Failed Emissions 3x - What else can I try?

[Done Deal DR]

Ok guys, here's the deal. I have a '92 Blazer with a TBI 350. Pre-OBD, so an emissions test is basically just exhaust emissions check. The motor is, as far as I know, completely stock. I don't even know if it's the original motor and transmission, and the vehicle has about 200k on the odometer. The motor runs strong and I honestly don't feel like I need any more power out of the thing. The maximum emissions output for AZ is at 25, I believe lbs of c02 emissions per mile. I know the numbers are correct but am not certain on the description as I'm certainly not an emissions expert.

During the first test my truck had an old cat and Flowmaster muffler of unknown age and condition. It registered at around 155 per mile, or a little over 6x the legal limit.

I ordered up a universal Magnaflow cat (model recommended by Magnaflow) and a Magnaflow muffler and had a new 3" exhaust fab'd up. Took a retest and registered around 125 per mile, 5x the legal limit.

Took it to a shop and had them install new plugs, plug wires, cap, EGR, and EGR solenoid. I would have done it myself but I would have been lazy and taken 2 days and needed it done ASAP as I'm trying to get my truck into a paint booth. Just took it in this morning and am registering 75 per mile, 3x the legal amount.

As far as I know and can see, there are no O2 sensors being a '92 pre-OBD truck. Is there any other common emission equipment failures that I am missing? This is getting time consuming and frustrating and I'm ready to be done with it. I'm probably going to take it to another shop that specializes in emissions, but thought I'd ask here first as I don't know what else I can even try and don't see anything else in my repair manual. These are simple trucks which I guess is why I'm so confused.

Thanks for any help you guys can provide.

 

[quietfly]

check your temps, maybe you have a low temp thermostat. if your running lower than 170 switch it out for a 195 just for your emissions test.

 

[Done Deal DR]

I just put a 195 in about 6 months ago. Anything else?

 

[Jaycenk]

Is the cat close enough to the manifolds? what about the air injection system? is it working?

 

[Done Deal DR]

Is the cat close enough to the manifolds? what about the air injection system? is it working?

The cat appears to be in the factory position. The manifolds lead to a short Y-pipe and it is directly attached to that Y-pipe.

I have to be honest, I don't know anything about the air system. I know there is a hose connected to the passenger exhaust manifold that goes somewhere but don't know much more than that unfortunately. Is that the air system you are referring to?

There is also an engine preheater hose connected to the air intake.

 

[SunlitComet]

You should have a oxy sensor in front of your converter somewhere. And to Clarify your are talking about Carbon dioxide or Carbon Monoxide?

 

[busafreak]

You should have a oxy sensor in front of your converter somewhere. And to Clarify your are talking about Carbon dioxide or Carbon Monoxide?

Agree^^^

Geez, why are they testing such an old vehicle? IL. Stopped testing 95 and older vehicles, and hence why I have a 95. (Soapbox time) eff the government and their whole emissions testing. If I was in your position, I would do a google search on denatured alcohol and drive away from the testing facilities with a smile on my face, and a middle finger extended at them while I move on with my life.. But thats just me..

(Stepping off soap box) yeah, look for that o2 sensor..

 

[Done Deal DR]

You should have a oxy sensor in front of your converter somewhere. And to Clarify your are talking about Carbon dioxide or Carbon Monoxide?

i will double check on both accounts.

Agree^^^

Geez, why are they testing such an old vehicle? IL. Stopped testing 95 and older vehicles, and hence why I have a 95. (Soapbox time) eff the government and their whole emissions testing. If I was in your position, I would do a google search on denatured alcohol and drive away from the testing facilities with a smile on my face, and a middle finger extended at them while I move on with my life.. But thats just me..

(Stepping off soap box) yeah, look for that o2 sensor..

I wish they stopped testing on vehicles older than '96. Not even close, here in Phoenix they stop testing vehicles made before 1968 (Yes, that's NINETEEN SIXTY SEVEN and earlier models). What a joke.




If I am in fact actually missing an O2 sensor that would certainly explain these readings, but I probably just missed it. I'll go check and get you guys an answer in a few minutes.

---------- Post added at 09:02 AM ---------- Previous post was at 08:47 AM ----------

I'm working from home today so I was able to go check it out. I confirmed there is NO O2 sensor anywhere on the Y-pipe all the way up to the cat. I didn't pop the hood but I don't see why a cat would be directly on just one of the manifolds. Can anybody else with a 92-94 confirm they have an O2 sensor on the Y-pipe?

In regards to the emissions, I actually underrated it and it was actually at 87.39 this last test yesterday. In any event, here are figures:

Hydrocarbons (HC) in GRAMS / MILE: 5.25 AZ State Requirement: 3.00 Difference: +2.25

Carbon Monoxide (CO) in GRAMS / MILE: 87.39 AZ State Requirement: 25.00 Difference: +62.39

The only thing I've managed to pass is "Oxides of Nitrogen (NOX). I registered a 3.23 on that with the AZ State Requirement at 5.00, and the visual inspection which is pretty relaxed.

