AJatx

I've been getting the P0171 CEL code with my truck. I never really had any major issues with the supercharger before the URD kit, but I read about the ping issue and I wanted to prevent it.

History:
I upgraded to the URD kit since I had issues with my truck and I thought it may have been the fuel pump since the engine wouldn't start and I ran out of gas. It turned out to be a bad idler pulley #2. Oh well, at least I have the URD kit (and a good stock fuel pump) that'll help provide margin for the supercharger set-up (I rarely experienced ping previously).
Through this excursion, I replaced the stock fuel pump with Walbro 190lph and spark plugs.
The fuel pump is noisey when the fuel is below a quarter tank. It just doesn't sound right and I don't think it's "normal operation" either. I kept double checking the fuel return and evaporator hoses to make sure it's not swapped (return dumps fuel into the little catch area near the intake of the fuel pump).

After installing a new idler pulley and verifying timing after re-assembly.
I had issues at WOT. So, I take everything apart and check for vacuum leaks. After adding zip ties to all vacuum ports, it seemed to respond better.
Then I install the URD FTC and the fuel injectors went in the truck a week later.
That's where the noise increases. I assume it's the "buzzing" sound people mention on this forum. I have this "rattling" sound of the nylon hose from both the FTC and the boost gauge now. I tried ziptying the lines to the firewall to prevent oscillation as pressure and vacuum changes, but the noise still exists. I'm starting to believe there is too many devices sourcing one port off the supercharger.

I go through base tuning and Gadget's map is pretty close to dead on in the vacuum regions throughout the rpm range. I did notice some rpm hunting on deceleration and figured it's something I need to tune out.
As many have experienced, I started to reset the ECU since it seemed to correct my tuning.

I'm pretty sure my map is rich for the set-up (stock pulley). I have issues with WOT, but at 60% throttle, I can hit 4psi with no issues.
OBDII shows leaning conditions when approaching above 4krpm.
The map was being tweaked until I ran into the CEL.
After doing some research on the forum, I cleaned the MAF multiple times but the CEL will come back.
The throttle body and throttle position sensor were cleaned twice, but CEL still happens (P0171). Also, re-did the gasket for the throttle body and cleaned the IAC since I had it out of the truck.
Next, I used Seafoam through the PVC and fuel tank. It didn't really help my idle nor did my truck smoke.
The oil is changed out since I performed the Seafoam treatment.
I change the MAF to one (Camry) I bought from a junkyard. I get CEL after couple hours of driving.
Replace the MAF with original (cleaned again) and CEL doesn't return for a couple weeks.
Now I'm getting CEL with no changes to the map nor the hardware, regularly when I go into boost (~1psi).

I check for vacuum leaks again thinking that air is bypassing the MAF; thus creating a lean condition. All the vaccum lines sourcing the supercharger are leak free (at least that's what I presume using a MightyVac on each hose and port). The FTC and boost gauge would slowly lose vacuum where the fuel pressure regulator and supercharger port held vacuum.

I'm not sure if the intake manifold to block gasket is not sealing correctly, but I'm not ready to throw $60 at a gasket to find out it's not the root cause.

Somebody referenced an ebayer with new MAF sensors for sale and I'm thinking about trying it, but after trying two MAF sensors, I have my doubts that the MAF is the root cause.

Another thought is the A/F ratio sensor is bad or dirty. Any suggestions for the O2 sensors? If they were bad, wouldn't the ECU throw a code for it?
URD has some good pricing on the sensors, but again, it's at least $80 to try it.
With the OBDII (BR), the O2 sensor voltage pulses. not sure if it's normal behavior, but you can see it pulse as if it were a PWM.

Just a little fustrated tonight so I'm open for suggestions.

At least my other cars are not OBDII and very straight forward when working on them.

J

ebelen1

I tried a new A/F (02) sensor and then a new MAF. The MAF cleared my code. Since you've done two MAF's I'd try the A/F sensor if you have high miles (>100k) on the original one. If not, I'd wait for someone w/ a s/c to chime in as I don't have one.

nrgetic99

Long shot. I had a bad gasket between the throttle body and the SC that threw the P0171 code. Looked ok but I must have knicked it or something on assy.

New gasket fixed the issue.

David

nrgetic99

Doh ! I see you did this...still a chance its bad...mine looked fine.

AJatx

Thanks nrgetic99. I made my gasket from gasket material and used a little RTV on it. It seals very well on oil pans I used on a couple rebuilds. However, it could be leaking somewhere. It's a cheap gasket so I'll give it a try.

I hear a hissing sound somewhere near the supercharger bypass valve. Not sure if it's normal since it doesn't appear to source from any port or vacuum line.

The annoying nylon line sound is still present at the FTC and the T-adapter for the boost line.

The idle has a stumble that is frequent. It appeared when I installed the injectors. The injectors didn't have any o-rings pinched, but I guess I'll remove everything and triple check.

