Failed smog
Fleet Mechanic
Joined: Nov 2022
Posts: 1,695
Likes: 415
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Laughing Gas
Joined: Jan 2023
Posts: 1,172
Likes: 114
is it possible that the line for it broke between the last smog and the one I just did, and it caused the emissions to go out of spec? I’m still fixing the manifold but I’m just so confused why it got worse even though I’ve made it run SO much better than when I got it.
Fleet Mechanic
Joined: Nov 2022
Posts: 1,695
Likes: 415
is it possible that the line for it broke between the last smog and the one I just did, and it caused the emissions to go out of spec? I’m still fixing the manifold but I’m just so confused why it got worse even though I’ve made it run SO much better than when I got it.
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Laughing Gas
Joined: Jan 2023
Posts: 1,172
Likes: 114
So I’m reading on octane right now, will I want to run 91 in it next time I take it for smog? I think that’s what was in it last time. I can check timing, possibly retard, and run 91 to help. If I can get it to pass without the manifold being fixed that’d be great cause I barely found a day that I can plan on doing it. If I have 3 tries free then I could try again with 91, the diverter valve fixed, and if it still fails I can fix the manifold and it will pass most likely. And I can just move shops if it doesn’t I think for more free tries. Cause then I could plan a whole weekend to worry about the manifold. I figure I’m gonna spend a while cleaning the manifold out and scraping gaskets and I’m already a little on the slow side for working on stuff. Along with needing to fix my lean condition, how would I go about fixing the EGR codes, how do I tell what type of EGR I have? I know there’s a lot of types for these trucks. It has a new EVP sensor since the old one didn’t pass the ohm test.
Hotshot
Joined: Jul 2020
Posts: 10,268
Likes: 2,563
From: Near Salt Lake City
I would be looking into the EVP code
The EGR valve lets burnt exhaust back into the engine to cool down the burn and lower NOx
So if the timing is too high you will be a bit hotter than a lower timing set
Make sure you are at ten degrees
Make sure your EGR valve is opening properly and you have the right size orifice in the valve itself
The EGR valve lets burnt exhaust back into the engine to cool down the burn and lower NOx
So if the timing is too high you will be a bit hotter than a lower timing set
Make sure you are at ten degrees
Make sure your EGR valve is opening properly and you have the right size orifice in the valve itself
Fleet Mechanic
Joined: Nov 2022
Posts: 1,695
Likes: 415
So I’m reading on octane right now, will I want to run 91 in it next time I take it for smog? I think that’s what was in it last time. I can check timing, possibly retard, and run 91 to help. If I can get it to pass without the manifold being fixed that’d be great cause I barely found a day that I can plan on doing it. If I have 3 tries free then I could try again with 91, the diverter valve fixed, and if it still fails I can fix the manifold and it will pass most likely. And I can just move shops if it doesn’t I think for more free tries. Cause then I could plan a whole weekend to worry about the manifold. I figure I’m gonna spend a while cleaning the manifold out and scraping gaskets and I’m already a little on the slow side for working on stuff. Along with needing to fix my lean condition, how would I go about fixing the EGR codes, how do I tell what type of EGR I have? I know there’s a lot of types for these trucks. It has a new EVP sensor since the old one didn’t pass the ohm test.
Lead Driver
Joined: Sep 2002
Posts: 9,473
Likes: 2,009
From: North Texas
Too lean also increases your NOx output. This is why some old Euro cars of mine fail...they have no O2 feedback for the EFI and lean cruise in the mid 15s AFR. Makes the NOx way higher, yet burn little fuel.
Anyway, yours is close. Do you have any oil leaks?
You said manifold leaks? Intake or exhaust?
Anyway, yours is close. Do you have any oil leaks?
You said manifold leaks? Intake or exhaust?
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Thread Starter
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Laughing Gas
Joined: Jan 2023
Posts: 1,172
Likes: 114
Too lean also increases your NOx output. This is why some old Euro cars of mine fail...they have no O2 feedback for the EFI and lean cruise in the mid 15s AFR. Makes the NOx way higher, yet burn little fuel.
Anyway, yours is close. Do you have any oil leaks?
You said manifold leaks? Intake or exhaust?
Anyway, yours is close. Do you have any oil leaks?
You said manifold leaks? Intake or exhaust?
I do have the gray evp. I’ve tried to figure this EGR thing out before, the EVP, EVR, both passed the ohm test once I replaced the EVP. The EVP had 5v, and the EVR had 12v. If I manually move the EGR valve with a vacuum pump, it will try to die. But I’m not sure how to test the EVR since it won’t allow the line to hold vacuum and it wont apply vacuum till I’m at cruise. I’m worried the back pressure thing is the issue. Cause I can’t afford a new exhaust.