 

[coleman84]

Emissions testing is the biggest crock ever. The nice thing about my wifes hummer...its' classified as a bus in Missouri = no emissions testing!

 

[busafreak]

You are close on your hc's, but ur way off on your co. You are running way rich. Yes your truck has an o2 sensor after the manifold on the passenger side. The connector is close to the trans. Get under there and find it.. Its before the cat. How many times can you fail in AZ?

I agree, emission testing is the biggest crock of crap. Here in Illinois, they made away with the tail pipe sniffers and the dynos. So its strictly plug and test..

 

[BattelWagun]

I agree, emission testing is the biggest crock of crap. Here in Illinois, they made away with the tail pipe sniffers and the dynos. So its strictly plug and test..

Thank God!!! Because honestly, I don't think I'd be passing anytime soon...

 

[Done Deal DR]

You are close on your hc's, but ur way off on your co. You are running way rich. Yes your truck has an o2 sensor after the manifold on the passenger side. The connector is close to the trans. Get under there and find it.. Its before the cat. How many times can you fail in AZ?

I agree, emission testing is the biggest crock of crap. Here in Illinois, they made away with the tail pipe sniffers and the dynos. So its strictly plug and test..

Well of course, that's obvious. Better than where I started at like 155 though. Not trying to be rude at all, I appreciate the help.

There is nothing on the Y-pipe. I will check again if there is one on the actual manifold...but again, I saw nothing on the Y-pipe that comes directly off the manifolds all the way up to the cat.

It's possible that if I'm supposed to have an o2 sensor and don't that is why it could be running rich, but I see no other reason I should be running rich given it's fuel injected. It's not like it has a carb on it that I can adjust the mixture with. *shrugs*

 

[BattelWagun]

I've seen it before when a vehicle is missing an O2 sensor, it goes into a gimp fuel mix mode and richens it up big time to prevent damage (the SES light usually comes on with that though. I've also seen it where it just leans itself out and dies, with no warning lights (damn volvo's....) I'm not sure how the hoes are designed to take it, but since you cant seen to find that sensor, it may have just never been reinstalled and your computer is richening it up because it doesn't know what the hell is going on at that stage...

Just my reasoning, if theres someone here who actually knows, feel free to correct me

 

[Done Deal DR]

I've seen it before when a vehicle is missing an O2 sensor, it goes into a gimp fuel mix mode and richens it up big time to prevent damage (the SES light usually comes on with that though. I've also seen it where it just leans itself out and dies, with no warning lights (damn volvo's....) I'm not sure how the hoes are designed to take it, but since you cant seen to find that sensor, it may have just never been reinstalled and your computer is richening it up because it doesn't know what the hell is going on at that stage...

Just my reasoning, if theres someone here who actually knows, feel free to correct me

It's certainly possible, but I've had a hard time finding info specific to these TBI's to know for sure.

All of my other vehicles have been OBD-II except for one other previous car, so this is a little new to me.

 

[busafreak]

Why you have to be all rude about it? Was just informing you incase you didnt know.. pfft!
Lol jk. All 88-95 have just that one, its hard to see if you are just bending over and looking. You have to really get under there and feel after it ys and before the cat. If you dont have one, it has been eliminated, and probably tie strapped somewhere like the obd1 rice boys do when running a test pipe since you are not throwing a code..

Mine is running rich right now and im hunting down the source. Im getting a new o2 sensor since my readings are crazy.. But check this out:

The pre-converter oxygen sensor is mounted in the exhaust system before the catalytic converter. The PCM monitors the varying voltage signal from the o2 sensor continuously to determine the required fuel injector pulse width, controling the engine air/fuel ratio.

 

[ezdaar]

your O2 is Very near the starter, either on the Ypipe at very top near connection to manifold, or on the manifold itself.

IF you dont "SEE" a O2 look for the bung, someone may have removed the O2 and put in a plug, basicly a large bolt to seal the massive hole.

You can also trace the O2 wire from front of the block, if stand infront of vehical, look towards passenger side of motor right below the TBI unit. you will see a large plastic conduit full of wires.

maybe 3 of these wires will continue towards front of engine and down the front of block.
2 of them will be starter wires. and one will be the single O2 wire, it will travel under the exhaust manifold past the starter to the Frame where its attached with some form of clip, then route back to the O2 sensor.

Now GM in all their glory revised this like 3 times. you may have a green wire as O2 or a violet colored wire.
There maybe 3 or simply 2 wires running from the large conduit uptop down towards the starter.

You may also have just a single green or violet wire branch off from the main conduit directly beside the TBI unit and cross over thevalve cover headed down between #6 and #8 exhaust ports..

