98 Camry V6 - EGR valve issues

#1

Okay, sorry, this is a bit of a long one, I’ll do my best to keep it from becoming a Russian novel.



My Check Engine light had was on. Ran the codes. ‘EGR too rich’, and ‘EGR position sensor’ were the results.



reset codes. They came back on instantly.



Fiddled with it for a while: Pulled off the position sensor which sits atop the valve and has a plunger which detects how far up/down the valve plate has moved. Car ran fine. Yanked the spring that held the valve down, and car idled very rough (as tho’ someone was tapping the accelerator every 1.5 seconds)



Replaced the position sensor with a new one and reset the codes. Car ran fine (it was plenty warm at that point) and codes did not immediately re-appear. So i went home (had been working at my cousin’s who has the code reader)



Next day, car started idling very rough again (that same accelerator tapping issue) and the check engine light came back on after about 40 minutes of driving.



So the valve moved very freely, there was no grime, no corrosion and the spring wasn’t stretched or weak. I don’t see any physical issues there. And, sadly, the Autozone near me doesn’t do that free checking of codes thing (and my cousin isn’t close by)



Anyone have any thoughts/suggestions before I call it a failure and take it to the shop to pay full price?



note: I’ve got 40 days left on my rejection sticker.

#2

Another thing to check when this code is displayed is the EGR vacuum control solenoid. This solenoid is controlled by the computer and controls when vacuum is applied to the EGR valve. If this solenoid has failed where it’s always allowing a vacuum to be applied to the EGR valve, the engine will run rough and the computer will set an excessive EGR gas flow code.

Follow the vacuum hose from the EGR valve to it’s vacuum source. Somewhere in between you’ll find the EGR vacuum control solenoid. Unplug and remove the solenoid and then try blowing thru the solenoid. If you can blow thru the solenoid, it’s defective and requires replacement.

Tester

#3

You seem like the type who will actually attempt something advised. Some look for a “silver bullet”.
The DTC (Diagnostic Trouble Code) tells you that the computer is seeing a signal of the wrong value, or time, than it (in its wisdom) expects. The Code does NOT say a part is bad (how would the computer know that?). It doesn’t mean a thing, contrary-wise, if, after thoroughly testing and examining, a sensor (or, actuator) is found defective. The difference is that one is an expensive GUESS, and the other is a KNOW.
Physical examination of the components is good, sometimes fruitful. Here is a physical examination of the EGR Temperature Sensor ($124): http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c152800926dc
Some repair shops (including dealers) would be glad to throw some (expensive) parts at the Codes; but, you may not want that “service”.
You need some basic tools: a multimeter (basic, $30), and a scan tool (or, code reader).The other tool you need is the repair manual (Haynes, Chilton’s, factory, online).
You can get the DTC HExx troubleshooting charts at www.alldata.com, either through your public library, or online for $25 per year subscription. Are you game?

#4

You need the wiring diagram for the circuits between the Engine Control Module (ECM --engine computer) and the EGR components. The wiring diagrams at alldata can be difficult. On this link, click on Diagram 6. http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c15280092892

#5

yeah, we ran the position sensor through a meter and were getting results that looked like a bad connection inside. The plunger, in addition, was making clicking noises which, when I checked out a new one, it should not. I think it just plain broke.

Looking at Solenoid next

#6

Try these on troubleshooting the vacuum control valve: http://www.toyotanation.com/forum/t96494.html
If you apply electrical power to something, be aware that some components operate on 5 volts, not 12 volts. If the power supply wire comes from the engine computer, it’s most likely is 5 volts.

#7

5v huh? Good to know. And nice link, it’s got a supplier for that part in there. Autozone doesn’t sell 'em apparently.

#8

Just to close this one out:

After replacing the EGR position sensor ($35 - $50) and resetting the codes the car started idling extremely rough. Cylinder misfire codes and more ‘P0402’ code goodness.

Spent about 6 hours multimetering everything and looking for what could still be causing the codes. Noticed teh idling was not as rough as it was shortly after replacing sensor.

Gave up, drove home, commuted to work a couple times after making appt at shop to have it fixed and the check engine light went off.

The moral of this story? Apparently the computer needs about 200 miles worth of data to get it running right once that sensor is replaced.

I’ve got me an inspection sticker now.

Thanks everyone for the help.