Idling issues

[David8a]

I have a 94, and I've been trying to chase a rough idle/ sometimes stalling that appears randomly but lately its been doing it constantly. I notice when I unplugged the vacuum line that goes to the fuel pressure regulator, it idles just fine. When I put it back on it starts to stumble and seems to misfire. Ive seen some post about a temperature sensor that regulates the vsv valve for the FPR but I dont know where to go from here.

 

[Malleus]

Does it happen when it's cold, warm, or both? The idle air control valve is notorious for causing idle problems inthe 2nd gen 80s.

If you want to trobleshoot the VSV, open the manual and read it. All the answers are in there.

 

[Brindleboxer]

Here is a link to the service manual, there is also an EWD in the resources section. https://forum.ih8mud.com/resources/1994-land-cruiser-service-manual-rm360u-18sep2025.286/

 

[David8a]

It happens when its cold and warm, im going to read into the service manual. Thank you!

 

[robnicko]

It may also pay to remove the throttle body and give it a good clean, especially the port that the IAC valve uses & back of the throttle plate

 

[David8a]

I cleaned the throttle body and where the IAC ports are and tested the IAC but I still get the same results when I started it back up, when I shift it into drive, it has no power and started to stumble and nearly dies.

 

[Malleus]

I cleaned the throttle body and where the IAC ports are and tested the IAC but I still get the same results when I started it back up, when I shift it into drive, it has no power and started to stumble and nearly dies.

There are two tests to verify the function of the IACV: one is electrical, which can be done while it's installed, and the other is mechanical, which requires removal to perform.

FWIW, when my '94 started doing this, I checked the IACV and it was corroded internally. It passed the electrical test but failed the mechanical; after I cleaned it, it passed both tests, but the engine still ran poorly. I replaced it with the '95–'97 version (the '93–'94 part is NLA) and it has run flawlessly since.

Also, in my case, it idled well when cold, but stumbled when the engine reached operating temperature, because the valve was in the wrong position and was allowing air to bypass the throttle body. I also thoroughly cleaned the throttle body, because it was full of carbon and oil from the PCV circuit.

I'm not saying this is your problem, but it's the first place I'd look for a solution on a 2nd gen 80. I've never had this problem on a 3rd gen.

 

[David8a]

Ill definitely look into it, would you happen to have the part number for the 95-97 one?

 

[Old Nick]

Ill definitely look into it, would you happen to have the part number for the 95-97 one?

Get your VIN ready. Enter it here: https://partsouq.com/

You'll find every part number that you could wish for, together with good diagrams.

Here is a US link to the part (no affiliation with the dealer): https://toyotaparts.ourismantoyotao...rol-2227066011?c=bD0xJm49U2VhcmNoIFJlc3VsdHM=

 

[Old Nick]

I've also got a '94 and swapped in the same part that @Malleus did. It worked like a charm.

Blown away by how expensive that part has gotten...

Even so, shop around and go OEM.

 

[David8a]

I finally had a chance to replace it when an oem one and it worked fine untill after a day. The truck would at least idle normal but it would then start to hesitate and stubble. What ive notice is that when I remove the vacuum line from the regulator and capped it, the truck ran fine. When I plug it back in it just starts to idle rough. Is there always supposed to be vacuum limiting the regulator? Theres vacuum at the regulator during idle and when I rev it up.