4.0 OHV identifying california emissions and advice on high idle/lean codes

[Michael Rogge]

Was suspecting that my engine needed new o2 sensors, according to rockauto they are different for cali and fed emissions. Attached are some pictures of relevant markings. Note that I don't know if the radiator support is original, the vehicle was in a front end collision a few owners ago as far as I can tell and the support is black when the truck is green. There is a very EGR-looking device between the exhaust manifold and intake, though if it is indeed an EGR that is a stupid design to put the EGR before the MAF and air filter.

I also have codes 172 (lean bank 1), 176 (lean bank 2), 136 (not switching bank 2), & 411 (KOER low speed idle test fail), what are the most common problems to cause this?

 

[Shran]

High idle & lean codes really point to a vacuum leak in my mind.

That deal on the air snorkel is not EGR, it's basically just a little valve that allows hot air off the exhaust to get pulled into the engine in cold weather.

 

[gaz]

@Michael Rogge
I would verify the fuel pressure on the rail immediately after shut down, then again after not running for 12-ish hours ..)

 

[Michael Rogge]

@Michael Rogge
I would verify the fuel pressure on the rail immediately after shut down, then again after not running for 12-ish hours ..)

What is the fuel pressure supposed to be for this engine? Should I check it when running as well?

 

[Michael Rogge]

High idle & lean codes really point to a vacuum leak in my mind.

That deal on the air snorkel is not EGR, it's basically just a little valve that allows hot air off the exhaust to get pulled into the engine in cold weather.

Glad to hear it’s not an egr
Was kind of hoping it was o2 sensors since those are a lot easier than intake gaskets (I already checked all the lines and none seem to be leaking), you’re probably right though

 

[gaz]

@Michael Rogge
Should read 38 while running, immediately after shutdown and 12 months later, even if the vehicle sat that long without being started or driven.

 

[Michael Rogge]

@Michael Rogge
Should read 38 while running, immediately after shutdown and 12 months later, even if the vehicle sat that long without being started or driven.

Got a tester, it reads 38 when the fuel pump is on but the engine is off, when the engine is on however it reads 31. When I then disconnect the vacuum line leading to the fuel pressure regulator it goes up to 39. Still waiting to see how it holds pressure but that might be inconclusive, I think the AutoZone rental gauge may leak.
Does this mean I need a new fuel pressure regulator or would a sensor be the more likely problem

 

[Michael Rogge]

Also, looked at other threads in this forum and there is no egr, that means it’s definitely not cali right?

 

[Michael Rogge]

Got a tester, it reads 38 when the fuel pump is on but the engine is off, when the engine is on however it reads 31. When I then disconnect the vacuum line leading to the fuel pressure regulator it goes up to 39. Still waiting to see how it holds pressure but that might be inconclusive, I think the AutoZone rental gauge may leak.
Does this mean I need a new fuel pressure regulator or would a sensor be the more likely problem

AutoZone gauge leaks, I can see a trickle of fuel coming out the bleeder so pressure retention is inconclusive

 

[Bill]

The sticker with the vacuum diagram states it conforms to EPA emissions. Order the EPA sensors.
For California vehicles it would say CARB.

 

[Shran]

If the sticker is gone or has obviously been changed and you have no EGR, I think it would be fairly safe to assume it's a federal emissions truck.

Regardless I would not put too much more time into your fuel pressure test, you have adequate pressure, so start chasing vacuum leaks. Like I said... lean codes and high idle immediately point to that... if you were just lean on one bank then my suggestion would be different.

 

[SenorNoob]

Got a tester, it reads 38 when the fuel pump is on but the engine is off, when the engine is on however it reads 31. When I then disconnect the vacuum line leading to the fuel pressure regulator it goes up to 39. Still waiting to see how it holds pressure but that might be inconclusive, I think the AutoZone rental gauge may leak.
Does this mean I need a new fuel pressure regulator or would a sensor be the more likely problem

This sounds like normal behavior but with low numbers. I wonder if the gauge is accurate?

As for O2 sensors, I'd be surprised if they are really different for California. Federal that year should have 2 and the sensors themselves are usually generic enough that you can buy a "universal" 4 wire without the connector...

 

[Michael Rogge]

This sounds like normal behavior but with low numbers. I wonder if the gauge is accurate?

As for O2 sensors, I'd be surprised if they are really different for California. Federal that year should have 2 and the sensors themselves are usually generic enough that you can buy a "universal" 4 wire without the connector...

How bad would it be to use a tire pressure gauge as a sanity check for the gauge? “Should read 38 when running” but reads 31 is a substantial difference.
Something I forgot to mention is that I’m getting pretty poor fuel mileage, wondering if that fuel pressure could cause worse mixing and lower mileage. I have learned over the year that I’ve owned this truck that everything the last few owners did to it was done wrong (Chinese wheel bearings with finger tight locknut, broken clips everywhere in the interior, left with terrible front alignment for a long time, radiator replaced with junkyard one and lost the shroud, transmission fluid seemingly never changed, etc), so I’ve been looking over everything adjacent to the problems it has for poor work quality.

 

[SenorNoob]

I'd expect it to work exactly once. Then the gas would dissolve a seal or something.