Quick question

Hey everyone,

I just recently installed a boost gauge in the '95 Riv, and while I was in there, I discovered that a vacuum hose was a little loose. No big deal, I stuck it back on there and it was tight. Must have been from when i changed my coupler. However, beside it, was another nipple/nozzle thing. I couldnt help but notice when I started the car up to test my boost gauge, I could hear a vacuum hiss coming from that area. See picture in this link:

http://www.zamiska.net/z/DSC02225.jpg

The nipple thing is above the rear valve cover between that blue plug and the elbow vacuum line. I have NO idea what this device is or if anything is supposed to be capping or attached to that nipple. I know the hiss is coming from that area but haven't beenable to test for the leak yet. Always been dark when I get home.

Also, I'm pretty sure it IS a vacuum leak coming from that area, being the nipple or not, because when I detach any other vacuum line, there's never any hiss from released vacuum.

Can anyone help me? I know I asked a lot of questions but if you need to know anything else, just ask me. I just want to get to the bottom of this. As well as change my O2 sensor, but that's for a different day .

Thanks all,

-Andrew Z

Yes there should be a hose on that. I'll grab you some pics when I get home from work 2nite of what should be connected to it, and where it goes.

Edit: and you should probally look into changing out all your vaccum lines, the one sneaking in at the top of your pic, you can see how its flakeing apart...

Ah...I KNEW there had to be something there. I can't tell where it goes though. I'm pretty familiar with the engine bay though so pictures are great, any direction as to where it's connected is helpful too.

And yes - that's the only vacuum line I haven't changed. Everything else is either good or replaced. Thanks for reminding me though...and thanks in advance for the pics!

There should be a hose that goes from that empty spot in your picture to the bottom left(when facing the engine) of the vacuum tap(the square thing screwed to your SC).
:

Spoiler:

The next hose on that square vacuum tap should go to a T, with one going to your vacuum box (that big square box at the back, a vertical connection) and the other going to your cruse control actuator.
This should make it clear as mud:

Spoiler:

I understand completely! Thanks a lot! Now I just have to wait until the daylight to check it out. I have a hose in the square vacuum block, but I'll bet you it's just hanging down behind the engine. I'll let you know tomorrow. Thanks again for the help and clearing up this situation! I'll get back to you all tomorrow .

Well that hose was exactly where i thought it would be. The end of it tucked down behind the engine. I plugged in the hose, so to speak, and now, SOMETIMES, when I'm coming to a stop my RPMs will fall drastically and go up and down about 3 RPMS before settling out. It's fine while driving but sometimes, and only sometimes, when coming to a stop and idling in drive that will happen. I think I'm going to replace the vac line tomorrow and see if that helps. I'm wondering if the system is just getting used to the new vacuum situation now that it's 'fixed', but since it does it only every once in a while, im not so sure. Any thoughts?

Thanks again Karma!

Well, drove the car around quite a bit today and I'm not sure anything has changed, despite me changing the crumbling factory vacuum lines. Though I can give better symptom situations now. It appears that the RPM wavering issue happens when the car has been sitting a minute, like in traffic, moves forward a bit, and you slow to a stop, and it does it again. During regular driving the car couldn't be better. I'm stuck here...

Could the car just be in the middle of a re-learn since, basically, it's vacuum system has completely changed since I fixed it? Should I unplug the PCM fuse and do a 'manual' re-learn?

manual relearn won't hurt but this could just be that the throttle body's dirty.

Albertj

Yeah I didn't think it could hurt. I'll double check the throttle body in the morning but it was clean when I got the car two months ago. Who knows though! It really seems like a computer problem. I wonder if it's a problem with the electronic component that my vacuum line was missing from?

Like I said, the problem is tolerable for now. It runs great under throttle and most of the time, the problem doesn't show. I'll try a re-learn tomorrow evening when I get home.

Hey I hope me using my old thread isn't a bad thing, but I have a related question to my own topic here.

In this picture: http://www.zamiska.net/z/DSC02225.jpg
...what exactly IS that thing? I reconnected the missing hose for it, as you may have read in this post, but I don't know what this component does. It sits in the rear-middle above the valve cover. It has one intake vacuum hose attached to it, that blue plug, and another hose that's similar to the flexible fuel line for the car.

What is that device?
Where does the hose that's similar to the fuel line go/end up?
Could this thing going bad lead to a false oxygen sensor reading?


The reason I ask is because when I finally fixed the vacuum hose, and attached it to that thing, my idle went crazy and I started getting a frequent PO171 (oxygen sensor lean) code and a random idle-hunting syndrome in Drive. My gas mileage bites as well.

Could a lean oxygen sensor reading cause my idle to go crazy?

I'm sorry I'm asking a lot of questions I'm just trying to cover some ground...

Thanks guys!

