P0141

Hello,
In my '97 Riviera I'm getting a multiple misfire code (P0300) and P0141, which is "O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)". My question is - Is this the first or second O2 sensor?
Thanks.
Mikel

Mikel, you even posted yourself "Sensor 2".....so to answer your question, yes.

Just making sure before I spend money.

Thanks.

Mikel wrote:

Hello,
 In my '97 Riviera I'm getting a multiple misfire code (P0300) and P0141, which is "O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 2)".  My question is - Is this the first or second O2 sensor?
Thanks.
Mikel

It's the one after the cat. It doesn't have any control over how the engine runs, it's just there purely for emissions.

I have been getting those error codes along with a severe stuttering in top gear under heavy throttle. This does not happen in the lower gears. I changed the downstream o2 sensor today and it is still happening.  I also got a P0302 error (cyl 2 misfire) today.  

When this started, I replaced the plug wires, as this had solved a very similar problem years ago, but it made no difference. Could a coil pack be going, causing the misfires and then the 02 sensor error codes?

The other part of the equation is that I have the infamous leaky coolant elbow. I haven't had time to fix it, so I've been adding coolant for the last few weeks. Not sure if that would have any effect elsewhere.

Thanks.

The stock coils are usually pretty robust. Have you checked/replaced the plugs? If not use AutoLite 104's gaped to .055"

FYI the two codes you posted are generally unrelated. The second O2 sensor isn't used for anything except the 'catalytic converter efficiency' testing. The Cyl2 misfire could be caused by a few things -

-plugs
-wires
-injectors

If you aren't positive that the coolant elbow is the source of your leak (do you have visual confirmation?) it's possible that the LIM gasket is leaking and you are sucking coolant into cyl #2 as well.

To test the injectors you can swap the #2 injector with another injector and see if the misfire code moves to the new cylinder with the injector or if it stays with the #2 cylinder.

Hello,
The elbow is visibly leaking. The plugs are Delco 41-101, gapped (the one I pulled) at about 0.060". The plugs are about 60K miles old. Wires are new.

The engine started doing something new today - Before it would only stutter -heavily- under heavy throttle in overdrive.

Now when I give it any moderate throttle it misses but in a continued manner.

Thank you all.

At 60k I would replace the plugs just under maintenance alone (yes, some cars can go 100k+ but I use and abuse).

I went to buy some Autolite 104s. My store has them in Iridium and Double Platinum. I got the latter ones. I hope I got the right ones.
Thanks.

You really only need 104's if you have modifications (smaller S/C pulley). We use them to help combat KR under boost. It won't hurt anything if you put them in. If anything, it'll help a little in the summer heat.

Changed plugs and wires and it made no difference. Old plugs looked all good. Car is missing heavily under throttle and has lost about 60% of the power, to the point it struggles to climb hills. Would a bad injector affect things so much? Thanks.

I would first check fuel pressure. Then check for a clogged cat or exhaust. Put a vacuum gauge on it. A stock 3800 fully warm in Park will make a full 20" of vacuum. If you rev the engine to about 1500-2000 RPM, in Park, and hold the throttle steady, it should maintain that vacuum. If it starts to fall off, the exhaust is clogged. A single clogged injector would give you a specific cylinder misfire code.

Thank you. What would be a good place to tap the vacuum gauge into?

Mikel wrote:

Thank you. What would be a good place to tap the vacuum gauge into?

I have a boost gauge installed permanently. I tapped into the vacuum line that runs across the back valve cover from the supercharger snout. That will show both vacuum and boost.

Hello,
I haven’t had a chance to check vacuum, but fuel level hovers between 40 and 45 PSI. One thing I noticed is that the typical coupler noise appears to be louder, I don’t know if it’s due to the now constant missing.
Thanks.

Check the pressure with the ignition on, engine not running. Should be 48-55 psi. Cycle the ignition switch on and off to get the highest pressure.

LARRY70GS wrote:

I would first check fuel pressure.  Then check for a clogged cat or exhaust.  Put a vacuum gauge on it.  A stock 3800 fully warm in Park will make a full 20" of vacuum.  If you rev the engine to about 1500-2000 RPM, in Park, and hold the throttle steady, it should maintain that vacuum.  If it starts to fall off, the exhaust is clogged.  A single clogged injector would give you a specific cylinder misfire code.

Hello,

- Fuel pressure:   About 50PSI when the ignition is turned on. The lowest it will go is 44PSI with the engine running

- Vacuum: I tapped the gauge into the empty nipple where the brake booster line goes.  At idle (which is now erratic) I get an unsteady 16-18 inches. Reading fluctuates about 1" up and down.

 Revving the engine above 1500RPM, it goes to about 18-19", also fluctuating about 1" up and down.

 In a couple of days, the car has gone from missing just at heavy throttle to driving like it's running on three cylinders. I'm going to check compression in the forward three cylinders tomorrow. Maybe the timing chain jumped? I can't imagine a single burned valve/blown head gasket causing such a loss in power.

Thanks.

Any chance you are mysteriously losing coolant? Have your lower intake manifold gaskets every been replaced?

The elbow under the compressor is leaking. I've been adding coolant until I can fix it.

Thanks.

The reason I asked is that you may be sucking coolant into the cylinders through rotted out lower intake manifold gaskets, possibly enough to cause it to run like crap sometimes.

I just pulled my 60K mile plugs and they all looked fairly normal. I'll post a photo in case I'm misjudging the colors...
Thanks.

Mikel wrote:

LARRY70GS wrote:

I would first check fuel pressure.  Then check for a clogged cat or exhaust.  Put a vacuum gauge on it.  A stock 3800 fully warm in Park will make a full 20" of vacuum.  If you rev the engine to about 1500-2000 RPM, in Park, and hold the throttle steady, it should maintain that vacuum.  If it starts to fall off, the exhaust is clogged.  A single clogged injector would give you a specific cylinder misfire code.

Hello,

- Fuel pressure:   About 50PSI when the ignition is turned on. The lowest it will go is 44PSI with the engine running

- Vacuum: I tapped the gauge into the empty nipple where the brake booster line goes.  At idle (which is now erratic) I get an unsteady 16-18 inches. Reading fluctuates about 1" up and down.

 Revving the engine above 1500RPM, it goes to about 18-19", also fluctuating about 1" up and down.

 In a couple of days, the car has gone from missing just at heavy throttle to driving like it's running on three cylinders. I'm going to check compression in the forward three cylinders tomorrow. Maybe the timing chain jumped? I can't imagine a single burned valve/blown head gasket causing such a loss in power.

Thanks.

Vacuum is low. It might be the intake gasket.

Would the intake gasket cause coolant to leak externally? There is coolant around the elbow, but I've been wondering if it may be coming from above.
Thank you.

The only thing directly above the coolant elbow is a flat sealing rubber strip that shouldn't contain any coolant. Unless the entire lower intake is filled with coolant... (which happens)

The coolant passages in the lower intake manifold aren't near the corners, so that's not likely the cause for an external leak. But I've seen those lower intake gaskets come out in incredibly terrible condition.