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Clogged EGR passages on 94 Loyale? Car doesn't die/stumble when opening EGR valve at idle.

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I need to pass emissions in California with my 1994 Loyale. When I took it in to get tested it passed everything except for the visual of the EGR system. The tech said that when he pushed the diaphragm on the EGR valve, the car should stumble and/or die, but it didn't, which he said was a symptom of clogged EGR passages.

I took the EGR valve off, cleaned it, the stem moves well, even when on the car and I increase throttle to 2500 rpms. The carbon deposits didn't look too bad. I tried to clean the passages with a speedometer cable and some carb cleaner. I found that I couldn't get it around some of the bends in the passages. I knocked some carbon loose and vacuumed it up and tried blowing air down the passages. When I reinstalled the valve again, the car still wouldn't change its idle when I pushed the diaphragm in to open the valve. In fact the car ran fine without the EGR valve on (it was louder since it was blowing exhaust gases out of the lower hole).

The EGR valve moves when applying vacuum and holds it when I keep the vaccum applied, so it doesn't leak when it is closed and is not seized. Also, the vacuum hoses don't seem to have a leak, since it opens at higher RPMs.

I also have a 35ohm resistor mounted on the purge valve solenoid instead of the old stuck solenoid in order to clear the CE light. Would this effect the car and keep it from dying when pushing the EGR valve diaphragm? Or is it a completely different system? The EGR solenoid is brand new.

What do you recommend that I do? Is the tech right? Are the EGR passages clogged? How do I get at them? I unscrewed the flare nuts that hold the 90º EGR pipe in place, but seemingly couldn't remove it without taking the intake manifold off. Also, I remember cleaning that pipe 10K miles ago when I did the head gaskets, so I imagine it is other passages?

Does anyone have a diagram of how the passages run? Any other tests I can do?

Many thanks!


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The resistor in place of the solenoid disables the solenoid, and make the ECU think it has a good solenoid attached.  CA cars have a 2 wire temperature sensor on the intake to detect the EGR gasses.  Non CA cars don't.   I have never had to do any other testing.  I have had the solenoid coil fail open - OEM ones almost always fail.  I replace them with a Toyota or Honda solenoid from similar age cars.  I am still running the SAME solenoids I swapped in 2 decades ago.  Anyway, I never noticed any engine drive ability issues due to the failed solenoid. 

When you were blowing air through the passages, did it go through the one from the valve to the intake?  You already proved the exhaust to the valve is ok.



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I didn't know where the air would come out at the intake, would I have to take apart the manifold to check that, or would I be able to tell with just the rubber manifold detached?

Yeah, the car drives fine and emission readings are good. The tech just needs the car to stumble when the EGR valve is manually pushed in in order to pass the car. Seems silly, since the car runs clean.

I think I found the 2 wire sensor. Is it the one that is mounted right by the upper (intake?) passage right by the EGR valve.

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Yes, that has to be the sensor.  It has to be close to where the port is.

Air blowing through the passage - Probably could hear it if you hold the throttle wide open while someone injects the air into the valve port.  The air passage from the EGR valve to the intake just opens into the intake passage, wherever it was convenient.    Any back pressure on the air source would be a sign the passage is blocked.

  No big mystery there.    I would have to try pushing the diaphragm thing tomorrow evening, when the car is running, and up to normal temp.   And see what happens.  The EGR solenoid disables the EGR valve - IIRC - to keep it shut while the engine warms up.


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  • 1 month later...

I finally got to it after having to work on other things and I found the problem. I removed the intake body and EGR valve. The passageway from the EGR to the intake has a tight turn that was clogged even though it looked clean from inside the intake manifold. I was able to shove a short section of speedometer cable down through the hole of the temperature sensor (right next to the EGR valve). I had to double back the front 2" of the speedo cable, spin it and pull it back and forth. All sorts of black gunk started falling out of the EGR passageway and get stuck on the cable, which I had to wipe off every 10 seconds or so. I tried to blow as much as possible of the gunk out, and when I finally was able to blow air from the EGR to intake manifold, I vacuumed up the loose gunk to not have it go into the engine.

When I reassembled everything, I was able to push the EGR diaphragm in and the engine instantly stuttered and eventually died, which is what the California smog tech looks for to make sure that the EGR system works. Finally ready for a re-test!

Thanks so much for your help, Dave!

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