The manifolds leak, at least the passenger but I’m thinking both do I can hear a tick from the passenger. The y pipe leaks where it connects For some reason the P.O. Cut the exhaust right before the axle on one side. So I only have 1 exhaust going to the back bumper.
Fleet Mechanic
Joined: Nov 2022
Posts: 1,695
Likes: 415
I have engine and transmission leaks. And I have intake and exhaust leaks
I do have the gray evp. I’ve tried to figure this EGR thing out before, the EVP, EVR, both passed the ohm test once I replaced the EVP. The EVP had 5v, and the EVR had 12v. If I manually move the EGR valve with a vacuum pump, it will try to die. But I’m not sure how to test the EVR since it won’t allow the line to hold vacuum and it wont apply vacuum till I’m at cruise. I’m worried the back pressure thing is the issue. Cause I can’t afford a new exhaust.
The manifolds leak, at least the passenger but I’m thinking both do I can hear a tick from the passenger. The y pipe leaks where it connects For some reason the P.O. Cut the exhaust right before the axle on one side. So I only have 1 exhaust going to the back bumper.
I do have the gray evp. I’ve tried to figure this EGR thing out before, the EVP, EVR, both passed the ohm test once I replaced the EVP. The EVP had 5v, and the EVR had 12v. If I manually move the EGR valve with a vacuum pump, it will try to die. But I’m not sure how to test the EVR since it won’t allow the line to hold vacuum and it wont apply vacuum till I’m at cruise. I’m worried the back pressure thing is the issue. Cause I can’t afford a new exhaust.
The manifolds leak, at least the passenger but I’m thinking both do I can hear a tick from the passenger. The y pipe leaks where it connects For some reason the P.O. Cut the exhaust right before the axle on one side. So I only have 1 exhaust going to the back bumper.
I read somewhere that new ones sometimes have too long a shaft, causing it to be out of range(I have code 34 as well, I just don't bother with it though, maybe some day)
Lead Driver
Joined: Sep 2002
Posts: 9,473
Likes: 2,009
From: North Texas
Any exhaust leaks pre O2 sensor? If so, I would address those before much else. The OE exhaust manifolds are well known to crack, mine were replaced in the late 90s just before I bought my truck in '99 (it is an '88). Can you post a pic of the Y pipe leak? It could be an easy fix.
I have been taught oil leaks can create vacuum leaks at least valve covers are easy to knock out with the updated gaskets from places like Felpro and the like.
I have been taught oil leaks can create vacuum leaks at least valve covers are easy to knock out with the updated gaskets from places like Felpro and the like.
Fleet Mechanic
Joined: Nov 2022
Posts: 1,695
Likes: 415
Here's a Haynes EVP sensor test procedure:
1. Disconnect the electrical connector on the EVP sensor and check for reference voltage from the computer with the ignition ON (engine not running) there should be approximately 5.0 volts
2. Next check the resistance of the EVP sensor. Working on the sensor side, check the resistance between EVP and VREF ILL, it should be approximately 5,000 ohms
3. Now apply 10 in.Hg of vacuum and check the resistance. It should be approximately 100 ohms. Watch for a decrease in resistance as vacuum is applied.
1. Disconnect the electrical connector on the EVP sensor and check for reference voltage from the computer with the ignition ON (engine not running) there should be approximately 5.0 volts
2. Next check the resistance of the EVP sensor. Working on the sensor side, check the resistance between EVP and VREF ILL, it should be approximately 5,000 ohms
3. Now apply 10 in.Hg of vacuum and check the resistance. It should be approximately 100 ohms. Watch for a decrease in resistance as vacuum is applied.
Thread Starter
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Laughing Gas
Joined: Jan 2023
Posts: 1,172
Likes: 114
Any exhaust leaks pre O2 sensor? If so, I would address those before much else. The OE exhaust manifolds are well known to crack, mine were replaced in the late 90s just before I bought my truck in '99 (it is an '88). Can you post a pic of the Y pipe leak? It could be an easy fix.
I have been taught oil leaks can create vacuum leaks at least valve covers are easy to knock out with the updated gaskets from places like Felpro and the like.
I have been taught oil leaks can create vacuum leaks at least valve covers are easy to knock out with the updated gaskets from places like Felpro and the like.
Oil leaks are from oil pan and rear main.
