Low idle frustrated (1 Viewer)

[Danger Cruiser]

On a hot day in July, I took my 97 Landcruiser Collector’s edition out for a spin.

It ran perfectly for 800 miles after my headgasket replacement then suddenly…

Something happened going down the highway at 70mph. When I came to the end of the exit, it stalled. It will always restart but it started to idle low. I mean really low like 100 rpm.

Here’s what I’ve done so far:

• Benchtested IAC valve per FSM. Checked out good, but I,
• Changed out IAC Valve with a known good IAC anyway.
• Set Timing to 3 degrees per FSM.
• Cleaned throttle body and all of the vacuum ports and passageways.
• Didn’t change anything so, I changed out the throttle body for a known good Throttle body including new OEM gasket bolts torqued to 15lbs.
• Changed intake air tube.
• Inspected ECM, A/C amplifier, Auto A/C Amplifier, and wiring harness for visible damage. No visible change.
• Changed all of the vacuum hoses.
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• It does not idle up at all on a cold start.
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• After it warms up to normal operating temp and the O2 sensors come online, it will idle at around 400 rpm.
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• It does not throw any codes unless I tighten the throttle cable to make it idle higher. Then I get po510 (Closed Throttle Position switch malfunction)
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• The AUTO air conditioning works including compressor, but the RPM does not go up when the A/C clutch comes on.
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• It is running great other than the idle. I’m getting 13.4 mpg and 0-60 in 10.86 seconds.
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• What am I missing? What should I try next besides order a hand throttle cable. Help please.

 

[Pierce]

Throttle position sensor adjustment or replacement? Just throwing ideas out there.

 

[Danger Cruiser]

I put on a different used one that came on the 2nd throttle body. Both of them tested good per FSM.

 

[LandLocked93]

Idle switch?

Battery terminals clean?

Could have been the 0-60 timing. 80's do not like that.

 

[Colbino]

I had a similar issue after my hg replacement. Drove it home without any issues. Then the next morning it would stall when I'd come to a stop or slow down for turns. The mechanic came out and looked everything over and found a ripped intake tube, retarded the timing he advanced earlier on and replaced the maf with a known good one. He took it for a spin and all was good so he left. When I got home however it would still stall out on me. Long story short the shop found that one of the pins that connected to the IAC was bent and not making contact when plugged in. Maybe disconnect yours and double check that nothing is bent and/or no longer making contact.

 

[Danger Cruiser]

I have another 96 cruiser but my son has it at college. I'm going to start swapping parts when he is home for fall break. The MAF is something I haven't messed with yet.

 

[swankstar]

Fuel filter? How many miles on vehicle?

 

[wfd175]

This is what happened with my new to me idle issue that was corrected. I have had this 80 for a couple years and never had this issue before.
I was on an extended trail trip (Kokopelli) and every once in a while I was having idle issues when we slowed down.
Of course it was hot and my fuel was boiling. We looked at a lot of things, intake hose. Intake fittings etc... I noticed slack in the throttle body cable I thought something was out of adjustment.There was a lot of vehicle things going on that weren’t normal. Prior to the trip I had converted my entire ac system to 134. Evap, cond, comp, drier, expansion valve. So I had many variables to consider.

As I was in and out of the truck a lot Every so often I was pulling the weather tech floor mat back into its normal position. It kept sliding towards the firewall.
Then I had an mental moment, I wonder if the floor mat is shoving something behind the gas pedal when it was slid way forward causing my issue, I’ll be a
Sob, while the truck was running I pulled the floor mat back and the idle went back to 600-800. Push it forward dropped to 100-200. I don’t know what it was pushing up on behind the pedal, but the mystery was solved. Sounds really simple and dumb but In the end my entire low idle issue was solved by keeping my weathertech floormat pulled back.

 

[Danger Cruiser]

I do have Weathertech floor mats.

 

[Danger Cruiser]

Fuel filter? How many miles on vehicle?

It has 207,000 miles. I replaced the fuel filter when I did the head gasket at 204k

 

[LandLocked93]

This is what happened with my new to me idle issue that was corrected. I have had this 80 for a couple years and never had this issue before.
I was on an extended trail trip (Kokopelli) and every once in a while I was having idle issues when we slowed down.
Of course it was hot and my fuel was boiling. We looked at a lot of things, intake hose. Intake fittings etc... I noticed slack in the throttle body cable I thought something was out of adjustment.There was a lot of vehicle things going on that weren’t normal. Prior to the trip I had converted my entire ac system to 134. Evap, cond, comp, drier, expansion valve. So I had many variables to consider.

As I was in and out of the truck a lot Every so often I was pulling the weather tech floor mat back into its normal position. It kept sliding towards the firewall.
Then I had an mental moment, I wonder if the floor mat is shoving something behind the gas pedal when it was slid way forward causing my issue, I’ll be a
Sob, while the truck was running I pulled the floor mat back and the idle went back to 600-800. Push it forward dropped to 100-200. I don’t know what it was pushing up on behind the pedal, but the mystery was solved. Sounds really simple and dumb but In the end my entire low idle issue was solved by keeping my weathertech floormat pulled back.

Wow. Coincidence for the win. Good to know for when I pop for decent floor mats one day.

