High Idle! Fzj80 idles at 3,000 RPM??

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jbee

jbee

Thank God for the deserts
10 Year
Joined
May 18, 2011
Threads
106
Messages
1,086
Location
Gilbert, AZ
Hi, thanks in advance for taking a look and for your advice. I have read every thread with 'high idle' in the title and have not found a solution.

1996 FZJ80. No mods. Has run great for the 800 miles in which I've had it, went wheeling (very light) one day and the next morning had this high idle thing happening. For the first day or so it would do that thing where it idled up-and-down between about 1500 and 2000. Then that gave way to just a straight 3200 Idle. Does not matter when the truck warms up, it will sit and Idle at 3200 all day long.
It drops down when I'm in gear but still wants to rev really high.

Attached are some photos of the rudimentary OBD2 reader that gives me real-time data while the motor is running. I'm a noob at what these readings mean. TPS load has since been adjusted to 10.2.

Here are the things that I have done that have not fixed/changed anything;
New throttle position sensor
new idle air control
Triple checked throttle cable for binding, even removed it to slide it back-and-forth. It is smooth as glass. Same for cruise cable.
Both cables seem to bottom out Properly at zero throttle.

Triple checked for holes in the air intake Bellows thingy. It's solid.

Removed and cleaned the throttle body, it was very clean, just wiped a little bit of goo off of the butterfly. One of the throttlebody bolts was loose, turned out it was too short. I replaced it with a proper size bold and torqued to spec. Gasket was in great shape.

Removed and carefully cleaned the MAF sensor.

Replaced all of the vacuum lines up top and made sure that the breather hoses are on and sealed.

I had check engine lights for oxygen sensors and EGR before, , I cleared them both to try to get new ones for this problem but have not gotten any yet.

Things I have not done yet:
Check MAF sensor per FSM.

Disconnect battery, is it possible something I did fixed it And the system needs to relearn? Battery has not been disconnected throughout this process.

Thanks again for any input.

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TPS is showing 7.5%, that does not seem right, although I don't have ODBII to compare. I would imagine it would say ~0.0%.
Does idle change with A/C on?
 
I adjusted TPS to 10.2% per forum advice after I took the photos.
A/c not working so the compressor does not kick on.
When I put the car in drive or reverse, Idle will kick down to 1400, but I have to hold onto the brake pretty tight.
 
That Is significant RPM, Is the T/body return spring bringing your T/cable and trans kick down back to Idel position.? That just seems to high not to be something mechanical holding the throttle open. I had some bad vaccume lines that Increased mine somewhat but probably not your problem. Good Lock !
 
Was wondering the same thing. Sounds like something is holding TB open. I don't think you can adjust the tps with it running at that high of rpm without knowing the cause or the actual position if the throttle plate
 
Have you tried testing your Idle Air Control valve per the FSM? Maybe pull it off and see how dirty it is where it seals to the throttle body? I think bad coolant temperature sensors can also do this as they make the car think it still needs to warm up so it keeps idling high.
 
Thanks for the help. IAC is new Aisin. I did not test it before I installed it.
While it's running, I can hold the throttle shut and I can feel The mechanism bottom out. It bottoms out on the TPS side and in the back on the throttle cable side. No play in the shaft.
When I had the throttle body apart I made sure that the butterfly is actually closing in the throat. There seems to be a proper amount of tension on the open side and then it would Snap shut when I let go.
I will pull off the rubber intake thing and confirm that it is closing inside now that I've installed the TB again.

I've been reading a lot about the temperature sensors, seem to be two of them. I saw where somebody said the temp sensor that talks to the ECU is the one I need to look at.
 
Have you checked your wire harness where it goes by the EGR? Maybe it's melted and something is shorted out?
 
Decided to disconnect the battery and put the EFI fuse and let everything reset.

Here's what I found.

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jbee said:
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I've been reading a lot about the temperature sensors, seem to be two of them. I saw where somebody said the temp sensor that talks to the ECU is the one I need to look at.
Click to expand...

That one is easy to test: If it's working will see a proper/expected coolant temp on your OBD2 device. If failed will get a PO115 and/or PO116 and the indicated coolant temp will be way out of range, the ones that I have seen were 284F, all of the time, motor cold or warm. This shouldn't cause your problem, if the ECU sees way out of range reading, it fail safes to 176F.

To run at that speed, the motor has to be getting air, throttle plate not closing, big air leak between the throttle plate and head, IAC, etc.
 
jbee said:
Decided to disconnect the battery and put the EFI fuse and let everything reset.

Here's what I found.
Click to expand...

That has been close to blowing, likely for significant time to melt without blowing. Don't see how it will cause you problem? If it's blown, no ECU power, so it is still delivering power. I have a amp draw meter that plugs into the fuse, if you want to barrow.
 
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