Idleing Woes

[Therealtotodile]

Hey all,
The Black Pearl has been running great, other than a loopy idle. It seems to never want to come down to 650, and usually sits like 800 when I'm in gear, about 1050 when in P.

I have been playing with both the IAC and TPS, and just did the o-ring mod on the IAC. Two o-rings made it so it wouldn't start, and one improved it a little bit. Instead of starting at 1800 rpm I now start at 1600 .

Anyways, now I'm playing with the TPS. I would assume that the idle RPM should be changing when I move that sensor through its range. However, it doesn't seem to change the behavior of my truck, even when I have it in the furthest or closest orientations. I kept reading that the idle is completely ECU controlled(1993 1FZFE), and that I may need to like pull the efi or just wait to get it to try and update itself. Curious if anyone has experience playing with the TPS -- I do not have the tools to do the diag using vaccuum and don't think I need it here. Just trying to understand if my TPS is faulty, which I think it may be. Spring in the TPS has good action, and it pulls back to the left strongly when the set screws are loose. For whatever reason, adjusting it is not changing my idle.

So, do I just need to wait longer after making an adjustment to see a result? Make sure I reset the ECU?

THANKS ALL

Chris

 

[jonheld]

First thing I would look at is the throttle cable. If it's too tight then the throttle plate is not closing all the way and the ISC won't work. There should be some slack in the cable at idle.

 

[MurderBird45]

First thing I would look at is the throttle cable. If it's too tight then the throttle plate is not closing all the way and the ISC won't work. There should be some slack in the cable at idle.

Yeah- quickest way to diagnose is to use your toe to pull up on the accelerator. If the rpm drops, it’s most likely your cable tension or the cable sticking.

 

[Therealtotodile]

Yeah- quickest way to diagnose is to use your toe to pull up on the accelerator. If the rpm drops, it’s most likely your cable tension or the cable sticking.

Hey guys, so the throttle cable is good, no changes in rpm when I toe up on the pedal. I also spent some more time playing with the TPS, and it is now set as far to the right(clockwise) as it can be spun. After pulling the efi and driving around, restarting the truck like 10 times, I got the P idle down to 800. In D its sitting at 700.

Getting closer! But still confused about the TPS haha . If anyone has insight here, why all the way to the right would make it a lower idle, id love to hear an explanation.

 

[jonheld]

Hey guys, so the throttle cable is good, no changes in rpm when I toe up on the pedal. I also spent some more time playing with the TPS, and it is now set as far to the right(clockwise) as it can be spun. After pulling the efi and driving around, restarting the truck like 10 times, I got the P idle down to 800. In D its sitting at 700.

Getting closer! But still confused about the TPS haha . If anyone has insight here, why all the way to the right would make it a lower idle, id love to hear an explanation.

Have you tested the ISC valve according to the FSM?

 

[MoJ]

Hey guys, so the throttle cable is good, no changes in rpm when I toe up on the pedal. I also spent some more time playing with the TPS, and it is now set as far to the right(clockwise) as it can be spun. After pulling the efi and driving around, restarting the truck like 10 times, I got the P idle down to 800. In D its sitting at 700.

Getting closer! But still confused about the TPS haha . If anyone has insight here, why all the way to the right would make it a lower idle, id love to hear an explanation.

I’m curious as to whether the TPS adjustment is simply masking/compensating for the true root cause.

 

[Therealtotodile]

I’m curious as to whether the TPS adjustment is simply masking/compensating for the true root cause.

IAC is NOT testing in spec. Multiple connection that are showing around 40 ohms. Should be 10-30. It will be ordered next paycheck. They're only like 50$ new. Aisin ones available.

 

[jonheld]

IAC is NOT testing in spec. Multiple connection that are showing around 40 ohms. Should be 10-30. It will be ordered next paycheck. They're only like 50$ new. Aisin ones available.

I would be less concerned with the static resistance across the 4 coils, especially if they're all reading close to the same resistance. It is a 4 coil stepper motor that can be tested by applying voltage to successive coil taps as documented in the FSM.

 

[Therealtotodile]

I would be less concerned with the static resistance across the 4 coils, especially if they're all reading close to the same resistance. It is a 4 coil stepper motor that can be tested by applying voltage to successive coil taps as documented in the FSM.

They are not all reading 40 ohms, some are 20ohms. got 20x2 and 40x2 for the 4 readings. Would you still say that its good even when two of the 4 are elevated a bit? I will jump it and see. I do not have that page that describes the testing with voltage applied in my redacted mud version of the fsm.

 

[jonheld]

They are not all reading 40 ohms, some are 20ohms. got 20x2 and 40x2 for the 4 readings. Would you still say that its good even when two of the 4 are elevated a bit? I will jump it and see. I do not have that page that describes the testing with voltage applied in my redacted mud version of the fsm.

This is from the 1996 FSM, but the pinouts and procedure is the same. Remember that it is a stepper motor. It won't spin. It will move in VERY small increments.
It will likely work with a 9 volt battery.

 

[jonheld]

Another thing to consider, coils usually short or open. They don't slightly increase in resistance.

 

[Therealtotodile]

Ended up being the IAC valve. Was able to source a new one and now she runs better than she ever has.

Salud!