 

[LandLocked93]

It has 207,000 miles. I replaced the fuel filter when I did the head gasket at 204k

When its idling low, if you gently begin to press on the lever to which the accel cable is connected (as if pressing the gas pedal), you should here a click from the area of the MAFS and your idle should immediately jump up in rpms. Slowly releasing pressure on that lever should produce the click again and your idle will drop too low (where it should idle normally instead).
Mine does that too and I've band aided it by adjusting accel cable nut, essentially changing where the TPS sees the throttle when fully released. It's not really a fix as drive time increases so does the idle speed and I find myself having to put my foot under the gas pedal and pull up to further release accel cable tension.

The true fix is still in debate, imo. Some say it's the TPS. But in your case, it doesn't appear to be. Others replace the entire throttle body, but some still return no joy thereafter. In my case it could be the accel cable itself being old, frayed, rusted in places, etc. But my driving style and the trails I do in the seasons I do them make the whole thing a minor annoyance at most.

If none of this applies, well shoot.

 

[Danger Cruiser]

Does your idle go up when you turn on the A/C? Mine does not change. If anything it goes down because of the extra drag the compressor has on the engine.

 

[LandLocked93]

Does your idle go up when you turn on the A/C? Mine does not change. If anything it goes down because of the extra drag the compressor has on the engine.

No, no it doesn't. It umm, well nothing happens when I hit the AC switch. Coincidentally I don't need AC at the times I'm behind the wheel hours at a time. But I would like to suss it out and get it going one day. Could be the taped up connector sitting loose atop the valve cover. No idea what it goes to yet.

 

[jonheld]

This is what happened with my new to me idle issue that was corrected. I have had this 80 for a couple years and never had this issue before.
I was on an extended trail trip (Kokopelli) and every once in a while I was having idle issues when we slowed down.
Of course it was hot and my fuel was boiling. We looked at a lot of things, intake hose. Intake fittings etc... I noticed slack in the throttle body cable I thought something was out of adjustment.There was a lot of vehicle things going on that weren’t normal. Prior to the trip I had converted my entire ac system to 134. Evap, cond, comp, drier, expansion valve. So I had many variables to consider.

As I was in and out of the truck a lot Every so often I was pulling the weather tech floor mat back into its normal position. It kept sliding towards the firewall.
Then I had an mental moment, I wonder if the floor mat is shoving something behind the gas pedal when it was slid way forward causing my issue, I’ll be a
Sob, while the truck was running I pulled the floor mat back and the idle went back to 600-800. Push it forward dropped to 100-200. I don’t know what it was pushing up on behind the pedal, but the mystery was solved. Sounds really simple and dumb but In the end my entire low idle issue was solved by keeping my weathertech floormat pulled back.

This sounds all wrong to me.
Once the throttle plate is at idle position, adding slack to the cable by pulling up on the accelerator pedal should make no difference. The throttle plate is already at rest.
This sounds like your throttle cable is way out of adjustment and your ISC/TPS has been moved to compensate.
The mechanical adjustments should be correct first.
The throttle cable should be adjusted at WOT with the pedal to the floor. At that position the throttle plate should just be touching the end stop at WOT.
That's it. The amount of slack at idle is meaningless because the idle is controlled by the ECU pushing the ISC. That is assuming that your TPS is adjusted correctly.
All of this is in the FSM.

 

[wfd175]

This sounds all wrong to me.
Once the throttle plate is at idle position, adding slack to the cable by pulling up on the accelerator pedal should make no difference. The throttle plate is already at rest.
This sounds like your throttle cable is way out of adjustment and your ISC/TPS has been moved to compensate.
The mechanical adjustments should be correct first.
The throttle cable should be adjusted at WOT with the pedal to the floor. At that position the throttle plate should just be touching the end stop at WOT.
That's it. The amount of slack at idle is meaningless because the idle is controlled by the ECU pushing the ISC. That is assuming that your TPS is adjusted correctly.
All of this is in the FSM.

The small amount slack was just one of many , many observations. We had a propane torch (not lit) hitting every vacuum hose connection trying to find a vacuum leak, checking every clamp and bolt. Just like a piss shirt bend bars, floormat shoved under the gas pedal lowers idle on my truck. It really is ok to not be completely disheartened when the solution isn’t in the FSM. It’s called the KISS method.

 

[jonheld]

The small amount slack was just one of many , many observations. We had a propane torch (not lit) hitting every vacuum hose connection trying to find a vacuum leak, checking every clamp and bolt. Just like a piss shirt bend bars, floormat shoved under the gas pedal lowers idle on my truck. It really is ok to not be completely disheartened when the solution isn’t in the FSM. It’s called the KISS method.

I guess you're missing my point.
If lifting up the accelerator pedal lowers the idle speed, then the throttle plate is not at rest on the endstop or there is something else out of adjustment. This has less to do with the FSM and more to do with basic mechanics.
Again, the mechanicals have to be adjusted before the electronics.

 

[LandLocked93]

I guess you're missing my point.
If lifting up the accelerator pedal lowers the idle speed, then the throttle plate is not at rest on the endstop or there is something else out of adjustment. This has less to do with the FSM and more to do with basic mechanics.
Again, the mechanicals have to be adjusted before the electronics.

I made the point of having to lift the throttle to lower the idle. And I'll confirm there is something in my setup not quite right. I have a few questions about it, but it's best for another thread when I'm done researching and testing. Thanks for the advice, btw.

 

[Danger Cruiser]

Solved! The TPS was out of spec. It was not turning on the idle circuit.

 

[LandLocked93]

Solved! The TPS was out of spec. It was not turning on the idle circuit.

Did you suss that yourself? If so, was it difficult? I've assumed my TPS was shot so the PO did something to make it good during the test drive.