1996 Corolla DX EGR Flow Insufficient

[mcmerulla]

So my check engine light came on a few weeks ago. Went to Autozone and had them run the trouble code: P0401 EGR Flow Insufficient. Sales rep. tells me "just replace your EGR valve and you should be fine". Naturally, I thank him and leave, and head to my house to do some of my own research. Based on what I've found on this forum, as well as other various online sources, I've been trying to troubleshoot/diagnose the system for the past few days. I bought a hand-held vacuum pump in order to do so. The car is a 1996 with 294,7XX miles. Here is what I have found so far from my diagnosis:

I. EGR Modulator (I removed this from my engine compartment to test)
A. Applied vacuum to bottom port; vacuum held steady for 30+ seconds
B. Blocked ports P + R with my fingers, and blew air into Q. Air passes through the little pinhole located under the filter

According to what I've read, this gives pretty good indication that the modulator is not at fault. Moving on...

II. EGR Valve
A. With car running, applied vacuum to small line going to top of EGR valve. Vacuum remained steady but engine did NOT stall; though it slowed very subtly.

Am I applying the vacuum to the wrong line? There are 2 lines that I see coming out of the EGR valve--one goes to the VSV, the other goes to the modulator. I have been applying vacuum to the line that runs to the VSV, on the top left hand side of the EGR valve.

B. With car running, removed hose from EGR valve and placed my finger over it. Idle stayed the SAME.

Based on this, it seems that the EGR valve may be at fault (clogged). I also checked the metal tube coming out of the valve (the one that connects to the bottom port of the modulator) and found some carbon buildup inside.

III. VSV
A. With the engine off, removed the orange electrical connector. Took a multimeter and touched the two prongs of the VSV--one with the positive probe, the other with the negative probe. Reversed positive and negative as well; did not really make a difference. The readings I got were between 43.1 - 45.1 ohms.

The normal resistance on the VSV should be between 37 and 44 ohms. Is it a problem that my reading was slightly higher than the "norm"?

IV. Using a 3-way adapter, I hooked up my vacuum pump between the modulator and the EGR valve as described in the Haynes manual. Since I do not have a tachometer on my car, I had to estimate RPMs by feel. Started the engine, and connected terminals TE1 and E1 on the test terminal. With the engine cold @2500 RPM, the vacuum reading was around 15 in Hg. As the engine got progressively warmer, the vacuum readings @2500 RPMs increased, all the way up to 20 in Hg when hot. I did notice the engine begin to run poorly as I neared the end of these tests.

According to my manual, the vacuum gauge should indicate no vacuum @2500 RPM when the engine is cold. So there seems to be a problem here, as well.

Since I am no mechanic, I was getting frustrated and wanted a second opinion. So I took it to the dealer today...sucked it up and paid $92 for the diagnostic fee. The guys there are really good, and the rep. is a great guy, as I've dealt with him in the past. After about an hour, he came out and told me that I would need to replace the EGR valve, the EGR modulator, and the VSV in order to ensure a proper repair. I then told him that I had ran some tests myself (as mentioned above), and he went on to tell me that with the EGR components not functioning, I could eventually ruin my cat. I asked him why I had to replace all three, and he said that if one component is bad, it can foul the other, and soon on down the road, I will have to replace it anyways...especially with the high mileage situation. I was quoted $578 plus tax for the entire job.

Here are my question(s). Does it seem like all of the tests above that I ran were correct (in other words, does my analysis seem logical?) And should I just bite the bullet and replace everything out of convenience, since I have so many miles on my car anyways? In my opinion, it seems like the EGR valve is the only thing at fault. The modulator and VSV seem easy enough to replace on my own, but I am not comfortable removing the accelerator cable and the throttle body in order to replace the EGR valve. If the problem is indeed the EGR valve, I will end up having the dealer replace it. While they're at it, I would have them clean out the throttle body, too.

The parts prices were as follows:

EGR Valve $242.75
EGR Modulator $96.96
VSV $139.50
EGR Gasket $5.26

I know that I can get these same exact factory parts for much cheaper online...especially the EGR valve.

So, any thoughts? I have done my research instead of just posted "blindly", and put a lot of effort into all of this, so any tips, suggestions, or opinions would be great. Thank you for your time!

[mcmerulla]

No advice at all, folks?

[Steelballz]

he has a valid point with replacint them all especially with the milage...if one is at fault, the others have been brought past their tolerances and may also be damaged/not functioning properly...so instead of changing one (genuine or spurious parts) and one of the other 2 bits giving way in a few months, you might aswell change all 3 and enjoy motoring

[mcmerulla]

Thanks Steel, that is exactly what I ended up doing. Ordered all three parts on Tuesday, along with the miscellaneous gaskets, nuts, and hoses. Total came to $316.18, including shipping. The dealer wanted almost $500 just for the parts! So already, I made out quite well.