Well, I can tell you that the unit in the picture is Fuel EVAP Control Solenoid.
The black "Fuel Hose" runs back to the gas tank or more correctly to the EVAP canister back under the car.
Evaporated gasoline, or fumes, are supposed to be burned by the engine through this system as opposed to, years ago, being vented to the atmosphere.
Yes, a lean O2 sensor reading can cause idle problems and bad fuel mileage.
One thing I can offer is try unplugging the vacuum line from the EVAP Sol. and plug that vacuum line so there is no air leak and drive as you normally would and report back.
The rest of your questions I'm not 100% sure of so I'll refrain from answering. Someone else with more definitive knowledge can answer for you.

Thanks Rick. I appreciate that information a lot. I knew it went to the gas tank I just wasn't sure what it did exactly. That clears up some things and leads me to believe it is not malfunctioning. I am having a problem, however, of the flexible line that goes to the tank staying on the nozzle on the solenoid. It likes to slide almost all the way off and even a tie wrap didn't help. But again, I don't think that is causing any of my problems. Even the Lean Oxygen Sensor code.

I did try unplugging the hoses and blah blah blah. The weird thing is, before I plugged the one vacuum hose back on (was never plugged in while I owned it the last couple months until 3 or 4 weeks ago) the engine ran GREAT. I would occasionally get an SES but the idle was always fine, until I plugged that in.

Someone once suggested the EGR going bad, but I don't think that's the case either because I unplgged it and nothing changed.

I can only assume, at this point, that my oxygen sensor is toast. My SES light is getting very frequent, sometimes never turning off all day, and my gas mileage has gone to crap - down to 16 mpg 50/50 driving. Lol I can't afford that. So from what I understand, my oxygen sensor is getting or GIVING a lean reading, causing the engine to receive and burn more fuel than it needs.

I've tested almost every place for vacuum leaks as well, and turned up nothing. Maybe I missed somewhere, but who knows.

Thanks again Rick, and ANY suggestions or information from anyone IS helpful to me. I'm pretty savvy with cars and getting better with these engines, so thanks in advance everyone!

If the O2 sensor is original you can try replacing it.
But that is what I call Shotgun maintenance, throwing parts at a problem when your not exactly sure what the source of the problem is.
I don't like doing things that way or recommending you do that either.
With a proper scanning/graphing tool a good Tech can watch the action of your O2 sensor during closed and open loop operation along with air fuel ratio's and determine if it is indeed a lazy sensor.
I know this cost's most people money but that is the way I determine if things are bad, good or going bad, but I have the diagnostic equipment available to me at times for free.
If you can find someone to hook it up that won't charge the diag fee, but will charge to replace the suspected bad components only, you will be better off. Because if that's not the problem then he is obligated to eat the poor diag and the cost of part, unless he chooses to re-install the old part.

Z-type wrote:

Someone once suggested the EGR going bad, but I don't think that's the case either because I unplgged it and nothing changed.

There should have been A difference here, I believe.

Yeah i don't WANT to just start putting parts on it, but that's why I'm getting it scanned again tomorrow (I hope) to see if i might have a new code. There's a lot of 'if's and maybe's' in this situation as you can see.

What kind of difference should unplugging the EGR have made? Would a faulty EGR cause my lean O2 sensor code? I know it could cause certain idling issues.

There is a guy a mile down the road who can read the codes, but I'm not sure if he can read diagnostic information or not. I'll ask tomorrow and I'll report what happens. Stupid early OB2 system...

Either way, I'm going to wait and see what everyone else has to say about what I should do here.

Summary:

-Mostly random Idle hunting while coasting or sitting, both while in Drive
-Lean O2 sensor code (intermittent PO171)
-Crummy gas mileage
-No vacuum leaks found

Rickw wrote:

Z-type wrote:

Someone once suggested the EGR going bad, but I don't think that's the case either because I unplgged it and nothing changed.

There should have been A difference here, I believe.

it should have set a code pulling the EGR,

Also that little hose thats popping off on the Evap, I had the same prob, even zip tie, i ended uping a little hose clamp. Never caused me any codes or problems with it off, or on though....

Ah ok Deekster...a code for the EGR would make sense. I spoke to two mechanics, with whom i am good friends, and they keep thinking it's a vacuum leak, even though i couldnt find one. I do wonder though, that fuel evaporation solonoid, is it some kind of open/close mechanism? I know that's a stupid question but I'm just making sure. I wonder if mine has somehow gone bad and is letting in more fuel vapor than it should and that's what's making my idle crazy at least. That still doesn't explain a vacuum leak BUT, my idling problems never came around until i re-attached a vacuum hose onto that fuel evap solenoid.

We'll, im going to go out to the garage and try a few things...

The fuel EVAP solenoid in this case is Open or Closed depending on how it is commanded.

