Oxygen Sensor

[GcDiaz]

1990 3.1L, 119k

So lately I've been having vacuum problems...I got codes 33 and 35 (IAC and MAP). I changed those, but in so doing I found the need to replace the EGR valve gasket (definitely a cause for low vacuum - the car had TWO of them on, both in piss poor shape). I replaced that, and the car seemed fine. No codes or anything. Except, I did notice a loud sucking sound coming from somewhere around the air filter. I took that enclosure apart, didn't see anything obvious, and upon restart the noise was gone. Checked the codes just in case and got nothing.

Then I go somewhere, and all of a sudden upon restart the car is dying on me at every stop. Even to the point where it'll start and die before I can put it in gear and give it gas. I got the car to my cousin's and left it alone for a bit. Then I restart it, and NOTHING. I gave it a lap around the block and it didn't even want to shut off. But now I'm getting code 44 (oxygen sensor lean), though I wasn't getting it before.


Any takers?

[wicked-irocz]

I think you were on the right track with the vaccum problem,  I would start cheap, check the pcv valve, see if it rattles.

[GcDiaz]

Yeah, it's like a mini maraca. I've got a similar thread going on BStuff; been posting the latest news there: http://www.bstuff.com/index.php?showtopic=28224

Feel free to opine.

Thanks.

[I-GOT-BOOST]

I think you might have a ground problem. Alolt of the time an intermitent problem is due to a faulty ground. Better check all your grounds. That would be a cheap, easy place to start.

[MAJ28]

My post from BStuff:

Usually if the crank sensor goes the car won't start PERIOD.

Usually a high idle is a result of some type of intake leak, which is the same symptoms as a vacuum leak (the vacuum is created by the PCV valve which is connected to the rear of the (upper?) intake manifold.

The idea is that the intake has the PCV (Positive Crankcase Ventilation) valve connected to it, so when the engine takes in air, the valve is also attempting to pull in air (since it's connected directly to the intake). You're intake functions as a big vacuum, because when the exhaust goes out it PULLS the new air and fuel in (like a siphon in a gas tank). So when you have a vacuum leak, you are letting extra air inside the intake and the computer tries to compensate with more fuel - which creates the high rpms you are experiencing.

I'm willing to bet with 99% certainty that it's a vacuum line or an intake manifold gasket leak. Air is getting in your intake somewhere it shouldn't be.

(An o2 sensor can create a terrible air/fuel ratio, but only within a certain margin of difference, nothing like this.  Also the o2 sensor only functions once it hits a certain temp (don't remember what º off hand), so it wouldn't screw anything up on a cold start - unless it was combition of issues.)

If you pull off a vacuum line and put your finger on it, is it sucking?  If not (or if it's very weak) then extra air is getting in another vacuum line or the intake.  (If it does seem to suck properly that won't mean *necesarily* that there is no leak.)

»Jason

[GcDiaz]

Alright, so tonight my cousin pulled out all the tools and went over this sucka. Checked the sparkplug wires, had spark in all of them so it's not a misfire issue. I'll sacrifice some dollars and get new sparkplugs tomorrow, just in case. Again, we went over the hoses and sprayed some brake cleaner to see if it would get sucked in somewhere - no go.
His scanner does report the MAP showing high voltage (4.xx), but I replaced that last week so it's not the part's fault. I mention to him what I read on BStuff about the TCC solenoid, and in checking that out we see this:


It was just hanging there, apparently severed, but we don't know how or from what. All we know is it comes from here:


Not even sure what that part is called, but that's what it looks like now after we plugged it. Sure enough, the scanner now shows the MAP voltage hovering around 1.55. Car is still not running at its best (same occasional rough idle upon start), but at least it's not almost-stalling anymore. Still, where was that cable supposed to go?

[MAJ28]

Which tube are you referring to in the 2nd picture?  I know there are vacuum lines in that general area (in the first pic) that would go to/from the evaporation canister - but someone will have to verify if that is the case.

»Jason

[GcDiaz]

The first picture shows the loose end of the line in the second picture (it's sitting right next to the IAC). Second picture shows where that line normally connects to the intake, after we plugged it with that short rubber thing.

You're looking at the driver's side front; evaporation canister is on the passenger side (the vacuum line that goes to the canister is the thicker of the three which are coming out from under the plenum) - and speaking of which, we also saw that the fuel tank-->canister line had been sliced open by one of the pulleys on that side. We fixed that too.

EDIT: Humbug, the symptoms persist. Did idle relearn today, got no codes, but the car is still going into 600 RPM-land when coming to a stop. Gotta unplug that TCC solenoid as soon as it cools down.

[MAJ28]

What the hell was that metal line doing going into his intake?  He covered it with that big black rubber piece, but why in the ---- would that be connected to an open tube that go down behind his radiator.

That is some wierd ****....  

»Jason

[GcDiaz]

Seems like my engine is a transplant from another GM vehicle (Grand Prix perhaps). One of the previous owner's receipts lists an engine rebuild. Guess they just swapped it instead. That sucker's gonna stay plugged.

[1988GTU]

My old 2.8 had that same setup for the metal line and plugged Plenum hole.  That is also how it stayed until I swapped it out.  Try looking for grounds that are snapped or gone?  The TCC is under the AIR BOX on the trans and is best if you take out the AIR BOX to get at it.  While you're at it, why not do a CAI/WAI cone style?  It'll make for a TCC easy access.

[GcDiaz]

I already got the TCC; it was right under the AIR BOX as you emphasized. I'd like a CAI; sometime in the future when I don't have better things to throw money at.
How would I identify the ground cables?

[1988GTU]

Usually black wires, or flat like cables.
They mostly turn GREEN (Corroded) and break cause they are brittle.
If they turn green and its in a spot where weather is not gettting to it, then something is not hooked up right or is loose.  (IE: Radio, Battery, Alt, Starter)

[GcDiaz]

Figured I'd post the latest nooz.

I cleaned out the throttlebody, and inmediately afterwards the car ran like a CHAMP, no stalling, no rough idle, no RPM swings. I figured I was done. I was wrong. Only a few hours later it was up to its old tricks. Haven't done anything since except get where I have to go, sometimes playing the stoplight-torquebrake game. Car is still rough-idling occasionally, and a new symptom is that when I come to a stop in gear, the RPMs will swing quickly between 1500 and 1000 as I slow down. Once I'm stopped, the revs stay at 1000. If I slow down in neutral the revs won't swing, but fall to 1000 and hold steady. This is all intermittent, but happens more often than not. What's got me real confused is that the car is acting as if it's a TCC malfunction, even tho the TCC is unplugged. Oh, and I still get the MAP high voltage/low vacuum code every now and then. Two folks have suggested an ECU failure. Thoughts?

[1988GTU]

Could be.  Do you have water leaks over by the ECU?