86.5 NA emissions fail

[Rennat]

First I want to thank everyone who has asked and answered posts. I have rebuilt my son's 86.5 NA. I have gone threu the TPS issues, high idle etc. I am struggling with the high NO emissions. I have replaced the O2 sensor, broght my CO in line, replaced the CAT and put my HC below emissions and now I have a question about the EGR system. I fail (2077@15mph and 1796@25mph). I have removed the tube to the EGR and just sucked on the end and yes the engine just about died. I have removed the VSV and bench tested and its functions correctly. I removed (for now) the air filter in the EGR modulator (real dirty). I am not sure when the VSV gets 12v to open and I can't measure the vacuum from the threottle body (very minimal) as I only have a NG guage in inches. Timing is set right on, idle is fine but you can smell the exhaust, seems rich. Any help would be greatly appreciated. Thanks. By the way a ohm meter was the best way to set the TPS accurately and consistently... when you have a good one.
Thanks.
Supra DAD

 

[Allan_MA70]

check your cold start injector isnt leaking

 

[Rennat]

Allan I had forgotten all about that! Thanks I'll check and post results. Thanks for the quick response.

 

[935motorsports]

Put a vacuum gauge on the egr vac line and drive around to verify that the egr valve is in fact getting VAC.

 

[Rennat]

Alright the cold start is completely dry, not even a trace of fuel. I have a vac guage that reads in hg and there is fluxuation at 2500 rpm when I "T" into the line down to the EGR.

 

[mrnickleye]

The EGR valve won't work if the 'transducer' (back pressure sensor) is not working properly. Toyota EGR valves are pretty sturdy, but the transducer is what fails. Replaced several this year (down at the shop).

 

[Rennat]

Mr Nickeleye that is aka the modulator! What has the VSV got to do with all this? Seems like it just vents the vac line to atmosphere! Does the ECU open the VSV after the EGR has opened?

 

[jetjock]

You should see vacuum under light throttle. It'll vary from 2-15 inches depending on throttle but will drop off as throttle becomes either heavy or closed. If you don't see this remove the modulator and feel for exhaust pulsations in the bottom line. Test the modulator as per the TSRM. Since you've already verified the EGR valve passages are open you can skip that step.

The VSV is nothing more than an EGR cutout. It's cuts vacuum and vents the EGR system to atmosphere (to force the EGR valve closed) when the coolant is cold, at WOT, and above 4000 rpm. It's a three way valve so be sure it's porting both ways. EGR is also disabled when a certain amount of air is passing through the AFM but in normal driving with a hot engine you should see vacuum to the EGR valve under light throttle.

If the mixture is correct and the cat is lit your NOx must come down. It's overly high for what would seem to be a working EGR and a new cat so I suspect either the mixture is wrong, the cat is defective, or it's not lit. This assumes you don't have any other NOx generators such as timing or cooling problems.

Also, what are the numbers for all 5 gases?

 

[Rennat]

Ahh jetjock! The five gases
15mph rpm 1851 %CO2 MEAS 14.3, %O2 MEAS 1.2, HC 4.3, CO .02, NO 2077
25mph rpm 2035 %CO2 MEAS 14.4, %O2 MEAS 1.0, HC 37, CO.02, NO 1796
The vac fluxation appears to be there as you mention.
HG did drop as you mentioned on the vac guage I have.
Going to try to test the modulator in the a.m. as I'll have another set of hands.
I have no way to check mixture as the air mass sensor appears to work correctly, how do you know where to set the adj screw? I have tried one turn off all the way down and this last time three turns back from all the way down, appears to be center. The air mass according to the TSRM is functioning correct. This is just digital vom checks.
What is lit? that you mention?
Thanks.

 

[Rennat]

Jetjock the cooling doesn't appear to be an issue as the coolant indicator reads mid line on the guage and the water is definitely circulating well. I cleaned all the water paths when I had the engine in pieces. I ran water thru the system for a couple of days, only driveway hours and the put coolant in after draining the system.

 

[Rennat]

I have checked the timing and it is rock steady at 10 deg BTD center... even had another set o feyes look and check to verify ... timing o.k.

 

[Nick M]

How does the car run? Good, bad, about average?

 

[Rennat]

The car is very strong, quiet and smooth. Spins tires in 2nd.

 

[jetjock]

Those numbers actually look pretty good. It's running a tad lean but otherwise the numbers show the engine control system to be working well. Course, they're taken after the cat so it's not a true picture of what the engine is doing but other than NOx they look pretty good. O2 is a bit high and that'll cause CO to be low but CO2 shows combustion efficiency is very good.

