I did the stupidest thing this morning. I was searching for a vacuum leak by spraying carb cleaner around the vacuum hoses without a fire extinguisher handy. Didn't find the vacuum leak, but started a fire on the back side of top of the engine which burnt a couple of minutes until I did get an extinguisher.
Now it idles at 700 drops to 600 then down to 400 then back up to 700. About a 4 second cycle. May or may not hesitate upon acceleration. Seems to run fine at all other speeds. Cannot find any burnt up wires, but this one vacuum hose was burnt in two. Cannot find where it goes. One end attaches to the tee in front of the driver near the hood. The other end doesn't attach to the connector clipped to the firewall center of the car near the top - it has all it's vacuum lines. The burnt end was lying on top of the engine near the PVC valve. See attached picture of hose and it's attachment point. The burnt end is above the top edge of the picture.

I was very lucky for being so naive.

My original problem was a PO171 and 174 codes. Looking for air intrusion. Guessing it ignited with a stray spark from the distributor area. Sprayed a little heavy back there without regard for the consequences.

If you have an idea where this goes I appreciate your help, if you think this is unrelated to the idle issue please advise. Thanks!

 

With the plastic air intake pipe off the top of the motor - look about half way back on the drivers side of the intake near where the PCV valve line goes into the intake.

 

I replaced my air intake system with an K&N setup and can see under it okay but do not see a connection point. Is it on the top of the engine near the PCV connections that this hose connects or to the intake itself? Maybe the connection point burnt off is it a plastic or metal connection point?
I will take off the airtake duct piping tonight and see if I can then see what I cannot see with it on. Thanks for your help.

 

On my 2000 which should be similar, PCV line goes onto the top of a plastic "can" that twists into the plastic section of the intake. Vacuum source for that rubber line is a tit on the side of the can at the top of it aimed toward rear drivers side of the motor.

 

do you think it is line #32 on the attached diagram?

 

THanks for your help. That was it. With the tit burnt off. What the heck is that part called, I need a replacement. Hopefully this will fix my idle problem.

 

I bought an inline vacuum coupler, sanded on end smooth, drilled out and cut off the burnt portions of the original vacuum connector. Inserted the coupler sanded end inward then used marine epoxy to adhere and seal the coupler in place. While replacing the hose I discovered some bad hose to the right of the T (see prev pic) that disappears into the fender well body. Cut that away, connected all the vacuum hoses and reassembled the air intake pipe. (ignore the temporary hose clamp that covers the tore flexible vacuum boot on the PCV pipe) The PO171 and 174 codes are gone. The fire led me to the vacuum leaks. Not a recommended troubleshooting process...
Thanks for your help RonJon

 

lol very unique way of finding your problem. glad it worked out

 

I've used carb cleaner to find vacuum leaks, it's a good method. Never had an explosion with it though. Now starting fluid (ether), well.... that's given me some exciting memories.