AJatx

I bought a new TB gasket from Toyota and installed it today. Before installation of the gasket, I cleaned both sides (TB and manifold) thoroughly.

Both the spare MAF (from junkyard Camry) and original MAF didn't ohm out when measuring between E2 and THA terminals. The manual states it should be in the range of 1kohm at room temperature.
Is that correct? I measure the MAF as a seperate unit (take out of intake).

J

AJatx

I found another thread that showed different pins to measure on the MAF (I somehow remember the Haynes manual being incorrect). Anyhow, pins 4 and 5 are for the hot wires. Both MAF sensors appear to be within spec at a certain temperature.

I tried to spray starter fluid to find leaks behind the TB. I didn't find anything except near the supercharger bypass valve. Since there was a hiss sound from that area, I used a stethoscope (long coolant hose) to listen to the area. The part where the bypass goes back into the main chamber (nearest to propellers) has the hiss sound. I believe it's blocked off when you press on the accelerator.
Another interesting sound is a clicking sound underneath the intake manifold. I assume it's an idle air control valve operating or my valves are ticking.
Turn off the truck to re-think what could be wrong...

Since I had some brake issues one day, I added more DOT3 brake fluid and top it off. While I searched for the brake fluid, I found an old bottle of Redline Fuel detergent. What the heck, I'll add some to my 5 gallons of fuel.
I turn on the truck and let it idle for a few minutes while I listen around the engine bay for air leaks. After another few minutes, I noticed the idle sounded a bit smoother. A few good tugs on the throttle cable and the engine sounded good. Not as much stumbling...
I decide to take it for a spin... the truck felt a bit stronger in the vacuum range. Let's see what it does under boost. It slightly studdered, but it didn't bog down. I hit the accelerator again and it felt smoother.
After each low boost run (2-3 psi), the acceleration felt smoother and less bog was noticed. No CEL so far.

So my theory is that either my fuel filter is clogged or my fuel feed line had build up. The major change done that caused a change in behavior is the fuel detergent. We'll see how it holds up tomorrow and I'll have my portable with me to check the OBDII data.

Where is a good place for BG44k? One dealership had it for $17. Sounds inflated to me.

Some people on this forum (and others) reported good results with BG44K.

J

AJatx

CEL is back (0171).

At least I can get into boost, but it does lean out so I still have an issue somewhere. That's with OD turned off. With OD on, it bogs big time. So, it only tells me that it's heavily affected under load (nothing new to me).

Continue to hunt for vacuum leaks...

AJatx

I kept hearing a hissing sound near the supercharger bypass valve where the L-shaped metal tube would meet the supercharger manifold. Spraying starter fluid in that spot would affect my idle significantly.

I confirmed at Magnuson that it is supposed to be sealed.
So, I unbolted the bypass assembly and pulled it out.
The O-ring near the actuator is toast (most of it was broken apart by heat?).
The other O(val)-ring is still together, but it doesn't seem to seal well.

So, I'm off to the hardware store to find a matching diameter O-ring.

AJatx

I also cleaned up the build up (looks like dissolved o-ring or RTV) on the actuator flange side.

It only requires a little elbow grease and 5mm allen wrench to remove 4 bolts.
Use loc-tite when re-assembling.

I'm going to put a little RTV on the beveled surface for assurance that it'll seal near the actuator.

MTL_4runner

I think you'll find that you found the source of your P0171 code now.

AJatx

More pictures of the clean up and o-ring installation.

I used the 2nd largest and thickest o-ring in the assorted pack I purchased from Home Depot. Put some lithium grease on it so it doesn't pinch on re-installation.

I added some Right Stuff RTV on the flange to ensure it seals.
Also add some loc-tite on the bolts.

No more leaks in this area. My idle is higher with no load now (at spec ~ 750).

However, I still have lean conditions under load at boost. So, there is still something wrong with my set-up. However, no CEL light as of yet but I still can't go WOT.
I'm pretty sure my fuel map is rich under boost.

Next thing is to perhaps install another fuel filter? I'm running out of ideas.
I replaced a couple of vacuum lines that were old (PCV and another bypass hose for emissions).

J

Stevo3

Im having the same exact issue you are having. And i kick myself in the a$$ even more because where i work its all dirt, and theres a lot of dust, and only god knows of how much dust i have sucked in there. When i did notice it on saturday night, i started to take it apart. but i have a the problem of the alen key not fitting in the 2 bolts that are closer to the S/C, How did you remove them? I was going to just put some the Hi Temp gasket sealer in a tube around that oval part. Now that i seen someone else have it off, i figure i may aswell do it the right way.

Im guessing you cut the allen key down a bit to make it fit in that tight spot.

AJatx

Cutting the allen wrench down may help, but I just unplugged the hoses to the actuator and vacuum ports, squeeze the allen wrench in there to break the bolt loose, then angled the allen wrench carefully with the longer end to pull the bolts out.

CEL finally came up. I'm not surprised since my truck is running a lean condition.

