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Discussion Starter · #1 ·
Ok here's the background.

99 frontier V6 4x4 auto non -sc.

Had an knock sensor code - fixed and replace in original location. Code gone

Few days truck gave me a p0301 code- engine misfire. Plugs & rotor recently changed. New wires changed were installed and new distributor cap. Misfire code gone.

I then get a p0510 code. Close Tps sensor.

Go to a buddies because truck was idling high. We adjust the TPS and the screw under the cable. Idle gets better.

Back out of driveway and p0120 TPS sensor code comes on. Drive 1/2 down the road and between 1st and 2nd rpms jump and truck jerks. We tried to adj TPS sensor no dice.

Drive truck back home. Truck has a loss of power I'm getting on the gas and it's barely responding.

Bought a new TPS sensor installed and backed the screw we ask this morning. Still same issues and code. No power, jumps from 1 to 2 and no power. Not sure what to do now.
 

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Sounds like since the TPS is calibrated correctly already the next step is you need to watch the TPS output as you press the throttle slowly from 0 to 100%

This can be done with a scan tool like torque or others

Its better with a scan tool because it's a lot easier to hook up and just watch the percentage rise

If you don't have one you can use a multimeter to watch the value rise

Sounds to me like you've got a dead spot and it will reach a certain value, then it will stop as you go through the dead spot, then it will jump to where your throttle position currently is once you pass the dead spot.

Even though you have a new TPS it sounds to me like there's an issue there, but i could be wrong

Ive never seen wire damage on enclosed engine looms on newer vehicles (I work on semi trucks and trailers, wires rub through fast if they are even close to touching anything at work) but if you're getting the right throttle values coming out of the TPS that doesn't necessarily mean it's the same going into the ECU

(In other words find out which pin is TPS output and check/compare to the value at the TPS itself)

If that's all good then I would check for vacuum leaks, mainly on the accordion ribs on the duct going from air box to throttle.

Thats a common failure spot, with age as the motor flexes and especially when the mounts start going bad, the ribs tear because the air box is fixed and solid so it move when the motor moves. Therefore the weakest point breaks (the ribs)

If you're sucking in air at any point past the maf, which would be unregistered air and the ECU doesn't know it's there

So it could cause idle problems. I had that same issue with hesitation, jumping and power loss on a similar v6 Toyota motor. Vacuum leaks after the maf caused the exact problem you're describing. It was hard to see and it took a lot of chasing vacuum lines but it turned out that one of the ribs on the duct was cracked, it would only open up when the engine moved so it would buck like crazy in 1st going to 2nd. Couldn't find it with propane at idle because the engine mounts didn't flex at idle so the crack stayed closed

Other than that I'm not sure and if it were me I would read up on the diagnostic tree for TPS in the FSM

Does the distributer rotor shaft have any play, or do you see any specs of metal under the cap? Distributers in these engines are a common failure and it fails internally at the bearing. You'll know by checking the shaft and looking for metal specs or shavings under the cap, it also may make a grinding noise as it turns when the engine is running

Listen closely with a screwdriver touching the distributer and your ear on the other end

Sent from my XT1080 using Tapatalk
 

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The screw you use to adjust the idle is on the IACV-AAC valve. It sounds like you adjusted the throttle drum stop screw on the throttle body, which is something you should never touch. If this is the case, you need to consult the factory service manual and adjust this first. Next, you have to adjust the Throttle Position Sensor per the factory service manual procedure, which involves using a set of feeler gauges and an ohmmeter to properly adjust it. Then, you would have to relearn the Closed Throttle Position. Once you get these items properly adjusted, you can see if you are still having problems and get back to us.
 

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Discussion Starter · #4 ·
There where 2 screws top which is the stop and the bottom and the fast idle. It was the bottom one and we revered the change. At this point the trucks in fail safe mode. I'll take it to the shop and let them calibrate the TPS and get me running right again. I just don't have time
 

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Discussion Starter · #5 ·
Well looks like the TPS sensor I got [wells] didn't have enough adj. that's fixed but had an injector go bad that caused the misfire done and a driveshaft bearing. Trucks back on the road and runs better than when I first got it
 
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