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Old 06-04-2012, 10:49 AM
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AxleIke AxleIke is offline
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Default Sc 3.4 P0171

Hey guys,

I have an issue right now with Baby Beast II. Quick specs on the truck:

218k miles, 3.4L, stock exhaust, gen 1 (grey) supercharger with stock pulley.

The SC was installed 2 months ago, and everything was hunky dory for a month.

Now, I am having a very strange CEL, P0171, System too Lean (bank 1), which I will explain. I have an OBDII scanner, so on my trip last week (I'll post some trip photos soon) I was able to narrow down the symptoms leading to the CEL.

The CEL comes on ONLY after running for a bit, and then stopping for more than a few seconds, say at a long traffic light, or stopping on the side of the road to take a picture or read a map. It ONLY comes on at idle, not under any load.

Originally, I thought this was an issue of the fuel system not being able to keep up with the SC, but that would only occur at WOT, not at idle.

UB suggested the O2 sensors going funky, but unfortunately, my scanner (at this point) doesn't read the sensors, only the CEL codes. I'm looking into whether or not I can upgrade. However, online, the other symptoms are the MAF, or a vacuum leak. I've checked the vacuum.

I need to get info on the sensors coming in, obviously, but for those guru's out there, can anyone think of any other things I can check into?

The code doesn't send the truck into limp, so performance isn't affected, but emissions will be a problem, as well as the fact that I personally cannot stand anything to be broken on my trucks.

Thanks!
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  #2  
Old 06-04-2012, 11:17 AM
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Red_Chili Red_Chili is offline
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Check to see if your TB gasket is backwards. DAMHIK. I would think you would notice crappy running though, so that is doubtful but possible.
Do you also have a fuel smell in the cab?
I had to add a hose clamp to the evap line next to the brake vacuum line, and even put in a check valve inline. Not sure the check valve is needed... but the hose clamp certainly was. Check valve couldn't hurt.
Old O2 sensors put a variable in the pot that is hard to account for... ND or Toyota only if you choose to replace.
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  #3  
Old 06-04-2012, 11:19 AM
thefatkid thefatkid is offline
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Quote:
Originally Posted by AxleIke View Post
Hey guys,

I have an issue right now with Baby Beast II. Quick specs on the truck:

218k miles, 3.4L, stock exhaust, gen 1 (grey) supercharger with stock pulley.

The SC was installed 2 months ago, and everything was hunky dory for a month.

Now, I am having a very strange CEL, P0171, System too Lean (bank 1), which I will explain. I have an OBDII scanner, so on my trip last week (I'll post some trip photos soon) I was able to narrow down the symptoms leading to the CEL.

The CEL comes on ONLY after running for a bit, and then stopping for more than a few seconds, say at a long traffic light, or stopping on the side of the road to take a picture or read a map. It ONLY comes on at idle, not under any load.

Originally, I thought this was an issue of the fuel system not being able to keep up with the SC, but that would only occur at WOT, not at idle.

UB suggested the O2 sensors going funky, but unfortunately, my scanner (at this point) doesn't read the sensors, only the CEL codes. I'm looking into whether or not I can upgrade. However, online, the other symptoms are the MAF, or a vacuum leak. I've checked the vacuum.

I need to get info on the sensors coming in, obviously, but for those guru's out there, can anyone think of any other things I can check into?

The code doesn't send the truck into limp, so performance isn't affected, but emissions will be a problem, as well as the fact that I personally cannot stand anything to be broken on my trucks.

Thanks!
Clean the airflow meter. Make sure to clean the hot wires "inside" the sensor. Electrical parts cleaner only as most others leave residue.
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Old 06-04-2012, 12:20 PM
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rover67 rover67 is offline
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Quote:
Originally Posted by thefatkid View Post
Clean the airflow meter. Make sure to clean the hot wires "inside" the sensor. Electrical parts cleaner only as most others leave residue.
Great suggestion. usually NAPA carries the CRC brand cleaner specifically for MAF Sensors. Use that as suggested above.

Does it have a K&N filter that may have too much oil on it? that can also contaminate the MAF sensor.

Other than that it could be something like an exhaust leak upstream of the o2.. but those have to get pretty bad for crap to go wonkey.. you'd probably hear it.
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Old 06-04-2012, 12:28 PM
thefatkid thefatkid is offline
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Usually the oxygen sensor monitors are tight enough that they will catch a faulty o2 prior to setting a p0171. This only goes for 96-2002 4runners.

If cleaning the airflow meter doesn't work, check fuel pressure. You should not see a drop under load and a starting pressure around 38psi. Next, check the supercharger bypass pipe (1st gen charger only). The o-ring gets dry in that pipe and cause an air leak. Your Data list for the code should tell you what direction to go, lean idle=air pipe, lean heavy cruise=fuel pump.
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  #6  
Old 06-04-2012, 01:26 PM
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Thanks all, I will check those.

Brian, the fact that it throws the code at idle only tells me it could be the air pipe. I am not sure where that is though?

The PO put a KN filter in, which I removed immediately upon purchasing the truck. I will try an clean out the MAF.

Bill, I don't know what sort of smell I have, but I certainly have something. However, it is not just my runner. My dad's runner (97) has the same thing, and it is there pre and post SC. Sort of a strong oil smell. Doesn't smell like gas. I don't think its related, but could be.
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Old 06-04-2012, 05:51 PM
thefatkid thefatkid is offline
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Remember that the light only turning on at idle. The fault could have set while on the throttle earlier. The light and a "logic" code have no relation to when the problem occured, only when the ECU determined that it was out of range. If it was a hard fault (open electrical circuit) the light would be indicator of actual fault time.

If you get time bring it by the dealer so I can check the datalist.
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Old 06-04-2012, 06:11 PM
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Probably not what you got going on, but I was reading a build thread just last night that had the same code coming from a supercharged 3.4

http://www.tacomaworld.com/forum/1st...oy-taco-4.html
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  #9  
Old 06-04-2012, 08:53 PM
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AxleIke AxleIke is offline
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Cool Brian,

Thanks 4Runner Luv, unfortunately, that is one of the first things I checked. However, I did the SC plumbing from memory and some very vague diagrams on the net. So, it could be totally wrong.

Also, it seems I may need a Hood scoop. The SC and throttle cable hit the hood. Only noticed it after a lot of bumpy roads. Bummer.
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  #10  
Old 06-05-2012, 09:18 AM
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Quote:
Originally Posted by thefatkid View Post
Clean the airflow meter. Make sure to clean the hot wires "inside" the sensor. Electrical parts cleaner only as most others leave residue.
x2

That is what was causing the code on my '97 FZJ80 with the MAF Mod and later year MAF.

We chased a bunch of stuff including installing new O2 sensors. CEL would come on ONLY at idle and fuel trims were fine at all other times. Even just having the AC on with the resultant bump in idle was enough to keep the CEL from coming on at idle.

Get some MAF cleaner and I'd be willing to bet that in less than a 1/2 hour your problem will be resolved
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