1997 1FZ Hiccupy idle and running rich (1 Viewer)

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Feb 12, 2015
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There is a way to "turn off" the EGR via a test plug. Read up on this thread. I have done this for the last 10k with no issues.

Have you checked your emissions setup like this? MPGs good?

I checked my EGR function tonight - applying vacuum kills the engine like the FSM says it should. It didn't seem to respond to applying and positive pressure, so that's good.

One of the modulator tests - air flow through Port Q test below and above 2500 RPMs seemed to pass fine.

However, I was unable to get any vacuum between the modulator and the EGR when the engine was hot, at any RPM. I might have c*cked that last test up, so I will try again tomorrow in the daylight.

Unless I decide to go down the EGR delete path, it looks like I need to re-check the vacuum system - not for leaks but for commanding the wrong airflows through the VCV or a dead VSV.

I have learned more than I never wanted to know about emissions controls... :censor:
 
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NJ
Have you checked your emissions setup like this? MPGs good?

I checked my EGR function tonight - applying vacuum kills the engine like the FSM says it should. It didn't seem to respond to applying and positive pressure, so that's good.

One of the modulator tests - air flow through Port Q test below and above 2500 RPMs seemed to pass fine.

However, I was unable to get any vacuum between the modulator and the EGR when the engine was hot, at any RPM. I might have c*cked that last test up, so I will try again tomorrow in the daylight.

Unless I decide to go down the EGR delete path, it looks like I need to re-check the vacuum system - not for leaks but for commanding the wrong airflows through the VCV or a dead VSV.

I have learned more than I never wanted to know about emissions controls... :censor:
My truck runs very well. I did re-do all of my vacuum lines during baselining like you are doing now. During that phase I found my VSV was faulty causing a P0401 code. Once replaced with new, the code cleared. I drove it around for a few thousand miles to verify it was fixed and then installed the HuddExpo "test" kit. I installed the kit to keep the intake cleaner and reduce heat near the harness even though I insulated it.
All of the above was done before I made any modifications such as the LandTank MAF kit and supercharger. I wanted the truck to run as designed before adding any components.

After inspection, the harness was wrapped in fiberglass heat tape and then with thermaflect tape.

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Joined
Feb 12, 2015
Messages
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Plano, TX
I wanted the truck to run as designed before adding any components.

After inspection, the harness was wrapped in fiberglass heat tape and then with thermaflect tape.

View attachment 2566380 View attachment 2566382

I am headed down your same path then. I ordered the HuddExpo kit, but I am going to get every single thing functioning as designed first, then start making mods.

Can't build a solid house on a shaky foundation, or some cheesy platitude like that. ;)

Question: If I suspect the modulator works, but is not getting the right inputs at the right time, does that point to VSV?
 
Joined
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Messages
92
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Plano, TX
During that phase I found my VSV was faulty causing a P0401 code. Once replaced with new, the code cleared.

I wish I could get all of that from under the manifold and redo it without taking the top of the intake off, but here we are. I saw a video of a guy fishing it out of there, but I am less than 6 months out from shoulder surgery, so there's no way I can contort myself into a space like that at the moment.
 
Joined
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Messages
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Plano, TX
If you haven’t replaced the O2 sensors I’d do that. I’ve been using the Denso parts for this for a while.

Ding ding ding!

After getting the Ultragauge setup I have only driven it 2-3 times, but not a single value was really off the charts, I had decided to just keep going with baselining and replacing things as I got to them, since a little hiccup in the idle was the only real symptom.

While driving around with my spouse yesterday the UG wouldn't shut up. Turns out it picked up a pending trouble code - P0136 - but it never got set after another 2 drive cycles and it never pended again either.

FSM says that's 100% positive for either 1) the O2 sensor itself, or 2) the wiring to/from the sensor. Not saying I don't have other issues, but doing the pair of O2s seems to be the next best item to tackle.

New Denso sensors en route - already picked up 6 new nuts for the O2 sensors and two OE Toyota gaskets in my last TPD order.
 
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Joined
Jun 16, 2020
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Portland, OR
I read into the thread a bit but didn’t see if you’ve already checked your o2 sensor voltages/ fuel trims with an obd2 diagnostic. I had similar symptoms and both o2 sensors were barely showing any voltage with the engine fully warm
 
Joined
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Messages
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Plano, TX
I read into the thread a bit but didn’t see if you’ve already checked your o2 sensor voltages/ fuel trims with an obd2 diagnostic. I had similar symptoms and both o2 sensors were barely showing any voltage with the engine fully warm

Some other life stuff has kinda gotten in the way but I will be back to this soon.

In short, yes. I got an Ultragauge and noticed I was getting very inconsistent voltages from the rear sensor and the front sensor seems a bit lazy. I’m sure once that is corrected and I disconnect the battery for a bit and it relearns all will be well.
 

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