VSV resistance interpretation

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, Skimlinks, and others.

bpenn1980

bpenn1980

SILVER Star
10 Year 15 Year
Joined
Nov 15, 2007
Threads
126
Messages
1,134
Location
Los Angeles
I had the VSV out on the bench this past week. Did the full testing and it appears to be working properly. I also heated it up with a hairdryer until it was too hot to touch it still appeared to function (air flow v no air flow).

My question is this:

I tested it at around 80-something degrees (ambient air temp) and the resistance read something like 57 Ohm, FSM states it should be tested at 68-degrees and get a reading of 30-33 Ohm. After I heated it up with the hair dryer the Ohm reading went up higher, like 85 Ohm or something. Didnt write the exact numbers down unfortunately.

Anyway, is my higher Ohm reading enough to warrant replacing the VSV? Sorry if this is a dumb question, I dont trust my electrical knowledge nor my understanding of the EGR system.

PS- I hate chasing EGR malfunctions....
 
These resistance readings are probably just fine. But the other test you should do is to apply 12v across the coil connections and see if the valve actually functions as it should. Air should not flow through when voltage is applied, but should flow freely with no voltage applied.

The EGR VSV is notorious for operating intermittently. I suspect that when it gets soaked with heat from the engine the coil opens up (i.e., resistance goes to infinity) and this causes the valve to be open when it shouldn't. The open VSV valve disables the EGR valve and (if you have OBD-II) you throw a P0401 code. Then you go to troubleshoot the system after everything cools down and low and behold, the VSV is working again. I doubt your hair dryer approach gets the VSV hot enough, at least not internally. Still, you have the right idea. The smart shopper price for the EGR VSV is $89, so kind of pricy to replace if you don't know for sure that's the problem.
 
Tom,
Thanks for your input. I was just reading an old 2007 thread where you were educating someone else on ohm readings and resistance of EGR components.

I agree, the hairdryer probably wasnt on long enough to really cook it thoroughly. I'm going to rig up RavenTai's method with the vacuum gauge in the cab so I can see in real time whether the VSV is open/closed when it should be. Fyi, the VSV did function properly with 12 volts applied straight off the battery both when it was at room temp and then after I heated it up a bit. So at least it is functioning when warm and when hairdryer hot, but maybe not with temps climbing toward 200*.

Vacuum modulator has 100% resistance to air pressure from the large port underneath which I understand indicates that the membrane is intact. Also was able to kill the engine while drawing a vacuum on the EGR valve with the other side plugged, so the EGR valve is responsive as well.

Seems like it is narrowing down to poor fitting vacuum line (still a couple I havent replaced) or the VSV fails when it gets really hot. Getting smogged in a month, so need to get this squared away before then.
 
Sounds like you've done all the easy stuff, Brad. So the vacuum-gauge-while-driving is the obvious next step. Post up what you discover.
 
Shoot. No vacuum.

I hooked up the vac gauge in both arrangements per Raventai's "alternate EGR tests" post and didnt get any vacuum in either arrangement. So, my VSV and vacuum modulator are bad, or I have a disconnected vacuum line/clog, or some combination of the above.

Since I just pulled the upper intake manifold and cleaned out the egr valve to intake passage AND the EGR to VSV passage through the manifold I know for a fact the two most common places for clogs are clear. I also replaced most all of the vacuum lines and cleaned the throttle body. Anyone have any tips?

My next step is to check the EGR valve/Vacuum Modulator hose since that wasnt replaced because it felt really snug. Maybe there's a clog on the nipple of the EGR valve.... grasping at straws here. Other than that, I didnt remove the EGR valve itself, so maybe there's a big carbon clog in the exhaust gas feedback tube?

