check the PCV hose - specifically the rubber elbow/connector - for a leak -
carb cleaner with the spray hose is easier and more effective to use than a propane torch -

 

Checked fuel pressure on rail and it's approx 40 PSI (i used a A/C guage which went up to 550 PSI...so at 40 PSI calibration is poor...consider it a ballpark). Does 40 PSI sound right?

Your fuel pressure is perfectly fine.

P.S.
I assume you meant fuel pressure went up to 55 psi. 550 would be catastrophic.

 

I think he fudged a 550 psi A/C gauge and is wondering if the 40 psi is not enough of a pressure to make that gauge read correctly.

Simple fix - rent a test set from a parts store. Maybe a bit difficult in Ontario. Takes 2 minutes with the engine beauty cover off.

Spec is 41- 47 psi at Key: ON and at running idle.

 

come on guys - PUT YOUR GLASSES ON -

i used a A/C guage which went up to 550 PSI

what he said was that the gauge he used to check the fuel pump pressure goes to 550 -
so - he wasn't sure how accurate the 40psi reading was -

 

come on guys - PUT YOUR GLASSES ON -

i used a A/C guage which went up to 550 PSI

what he said was that the gauge he used to check the fuel pump pressure goes to 550 -
so - he wasn't sure how accurate the 40psi reading was -

Oops! Glasses on now. I totally misread that one.

 

Ft of +% means the computer is adding fuel to one side. You need to look for components that are unique to that side. If the FT was up for both sides, then the component is shared on both sides (fpr, fuel pump)

So, check
- plugs, wires, injectors, ignition harness, o2 sensor

 

Arrrgggh....this is not going well. I just replaced the B1S1 O2 sensor because I was sure that was the cause (and it's 19 yr old original). A serious PIA job...

After replacement B1 SFT=30% LFT=20%. Wow, 50% added to B1. What is going on?

1. Did I replace the wrong O2 sensor? I assumed B1 was against the firewall.

I have now replaced B1S1 O2 sensor, new spark plugs, cleaned all fuel injectors, and replaced PCV valve on B1.

2. What's left that can cause this problem?

I tried spraying brake cleaner around B1 injectors and around intake manifold and STFT did not change. I will repeat this step in case I was sloppy the first time around. I assume that a massive air leak is the only cause left. Other ideas?

3. If it's an air leak, where else could air be leaking in? (If that's the cause)

4. Could a FPR or fuel pump output cause B1 STFT to increase like this? (But B2 is fine??). If so I'll rent or buy a proper gauge.

5. Just a theory - could one of the 8 O-rings (gasket) on plenum leak towards the center of the engine? I did replace these 2 yr ago when I fixed a plenum throttle body gasket. Seems unlikely (why would that fail)...but it explains why I cannot change STFT by adding propane on outside of plenum

Here's a scan of O2 & STFT for bank1 (left side of image) and bank2 (right side of image). As you can see B1S1 O2 reads 0.060v and is stuck there, (bottom left) and B1 STFT is >30% (top left) and is stuck there.

 

If it's an air leak, where else could air be leaking in? (If that's the cause)

Did you check that intake plenum duct for tears? It is usually at the 6:00 position, so it's hard to see. Flex the duct with your finger while spraying some Brakclean or such and listen for an RPM increase.

 

You likely have a wiring problem on bank one or a bad o2 sensor. The voltage on the sensor should be cycling indicating the STFT changes being made. Since its showing 0 v, either no control signal is being sent, the return signal is lost or the sensor is bad.

 

I replaced the O2 sensor today (see above), and at engine off the sensor shows 0.450v (middle of range). I see the sensor voltage decline to 0 as the engine starts running so appears accurate. As well, previous sensor did the same. (I assumed bad sensor, expensive mistake)

 

Probably wiring that is losing conductivity as it heats up

 

The wiring which passes the hot area is part of the sensor pigtail. So since I've replaced the sensor (and therefore pigtail) it seems unlikely...but on my list of possibilities

 

Wouldn't a tear on the plenum intake gasket cause STFT to increase on both banks? For some reason only bank 1 FT is maxed, while bank 2 FT looks normal.

 

Screw a bunch of senseless graphs and readings. P 0171 and P 0174 are most usually caused by lean fuel mixtures on one or both banks. Most often caused by air/vacuum leaks and not O2 sensors.

As posted, check for leaks. Bank 1 is the PCV side. Start there.

Then start looking at fuel delivery problems. A bad plug or coil would cause a rich mixture, so that's out.

 

Submariner409: Ok I started with a fuel pressure check. I found one to rent locally.

It shows 35 PSI at idle. It briefly spikes to 41 at start but goes right back to 35 PSI.

If I pull the vacuum hose from the FPR then pressure jumps to 45 PSI. When I restore vacuum pressure drops to 35 PSI.

Does this mean a bad FPR? Could this cause the problem on Bank 1 only? (Wouldn't both banks be affected by low pressure, or would the last 4 cyl (bank 1) get the least fuel).

