I have a 93 Toyota pickup 2WD 3.0L V6. I failed smog test because of super high NO. I have a bad EGR temp sensor. Is this the only problem or is there more area I should look into before I go retest?

ECS: Failed: Wiring to Sensor (must be EGR related)
Failed: Other Emission Related Components (what can this be, EGR related?

Below is my smog test results:

%CO2 %O2 HC (ppm) CO
RPM MAX AVE MEAS MAX AVE MEAS
15 mph 1614 13.9 1.9 92 19 14 .70 .09 .05
25 mph 1565 13.8 2.0 57 13 18 .84 .08 .04


NO (ppm)
MAX AVE MEAS
15 mph 533 173 856
25 mph 786 177 1259

 

My last emissions test had my truck failing for the same reason. High NOX.
I also have a 3.0 L in a '88 4X4. My problem turned out to be the catalytic converter. When I replaced that, the NOX numbers came way down. Something to consider if you still have the high reading after fixing the EGR issue.

 

I know there is a thread on here that has a ton of information on this but cant find it. Some of the high points I remember is a

Properly functioning EGR. I have gotten several EGRs working, just need a real ggod cleaning.

You need a factory catalytic converter, may want to use it just for smog test. The aftermarket converter usually wont pass.

A fresh tuneup.

Post your results when done and I will try to mark the thread for the emsissions test.

 

I just found out the the vacuum hose were all connected to the wrong VSV's that is why CEL is on. I do not have a bad EGR Gas Temp Sensor as I mentioned above. My question is does having the wrong vacuum hose connecting to the wrong place produce high NOX. Just want to know before going in for my free smog retest.

Thanks

 

If the CEL indicated a problem with the EGR system, and the actual problem was misrouted vacuum hoses, then yes, I would expect the smog test to go much better with the hoses routed correctly, assuming your CEL light is now off and stays off. The sole purpose of the EGR system is to reduce NOX - it pretty much has to work for you to pass the NOX smog test.

 

The EGR code (71) is triggered by the temp sensor; the EGR system re-routes exhaust gas under certain circumstances to the plenum, so the ECU looks for the necessary temperature rise in that tube at the appropriate times. Cold tube => code 71.

SO, if you successfully removed the code by straightening out the vacuum lines, then you should be good to go; you have your ECU stamp of approval. Of course, you may not have successfully fixed the lines (the CEL may come on later), or you may have several things wrong (your EGR tube is so clogged that getting exhaust into it isn't enough).

As RJR hints, most NOx failures are from a completely mucked-up EGR system, so if it were my truck, I'd head for the retest.

Good luck!

 

Follow up.....Put all the vacuum hose in the right place and pass smog, NOX measured low 200's.

Thanks for everyone's help. Great forum and people on here.

 

Great! Thanks for letting us know!

 

Do u have pic of the. Routing of the vaccum lines

 

1988 SR5 with injected California 3RE. Failed California smog because of NOx a little over the limit.

The problem turned out to be a plugged port in the EGR, which connected to the bottom of the EGR Vacuum Modulator with a hose. I removed the connecting hose, sprayed carb cleaner into the small metal EGR port tube, let it marinate, then shoved a wire in and worked it back and forth. Started up the engine and got a wiff of carb cleaner coming out of the tube, then exhaust gas coming out. Stopped engine, replace the connecting hose, and went back to the smog station. Passed with NOx about 1/3 of the legal limit.

Easy fix, without removing the whole EGR assembly.

 

how much of a difference did the cat make? I just tried to smog my 88 and box levels were 1606, the limit is 704.
dos the new cat make that much of a difference?