. But it gets noticible when you stop and idle. The car lopes like it has a massive vacuum leak.

 

However, I stopped in a parking lot w/the car loping/idling and popped the hood to listen. Suddenly I heard a click and the idle then was perfect and smooth.

 

Drove later that day again, and the same issue developed (and also went back away).

 

I was reading about the EVAP Purge solenoid and it causing similar issues when bad.

 

Could a EVAP Solenoid which is failing cause a very rough idle (same as unplugging a main vacuum line while the car is running), and then clear up (presumably if the PCM purges then stops, or vice-versa)?

 

The fact I heard a 'click' when the idle got better leads me to believe sensor of some sort.

 

I also thought about a sticking solenoid on my EGR Valve (the 3-solenoid digital valve).

 

This is on my 95 DOHC.

 

Lastly, I'm currently driving w/the EGR connector unplugged to eliminate that as a possibility. However, what happens if I just unplug the EVAP Purge Solenoid connector for a day or two? Will the car run fine but just throw a code? Or is this not a good idea?

 

Idle also surges at cold startup (only 200-300 rpms up and down) for a minute or two, but doesn't ALWAYS surge. Plus I've had a small (negligable) off-idle stumble/hesitation. New IAC, TPS, Intake Gaskets (upper/lower), O2 sensor, many new vac lines, swapped in a 2nd PCM, among many other misc. things. Just for reference of what's been checked/replaced.

 

Thanks for reading my long post,

 

WhiteMonteZZZ

[Spoon]

I think a sticking purge solenoid will set a code, but i'm not 100% sure. I'd try taking off the egr and making sure theres no carbon keeping the pintles open.

[WhiteMonteZZZ]

I think a sticking purge solenoid will set a code, but i'm not 100% sure. I'd try taking off the egr and making sure theres no carbon keeping the pintles open.

 

Well the car's been driven w/ the EGR unplugged. Problem hasn't yet come back. I think a solenoid on the EGR was sticking. I had the car idling 15 mins or so today after driving it and the idle never fluctuated. I might just leave the egr unplugged the rest of this winter, and remove/cap it in spring.