93 80 series stall/stumble ONLY IN PARK (1 Viewer)

[Briguytoyota]

Okay im just about at my wits end and im a week out from moab. my 80 series was running like a top but as of a month ago but it's developing worse and worse when i throw the truck in park and its at operating temp the truck will stumble and miss fire and even stall sometimes ONLY IN PARK/N nothing major has happened to the truck since this has started but everything is already just about new on her
IAC fuel injectors fuel pump fuel filter air filter intake boot spark plugs and wires the distributor cap and dizzy are new aswell the wiring harness is good and has no worn or chewed up wires and was been re protected my egr is deleted new 02 sensors new brake booster and master cyl its not a vacuum leak
As all my vacuum lines are brand new and replaced and spraying carb and choke cleaner in the engine bay has zero impact on idle
The truck idles like a top in drive and when i have the A/C on in park she idles fine aswell it's purely when in park no load she will stumble and stall i have no power issues up the hills no CEL and she fires right up weather at operation temp or ice cold
The truck is a 1993 fzj80 215k on the clock and i have checked all the grounds and wiring harnesses im at a loss
Like i said no major work really got done to provoke the issue it was running like she did off the sales lot and as long as i leave her in drive i have zero idle problems but if i have to get out of the truck i have to shut it off
Please help!
Here are the videos of the symptoms

 

[Desertmedic80]

Timing? I replaced my distributor recently and when first starting it would run under load but shut down at idol until I got it dialed in a little better. Something that can be checked. Sounds like you have done everything else within reason.

 

[LandLocked93]

Uhhh...neutral safety switch? On the basis that in the second video whatever gear you're in does not show on the dash until you shift into park.
And I suppose the zero oil pressure indication is of no concern at this point.

 

[Briguytoyota]

Uhhh...neutral safety switch? On the basis that in the second video whatever gear you're in does not show on the dash until you shift into park.
And I suppose the zero oil pressure indication is of no concern at this point.

The light on the dash does show what gear im in just my drive bulb is just burned out been that way since i got it and my oil pressure is good i check it with a mechanical gauge every oil change just the dash gauge is dead for whatever reason
Would the neutral safety switch cause it to stumble and stall though?

 

[Briguytoyota]

Timing? I replaced my distributor recently and when first starting it would run under load but shut down at idol until I got it dialed in a little better. Something that can be checked. Sounds like you have done everything else within reason.

My timing was bang on last i checked when i did my dizzy and cap i can check again but when i take it outta gear sometimes it will idle for 3-5 minutes and then present the issue sometimes its right after start up

 

[gummycarbs]

Doesn't happen in neutral? Literally only in park?

 

[Briguytoyota]

Doesn't happen in neutral? Literally only in park?

Neutral and park

 

[gummycarbs]

Neutral and park

In that case, I would probably be looking at the intake, IAC, EGR modulator and vacuum lines. My weird low idle issues were seemingly due to everything being packed with carbon. Just my personal experience.

 

[Desertmedic80]

With all the work you have done is there any part or group of parts that you replaced right before the problem started? The PO of my 80 replaced the distributor due to a leaking gear drive shaft and I ended up chasing a cam position light for weeks only to determine that the "new distributor" was a POS. You may have got your hands on a bad part.

 

[Briguytoyota]

In that case, I would probably be looking at the intake, IAC, EGR modulator and vacuum lines. My weird low idle issues were seemingly due to everything being packed with carbon. Just my personal experie

IAC has already been replaced intake is confirmed good and not torn EGR is deleted and all my vacuum lines are new

 

[gummycarbs]

Oh, and I would get an intermittent cutout similar to that when an NTK TPS from RockAuto went bad after a few months. Original TPS seemed to cause surging at high RPM, high load. The NTK worked great for awhile but then the cutting out started. A used Toyota TPS fixed both issues. No error code was thrown. Unfortunately, I can't recall if it only cut out in park/neutral.

