P0174 code and very rough idle

[Pilot Laslo]

Hello
As of this morning the engine ran very rough at idle and at 1500 rpm
I scanned it and got p0174 (lean mixture)
Any advice on where to look would be great.
Also I do have the code p1336 (camshaft position) but it’s been like that ever since I’ve got it and it went away till just recently it came back on the scanner

What I’ve done so far
New Fuel filter
Sprayed all lines with soapy water to look for leaks
Cleaned MAF sensor

 

[RonD]

P1336 can be cam synchro or crank's harmonic balancer, it means the signal from either the crank sensor or cam sensor is erratic, so not a "bad" sensor issue specifically, could possibly be a wiring issue as well, but long shot
If cam synchro is wobbling or cranks ring gear is, then the AC pulse from these sensors will be "erratic"

Could also be the alternator, alternators generate AC voltage, then use diode pairs to change AC volts to DC, if there is AC voltage leaking out that WILL cause issues with crank and cam sensors since they both generate their own weaker AC voltage signals


How old are the O2 sensors, they last 125k miles or 12 years?
On a V6 or V8 engine when only 1 side, 1 bank, shows a lean or rich code first suspect is the O2 sensor on that bank of the engine
Because a vacuum leak, MAF or fuel pressure issue should/would effect BOTH banks of an engine

If your upstream O2s are older replace BOTH

 

[Pilot Laslo]

Tested the o2 with my scanner and it’s showing b1s2 never getting any voltage?
Would this cause issues with bay 2 even though it’s bay 1?

 

[RonD]

Bank 1 is passenger side of engine
Bank 2 is drivers side

Sensor 1 is any upstream O2 sensor, close to exhaust manifold
Sensor 2 is any downstream O2 sensor, after Cat Converters

So B1S1 would be upstream O2 sensor on passenger side, its showing a Rich burn
.1volt is Lean burn, too much oxygen
.9v is Rich burn, too lttle oxygen
The "O" in O2 means oxygen

B2S1 would the where P0174 comes from, computer is having to add more fuel than calculated to get O2 sensor(B2S1) to show .3-.5volts

And B1S2 is the downstream O2 sensor on passenger side, and the only downstream O2 unless you have dual exhaust system
It should read .7 to .8v as little oxygen should be left in exhaust after Cat Converters burn up pollutants

But...................O2 sensors need to be above 650degF or they can not work, so can only be tested after engine/exhaust is fully warmed up
Thats what Open and Closed Loop means
The computer is in Open loop until O2 sensors start to work, i.e. they start to generate their own voltage, then computer can go into Closed Loop and use the O2 sensors to get best "burn" so best MPG

So not sure when you tested O2s?
Had engine been running for 5 to 10min?
Also need to test at 1,500-2500rpms, idle doesn't use O2 sensors

 

[Pilot Laslo]

Bank 1 is passenger side of engine
Bank 2 is drivers side

Sensor 1 is any upstream O2 sensor, close to exhaust manifold
Sensor 2 is any downstream O2 sensor, after Cat Converters

So B1S1 would be upstream O2 sensor on passenger side, its showing a Rich burn
.1volt is Lean burn, too much oxygen
.9v is Rich burn, too lttle oxygen
The "O" in O2 means oxygen

B2S1 would the where P0174 comes from, computer is having to add more fuel than calculated to get O2 sensor(B2S1) to show .3-.5volts

And B1S2 is the downstream O2 sensor on passenger side, and the only downstream O2 unless you have dual exhaust system
It should read .7 to .8v as little oxygen should be left in exhaust after Cat Converters burn up pollutants

But...................O2 sensors need to be above 650degF or they can not work, so can only be tested after engine/exhaust is fully warmed up
Thats what Open and Closed Loop means
The computer is in Open loop until O2 sensors start to work, i.e. they start to generate their own voltage, then computer can go into Closed Loop and use the O2 sensors to get best "burn" so best MPG

So not sure when you tested O2s?
Had engine been running for 5 to 10min?
Also need to test at 1,500-2500rpms, idle doesn't use O2 sensors

Tested it again after it ran for 10 minutes
All o2 sensors seems to be good now
Any idea of why it’s idling so rough?

 

[Pilot Laslo]

Tested it again after it ran for 10 minutes
All o2 sensors seems to be good now
Any idea of why it’s idling so rough?

The bay 2 s 1 averages .5v at 1500 rpm
But with many spikes and drops as seen in graph

 

[Dirtman]

That's normal. Upstream o2 sensors constantly switch from rich to lean as the fuel trims are adjusted rapidly. The downstream sensors should remain consistent.

 

[Pilot Laslo]

Solution!
I replaced my ignition coils (still under warranty from advanced auto parts) and it fixed the vibrations!

Figured out I also had a burned out check engine light so never knew if I was getting codes.

we will see after awhile if the code comes back up for it being lean.

But no misfires!
thanks everyone

 

[RonD]

Good work

Yes, a misfire will cause a false Lean code because no oxygen is burn in that cylinder so O2 sees that extra oxygen as a lean burn

 

[Dirtman]

I always thought misfires gave false rich codes since they are sending more unburnt fuel into the exhaust. Learn something new everyday. Ron is smaht.

 

[RonD]

O2s can only see Oxygen

 

[Pilot Laslo]

Ok so the issue came back!!!
It was all good till I got on the highway and it struggled to accelerate to 70 more than usual
And once I was at 70 the exhaust definitely didn’t sounds like it was flowing smoothly and after about 5 miles the engine kinda stalled out and loose several hundred rpm abruptly, I speed back up and it did it again.
Once I got off highway I’m now having the same idling problems!
Any ideas are greatly appreciated

 

[RonD]

Could be partially blocked exhaust system, you can test for that with a vacuum gauge

 

[Pilot Laslo]

Replaced PCV valve, no luck
Noticed the hose going to intake was being pinched so I’m trying to find a new one to order.
I also noticed when I pulled the plastic tube out of the intake the outside of it was pretty oily, is it ok for it to be oily??

 

[RonD]

Yes, there will be some oil inside and outside on the PCV hose, its from "blow-by" in the crank case, it vaporizes some of the oil coating on cylinder walls and piston sides as it passes by
The PCV Valve is there to pull the Blow-by gases(exhaust) out of the engine to be re-burned, unfortunately the oil vapor comes with it