EGR Error code wont go away (2 Viewers)

[nashqadri]

When I picked up the truck back in Sept ’24… the EGR issue was already there. Figured it’d be a quick fix… but man, it turned into a bit of a headache. I swapped out the EGR valve, tested the EGR modulator… that seemed to be doing its job. Still couldn’t get it sorted so I handed it over to a reputable shop. They replaced the EGR valve again… didn’t help… messed around with the hoses too but that didn’t hold up either. Light came back on right after the OBD cycle. That runaround cost me $600 including a SMOG test. Honestly starting to feel like he pulled a fast one. Since I told him I needed to pass smog to get the tags renewed. I think he saw the chance and just cleared the codes ran the smog test… and handed me a report that said “PASSED.” I thought sweet it’s finally fixed… renewed the registration and everything. But sure enough after a hundred miles or so the error popped right back up. Now the same guy is telling me the intake manifold isn’t pulling any vacuum… which didn’t sit right. I looked into it and yeah….. seems like that’d be pretty rare if the motor’s running fine.

So now I’m wondering… what’s the real issue here… and what’s the next move to actually fix it? Appreciate your help.

 

[tech_dog]

I'd say the first step is confirming if he's right about vacuum, because that does seem strange. You could have leaks at ventilation hoses, brake boost, vacuum lines, valve cover gasket, air intake, etc. In my experience, FZJ80s don't like unmetered air leaking in, and the EGR is vacuum controlled.

Do you have decent brake boost? Do you run rough at idle?

 

[nashqadri]

I'd say the first step is confirming if he's right about vacuum, because that does seem strange. You could have leaks at ventilation hoses, brake boost, vacuum lines, valve cover gasket, air intake, etc. In my experience, FZJ80s don't like unmetered air leaking in, and the EGR is vacuum controlled.

Do you have decent brake boost? Do you run rough at idle?

Idle running is perfect at 750 rpm. Brake is also good.

 

[Shipwreck]

What error code are you throwing?
PO401? 403? 71?
If it is a 401 code, the next step is to test the function of your vacuum switching valve (VSV). A failed VSV is one of the most common reasons for a PO401 code. Clogged vacuum lines and bad modulator are also possibilities.
BTW, 750 is a high idle speed for a warm engine. You should be around 650 rpm.

 

[tech_dog]

Brake boost runs on vacuum, so that's a contradiction to what he told you. If he just checked the vacuum lines at the EGR, it could mean some of the other switching isn't working, one of the small lines is leaking or clogged, etc. There's a lot going on with the vacuum path to the EGR. I just replaced all this stuff during my valve cover gasket job, and it was showing its age :

 

[nashqadri]

I didn’t realize the brakes pull vacuum off the intake manifold… that actually makes a lotta sense now. Before I dive into swapping out all the vacuum lines, I’m thinking it might be smarter to run a smoke test first… just to see exactly where it’s leaking from. Bet replacing those hoses is gonna be a bit of a fight. You think I’ll need to pull the throttle body… or am I looking at yanking the whole intake manifold?

 

[BTLSHP]

I have a 1994 that had a persistent CEL 71 code and a forum member got me through a pretty comprehensive rehab of the system. Almost every element had a problem - except the vacuum lines. Follow the FSM


Here is my thread on the topic....only missing point is the VSV would not hold a vacuum.

CEL 71 - Where am I?

We have had P0401 on and off for a couple of years. When I replaced all the hoses in May a removed the EGR, TB and Upper Intake I sort of ignored the FSM test procedure in favor of just doing things. Until last Friday, I felt like I had gotten away with one. But it is back. In May: Passages...

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