First and Second Day of Ownership - P0401

[togles]

Well, the honeymoon was short lived from purchasing this thing Friday afternoon The previous owner cleared the P0401 so I got it on my ride home. So I dug in Saturday afternoon and started researching, was up until 4:30am today watching 50-60of EGR and EVAP system videos and reading tons of forum posts and talking to AI. I had no prior experience with troubleshooting or even a good understanding of EVAP and EGR systems, but after all the research last night, I woke up at 7:30 and felt confident enough to tear into this and have been working on it for 12 hours today.

Results -
EGR is good. I am able to open and close the diaphragm with a vacuum tool so I am good there.
I have a bad EGR Vacum Modulator, totally clogged up, deteriorated. On order.
I also have a bad VSV, its essentially stuck.
VSV Observations/Learning -
It measures 35.4 ohms, so electrically speaking its good, however, its clogged up and malfunctioning as it is stuck closed and will not release vacuum / open when 12v is disconnected.
The VSV is open(ie flowing freely) with no voltage applied. When applying 12v, it clicks and at that point it closes the valve, allowing for vacuum pressure to build. In my case, the VSV that I removed from the truck was initially open when I first started messing with bench testing it, air flowing freely. I applied 12v to it and was able to pull solid vacuums with 12 volts applied on both ports of the VSV, and when removing the voltage, the vacuum would drop immediately. So initially I was thinking I was good with the VSV. However, after the 2nd or 3rd time, when removing the voltage, vacuum remained, it was just stuck at that point. I bench tested the Doorman 911-850 that someone else mentioned using and that operated very much the same way, as my initial tests on the stock one, but its was working 100% of the time. I would have stuck with it but the plug from the ECU harness VSV wont plug into this Doorman part so I returned it and am going to get it from Toyota I think.

Other than that, I am definitely relocating my new VSV when I get it to outside of the intake manifold, trying to work on that in the future with it mounted under the intake manifold is for the birds.

Ill try to keep this thread updated as I go along and complete this job.

Below is my VSV Bench test setup.

Here are some pics of the VSV after unbolting from the underside of the intake manifold.

 

[togles]

Here is a pic of the vacuum port on the underside / back part of the intake manifold. Just above this on the outside of the intake manifold would be the vacuum port that the EGR valve is connected to. These are connected. From under the manifold, the vacuum hose would connect to the VSV valve, the drivers side port for lack of a better reference.

 

[george_tlc]

Good debugging. Yep, the VSV can become intermittent, working for a bunch of time and then getting stuck. So, code comes, goes away, comes back. Eventually it just gets stuck and the code will continue to return even after clearing with a scanner.

I replaced mine years ago (probably close to 10), the factory ones last many years, I've replaced only once in my 29 or so years of ownership and have a spare sitting for the next time around. At that stage, removing the intake manifold (which is reasonably easy) is worthwhile if for no other reason than to replace the spaghetti of vacuum lines under there Toyota sells cut lengths of the vacuum line and you then just cut to fit.

cheers,
george.

 

[george_tlc]

And you only remove the top 'half' of the intake manifold, so other than some long extensions to reach some of the bolts that are only accessible from below, it's an easy job. To be 'factory correct', just have a new metal gasket on hand ready for replacement, ditto for the throttle body to upper intake metal gasket.

cheers,
george.

 

[togles]

And you only remove the top 'half' of the intake manifold, so other than some long extensions to reach some of the bolts that are only accessible from below, it's an easy job. To be 'factory correct', just have a new metal gasket on hand ready for replacement, ditto for the throttle body to upper intake metal gasket.

cheers,
george.

Thanks, yeah i have to call Toyota tomorrow to try and get the egr and throttle body gaskets, as well as the vacuum modulator and vsv and about 30 feet of this vacuum line lol.

 

[Brindleboxer]

IIRC I ordered 90999-92004 for the vacuum line. This is the smaller diameter but there are a couple larger hoses that can be ordered separately.