Either way the O2 Wire routes, your starter wires WILL run from rear top of engine to fron, then down behind water pump and back to starter.

Just follow the wires and you will find either a empty plug or the O2.

Also sumthin stupid to sk, consdiering this particular engine has two temp sensors.
Dos the temp guage work? if yess thats telling you that atleast ONE temp sensor is good..
Theres one on driver side below exhaust port 1 and another up top just behind your thermostat.

One work the guage and the guage ONLY, the other is what the ECU uses.
If the ECU temp sensor is bad it will cause excessive rich conditions. as the ECU thinks your engine is cold at all times.

Also check the ground wires up near thermostat housing, they LOVE to corrode! they are the ones on the stud held down by a nut on said stud. Have fun breakin that ***** loose..

 

[busafreak]

Good points ezdaar on the thermostat sensor and the ground.. if u do decide to replace it, dont buy the cheap one.. ask me how I know.. lol

 

[ezdaar]

Your O2 sensor wire is violet or purple, what ever its faded or stained to.. Use Berrymans B-12 to clean them fast and easy to see colors..
Just a quick spritz of the stuff... its VERY powerfull..

 

[Done Deal DR]

your O2 is Very near the starter, either on the Ypipe at very top near connection to manifold, or on the manifold itself.

IF you dont "SEE" a O2 look for the bung, someone may have removed the O2 and put in a plug, basicly a large bolt to seal the massive hole.

You can also trace the O2 wire from front of the block, if stand infront of vehical, look towards passenger side of motor right below the TBI unit. you will see a large plastic conduit full of wires.

maybe 3 of these wires will continue towards front of engine and down the front of block.
2 of them will be starter wires. and one will be the single O2 wire, it will travel under the exhaust manifold past the starter to the Frame where its attached with some form of clip, then route back to the O2 sensor.

Now GM in all their glory revised this like 3 times. you may have a green wire as O2 or a violet colored wire.
There maybe 3 or simply 2 wires running from the large conduit uptop down towards the starter.

You may also have just a single green or violet wire branch off from the main conduit directly beside the TBI unit and cross over thevalve cover headed down between #6 and #8 exhaust ports..

Either way the O2 Wire routes, your starter wires WILL run from rear top of engine to fron, then down behind water pump and back to starter.

Just follow the wires and you will find either a empty plug or the O2.

Also sumthin stupid to sk, consdiering this particular engine has two temp sensors.
Dos the temp guage work? if yess thats telling you that atleast ONE temp sensor is good..
Theres one on driver side below exhaust port 1 and another up top just behind your thermostat.

One work the guage and the guage ONLY, the other is what the ECU uses.
If the ECU temp sensor is bad it will cause excessive rich conditions. as the ECU thinks your engine is cold at all times.

Also check the ground wires up near thermostat housing, they LOVE to corrode! they are the ones on the stud held down by a nut on said stud. Have fun breakin that ***** loose..

LOTS of good information here, thank you sir!

I will triple check for the o2 sensor and bung. I guess part of me fears it has been completely eliminated (as far as the bung) when at some point in it's previous life the exhaust system was swapped. I fear at that time a new y-pipe was fabricated without a bung or o2 sensor. That may be unfounded as I have no way of knowing if it's original or not, but I guess we will see.

If I can't find it, I will try to trace the 3 wires as you said and see what I find.

My temp gauge does work, but of course without swapping the other I'd have no way of knowing if the secondary sensor that sends the signal to the ECM is in fact working.

More than likely, it's something relatively simple that will be a complete PITA to track down. I really need to figure this out so I can get it to pass emissions, get it painted, and start to use it as I originally intended (camping and tow truck for some PWC's). I have other cars I drive for everything else, which is why this situation sucks even more.

---------- Post added at 03:42 PM ---------- Previous post was at 03:34 PM ----------

Your O2 sensor wire is violet or purple, what ever its faded or stained to.. Use Berrymans B-12 to clean them fast and easy to see colors..
Just a quick spritz of the stuff... its VERY powerfull..

The verdict is in, it DOES have an o2 sensor. It is located on the passenger manifold before the y-pipe, directly by the #7 cylinder. Of course no way to know if it's good or not just be looking at it (wouldn't that be great?).

So at this point it looks like logical deductions would be to try a new o2 sensor (I'll get a good one if I do busafreak lol), and/or new secondary temp sensor/sending unit?

 

[ezdaar]

test it, get multi meter, put it on ohms setting, hook multi eter black to ground on vehical, and red to o2 wire.. Fire up engine. see if it changes ohms..

That will tell you if it "Works" but not if its in tolerances... that sensor is dirt cheap just replace it..
BESHURE to put a TINY amount of NICKLE anti seize on the TOP threads,, aka closest to sensor main body, NOT near tip!

As it gets hot it gets runny and will spread. IF it gets into that coverd area aka tip it RUINS it..

But this will keep that POS from rusting in.