Read On.

From the FSM a DTC P0171 could result from the the following:
Fuel pressure too low and result in poor performance.
Have you checked the fuel pressure for proper readings yet. Or do you have all the vacuum lines hooked up correctly, especially to the fuel pressure regulator.

As far as the EVAP system goes, When the engine is running, the fuel vapor is purged from the carbon element by intake air flow and consumed in the normal combustion process.
The EVAP purge valve allows manifold vacuum to purge the canister. The PCM supplies a ground to energize the EVAP purge valve (purge on). The EVAP purge valve control is is Pulse Width Modulated (PWM) or turned ON and OFF several times a second.
The PCM controlled PWM output is commanded when the appropriate conditions have been met:
1) Engine coolant above 77* F
2) After the engine has been running about 3 minutes on a cold start or 45 sec's on a warm start.
3) The vehicle is operating in closed loop fuel control.
There is quite a bit more, actually more than I can get into here on this site.
You would need an FSM as there is much more to this topic than I realized. Another page full of data on the operation and diagnostics of the EVAP system alone.
Sorry I can't help much more than this. You'll need to get an FSM for your year vehicle as this data comes from an 1998 book and am not 100% sure it is the same for your car.
I guess for a "Quick Question" there is no quick answer.

Thank you Rick that is all very educating information. It makes sense. In reading that and checking the EVAP solenoid, everything appears to be working correctly with that system. Thank you very much again!

Updates after fiddling around for an hour and a half:

-EGR appears to function normally
-IAC valve is a little dirty but functioning (didn't have the tool at home to do this so i couldn't clean it while it was out prior)
-MAF is clean
-EVAP solenoid works correctly
-Fuel injectors do not appear to be the source of the vacuum leak

After much thinking and observing the past few days, I've also concluded the following:

-Cray idle and SES only occur during operating temperatures
-Crazy idle will come around most often when coasting or idling in drive
-Crazy idle seems to be triggered by a sudden release of the gas pedal


I know this is going to add to the confusion, but I have other thoughts:

Perhaps the fuel pressure regulator is going bad? I have a fuel pressure gauge to attach to the rail but won't be able to test until tomorrow, and only if it's not raining (complicated garage situation). if the regulator is going bad, would that not explain the crazy idle and lean sensor readings? I don't think this would explain why it's so random, but I'm not sure.

Maybe the oxygen sensor is simply bad, so when it reads lean it's dumping too much fuel into the cylinders, causing the idle to jump and fall?

I'm sorry this so hard to keep track of, but I like to get all my thoughts down at once while I'm remembering them lol. Thanks guys!....

This is where a diagnostic tool would help you.
You could be monitoring the O2 sensor, the air/fuel ratio and fuel pressure at the same time and make a more educated assumption.

I agree, but no one around here can do it. I was lucky to find the guy that could even read my computer's codes. He's kind of an @$$hole though so I don't think I'll be heading back there.

It'd be nice to get a hold of something like that....then I could handle all the computer crap myself...

Back again. Just wanted to point out something I noticed. My vacuum/boost gauge at operating temperature, in drive, and idling, is only 17 HGin (orwhatever that measurement is. Also, I'm only getting 6 lbs of boost which i find to be coming up short compared to most people. Both indications of a vacuum leak. At this point, because of all the testing, poking, and prodding I've done, as well as some professional opinions, I've decided I do have a vacuum leak. Now I just have to find it. Next, when I get a free hour or so, I'm going to replace my injector rings/gaskets, because I didn't do it when I replaced my supercharger coupler quiet . I'm also thinking of trying to retorque my supercharger bolts to make sure that gasket isn't leaking, even though a spray leak test didn't show any. We'll see what happens...more later...

I know I haven't posted in a while, but of course, this issue is ongoing.....

It's getting bad. The idle fluctuations are more common than ever, the engine light doesn't stay off for long....sigh. But, I think I made some headway. I noticed when I got the car that some of the engine block in various places looked wet. I knew my valve covers needed done so I assumed it was oil and moved on with my life and changed the valve cover gaskets. Well, I checked it out a little bit ago and it appears my engine block still looks 'wet'. I noticed my engine coolant has gotten pretty low in the last 3 months. Maybe like an inch and a half of it's level. That's a lot. I've come to a conclusion...

...since the car runs fine under load/throttle/whathaveyou, I have to assume my lower intake manifold gasket is bad. Therefore also causing a vacuum leak, causing my oxygen sensor to get insane.

Does it make sense to anyone?

I guess that's possible, but in my case (I have a confirmed LIM gasket leak) the first sign that the LIM gasket was going bad were deposits found on the spark plugs, from coolant seeping into the cylinders. That was at least 30k miles go, and so far none of the symptoms you're describing.