mickeydim468

Problem 1:
Code 21. I know it is O2 sensor, but where is the best place to test voltage to check for operation. Only throws code every once in a while. Is this an indication of wiring, or more likely the sensor itself?

Problem 2:
After driving for 20 minutes or so, if I stop and idle for a few minutes, I smell gas. Not exhaust, but fresh gas smell coming in from dash area. Where might this gas smell be coming from?

Thanks in advance for any help!

Mike!

Gamefreakgc

1. See http://personal.utulsa.edu/~nathan-b...01heatedox.pdf. Follow it step-by-step and it'll tell you what's wrong. The first check is the wire coupling just above the sensor, you'll find it if you start at the o2 sensor and move up the wire. The second and much longer process is using a mulimeter and the diagnostic ports located off the fuse box on the passenger side of the engine. You'll need someone on the gas while you read the multimeter, unless you've got some 6 foot wires on the thing. Did it with my wife a month ago when I got a code 25. Wasn't the sensor but it all worked as it should. Make sure your multimeter is sensitive enough to measure the "8 in 10 seconds" part.

2. I'm not an expert, but a gas smell is ALWAYS bad. You've probably got a gas leak on the hoses leading to your injectors. Get that looked at ASAP, if the fumes are strong enough and hit your spark plugs it'll be all bad. You can jump terminals in the diagnostic port with ignition on and the engine off, which will run the fuel pump but nothing else. It's FP and +B. Don't use this as a final solution since any gas leak is a serious hazard.

P.S. to "jump" terminals, take a paperclip and connect it to the two terminals. You can jump E1 and TE1 with a paperclip and then use your multimeter to jump the others when you are doing the o2 check. Paperclip will work with the fuel one too.

mickeydim468

Is the SST a jumper that you talked about?

Gamefreakgc

In this case, yes, a paperclip does the same job. Other parts of the Factory Service Manual will reference other Special Service Tools, there's all sorts of odd tools referenced that you or I would never have.

mickeydim468

OK Gotcha! Thanks. I'll test it after work then. I'll let you know what I figger out.

scope103

Code 21 is a problem in the HEATER circuit, not the sensor circuit. So using a multimeter on Ox1 won't do anything for that Code. (Very good for a code 25, though.)

Gas smell can be from the vapor canister, which is not being emptied because you've broken a nipple off the Thermal Vacuum Valve. That's not "super-bad" but should be fixed. But as gamefreakgc says, gas smell could be a sign of something that is super-bad. Another possibility is a loose indicator screw in the end of the pulsation damper (that will leak a dangerous amount of gasoline).

So carry a roll of paper towels, and the next time you stop, pop the hood. Hop out and feel around with the paper towel. If it comes up wet with gas, fix it! (Meanwhile, DO carry a fire extinguisher ...)

And in case no one else says it, it warms my heart when someone references the service manual.

mickeydim468

OK so how do I troubleshoot this problem then?

What does this look like, and where is it in the engine compartment?
NOTE: I also have noticed a lower gas mileage too. Do you think either of these issues may be the cause? Avg MPG is about 13 city.

Where is the pulsation damper? Where do I hold the paper towels?

I do 24/7 anyway.

Thanks again!

Mike!

Gamefreakgc

Ahh, my bad. Yeah, looking at it a second time I noticed the difference. Here's what the FSM says for code 21:

• Open or short in heater circuit
of heated oxygen sensor
• Heated oxygen sensor heater
• ECM
• Open or short in heated oxygen
sensor circuit
• Heated oxygen sensor

That's confusing. . Lol! So it looks like the process I listed might find the issue, but not likely. Then you'll be back at square one. I'm not familiar with the sensor heater circutry... not sure where that is in the FSM either.

scope103

Come on, I can't do everything for you. You don't even need to pay for the manual!

Start with http://personal.utulsa.edu/~nathan-b...42oxygense.pdf The manual will also tell you where the TVV is and where the pulsation damper is. (You will have to browse through it, but it's a rewarding experience.) If you have a broken nipple on the TVV (VERY common), you can search here for people who have successfully (they say) repaired one. Or $45-55 at the dealer.