 

[Briguytoyota]

With all the work you have done is there any part or group of parts that you replaced right before the problem started? The PO of my 80 replaced the distributor due to a leaking gear drive shaft and I ended up chasing a cam position light for weeks only to determine that the "new distributor" was a POS. You may have got your hands on a bad part.

Nothing major besides oil changes was touched for about 3 months before this issue presented itself most everything in there besides the intake boot is OEM toyota its very bizarre i can find people with issues on their trucks stalling in gear but seemingly im the only one with idle no load issues

 

[gummycarbs]

IAC has already been replaced intake is confirmed good and not torn EGR is deleted and all my vacuum lines are new

Has the intake been cleaned though? My problem was carbon, maybe from the broken membrane in the EGR modulator. Even the IAC passage was significantly packed with it.

 

[Briguytoyota]

Has the intake been cleaned though? My problem was carbon, maybe from the broken membrane in the EGR modulator. Even the IAC passage was significantly packed with it.

The intake was cleaned really good when i did the injectors and the throttle body was purged at the same time
If my egr is deleted with the huddexpo kit the membrane should be a non issue im assuming

 

[93yotasr5]

Check some of the hard vacuum lines coming off the top plenum. They get blocked up pretty easily and can be cleaned out with a small piece of wire. After changing all of those parts out, did you reset the ECU?

 

[Briguytoyota]

Check some of the hard vacuum lines coming off the top plenum. They get blocked up pretty easily and can be cleaned out with a small piece of wire. After changing all of those parts out, did you reset the ECU

Yeah those parts are not recently replaced atleast nowhere within the time frame this issue presented its self so the battery has been outta the truck for extended periods of time to do idle relearn a few times

 

[LandLocked93]

The light on the dash does show what gear im in just my drive bulb is just burned out been that way since i got it and my oil pressure is good i check it with a mechanical gauge every oil change just the dash gauge is dead for whatever reason
Would the neutral safety switch cause it to stumble and stall though?

Copy that.
Is it stalling to cutting off or sort of moving between park idle and 'drive idle' (if that's a such a thing)? The NSS can send mixed signals to what it talks to to tell what gear the truck is in. I don't know the full details, but yes a NSS going bad can cause all sorts of issues. It did for me. Not sure the best way to rule it out tho without swapping in a new one.

 

[Briguytoyota]

Copy that.
Is it stalling to cutting off or sort of moving between park idle and 'drive idle' (if that's a such a thing)? The NSS can send mixed signals to what it talks to to tell what gear the truck is in. I don't know the full details, but yes a NSS going bad can cause all sorts of issues. It did for me. Not sure the best way to rule it out tho without swapping in a new one.

How do you mean? Stalling to cutting off or moving between park idle and drive idle

 

[LandLocked93]

How do you mean? Stalling to cutting off or moving between park idle and drive idle

When you say it's stalling, is the engine actually cutting out? (shutting off)

I just mean that when shifting to park, there is an idle switch up on the intake that is engaged to make the truck idle out of gear.
When shifting to drive, that switch is disengaged to up the timing and put more fuel in the engine to idle in gear.
The video makes it look like that's what's doing, like the idle switch engaging/disengaging.
But I guess in reality, the idle would be surging in that scenario, and not dropping as shown in the video.
Anyhoo...

 

[Briguytoyota]

When you say it's stalling, is the engine actually cutting out? (shutting off)

I just mean that when shifting to park, there is an idle switch up on the intake that is engaged to make the truck idle out of gear.
When shifting to drive, that switch is disengaged to up the timing and put more fuel in the engine to idle in gear.
The video makes it look like that's what's doing, like the idle switch engaging/disengaging.
But I guess in reality, the idle would be surging in that scenario, and not dropping as shown in the video.
Anyhoo...

Yeah the second video shows the truck actually quitting on me it true stalls out about every 4 times it stumbles
And yeah ill throw the truck into park or neutral and it will up idle from 600 to 650 and sometimes it will immediately present the issue other times it will hold good for a few minutes but almost always presents the issue