Diagnosing EGR System

[t9582]

I have had the check engine light on my car(1998 Toyota Camry 4cyl 2.2L) for a while now, and just recently I decided to take the time to fix things up. So I bough a code reader and got P0401 which is EGR Insufficient. I reset it just for the heck of it. About 20 miles later it came back on. Then I did and lot of research and read dozens of post and now I am stuck and in need of some help. So first I cleaned out the EGR valve with some carb cleaner and replaced the gasket. I reset the code and then about 20 miles later the light came back on. Then I inspected the EGR modulator. The filter was not very dirty at all, there was just one small dark black spot. After some more research I found that the Vacuum Switch Valve was a common problem and so I went ahead and replaced the part with a new one. I reset the code, but then the weird thing was that the check engine light came on within 10 secs. I reset it again and came up with the same result. So I guess my question is why would replacing the EGR VSV cause my check engine light to come on sooner than it did before? Also, does a small dark spot on the modulator mean it needs to be replaced(one guy posted that it did)? Any help, suggestions, or past experiences would be great. Thank you.

[93celicaconv]

What code was set after running the engine with the EGR VSV replaced? Still P0401?

If your EGR VSV was bad, it might not have opened your EGR valve for awhile (you didn't say how long you ran with your check engine light on). So your exhaust is trying to go through the tube to the EGR valve, but it hasn't let any exhaust through for a long time, so possibly your EGR exhaust side tube became plugged during this period. Perhaps the area between the EGR valve and the intake became plugged too. When the EGR is off, it is normal for a service tech to make sure both sides are completely free of obstructions before putting the valve back in. Compressed air tends to work good. If you can run the engine with the EGR out, this will tell you if the exhaust side and intake manifold side are open (or they may open by themselves with the engine running).

Or, you can leave the EGR in, run the engine until it reaches normal operating temperature, pull the vacumm line off the EGR, then put a long extra vacuum line on the EGR valve, and pull a vacuum on this line to the EGR (you can either use a brake bleeder vacuum source, or just pull a vacuum with your mouth over the line) and see if the engine starts to stumble or shuts down. If it does, then the ports and EGR valve are operating correctly. If it does not, your problem is either the ports are bad or the EGR valve itself is no longer opening.

[t9582]

Thank you, I will give it a shot. You could be right because I ran the car for like 8 months with the check engine light on.

[73sport]

These are a pretty complex system and I would venture to guess you could have multiple issues going on.

Take a look in here and follow the trouble shooting steps to test each of the sub-systems as throwing money at it may not give the results you want. After you take a look through the Emmisions section and do some prelimanary test, come on back and ask questions on what doesn't make sense if anything. If you have an ohm meter and hand held vacuum pump you can test most of the circuits by following the troubleshooting guides in the manual.

As 93 pointed, if you apply Vacuum directly to the EGR valve it should make an idling engine stumble. Confirm the plumbing also raises in temperature (raise idles to speed this up) so you can tell the difference between an air leak and hot exhaust gases.

Here's the info you need.
http://www.camrystuff.com/index.php?page=Gen4_Manuals

Toyota Gen4 (1997-2001) Camry Repair Manuals

Many thanks to "DrXenon" on ToyotaNation for providing these manuals.

Note: * indicates file contains one half for 5S-FE, one half for 1MZ-FE

• Service Specifications (260KB, 72 pages)
• Air Conditioning (936KB, 93 pages)
• Automatic Transaxle (I4) (4.7MB, 170 pages)
• Body Electrical (1.6MB, 128 pages)
• Charging* (520KB, 32 pages)
• Coolant* (1.2MB, 72 pages)
• Diagnostics (5.2MB, 937 pages)
• Emission Control* (708KB, 35 pages)
• Engine Mechanical (I4) (2.9MB, 114 pages)
• Ignition* (400KB, 24 pages)
• Maintenance (72KB, 9 pages)
• Manual Transaxle* - S51 is for 5S-FE, E153 is for 1MZ-FE (1.5MB, 92 pages)
• SFI* (Sequential Fuel Injection) (2.4MB, 141 pages)
• Starting* (580KB, 40 pages)

[t9582]

Turns out it was the VSV. The check engine light was coming back on because there was a loose cable that I had forgotten to put back in when I was testing everything. Thanks for all the help.

[93celicaconv]

Yep, that would do it too. Glad you found it.