Toyota Repair: Supra Emissions Failure, vacuum pipes, modulator valve

Question
Follow up question:
If the small pipes are clogged with carbon, what do you suggest to use to clean them out? Like you mention they are small. I am wondering is engine cleaner would work or not.
Thanks
Glenn D

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Followup To
Question -
Hello
Let me start by saying thanks again for the advice re: my recent Previa engine death. Your advice was right on: I swapped the ignition coil and all is well! Still going 260K miles and strong!

Now for my Supra: It failed the Nox part of the emissions test. At 190K miles I begin to expect this.

I typically zero in on a couple of components: the catilytic(sp?) converter and the EGR valve.

Some history:

The converter was replaced in 2000.

The EGR valve has never been replaced. I pulled it once to clean it, which was an ALMIGHTY PAIN!

I tend to think that it is the EGR valve. Any ideas on how best to replace? From underneath? Upside down ? :)

Thanks in advance.

Answer -
A common problem is the EGR modulator valve mounted on top of the egr valve, you can check it by removing it and checking to see if air can pass through the bottom port, if so, it needs to be replaced, the small vacuum pipes on the throttle body also tend to clog up, they provide vacuum to the modulator and the egr valve, in extreme cases the passage through the cylinder head or the egr pipe get carboned up, the best way to go about finding out just what is causing the egr malfunction is to check the system with a vacuum gauge/vacuum pump, you can apply vacuum directly to the egr valve and see if the engine dies at idle, if so, the egr valve and the passages are clear and the problem is probably with the vac ports or the modulator(this is the case about 90% of the time)

Answer
The vacuum pipes can be cleaned out with a paper clip,but the port in the throttle body is much smaller use a very small piece of wire available at the hardware store, then spray some throttle body cleaner in to remove anything that may be left. The best way is to remove the throttle body completely and clean the passages with wire and compressed air and some throttle body cleaner.