Lean condition... Could broken EVAP VSV be the culprit?

Joined
Oct 3, 2022
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Florida
93 FZJ80 OBD1

My rig is running rough/weak and I'm getting a lean code from OBD1. I noticed that the horizontal nipple was broken off the EVAP VSV and the line running to it was the source of a vacuum leak. So I just capped it off and tested the vacuum pressure, it is holding.

I presume the VSV is not operational since I just capped the line. Could this have anything to do with a lean condition?

I've already changed spark plugs, wires, distributor cap, distributor rotor, and pcv valve. I also installed o2 sensors, catalytic converters within the last 2 years. So I don't think any of these are the culprits.

I'm still learning about all this stuff so forgive my ignorance if my question is stupid.
 
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Not saying your broken VSV is the reason behind the lean condition but the introduction of un-metered air can cause a rough idle possible lean condition.

Take some starter fluid or even water and as the LC idles spray it on around the VSV and if the idle changes that is where your vacuum leak is.
 
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Not saying your broken VSV is the reason behind the lean condition but the introduction of un-metered air can cause a rough idle possible lean condition.

Take some starter fluid or even water and as the LC idles spray it on around the VSV and if the idle changes that is where your vacuum leak is.
Thanks for the response Scott. I tried that and there does not appear to be a vacuum leak. I capped the line that was going to the VSV and the nipple on the VSV is not sucking in air (it must be stuck closed or something). I also tested the vacuum pressure and it is holding 20".
 
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Thanks for the response Scott. I tried that and there does not appear to be a vacuum leak. I capped the line that was going to the VSV and the nipple on the VSV is not sucking in air (it must be stuck closed or something). I also tested the vacuum pressure and it is holding 20".

Then try spraying around all the vacuum lines and see if things change, also check your rubber intake tube for cracks.

Injectors could be clogged as well causing a lean condition.

What did the plugs look like when you pulled them out?

Spark plugs can tell you something based off how they look.
 
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Worland, WY

Spraying parts cleaner only gets you so far and in my experience is a waste of time.
I was thinking about making one of these with an old coffee cup tapped in the lid with a fitting and some smoke bombs . . .🤷‍♂️ 🤔
 
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Seattle, WA/ Jacksonville, OR
I was thinking about making one of these with an old coffee cup tapped in the lid with a fitting and some smoke bombs . . .🤷‍♂️ 🤔
I mean anything is better than the parts cleaner. Essentially all it is baby oil on a hot plate and a pressure regulator. Even just introducing like 5 psi into the intake tube and spraying joints with soapy water will give better results.
 
Joined
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Look fir cracks in the intake tube in the ribs.
Thanks for the suggestion. I actually just replaced that a couple of months ago because it was a leak source.

I also removed my EGR shortly before this became a problem, any issues there you think? I capped all the lines and the EGR pipe and used a new gasket with the Wits End 'keychain.'
 
Joined
Aug 3, 2020
Messages
37
Location
California
93 FZJ80 OBD1

My rig is running rough/weak and I'm getting a lean code from OBD1. I noticed that the horizontal nipple was broken off the EVAP VSV and the line running to it was the source of a vacuum leak. So I just capped it off and tested the vacuum pressure, it is holding.

I presume the VSV is not operational since I just capped the line. Could this have anything to do with a lean condition?

I've already changed spark plugs, wires, distributor cap, distributor rotor, and pcv valve. I also installed o2 sensors, catalytic converters within the last 2 years. So I don't think any of these are the culprits.

I'm still learning about all this stuff so forgive my ignorance if my question is stupid.
I've already changed spark plugs, wires, distributor cap, distributor rotor, and pcv valve. I also installed o2 sensors, catalytic converters within the last 2 years. So I don't think any of these are the culprits.

I went through exactly the same routine in the last 2 years on my 94. What I had left with after replacing all those parts was the error cod 25. One problem I found was the exhaust leak at the backend of the bank 2 catalytic converter. The leak was big enough to damage new oxygen sensors. The second problem was the heater power/voltage to the oxygen sensor on bank 2. I was getting 12V with ignition on and 5V with the engine running on bank2, whereas 12V and 14.2V on bank 1, respectively. The ECM was not generating 14.2V for the bank 2 sensor. I looked into the ECM and found that it had a bad soldering spot/open circuit at the 5W resistor. After I fixed the spot, I got 14.2V and I was finally able to get rid of the lean code.
 
Joined
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I've already changed spark plugs, wires, distributor cap, distributor rotor, and pcv valve. I also installed o2 sensors, catalytic converters within the last 2 years. So I don't think any of these are the culprits.

I went through exactly the same routine in the last 2 years on my 94. What I had left with after replacing all those parts was the error cod 25. One problem I found was the exhaust leak at the backend of the bank 2 catalytic converter. The leak was big enough to damage new oxygen sensors. The second problem was the heater power/voltage to the oxygen sensor on bank 2. I was getting 12V with ignition on and 5V with the engine running on bank2, whereas 12V and 14.2V on bank 1, respectively. The ECM was not generating 14.2V for the bank 2 sensor. I looked into the ECM and found that it had a bad soldering spot/open circuit at the 5W resistor. After I fixed the spot, I got 14.2V and I was finally able to get rid of the lean code.
I actually took it down to Landcruiser Heaven in Miami a couple weeks ago and it turned out to be a wiring issue Running like a champ now!
 
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new york
what wiring issue did it have? curious when would your system go too lean? I just took it for a drive today and noticed that the STFT would rise up to 20% whenever I let go of the throttle. At idle and when I depress the gas, the STFT hovers around [-10,10] which should be within normal condition.

Screenshot_20221213-194925_OBD Auto Doctor.jpg

Screenshot_20221213-195053_OBD Auto Doctor.jpg


I also want to add that I recently put a ground strap connecting the cylinder head to the firewall.

I just got it from the mechanic the weekend prior where they fixed my engine stalling caused by flooded engine by replacing the distributor cap, wires and spark plugs.
 
Joined
Oct 3, 2022
Messages
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Florida
what wiring issue did it have? curious when would your system go too lean? I just took it for a drive today and noticed that the STFT would rise up to 20% whenever I let go of the throttle. At idle and when I depress the gas, the STFT hovers around [-10,10] which should be within normal condition.

View attachment 3193046
View attachment 3193047

I also want to add that I recently put a ground strap connecting the cylinder head to the firewall.

I just got it from the mechanic the weekend prior where they fixed my engine stalling caused by flooded engine by replacing the distributor cap, wires and spark plugs.
The prior owner had broke the clips on the fuel injector plugs and they weren’t making a good connection on cylinder six. The vibration of the engine was slowly wiggling the plug off.
 

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