Fast Idle (1 Viewer)

Joined
May 6, 2018
Messages
25
Location
Oklahoma
Have a new to me ‘99 Land Cruiser 285k miles with a good dealer service history. Did some basic maintenance this weekend and now have a fast idle that I can’t figure out.

1. Disconnected battery terminals and cleaned. Left disconnected over 30 minutes to reset ECM
2. New OEM air filter
3. Cleaned MAF Sensor with CRC MAF cleaner (careful not to touch the electrodes)
4. Cleaned the throttle body with CRC throttle body cleaner. Did not remove from engine, just held butterfly open manually with my fingers.
5. Reconnected battery terminals putting dielectric grease on the posts first.

Started up with an initial idle around 2,000 RPM, after a while idling in park it dropped down to the 1,400-1,600 range and seems to have settled in there. In gear idles around 1,000 or little higher. Drove it around town and on the highway for 30-40 miles and no change.

Not picking up any codes with my scan gauge.

Today I disconnected the battery again and let the ECM reset with same results. Inspected all vacuum hoses and they all are connected and look good with no cracking. Throttle body butterfly is not tight against it’s back stop with key off (has a little movement when I push back at the bottom but not much). Compared that with the throttle body butterfly on my ‘02 LX470 and about the same. Took the MAF sensor off my LX470 and put that on the Land Cruiser, disconnected battery to reset the ECM. Same result, with initial 2,000 RPM then settling in at 1400-1600. So I think I’ve ruled the MAF sensor out as the culprit.

Before doing all of the above the
8FD36F3B-938B-4A8E-9F56-4BA5E35EA542.jpeg
Park was in the 700-800 RMP range.

Any ideas on what might be causing my fast idle?
 
Joined
May 6, 2018
Messages
25
Location
Oklahoma
If you have the appropriate tool, what is the engine load and throttle position at idle on both trucks using the same MAF?
Unfortunately I don’t. Bought the Land Cruiser for my son to drive while at college in Colorado. Am out here in Colorado for the weekend and was hoping to figure it out before I head back to Oklahoma tomorrow after noon.
 

MJK

Joined
Mar 13, 2020
Messages
472
Location
Tucson
If there is a little slack in the cable when closed, I'd call that normal. And if you have not had the throttle body off, then I don't know where any air leaks beyond that point would come from. Sorry, no idea.
 
Joined
Nov 4, 2007
Messages
10,326
Location
Colorado
Since you compared butterfly and both open a hair. Id say that is normal. But "about the same"! So is the same or not?
 
Joined
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Location
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Try this. Drive it around until at op temp. Stop and shut off. Started and drive. Repeat 3 times. If still idling high, stop engine and disconnect throttle cable and start while still at op temp. See what happens. I'm thinking this should eliminate throttle cable/pedal holding open.

Make sure AC compressor set to off and all accessories. Try transmission in N & P. Also look at the clutch on compressor, while engine running..

Note:
No tool needed to disconnect cable. Just turn the halve circle cable guide on T-bady and release the cable at end from halve circle.
 
Joined
May 6, 2018
Messages
25
Location
Oklahoma
If you have the appropriate tool, what is the engine load and throttle position at idle on both trucks using the same MAF?
Using ScanGuage the ‘99 LandCruiser warmed up and at idle RPM is ~1,400, TPS 12, LOD is 16. Same conditions on ‘02 LX idle RPM is ~700, TPS 13, LOD 13.
 
Joined
Nov 4, 2007
Messages
10,326
Location
Colorado
Also if you've not yet started the engine, so it's cold. Check coolant level under the radiator cap! Best if front end high than rear. Rig needs to be at least level.

Also can you read the ECT (engine coolant temp) see if your 184F to 187F or higher once at operating temp.
 
Joined
May 6, 2018
Messages
25
Location
Oklahoma
Also if you've not yet started the engine, so it's cold. Check coolant level under the radiator cap! Best if front end high than rear. Rig needs to be at least level.

Also can you read the ECT (engine coolant temp) see if your 184F to 187F or higher once at operating temp.
Engine cold and parked on slight incline with front higher coolant is at bottom of filler neck. Part of my maintenance while cleaning the MAF sensor and throttle body, was topping off coolant with Toyota red and replacing radiator cap with new OEM cap. Before topping off coolant was just above coils.

After warmed up temp now reading 191F.
 
Joined
May 6, 2018
Messages
25
Location
Oklahoma
Try this. Drive it around until at op temp. Stop and shut off. Started and drive. Repeat 3 times. If still idling high, stop engine and disconnect throttle cable and start while still at op temp. See what happens. I'm thinking this should eliminate throttle cable/pedal holding open.

Make sure AC compressor set to off and all accessories. Try transmission in N & P. Also look at the clutch on compressor, while engine running..

Note:
No tool needed to disconnect cable. Just turn the halve circle cable guide on T-bady and release the cable at end from halve circle.
Did all of the above. Still idling high. No change with disconnected throttle cable. AC compressor clutch stopped with AC off, spinning with AC on.

Will say that when starting, every time, idle jumps up to about 1,800 RPM, drops almost immediately to 1,400, then jumps up to 1,800 and immediately back down to 1,400 and stays there.
 
Joined
Nov 4, 2007
Messages
10,326
Location
Colorado
You running a bit hot. I'd look for 184 -187F, at lower side today w/OAT of 72f and overcast in Denver. But 193F is not going to cause this idle issue. Check ST & LT fuel trims, just for reference.

If all 4 vacuum lines on on the air pipe, and both on the vane pump idle up control. I can't think of anything you could have done with a simple tune, to cause this. With possible exception of opening throttle body by pushing on it butterflies with fingers, while key in IG and ON (battery connected). Even then, hard to imagine you damaged the throttle body workings.

If issue with pedal position sensor, idle control system, throttle/ TPs you should at minimum have a pending code by now if not a CEL.
 
Joined
May 6, 2018
Messages
25
Location
Oklahoma
You running a bit hot. I'd look for 184 -187F, at lower side today w/OAT of 72f and overcast in Denver. But 193F is not going to cause this idle issue. Check ST & LT fuel trims, just for reference.

If all 4 vacuum lines on on the air pipe, and both on the vane pump idle up control. I can't think of anything you could have done with a simple tune, to cause this. With possible exception of opening throttle body by pushing on it butterflies with fingers, while key in IG and ON (battery connected). Even then, hard to imagine you damaged the throttle body workings.

If issue with pedal position sensor, idle control system, throttle/ TPs you should at minimum have a pending code by now if not a CEL.
It’s sunny and 75F OAT in Trinidad today. Temp seems to fluctuate between 188F and has gotten as high as 197F. 188F downhill on highway and 197F after uphill in town. Seems to spend most time around 193F. Will have to try to figure that out next.

I can’t figure out how to get the ST and LT fuel trim readings on the scanguage.
 

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