89 K5 (V10). Smallblock 350. High NOX. Smog fail. EGR? CAT?

[buckallred]

I failed smog because (according to the smog guy), probably EGR valve being clogged.

Ordered a new one. I haven't got the old one out yet, but based on looking at it in the engine bay, it looks to match.

Concern is on the third photo, you can see that the tube/intake thing is nearly entirely blocked except for a tiny pinhole. Is that correct? That seems strange and I thought that the exhaust gases would blow in the tube/intake thing, and it should not be blocked except for that tiny pinhole.

All advice and comments are appreciated. Thank you!

 

[Chickntrk]

That should be a vaccuum line that hooks on there, looks like maybe they didn’t clean it all the way out during casting but it should still pull vacuum through there

 

[Wes Harden]

Chances are good that the intake manifold egr passages are blocked with hard carbon.
If the egr vacuum diagram is not ruptured, and is being provided vacuum when needed, then the egr is probably good.

The last picture on your post is for the vacuum signal to open the egr. The exhaust gas pintle is on the side that bolts to the intake manifold.

 

[dyeager535]

With many vacuum operated devices GM regulated the speed of "change" by restricting or opening the orifice (edit: Vacuum advance comes to mind). There are many variations of the EGR valves, I'd make sure what you pull off matches.

The aftermarket has a bad habit of making "universal" EGR's, when they are not. Ultimately, performance is all that matters though.

As mentioned already, with this much age, cleaning up the passages in the intake and whatever you can get to on the EGR might solve your issue(s).

 

[buckallred]

Thanks for the replies. So @Wes Harden , that means to remove the old EGR (make sure it looks identical to the new/replacement Dorman unit), then clean out the intake manifold EGR passages as best I can, correct?

That would involve spraying WD40 or similar on a rag and reaching in there as best I can with a finger/rag and removing the hard carbon?

All advice is appreciated, at my idiot level I need it! thanks.

 

[Wes Harden]

Yes something to soften the carbon is needed. You might actually need to use a punch and and mallet, drill bit and drill motor.
Keep a shop vac running to suck out the debris as you work.
Good luck

 

[buckallred]

Yes something to soften the carbon is needed. You might actually need to use a punch and and mallet, drill bit and drill motor.
Keep a shop vac running to suck out the debris as you work.
Good luck

if carbon flakes fall into the intake, any massive problem there?

 

[buckallred]

OK. Old EGR is off, looks identical to new one, new one is installed. They both have those tiny pinhole things where the vacuum tube presses onto it.

When I removed the old one, It was very hard to get a visual into the holes where the old one was. I soaked a rag i PB blaster and stuck my finger in the holes and cleaned them up as best I could. I didn't get a chisel or shopvac or anything, and I believe I probably should have, but I'm hoping everything will be okay.

Everything cranks and runs as it should. Of course the rubber hits the road when I re-test smog.

Anyone doing this job needs to know that reaching the two bolts for the EGR valve is a pretty good bitch. I couldn't get any socket in there at all and I couldn't get a ratcheting closed-end wrench in there. The only thing I could do is get a box end wrench over the bolt and turn it about a third of a turn at a time, if even that. So it's slow and on a lifted truck hard to reach. Have to start with the far/center EGR bolt (standing on a footstool at the passenger side wheel), then the near / passenger side bolt is slightly easier to get to and deal with. But it's another one of those things where you want to choke whatever engineer thought it would be okay to make an EGR valve, which obviously wears out and will need to be replaced, a headache to get in and out when it should be easy.

 

[Wes Harden]

Yep engineers ??? So with the truck running using glove and or a rag open squeeze the diaphragm open( or a vacuum pump if available), if the engine stalls the passages are open.

After the engine is warm revving the engine to 2500ish rpm the computer might command the egr to open, you can feel the diaphragm plate move. It will be HOT so don't burn your hand. If is does move, and the truck stalls at idle when you move it, chances are good it pass that part of the emissions gauntlet.

 

[4X4ForDad]

Something to think about...Use a 2 part distributor bolt tool. One side should be 9/16 and the the other side a 1/2. Both sides are 12 point. The tool can be separated to use the size you need with a sliding "T" bar for leverage. Available at Auto Zone. Part #70-035 or SKU 914110.

 

[buckallred]

Yep engineers ??? So with the truck running using glove and or a rag open squeeze the diaphragm open( or a vacuum pump if available), if the engine stalls the passages are open.

After the engine is warm revving the engine to 2500ish rpm the computer might command the egr to open, you can feel the diaphragm plate move. It will be HOT so don't burn your hand. If is does move, and the truck stalls at idle when you move it, chances are good it pass that part of the emissions gauntlet.

I returned to smog after replacing the EGR valve. Fail, high NOX, again.

I got home and cranked the engine, reached in there and squeezed the EGR valve diaphragm. The engine immediately began running rough, stumbling. So I believe that means the EGR valve is functioning correctly & the passages are not clogged.