I suggest a paper towel to look for gasoline leaks because gasoline is so volatile you'll rarely see it dripping all the way down to the pavement. On a 3vze, the pulsation damper is at the back end of the passenger-side fuel rail. But YOUR leak is where ever you find it.

mickeydim468

That's why I am here asking for help. Reading the FSM is like reading another language to me.

Mike!

Gamefreakgc

When it comes to diagnosis, yeah it's confusing at times. I have to read it over several times until it makes sense. For the normal assembly/dissasembly though, it makes more sense.

I scanned the FSM but couldn't locate a way to check the heater circuits. It's in there somewhere, I just can't find it...

Here's a bit about the wiring though: http://personal.utulsa.edu/~nathan-b...86troubles.pdf. Look at page EG2-199. There's wiring that goes from your oxygen sensor heater to your ECM (Engine Control Module/Unit, also ECU) which is located in the paneling on the passenger side cab. For location reference, the driver's side panel (next to the pedals) has your fuse box, the passenger's side panel has your ECM. There's no easy access flap for the ECM though.

If it's a wiring issue you can follow the wires from the oxygen sensor heater to the ECM and see if there's any damage. I've not had any wires in my truck go bad (and mine's a 91) so I'm not confident this is the issue.

mickeydim468

OK, I got in the back and felt for gas. Didn't even need paper towel. There is a plastic cover over my damper and when I took off the cover, gas fell out in a stream all over my hand. The screw is still in there, but I can't get to it unless I have a short #1 screwdriver. I have one somewhere around here. I couldn't find or feel the O-ring on the screw. That may be all I am missing. Any thoughts?

Still haven't gotten to O2 sensor issue yet. Gas leak takes precedence. I'll let you know what I find.

Thanks for the additional help Gamefreak and Scope103 too! Couldn't have gotten this far without you.

Mike!

mickeydim468

I just done screwed the pooch! There is a little vacuum gadget right next to the damper and I bumped the top hose nipple and it broke right off. What the heck is that thing? Can I fix it with super glue and epoxy? Or am I stuck trying to find one of those too? How much are they and what do I ask for at the parts house?

Mike!

mickeydim468

I figgered it out... It is the TVV that Scope103 mentioned earlier. That is a thermal vacuum valve. If I splice and bypass it, how rough will it idle until it warms up?

Mike!

dsmbuddy

You shouldn't have a bad cold idle if you bypass it. Try tightening the screw and see if the leak stops.

Easy check for the O2 sensor heater circuit - unplug the sensor and one the sensor side harness you should have a blue, white and two black wires. Ohm out the two black wires, this is the heater circuit. I believe the spec is somewhere around 14-16 ohms at room temp. If you measure OL, your heater is burned out and you need to replace the sensor.

Good luck with the fuel leak!

scope103

You can run with the broken TVV without much trouble. On the canister side you will probably smell some fuel vapors, but it's not a big deal (contrasted with your leaking fuel pressure damper, which is a big deal).

On the throttle body side of the TVV you now have a small vacuum leak, which shouldn't be a problem (it will happen when the TVV opens, when it is warm). You can plug that line, but I wouldn't. You want to fix the TVV before too much longer, so don't do much to put that off.

mickeydim468

Since I broke the nipple, I decided to pull the plenum. I got to the damper and got it off. I could blow air through it from either end. The screw is still there but when I removed it, the O-ring looks like some warped pancake on steroids or something.

I grabbed an old lawn mower carb rebuild kit I had laying around and got out some cork material. I made a new gasket for the screw with a razor blade and re-seated the screw into the damper.

How tight should this screw be. As tight as I can get it without breaking it? That is where I have it now. It isn't holding something that is supposed to move in and out right?

Oh yeah, I also fixed the nipple on the TVV. I'll post that fix in another reply.

Mike!

mickeydim468

Well, I just got done putting everything back together and it is still leaking gas. Not sure if it is out of the screw hole (Highly doubtful) or the crush washers. My guess it is the crush washers. I tried to reuse the original washers. I guess I am going to bite the bullet and order the part locally. I found one for $97.99, so I guess that's what I'll buy.

Why is that screw in there in the first place? The replacement parts I am finding do not have it.

Mike!

scope103

[source: www.autoshop101.com]

mickeydim468

Thanks Scope! I have the part on order. Be here Tuesday!