ERG valve question

Can a bad EGR valve cause engine misfires? I am wondering if my EGR is stuck open. I cruise down the highway the car runs like a champ. I pull off the highway and come to a stop sign and the idle is severly rough, or it is normal. If I shut the car off and restart it it idles nomally. Any thoughts or other problems to look for. 1997 Camry, v6 175,000 miles

Yes it can. If the EGR valve is stuck open at idle it will cause a rough idle condition.

If the EGR is stuck open, would turning the car off then restarting it reset the stuck valve?

If you have a gasketed flanged connection where the EGR line attaches to the manifold, you can test this theory by slipping in a blind flange (a gasket with no hole in it) into the connection to plug the line. If the problem goes away, the EGR is either stuck open or is being told to open inappropriately. I don’t know how your EGR is controlled, but there is usually a vacuum signal involved, so check the vacuum hoses. There may also be a vacuum amplifier diaphragm in that circuit.

I cleaned and freed up my EGR by soaking it in Sea Foam engine cleaner. After 250k miles, it appeared to be lined with tar.

I did have a check engine light that stated problems the EGR but found that the vacuum switch that is electronically powered the EGR was faulty. I replaced it with a new OEM one. The problem was there before and after the vacuum switch replacement. I am begining to think the EGR is not involved in my idle problem, I’ll do the blind flange trick to see what becomes of it. That was a good test idea thank you. Oh, forgot to tell you I did try to clean the EGR with Chemtool B-12 air intake cleaner a few days ago. I kept spraying it until the cleaner came out the same color as it went in.

DISCONNECT the valve for a while and see it THAT cures the problem. The CEL might come on, but you can reset it later…Disconnecting the valve for a short period (or long period) won’t hurt anything…

No. If piece of carbon is preventing the valve from closing then the only way to fix it is to remove the valve and clean it.