Lite Detonation On 1-3 Pistons

g96v6-250k

Member
Aug 15, 2012
91
1
8
96 3.8 stock
i have a hint of pre-ignition on the ps of the engine at 80-90 percent throttle and p0174 bank 2 too lean.
seems like never at wot. back in 2010 i had a stuck injector that opened up with cleaners. time for flow measurement on ultra-sonic machine? some hard carbon acting as glow plugs? any ideas? car never had this before. does this eec support cylinder trim table function? i dont trust the inspection stations :p
 
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System Too Lean (Bank 2)
What does that mean?

Basically this means that an oxygen sensor in bank 2 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 2 is generally the side of the engine that doesn't have cylinder #1.
Note: This DTC is very similar to P0171, and in fact your vehicle may show both codes at the same time.
Symptoms

You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.
Causes

A code P0174 may mean that one or more of the following has happened:
  • The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
  • There could be a vacuum leak downstream of the MAF sensor.
  • Bad 02 Sensor
Possible Solutions

Possible solutions include:
  • In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
  • Inspect all vacuum and PCV hoses, replace if necessary
  • Check for a dirty fuel filter and proper fuel pressure
  • Replace 02 sensor
 
i should have added: the car had a vibration and fuel economy problem with no DTC for 3 years that ended when i replaced the maf with a brand new one. next day after maf was replaced i have p0-174 bank 2 too lean. could a lower intake manifold leak be the issue?
i always feel it a bit when it pings on 87 octane which was never a problem in the past, so i might try some 93 octane to see if its possibly a carbon problem. i do all my own diagnosis and repairs so i have cleared this code 3 times and it keeps returning eventually. never a code for bank one.
i was guessing its 1-3 because thats where it sounds like its at, but it could very well be pistons 4-6
 
Other possible reasons for the system lean codes are: exhaust leak near 02 sensor or the 02 sensor itself is lazy and not reading the exhaust correctly and thus the fuel trim is being driven lean because the 02 sensor "thinks" that the system is rich. The best way to diag. this issue is to have a scan tool that can read live data stream from the 02 sensors. Then you can watch the switch rates of the 02 sensors and see if the voltage swing is correct or not. Also watching long term and short term fuel trims can give you more information and point you in the correct direction for repair.
 
thanks for the help. i think i will be swapping 02s. all i have is a basic code reader so i cant check STFT or LTFT. i have a new bosch upstream 02 that i have sitting. do you think its ok to throw that in with the other side having the NTK type from factory? should i do both up and downstream or is the upstream most likely the issue? any idea if these eec-v support the fuel correction/cylinder fuel trim for adjusting each injector? i want to know this incase i never get anywhere with this problem as i dont trust most inspection stations.
 
i should have added: the car had a vibration and fuel economy problem with no DTC for 3 years that ended when i replaced the maf with a brand new one. next day after maf was replaced i have p0-174 bank 2 too lean. could a lower intake manifold leak be the issue?
i always feel it a bit when it pings on 87 octane which was never a problem in the past, so i might try some 93 octane to see if its possibly a carbon problem. i do all my own diagnosis and repairs so i have cleared this code 3 times and it keeps returning eventually. never a code for bank one.
i was guessing its 1-3 because thats where it sounds like its at, but it could very well be pistons 4-6


I would say that the problem is with your MAF since you say that you didn't get the code unitl the day after you swapped it out.
 
the maf is brand new and under warranty but it was purchased for a 4.6 v8 engine and has about 500 miles on it. should i get one for a v6? the old maf had the engine vibrating badly and running rich "gas mileage was weak" with no codes to try and pinpoint the problem. the new maf stopped the engine vibration/shaking and fuel milage is up about 8-10 mpg easily. im also dealing with a intermittent p0443 for purge on hot days only, but i swapped purge valve for the third time and havent had this in about a 3 days now. this thing is a pita. i want to blame injector/s as they have 250k miles and atleast 1 has locked up on me in the past. i just opened it with cleaners and some revs. engine performance is now perfect some days and slightly off other days. plz help.
 
I would say that the problem is with your MAF since you say that you didn't get the code unitl the day after you swapped it out.
i had the pre-igniton pinging before the maf swap but i could only make its happen up large hills or mountains after about 15-30 seconds of full power, wot or in the 90 percent range. but never the code. when its came on its was so loud it sounded like a rod let go and i had to back out fast. i think the maf change is when the pcm could finally understand what might be going on.
 
i had the pre-igniton pinging before the maf swap but i could only make its happen up large hills or mountains after about 30 seconds of full power, wot or in the 90 percent range. but never the code


I might try cleaning up the old sensor and retrying it before throwing parts at it. You might also look for a vac leak in the inlet tract.