Fuel filter isn't too expensive and I'll replace it in the next couple of days.
I'm starting to suspect the fuel pressure regulator. So, I guess I'll need to cut open the fuel line so I can insert the fuel pressure gauge. This procedure is going to cost me though. Maybe I'll use a spare aftermarket (Aeromotive) FPR with a fuel pressure gauge attached.

Stevo3

Well, I'd like to add on to the removal of those 2 hard to reach hex bolts, I went and bought a #5 allen that has the rounded ends. Worked great, removed them with ease. But I removed the bypass valve aswell. I know they are set by the manufacture, but when i had bought it, it was loose so i had to set it myself, if its correct or not i dont know.

My O-ring was smooshed aswell, had a lot of suction on there with the old one. I would cover it with my hand and the idle would drastically change.

After Re-Assembly, the idle is back to where it was before i had put the S/C on. Drove around for about 20 miles, no light yet, and let it sit and idle for about 15 minutes and not light. So im hoping that fixed the problem. Before MTL_4runner guided me to this section I had replaced the MAF($300) a remanufactured one. I think im just going to sell it on ebay or something since i cannot return it. I also changed my fuel filter aswell, so im good to go i hope! And to let you know im running stock injectors and pump. But if i get the CEL ill be back ot let you know.

I'm very glad someone else has a S/C like mine because i was about to just silicone around that entire piece. And i thank you very much for posting the pics and giving a good explanation of what and how you did the things.



And this is another reason why

later on,
Stevo

MTL_4runner

If you have eliminated all your vacuum leaks then next I would definately check the fuel pressure on the rails because I remember Gadget saying he had a similar situation and the FPR was indeed bad. You can use just an aftermarket guage or they also sell fuel pressure tester kits online (may be a bit more $$$$ than just a standard guage, but it will also likely be a bit more accurate as well). The aftermarket guage may be a bit easier since you can mount it inside and view it while test driving (should be accurate enough for your purposes......check the +/- specs before buying).

Stevo3, very glad you got yours fixed.....hopefully that was all that was wrong with yours and the CEL is out for good. You might want to consider the URD fuel upgrades and the valve body mod to prevent future issues as well. Just my $0.02 anyway.

Stevo3

I have been looking at the injectors and the pump for a while now, I have just been worried about getting rid of the dang CEL before emmisions comes up. Let alone i dumped the wasted money into that MAF, And I aslo just lifted my truck 3''. I plan on getting the Sway-A-Way racerunners to swap out the 3'' spacer lift. And get Goodyear 285/75/16 Mud Terrain's first, to even out the lift to the stock tires looks kinda goofy right now.

But your 2 cents are always heard by me with 6000+ posts i figure you ought to know quite abit about stuff around here.

I plan on selling the 96 4R MAF for, I wanna try and get this but doubt i will, $200. If you know anyone let them know.

And once again thanks for your help!

AJatx

Figured out the occasional stumble in idle. It's due to spark plug gapping. The plugs look rich when I pulled them. The gap is about 0.015" off.

However, still have the lean P0171 issue. I noticed that the truck doesn't like to be on a steep slope. When trying to start, it took a couple attempts. I understand that going up a hill will induce more load, but starting should've been consistent.

I verified my fuel injectors have continuity with the main harness. Fuel is being injected in each cylinder.
The gasket for TB is installed correctly and appears to seal.

I did notice the front stud for the supercharger to block was a little loose.

Hopefully I can find an adapter for my fuel pressure gauge.
Also, I didn't cut the fuel intake piping when I installed the Walbro 190lph fuel pump. Instead, I bent the bottom arm of the bracket and the fuel pump and filter appear to fit snugly. Maybe over time, it pinched?

The O2 sensors have not been changed and the truck has about 110k miles.

Stevo3

Well, I am very happy now, its been over 100 miles and over a week of stop and go traffic, the dreaded P0171 code is finally gone!

That still may not mean its not still lean, but, I will pass emmisions now. And if the problem comes back that will be the first thing to look at. I used a skinnier O-Ring because it would not go back in, even tried to force it in. was a no go.

Im kickin my self in the ass . turned out to be a dang 59 cent o-ring, and i spend 300 on a MAF

Thank you AJatx for sharing your problem.

And thanks MTL_4runner for directing me to this thread!

AJatx

UPDATE from 11/04/06:
The P0171 code kept popping up after each hose replaced or gasket replaced.
I then started to see P0125 code with the P0171. So, I replaced the O2 sensors (I replaced both when I probably only needed to replace the front) and I don't get the P0171 nor the P0125 code.

So, the CEL is now solved. However, I think I'm still running lean on moderate boost. The buzzing or ticking noise I hear inside the truck is still present (it sounds like it could be a leak from a nylon line). You can feel the pulsations of this buzz in the fuel return line and pressure line at the FPR (aftermarket). I have determined that the nylon tubing on both the FTC and boost gauge do not contribute to this noise.

I'm going to swap out the FPR with a stock one to see if the noise and the WOT issue are solved.