This is really annoying. My wife is already suggesting that I should "let a professional take care of it." :o
 
First off, tell your wife, in a friendly and soft voice but with firm conviction, that you already know more about the issue than the so-called "professionals" do and taking it to someone else at this point will only end up costing a pile of money. Tell her you are a member of an on-line "self help group" and have shared your deepest inner feelings with them and they have strongly encouraged you to stay on the present path to the personal freedom and power that true knowledge provides. Tell her that, like all good things in life, enlightenment takes time to achieve and you can't rush it. I'm sure she'll understand. :lol:

Now that the hard part is out of the way you can move on the the technical part. I think you're clearly moving forward. You've gone from "why is my EGR system broken?" to "why don't I have vacuum when I should?". Do you have a FSM? It tells you how to use a vacuum gauge to check out the various components in the EGR system while sitting in your driveway. Maybe you've got a clogged vacuum port somewhere or a cracked rubber hose. From prior tests it appears your modular doesn't have a perforated diaphragm, so that's probably good. The EGR valve rarely fails and your previous test yielded the expected stumbling/dying of the motor, so that sounds good to me. And the VSV tests good on the bench, so the valve itself is likely good. So assume, at least for the moment, that those three key components are fine and move on to other stuff. Is the valve getting voltage from the ECU? (No voltage = free flowing VSV = disabled EGR) Check the connectors (both at the VSV itself and a second one in front of the throttle position sensor) to make sure they look good and are fully seated, and at least consider wiring up a light or voltmeter in parallel to the VSV so you can verify it's getting a signal from the ECU. Follow the vacuum hose "wiring" diagram on the underside of the hood and verify stuff is hooked up correctly. Either you're not getting vacuum because a port is clogged or there's a leak in the system. If you plug off the port to the modular that comes from the VSV do you get normal vacuum readings? If you do then it's something to do with the VSV. If not, then I'd say it's a leak.

I'm sure you seen these other great Mud threads, but for those that may come after you here are my favorite EGR troubleshooting links:

EGR Systems - how it works
https://forum.ih8mud.com/80-series-tech/469674-checking-vsv-egr-without-removing-vsv-itself.html
https://forum.ih8mud.com/80-series-tech/111750-alternate-egr-tests-p0401.html
https://forum.ih8mud.com/80-series-tech/211364-checking-vsv-egr-easy-way-p0401.html
https://forum.ih8mud.com/80-series-...er-dreaded-401-thread-few-diag-questions.html
https://forum.ih8mud.com/80-series-tech/203948-replacement-vsv-spanish.html

And keep us posted on your progress!
 
Oh yeah, one more tidbit of info. The EGR VSV (p/n 90910-12079) is the same in an FJ62, FJ80, and FZJ80. So the same valve was used from 08/1987 - 09/1997. So if you're looking through a pick 'n pull, you've got a decade's worth of vehicles to consider.
 
Last edited:
haha, too funny! She's actually great about this "land cruiser thing" and is as cheap as me, so I usually get a free pass to buy tools etc in the name of saving $. Not to mention I enjoy working on the truck most of the time. I think she was trying to give me an easy out since I was frustrated and whining, but of course I took it to mean she thought I failed and I should give up. haha....how do men and women live together :meh:

I could go on about her indoctrination to the awesomeness that is IH8MUD, but I'll get back on topic.

Thanks for the idea to check the electrical. I foolishly forgot to use my voltmeter to make sure the VSV is receiving voltage at 2,500rpm, but I did check continuity from the plug and got 40.5 ohm. Again, this is out of 30-33 Ohm range stated in the FSM.

I did the FSM testing and the modulator appears to be compromised. Knocked out a very small pile of black carbon from the little hole below the filter on the modulator as well. To double check I rigged up current to close the VSV and tested pulling vacuum from the valve against the vsv (pass), and then from the modulator against the valve and vsv (fail). I should probably check to make sure the voltage is actually reaching the vsv before I buy the modulator but it looks like I found the problem.

Thanks for the hand holding Tom. It helps to have a sounding board. I'll post up with the final result.
 
Replaced the vacuum modulator, did two drive cycles above 55mph for 5min (longer and faster actually) and no CEL.

I guess the trick with EGR issues is be extremely thorough. I should have caught this much earlier. Anyway, the resistance readings I got off the VSV are apparently ok for anyone else curious.

Glad I can go get smogged now.
 
Congratulations, Brad! Glad you nailed the problem.
 
You must log in or register to reply here.

Share this page

Back
Top Bottom