The problem is since NOx is already near it's max at the correct mixture and increases as you go lean any leaness just makes things worse. The cat needs a certain amount of CO to reduce NOx and since CO falls as the mixture goes lean this also makes things worse.

Midrange on the temp gage? I've never seen a Spura in good condition run that high but it could be gage error. Mine has never run more than 1/3rd under any condition. If the mixture is correct high NOx before the cat is caused by anything that results in high combustion temps. Be sure the cooling system and fan clutch are in good shape. You could also have leaness in one cylinder but that's reaching.

It *appears* your mixture is close enough and the EGR is working properly. That leaves the cat itself. When I say "lit" I mean the cat has reached the operating temp needed to work. You can check that by measuring the difference between it's inlet and outlet. By the looks of your HC it appears to have lit off so the NOx is either a bad reduction bed in the cat or is so high upstream the cat can't handle it. It's not one of those cheap cats is it? How big is it? Also be sure the exhaust isn't restricted in any fashion.

The best thing to do is have the gases measured before the cat. This would tell you cat efficiency. Based on everything you've written I'd be looking at the cat and perhaps for a small vac leak because the loop seems shifted a bit lean. (I'd also check the O2 sensor is swinging with a mid point of 450 millivolts). Still, it's not that lean and any cat worthy of the name should be able to handle the NOx.

Verify the EGR is indeed working. If you apply vacuum directly to the EGR valve the engine runs rough right? Be sure the modulator is working and the exhaust path to the modulator is open. If you really want to be sure everything is working remove the EGR connection to the intake manifold (plug the hole in the manifold) and run a hose from the EGR valve outlet into a bucket of water. Spool the engine to at least 3000 rpm and see if you get EGR when the vac gage shows you should. If you do either you have higher than normal combustion temps or the cat is dead. Remember, the cat has two separate portions, one of which is dedicated to Nox reduction and that reduction bed relies on some CO to work.

What adjustment screw are you refering to?

 

[Rennat]

I'll work on the EGR testing today and check the O2. Thanks.
The adjustment screw on the air mass module on the intake side.
The cat was same size as what came off - stock replacement.
Thanks again and I'll update later today.
Greatly appreciate ALL thoughts.
Got to move from Cali!

 

[jetjock]

The People's Republic of Kalifornia. A more oppressive state doesn't exist. The weather is nice though.

Stock cat? Hmmm....it's a good one. Should easily do the job and then some even with a slightly lean mixture. I assume it's new and not used.

Verify EGR and be sure the cat's hot lit. Check the O2 signal for at least 8 counts in 10 seconds and a midpoint of 450 mv. Looks like it's working though so you either have a bad cat or a NOx generator that's overwhelming it. The cat needs a very narow range of feed gas composition to work right but it sounds as if you have it so focus on temps and cat operation.

In a perfect world the O2 would be down a bit and the CO be higher (they should be about equal at .5 % or so) but the cat should work with what you have, just not at it's best efficiency.

Since this is an N/A car the AFM screw is used to set idle mixture. Messing with it is not a good idea. Look for a code stamped into the AFM body. That number is the MM from the screw head to the top of the AFM body. It's where the screw was set at the factory to calibrate the AFM to get the correct idle mixture. Set it back to that.

 

[fiyota]

jetjock... I've heard of supras running at 1/2 the guage at operating temp and others running at 1/3... mine had always been at 1/2 when running normally (then would overheat due to bhg)... but when it was fine it was at 1/2... hmm... damn factory temp guage.

(sorry for the off topic post on your thread)

 

[jetjock]

I'm not disputing that, just that of the half dozen or so I've seen none run more than about a third. I doubt his problem is coolant system related but I felt I should point it out anyway.

 

[Rennat]

Fotosoup no prob. Nice to hear that others have same reading and all is ok.
Jetjock I am on my way to check the O2 and I'll check the AFM screw setting (once I find the numbers) Thanks and I'll be back.
I think I'll get a Supra for my younger son so than I'll have parts to swap!
From the great state of Kali!

 

[jetjock]

You can wing it on the AFM screw by watching the VF signal. Best to set the screw back to the measurement stamped in the AFM body though. When you find the code post it and I'll decipher it for you. Not hard to do but eaiser than writing it all out. Btw, I just had mine smogged and before I took it in I checked it and guess what? High NOx. Turned out to be a small vac leak and a sick cat. I had a cheapie one on there for a few years. They don't call 'em "one pass" cats for nothing.