My sister-in-law's 93 Expo just failed the EGR valve functional test on her smog check. The car has also had a history of the check engine light coming on and off, a rough idle, and cyclically revving at slow speeds.
I'm pretty sure all this points to a clogged up TPS sensor in the throttle body. I'm going to clean it out and see if that clears up some of these problems.
Does anybody know how to perform a functional test of an EGR valve?
I have a 2.4 Expo and the EGR needs to be cleaned about every 40-50K. It's a simple thing. Just unbolt it (save the gasket!) and scrub it with carb spray. Or have it blasted with a soft media. Probably a temp sensor screwed into the side of the valve too. That can go bad on occasion. It will cause a CEL if bad or dirty. Clean the probe on the sensor carefully. I would do a house cleaning on the EGR stuff before I fiddle with the TPS. From my own experience I would almost bet your CEL problems might well go away once the EGR is clean......I might be wrong too!
EGR was packed with soot. I cleaned it, and as far into the intake manifold as I could get with my brush and spray. Thanks for the advice.
What does CEL stand for?
40-50K.
CEL= check engine light. Something else I forgot...My Expo EGR is actuated via vacuum from solenoids on the firewall. You can test the movement of the EGR pintle with a hand vac pump. That actuator diaprhagm could fail? Also the solenoids could stick or fail electrically. Me Expo is a 95 and I am assuming the systems are the same as yours? It's fun when you conquer it!
Check Engine Light (CEL). Same thing as Check Gauges, which is actually totally misleading and a throw back to olden times.
Well, the CEL (see, I'm an insider, now!) hasn't come back on after about 15 miles of mixed driving. Sometimes in the past, it would stay off for a few days after I'd had the battery disconnected, so only time will tell.
I guess what I meant by "checking EGR function" was the specific test the smog checker does to give you a pass/fail. I seem to remember that applying vacuum (opening the valve) should stall the engine at idle when it's hot.
There is no way in hell the EGR worked before (completely filled with oily soot--I previously fixed cracked valve stem seals which caused smoke and oil loss). I just wanted to see if I something else is wrong with the system before my in-law blows another 30 bucks on the smog check.
intake
Another thought...If it was burning a bit of oil your O2 sensor may have a good coat of soot as well. That carbon is a great heat insulator. It's probably screwed in just before the cat. A careful washdown of its business end might help with the smog problem..?
Well it passed the emissions tests--just not the functional test. In California, the smog consists of emissions, some visual checks (no loose vacuum hoses), and a few functional tests. The only thing the Expo failed was the functional test of the EGR valve. I'm pretty sure cleaning it out fixed it. It certainly could not have worked right before.
The check engine light still hasn't come on after about 30 miles of mixed driving. I'm almost ready to call it a success.
I'll bet your safe. Whenever my Expo light would come on I would just dust out the EGR stuff and the light would be gone. A minor thing really. It is the best car I have ever owned. I have had it for 10 years and it runs as well as the day I brought it home. Still pushes
30MPG on Summer gas and it is AWD. Pretty much bulletproof......I'll be hard pressed to find anything as good.MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.