I think I have normal power under acceleration...in case that is a clue. Also, car smells like its running rich. I also got a new P0171 (bank1 lean) and P1133 (B1S2 O2S insufficient switching) today..

 

Yes, plenum tears and FPR issues would affect STFT on both sides.

Items on one side that would create a lean condition include manifold gasket, injector, injector wiring.

 

Fuel rail pressure would be constant (equal everywhere) in the rail - it's a hydraulic system.

The normal fuel pressure spec for the car is 41 - 47 psi at idle, vacuum connected. 35 psi is 20% low.

B1S2 is the after-cat sensor.

 

Easy way to figure out what sensor is what is to disconnect one and look at the "live" data when the motor is running. Unplug one... what is it? B1 or B2?

O2 sensors are notoriously faulty though depending upon who has been and what has been done to the car thru its life, it could be anything upstream of the exhaust as others have said.

My .02 is that even if an O2 sensor is causing one Bank to load up on fuel, the rough running should be less detectable at high RPM or under heavy load.

 

His engine has 3 O2 sensors -

B2S1 is in the left bank exhaust collector
B1S1 is in the top of the right bank exhaust manifold
B1S2 is the after-cat sensor.

These sensors are very reliable - unless the owner is a snake oil user - then all bets are off.

Pre-2000 Northstars are different. Post-2005 Northstars are different.

 

Minor typo, I mean B1S1 is the reason for the lean code. I just replaced B1S1 O2 sensor yesterday (with another Delco), so since problem spans 2 different O2 sensors, I should probably assume O2 sensors are ok...

Since fuel pressure is low that's the only real clue I have at the moment. So, I have ordered a new FPR (none available in Canada) so by the weekend I will update the group on status after replacing FPR. I can't imagine why FPR would affect only bank 1...but I'm running out of options. I read another post on cadillacforums about someone who took their car to GM with these 2 codes, and GM just kept replacing parts. I figure I can do that too. So long as I'm not doing something stupid.

Speaking of stupid, I replaced the O2 sensor on bank 1. Which I ASSUME is at the firewall side. If not please let me know so I can kick myself for wasting $...

 

Disconnect the sensor and read the "live" data on your scanner... you'll know for sure if you changed the correct one or not.

 

Please read Post #20 again.

 

If you pulled the vacuum line off of the FPR and there is no raw fuel present, it is OK.

 

OK - the mystery deepens...(shi!t)

I replaced the fuel pressure regulator with a new Delco. After installation still show 35 PSI on the fuel rail. Perhaps rented gauge is off? Either way, engine has lots of power at high peed so I doubt that's it. But I can't explain it. All injectors are clicking nicely (and I just cleaned each of them).

Next, I did a very thorough check for air leaks, and it all looks tight. No hissing, vac is 19 PSI at the TB. I sprayed lots of brake cleaner and no change in O2 or STFT.

So now, no air leaks and fuel seems ok. Here's what I think is the key. When I start the car it runs fine in open loop, as it warms car goes to closed loop. Still ok. A few more minutes of running and suddenly B1S1 drops to 0.02v stays there (or sometimes stays at 0.5v). And does NOT MOVE until engine is cold. However, I have noticed hard acceleration does cause a blip on the O2 voltages and sometimes recovers (O2 voltage cycles).

I measure the voltage and pins 52 and 53 on C1 at the PCM. And I can confirm the voltage there is hovering around 0 (but when engine not fully up to temp voltatge was cycling around 0.3v-0.9v.) So it APPEARS that the PCM is correctly reading a stuck low O2 sensor. Once the engine is cold again all returns to normal and I start again.

I measured resistance from the O2 sensor connector to the PCM and both wire are very low resistance, so likely not wiring.

So now what? Based on Submariner's comment (#20) these O2 sensors are very reliable. What are the odds that my last one failed (19 yr old), and my new one has the same problem (1 week old)?

Could this be related to the O2 sensor not being hot enough? During hard acceleration or higher speed if it recovers perhaps the sensor is not hot enough at lower speeds. At idle could the sensor go under 600 degrees, and what if the O2 heater is not working? (Bad ground, not voltage from PCM). Could that be a clue? Does the PCM turn on the heater at lower speeds? Could bad PCM output to the O2 heater cause this?

Not sure where to look next.

 

Stick with the facts. There is a problem with B1S1 whether it is the sensor itself or the wiring.

 

I'm not sure what you are recommending. I know there is a B1S1 related DTC...but not the cause. I can't find a vac leak, and fuel pressure is fine, and injectors appear to work. Are you suggesting further diagnosis of B1S1? (If so please be specific)

 

When the voltage from an O2 sensor is wonky:

Step 1: confirm the exact location of the sensor and replace it with OEM quality new sensor

If step 1 does not fix the problem...

Step 2: meter the feed voltages and ground connections with a multimeter at the sensor connector and work backward from there. 5vdc feed and ground is ok?