Hi again, I'm looking for help on a structured way to troubleshoot this problem, it seems like I'm just blindly doing crap that isn't helping anything.

First , the issue is a rough idle with misfires, at first the codes were insufficient EGR air flow and random misfires. I cleaned the EGR valve (which was frozen solid with carbon, now appears to be clear and functioning), and I cleaned the EGR channels to and from the EGR valve. I also cleaned my intake manifold which had carbon boulders sitting in it. I tried to clean the IAC valve but really didn't accomplish much besides wiping out a little carbon dust, not much else to do to that. I've replace spark plugs which were all covered with hard white crust. Replaced cap and rotor. The plug wires are new as of last summer.

So now the codes are EGR valve lift insufficient detected and random misfires. My plan today is to test the voltage to the EGR valve and test again for vacuum leaks. I'm not optimistic that what I do today will help anything.

I'm a decent troubleshooter, but not really with automotive issues, simply due to lack of experience. I'm looking for a solid way forward from here to actually find and solve my rough idle and misfire problem. Any input would be appreciated.

 

Even though I haven't recieved any replies, I'm going to post the latest, maybe in the end it'll help someone else.

Things I've done already-

• Cleaned and tested pintle (sp?) action on egr valve, works (12v to pins 4 & 6)
• Replaced plugs, cap, rotor, wires
• Cleaned all plugs and other related connections, replaced multiple vacuum lines.

I located the following info on the web and made use of some of it:

"
• EGR connector power to ground voltage with car idling is 7.3V (this is good, not enough voltage to open valve)

• EGR connector reference voltage to sensor ground with car idling is 4.99V (good)

• EGR valve sensor input to sensor ground resistance is 1.6k ohms (good, under 100k ohms)

• EGR valve sensor input to reference voltage resistance is 4.3k ohms (good, under 100k ohms)

• EGR valve apply battery voltage to power and ground with car idling - this easily stalls the engine. Just a quick tap is enough to induce rough idle. Any longer than that and it stalls. This confirms my guess regarding the EGR passages from the exhaust manifold and to the upper intake - they are relatively clear. So I don't need to mess around with gaining access to and cleaning these passages."

The final test of putting power to the egr valve while idling which should make the car stumble, if not stall, had no effect when I tried it. I could hear the valve activating when I applied power but the idle stayed the same.

So...

I took the egr valve off, stuffed a shop rag in the manifold side egr channel to maintain manifold vacuum, and started the car. I put my hand over the opening of the exhaust side egr channel and there was nothing coming out. I figured exhaust would freely flow from this channel, but since it isn't it explains the test not working. After that, just to see what would happen, I pulled the shop rag out of the manifold side egr channel and wow! It sounded like a tornado sucking in air and the rpms went from idle immediately way up, then down, up, down etc. until i killed the engine.

My exhaust side channel is as clear as I can get it all the way in until I hit a wall or bend of some sort 4 to 6 inches in. I don't know what's behind that, how to clear it, or even if exhaust is supposed to come out freely as I was expecting to see during my experiment.

I ordered a new egr valve, new map sensor, and new up and downstream o2 sensors. When they arrive I'll install them but don't have much hope of it changing anything.

Not sure where to go from here, it seems to idle ok when first started in the morning until it warms up, then it drives ok but doesn't idle well at all. It starts misfiring and my CEL starts blinking, I have to raise rpms up to about 2k and hold it there to get it to stop.

I'll continue to post my adventures in troubleshooting.

PS, today I stripped the threads out with one of my valve cover screws. Yay!

 

In case anyone runs into the same issue (rough idle, misfires), I ended up doing a "cranking compression test" which is a simple test I didn't know about- I'm not a mechanic, just a guy trying to keep his car running, and found I have a compression issue. If anyone is curious about this testing method, there are good videos on YT about it.