Could I need new catalytic converters? I replaced them not many miles ago at all, maybe 10 or 20,000 because the vehicle gets driven only on the weekends in good weather. But it may have been 8 or 10 years ago.

Any and all advice is appreciated as always.

 

[buckallred]

Also: I I'm pretty sure it has some Lucas upper cylinder lubricant/fuel additive in the tank. I remember the label of this stuff saying that it "BURNS HOT HOT!!"

Fuel Treatment – Lucas Oil Products, Inc. – Keep That Engine Alive!

lucasoil.com

Is this a completely crazy idea, or could that stuff actually make the combustion chamber hot enough to cause high NOX readings? For that matter, I wonder whether that stuff burning may cause problems for smog testing.

 

[Wes Harden]

The egr passages are flowing gasses, that's good. But is the egr opening when it should. The vacuum control side still needs to function.
Okay try retarding the base timing by 2 degrees, open the gaps on all your spark plugs, to .060. be sure to put them back. Decarbon the pistons with seafoam, or water.
The above will work if you just barely outside the range. If you are way outside the limit then a new cat will probably do it.
Cooling system is in good shape?

 

[buckallred]

I'm way outside the range. I don't remember the number but something like triple the maximum allowed amount. Cooling system is in good shape.

I might go ahead and get the $50 EGR solenoid and replace it. Just to be sure.

I'm going to have a smog repair shop take a look at it. Probably will go ahead and replace the cats. Great.. sigh

 

[dyeager535]

"Cats" are not original.

These only came with one converter. Has this thing passed smog before? Converters need to be a specific temp to work properly, this is probably why adding cats to a vehicle is against federal law.

Not saying it is the reason you are failing, but cutting exhaust flow in half could certainly drive inlet temps down if the converters aren't placed properly. If this thing has passed before with the cats being well used, then less likely to be the cause.

 

[buckallred]

@dyeager535 @Wes Harden

yes it has passed many times before. It has 1 cat, I had it replaced several years ago (I misspoke when I said "cats").

What about the theory that the Lucas upper cylinder lubricant is causing the high NOX? Thanks for the advice.

 

[Wes Harden]

Noylt even sure what Lucas product that is. if this stuff coats the top of the piston and or combustion chamber, it could possibly increase compression. High compression makes nox.

@dyeager535 has a point if the cat is not hot or cooled off before the test. Thou iirc the test procedure will have tech do a catalytic warm up.

 

[1-ton]

High NOx means your trucks fuel mixture is too lean. Check for vacuum leaks. This will make your engine run lean.

 

[scouthead]

with an OBD1 vehicle that is going to get the sniffer up the pooper... never ever ever take your vehicle to be tested unless:

1) it just had an oil change with good quality oil
2) the gas is FRESH -not 1/2 tank of something that was sitting- drain that garbage or drive around until it has been consumed, and then fill it up with NEW good quality gasoline
3)) the engine is FULLY warmed up when you arrive at the smog station.


I have literally been AMAZED at the difference old oil or old gas makes at passing a test here in CA, and dont even think about getting the thing tested if its not fully warmed up. You need the coolant at the correct temp, the heads needs to be hot, and the cat needs to be hot.


the only time my 1988 K5 ever came close to failing a smog test (well technically it did for a minute) -it had been sitting for a few months. I fired it up - jumped in, ran over to the smog place about 5-7 miles away. engine coolant temp was barely coming to temp when i got there. It failed in several categories by quite a bit. I was really surprised! what the hell- this thing always passes, and the cat is fairly new!

owner of the smog place came over and said; "has this truck been sitting? - go change the oil and fill up with fresh gas. come back and we will test again."
i was not sold on that making a difference and figured i needed a new egr, or cat... but i did it, and went back, and the truck passed with FLYING COLORS. the tech doing the test told me he was worried I was going to get him in trouble, and must have added something to the gas tank that was illegal. -NOPE!

Any more, why take the risk of not passing the test? - i drive around for quite a while before an emissions test, and spend some time driving in 2nd with the rpms up... and when Im sure the thing is HOT, i pull into the smog testing station and leave the truck running in their parking lot. it stays running until the tech goes and pulls it inside to do the test.

 

[buckallred]

@scouthead

Thanks for the excellent info. I haven't had a chance to mess with it yet, but I have changed out the EGR valve and the EGR vacuum control device.

The gas in the vehicle is many months old. Additionally, I'm pretty sure I dumped a significant amount of Lucas upper cylinder lubricant gas additive in it, which may have made things even worse (emissions).

So, next task is use/burn nearly all the gas in the tank, then add fresh gas and even let that run through a little bit. Change the oil. Drive the thing until it's good and hot and then leave it idling in the smog place parking lot. Hopefully all of that will put this issue behind me.