What I mean is: You don't know that swapping in the new maf has fixed anything. All you really have is a new symptom.
 
I might try cleaning up the old sensor and retrying it before throwing parts at it. You might also look for a vac leak in the inlet tract.

What I mean is: You don't know that swapping in the new maf has fixed anything. All you really have is a new symptom.

but the maf has greatly improved fuel consumption and vibration/shaking pr0blem which started overnight years ago. have not had any sulfer smell yet also. had all 4 02s out a year ago trying to fix this problem that the maf replacement fixed. they all reacted properly with a bench test when torched. 0 to 1 very fast and back to 0 with no heat. i'll torch and clean them again. im also trying 93 octane next fuel up
 
but the maf has greatly improved fuel consumption and vibration/shaking pr0blem which started overnight years ago. have not had any sulfer smell yet also.


Right... all things that can also be attributed to a dirty maf and/or vacuum leak. I would be surprised at this point, if you had a malfunctioning 02 sensor. I think you still need to identify the problem before swapping out parts. Sounds to me like you're getting unmetered air in there some how.
 
Right... all things that can also be attributed to a dirty maf and/or vacuum leak. I would be surprised at this point, if you had a malfunctioning 02 sensor. I think you still need to identify the problem before swapping out parts. Sounds to me like you're getting unmetered air in there some how.

lower intake manifold? everything else was checked. i have inspected all vac lines. possibly a egr regulater failure as this does a controlled vac leak?
 
You looked at PCV/oil breather? Does it happen to plug into the same side that's indicating lean?

pcv valve is PS valve cover "1,2,3" bank 2 is DS 4,5,6, correct? i have p0174 bank 2 lean.
i have convinced myself its the injectors flow rate or pcm failure, slim chance of wiring.
this is just a tough one because the engine runs very well most of the time except for the slight pinging and occasional lite vibration.
 
pcv valve is PS valve cover "1,2,3" bank 2 is DS 4,5,6, correct? i have p0174 bank 2 lean.
i have convinced myself its the injectors flow rate or pcm failure, slim chance of wiring.
this is just a tough one because the engine runs very well most of the time except for the slight pinging and occasional lite vibration.

You could potentially have a sticking injector. A can of Sea Foam probably wouldn't hurt. I think it's more likely that you've got a vac leak someplace. Have you done the starting fluid test yet?
 
have done many many types of injector cleaners in the past few years including a whole bottle of seafoam/berrymans with a quarter tank. i went as far as to let in sit for 2 days with it in the fuel rail.

tonight i put some 93 in and gave her hell when i had followed a rousch, i could not get it to ping and vibration levels were damn near none like it should be. how does this pcm determine spark knock/detonation, im pretty sure it has no knock sensor so i guess it goes off of the Crank position sensor signal correct? im now feeling like after 4 years of bad fuel mileage and no hard runs "because it vibrated so badly" it has built up some carbon thats glowing and pre-igniting the 87 octane. the 93 seems to make it like new again and pulls harder/smoother.
in the past i had run into a 2.3T with serious issues that were solved with new injecter nozzle tips, i forget if this setup has these. maybe something to look into?

another question i have is, could the cam chain be stretched so much that the cam angle is off to the point that it will require higher octane to run properly under high load? thank you for your time. i forgot how well this 6 moves and my chest was pumping nicely also. hehe
 
i was able to get it to ping again, this time very briefly with the 93 octane as opposed to constantly with 87. it seems with 93 the pcm can quickly correct it by adding fuel or changing spark timing. could this be strictly a heat issue? should i be looking for crankcase air entering into the lower manifold???? it never had a problem in the past with 87. does 93 have no ethenol that is possibly screwing with the injectors?? im lost. you guys are awesome if you can help me figure this. BTW it is not a high octane tune
 
figured it out, 2 injectors on bank 2 were spraying badly and with low flow. i took them out and sealed a bottle of carb cleaner to them with a rubber hose and made them spray untill the jets work perfect. at first test the spray was shooting to the side rather than strait. runs like new again and no more pinging or code for lean bank 2.
 
yes, i know about the snap-on machine thatdoes ultra-sonic cleaning and flow measure but i never searched around to find someone that has one. do you know about how much a shop would charge me to put my injectors on the machine, or where i can find one?
i think i got them working like new from what the spray pattern looked like. i made sure that all four jet holes were spraying nice before i was happy with each injector.
also now i can cruise with engine at 1200 rpm and i cant feel the motor. before i had to keep them above 1600 to avoid rumble/vibration. mpg went up a few also and no pinging at any throttle percentage. im happy.