JDM FZJ, terrible idle, everything tried (SOLVED) (1 Viewer)

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Joined
Jan 10, 2021
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Location
Ohio, USA
Hi all, after many, MANY hours scouring 'Mud for a solution, I come to you for help...

Here's the lay of the land..... 1995 JDM FZJ80, bone stock 1FZ and A442F, both in really good condition mechanically, but CONTSANTLY having idle and power loss issues. Starts fine after 2-3 rolls on the starter, revs to 1800, drops down to around 1200, once the loop closes it sits right at 400rpm in neutral and trips over itself constantly, and by constantly, I mean it sounds like its about to stall any time you rev it, in any gear. This all started after a decent 900mi road trip, during which the rig ran PERFECTLY the entire time.

Here's what I've done to fix it:

EGR completely deleted(non-OBD so no paperclip needed), upper and lower intake mani gaskets, new TB gasket, new IAC o-ring, o2 sensors (twice), IAC and TPS replaced, every vacuum line and hose replaced, new oil cap, new intake tube, everything unuser capped off, new coil, new complete oem dizzy, new wires, new plugs with correct gap, adjusted both the throttle and kickdown cables, timing set to both OEM spec and advanced a little, neither to any avail, EGR tube harness melting issue is not present, everything has been plugged in and replugged in 5 times at least, no loss of continuity ANYWHERE.

I am totally and completely beat by this. I am a Toyota Tech, ASE Master and the works, and CANNOT figure this out at all, nor can some more experienced Masters in my shop, hence all the parts thrown at it. It's really starting to beat me up that I can't figure out what is wrong!

EDIT: I've already sprayed the ENTIRE intake track with starting fluid to try to help find a vac leak, as well as positive and negative pressure testing on the intake, both yielding results within OEM spec
 
Have you been throug a couple of tanks of has yet? Fuel filter also
Yes, 3-4 tanks since issue began, have not done fuel filter yet, but rail pressure tested good at idle
 
So, you started it up on day after the trip and what you describe is what it was doing? Or, it was running fine one second and then it began doing what you describe the next moment?

It idles smooth but slow and rpm gain is weak if at all? Idles not so smooth but slow with poor rpm gain?

And after doing all the work you did and replacing all those parts there was no change?

Slow idle can happen for the next 15 starts or so after the ECM looses power like when the battery is disconnected or efi fuse is removed.

Air filter?
Fuel delivery?
Head gasket??
ECM wiring condition behind the glove compartment?
 
So, you started it up on day after the trip and what you describe is what it was doing? Or, it was running fine one second and then it began doing what you describe the next moment?

It idles smooth but slow and rpm gain is weak if at all? Idles not so smooth but slow with poor rpm gain?

And after doing all the work you did and replacing all those parts there was no change?

Slow idle can happen for then next 15 starts or so after the ECM looses power line when the battery is disconnected or efi fuse is removed.

Air filter?
Fuel delivery?
Head gasket??
ECM wiring condition behind the glove compartment?
air filter is a new OEM unit replaced 5 months ago, looks good upon visual
as I said to solve, havent changed anything here in the fueling department but rail pressure on idle is within spec
Headgasket passes comp test, and cylinders pass leakdown
ECM wiring is in good condition both on engine side and ECM side, as I said, no loss of continuity that I could find

Correct, started up day after the trip for work around 8am, car had been sitting for about 7-9hr at that point. rought idle, sounds like its down a cylinder for a few seconds, then comes back to 6 but super lumpy and low.

Idle is NOT, NOT smooth, like it has an effing cam alomst. sits around 400rpm, then goes dead to zero and hops up when the throttle is depressed. Noticable loss of power in gear under driving loads.

It has been FAR more than 15 starts since last battery disconnect, this began about 2 weeks ago, and I've been privately chasing tail since.
 
It's really non-OBD and it has O2 sensors?

I'll bet it's an OBD1 and you can test on the plug on the firewall under hood.

OK, you're Toyota Tech. What brand parts did you install on all these replacement items? Believe me, it's helpful to know, but you didn't specifically state it.

Sounds to me like it's the VAF/MAF/whateverthehellitis on this year.
 
Maybe the ghetto MAF “upgrade” is living up to its name???
funnily enough, the problem gets worse swapping back to OEM MAF...

It's really non-OBD and it has O2 sensors?

I'll bet it's an OBD1 and you can test on the plug on the firewall under hood.

OK, you're Toyota Tech. What brand parts did you install on all these replacement items? Believe me, it's helpful to know, but you didn't specifically state it.

Sounds to me like it's the VAF/MAF/whateverthehellitis on this year.
regarding MAF ^^^

I used all OEM Toyota parts on everything, besides plugs and coil.

You are correct about the plug on the firewall. OBD1. No codes other than a faulty block water temp sensor.
 
TPS - Throttle Position Sensor
IAC - Idle Air Control
The TPS is about $95 from the dealer and can be adjusted. FSM says idle rpm should be 650. Connect Torque app and bluetooth OBD2 to read data. Physically turn the TPS while watching the rpm's.
The IAC is about $300 but doesn't fail as often as the TPS. The IAC can get gummed up with junk and needs to be cleaned out.
 
TPS - Throttle Position Sensor
IAC - Idle Air Control
The TPS is about $95 from the dealer and can be adjusted. FSM says idle rpm should be 650. Connect Torque app and bluetooth OBD2 to read data. Physically turn the TPS while watching the rpm's.
The IAC is about $300 but doesn't fail as often as the TPS. The IAC can get gummed up with junk and needs to be cleaned out.
Both are BRAND NEW OEM parts. TPS is actually adjusted to OEM spec, not to "tune" idle which is technically incorrect.

Quoting FSM here: "Turn the TPS until deflection on an ohmmeter with vacuum applied to the TB"
 
Was it doing this before you changed the coil?

Why did you change the coil?

You do realize that the water temp sensor tells the ECU to be in open loop / closed loop and affects fuel pump pressure, right?
 
Was it doing this before you changed the coil?

Why did you change the coil?

You do realize that the water temp sensor tells the ECU to be in open loop / closed loop and affects fuel pump pressure, right?
I did not know this actually, so Ill change that out ASAP.

I changed the coil because the one that was in there tested out of spec. Problem started before the coil was changed
 
There are three coolant temp sensors.
 
Might as well replace them all. Do you have P/N off hand? if not I can look them up.
I’m not in a position to supply the requested information at the moment.
 
I’m not in a position to supply the requested information at the moment.
No worries. Looking through AllData and refrencing the FSM, it only shows one water temp sensor (W3) and one water temp switch (W4)
 
Water temp sensor for ecu. If my memory is correct it will be the third in line from rad towards driver.
89422-35010 hopefully this is the one.
There are two water temp sensors.
The one closet to rad is for the gauge.
 

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