 

[togles]

Update - I completed my work on the truck yesterday, replacing the egr vacuum modulator, the vsv and all of the vacuum lines. I have since driven 25 miles last night, in town and freeway, another idle session in the driveway last night and this morning, no check engine light followed by more in town driving and more freeway driving, stopping and idling, turning off, waiting to cool, getting back on the freeway, driving home, etc. I have put over 60 miles in total since repair. I am trying to run the smog readiness on my obd reader tool/app, i am using BlueDriver. Last night and this morning, there are two pending items, "catalyst vehicle has not yet completed this test" and "egr and/or vvt system unknown until check performed". No check engine light anymore!! However, these incomplete tests are preventing me from a trip to the smog shop, Its acceptable to have 1 incomplete but I cannot pass with 2 incompletes. I have read the TSB on readiness monitor drive patterns now for these 2 items and while i havent followed it to a T I feel like its probably really close. I dont think it would be even possible to follow these instructions anywhere around where I live due to traffic unless I head out at 3-4am and try to do these. Any thoughts on when I might see these clear? Do I just need to drive more miles?

 

[Brindleboxer]

First, congratulation on tackling this and doing the troubleshooting.

I would suggest put a few more cycles and see if it "resets". IIRC, the catalyst incomplete test should clear from driving.

If this doesn't work you could disconnect the battery for about 15 minutes and then drive again, it may reset the perimeters and allow the codes to clear.

Also, I would throw your vehicle information in your signature line so everyone knows and you don't have to keep typing it with every post.

 

[togles]

First, congratulation on tackling this and doing the troubleshooting.

I would suggest put a few more cycles and see if it "resets". IIRC, the catalyst incomplete test should clear from driving.

If this doesn't work you could disconnect the battery for about 15 minutes and then drive again, it may reset the perimeters and allow the codes to clear.

Also, I would throw your vehicle information in your signature line so everyone knows and you don't have to keep typing it with every post.

Thanks for the suggestion. I updated my signature

 

[Brindleboxer]

I assume you also were able to fix your heater control valve issue from the other post as well. I know it isn't fun to buy a vehicle and then have to jump in and fix things just to enjoy it but owning an 80 the repairs are part of the journey and you get to know your truck better with each one.

Heck, these items would have been on the baseline list somewhere maybe just not at the top.

 

[BTLSHP]

Getting at the EGR code was the most painful part of a rehab of our '94. I failed to go after it systematically like you and it took way too long to learn what you did - the VSV was electrically fine but would not hold vacuum for more than about 30 seconds if that.

Congratulations on following the manual and hopefully your approach pays dividends elsewhere.

 

[togles]

I assume you also were able to fix your heater control valve issue from the other post as well. I know it isn't fun to buy a vehicle and then have to jump in and fix things just to enjoy it but owning an 80 the repairs are part of the journey and you get to know your truck better with each one.

Heck, these items would have been on the baseline list somewhere maybe just not at the top.

Heater control valve was not on my list but it is now lol. I bought this thing as a project, so I am happy to have things to do with it, to work on and make it better. The list keeps growing I want to do the distributer o ring, oil pump o ring seal, and front crank seal as my next project. The oil is leaking bad from the oil pump, not so much the distributer and front crank. I also need to flush the coolant system, and have some obvious hose replacement/re-jiggering of all that stuff, i have the original pesky hose, rusted pipe too. So I think my plan is going to be to tackle all of this as one big job next, along w draining and filling the oil and maybe redoing the oil pan gasket at that time too.

 

[BTLSHP]

I started off thinking 5k including a new interior, I wound up at around 12k. The engine & transmission were fine. So, we went about making it reliable as possible with Toyota parts or equivalent (Asin/Gates transmission hose).

It took me too long and finding someone willing to follow the FSM on the windshield took too much effort. The end result made it all worthwhile. The car moved to Denver where it is more common than around DC.

I enjoyed the journey wrenching on it, and then people on these pages were incredibly helpful at every step.

 

[togles]

Update - Smog passed! Plated and Registered in my name now.

My Blue Driver bluetooth obd2 dongle and app were the culprit to my egr and catalyst staying in incomplete status. I took it to a friends shop and plugged in his obd2 reader and egr was complete, catalyst still incomplete. You can have 1 incomplete but not 2, so smog is done! Now I am going to smash my Blue Driver dongle with a hammer because it cost me over 100 bux in gas needlessly driving around trying to clear these things.

THANKS EVERYONE!!