94LC Failed CA smog no EGR vacuum when revving. (1 Viewer)

May

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Feb 20, 2017
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Merry Xmas folks.


fz1boxer...I was considering that in the mix as well.
Read some post about some 94 owners having problems with
code 25/26 that was caused by a bad pair valve.
The valve on the pair that is causing me problems is the one closest to the firewall.
I even did a leak test on the intake manifold and couldn't find a leak.
Sure enough when I opened up the pair valve the aforementioned valve
was the dirtiest and doesn't operate smoothly. Since I plugged it no more code 25/26.
Tried to clean the stuck valve but couldn't get it as smooth as the other one close to the fan.

The vacuum line from the pair valve goes straight to a metal T pipe under
the intake chamber which supplies vacuum to the EGR VSV on one end and pair valve on the other end.
The clog was where all 3 meet.
Probably from the carbon deposits from the stuck pair valve and with the leaking modulator contributing to the deposit.
I made sure the valves were closed before I reinstalled the top cover of the pair valve housing.

However the only thing I did to disable the pair was to plug the big hose end by
the air filter housing and the small vacuum hose leading to the pair valve.
You don't hear the gurgling sound anymore at startup and the CEL for code 25/26 stopped.
Immediately after the quasi disabling of the pair I noticed that pickup at wide open throttle is not as responsive.

I have a snorkel and was wondering if that contributes
to the air intake volume while stationary affecting egr vacuum.
I'll remove the hose connecting the snorkel to the air filter housing first and check as it's easy.
Then re-enable the pair and check.
Thanks.
 
Joined
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georgia
Man i am sorry you have to go through all that for a 25 year old vehicle,emissions wise it should get passed and not failed just because the egr is not pulling vacuum.
 

May

Joined
Feb 20, 2017
Messages
65
Location
Los Angeles, CA
Yes I thought about that myself.
All this for a 25 yr old vehicle.
I must be a crazy die hard LC fan.
Actually it’s the only family vehicle we have right now and can’t afford another one at the moment.

I would have not been able to afford hiring someone to do all this work but was contemplating to have the stealership use their diag tool to save me time and tell me what needs to be done and I can do the work. On the other hand I have learned alot on how to fix this classic truck of ours and feel good knowing I know something on how to fix it. So much to learn.

I want to get the toyobd so I can do a freeze frame data comparing Park and drive conditions but they are out of stock at the moment. I bought an obd1 to obd2 cable converter and an obd2 reader on Amazon. My phone detects it in Bluetooth mode but the tool won’t connect with my ecu.
 
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Messages
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georgia
MAY
just for s***s and giggles i pulled apart my EGR assembly kind of,there is a tube that comes off mine that is vacuum,it was completely plugged all the way through,also the temp sensor was caked with carbon and the port where it screws in was 90% plugged up
 
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IMG_0680.JPG
 

May

Joined
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Location
Los Angeles, CA
fz1boxer...I'm glad you found the clog. Your EGR passage on the intake chamber might be in the same condition.
 

May

Joined
Feb 20, 2017
Messages
65
Location
Los Angeles, CA
I was pressured to pass smog soon.
Have till Jan 8th(30 days from initial test of Dec 10th) to get a free retest but registration is due Feb 8th.
My plan, which will cost more money is to get an obd1 reader for further testing, replace VAF and Pair.
Removing the hose from the snorkel to the air filter housing was no help.

Remembered what he said after the smog test.." - older vehicles might show vacuum on the dyno."
Was able get in touch with a super cool Toyota engineer who mentioned
that's what they used to do with brand new 4wds back then.
With that as an incentive I couldn't let the free retest expire
knowing that it will pass EGR on the dyno plus it wouldn't cost me extra money.

So called him and he preferred that I remove the front driveshaft instead of the rear.
He gave a reason but I don't remember what he said.
The good part of this is that I get to remove a driveshaft which is my first
time and experience how the 80 behaves with only one.

Removed front driveshaft which wasn't as hard as I thought.
Luckily I installed my CDL button last year so I locked it in in Hi.
Test drove it yesterday to make sure it ran well but I felt uncomfortable thinking something might snap, lol.

When I saw him I told him that I removed the driveshaft as he instructed.
Also told him that I worked on it a lot by removing the intake, cleaning all the carbon
blockages and replacing the hoses.
Then informed him that I verified that there there is vacuum going to port Q and R
of the modulator, from the modulator to the EGR, low egr backpressure under the modulator
and that to get a high vacuum reading he will have to pull out the hose to Port R, place a
new hose and attach it to another intake port. He nodded his head and
said "that's how it works on Toyota's"
It's not that I was telling him how to do his job.
Just thought my chances would be higher if he knew I worked hard on trying to fix it and win some brownie points haha.
Most importantly I told him that per FSM there is only low vacuum at 2500rpm then
he said "Yeah I won't even have to go that high for the rpm's". Cool!!!!
His attitude was so different compared to the first test when he said "..you have some major problems. There is no EGR vacuum. Usually happens with older vehicles...older vehicles might show vacuum on the dyno." Then he pointed to the dyno tracks and asked me how our truck's 4wd system works.

Thought he was just going to test the egr on the dyno but he repeated the emission test.
I'm glad I drove on the freeway for a little bit before heading there even if the cats where new just to be safe.
Watched him test the egr vacuum with their white hand vacuum pump with the truck
on the dyno then he repeated the process of killing the engine by appling vacuum to the egr.
He didn't even test the remainder of the system!!
I knew I passed the egr test as soon as he proceeded to redo the emission test.
Anywho that's my first experience for smogging my 80.

As it is, still no VSV power while in park, only in D.
At least this will buy me time till the next smog test to find my problem if indeed
the '94s can get VSV power while in Park otherwise it's driveshaft removal again.
 

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