1fz-fe rough idle/misfire no CEL - Solved - non OEM temp sensor cause (1 Viewer)

[The Moose Trophy]

My fzj80 isn't running smoothly, slight misfire, ticking from the front/top of the engine. No CEL (sadly) and it runs okay. When the engine is cold, and I first start it up it runs absolutely amazing, no ticking, not misfire, no shaking. Once it warms up and starts reading the sensors it runs rough. Idle settles around 650 + or - 50. Idles around 1000 rpm in Drive.

First off what has been done to the vehicle (348k miles): ALL parts OEM unless Stated:

- Engine rebuild (top and bottom full refresh) 15k ago
- new fuel injectors
-new engine wiring loom
- new cooling system hoses, radiator, thermostat, water pump
- new TPS
- new O2 sensors (denso)
- new Mangaflow y-pipe and second cat (my old ones were shot)
- new distributor (cardone)
-new sparkplugs (less than 1k ago iridium)
- new spark plug wires
-new air filter
- new fuel filter
- new fuel pump and sending unit
- EGR delete
- new ignition coil
- new fuel regulator
- newish belts (20k)
- swapped main pulley
- new fan clutch and blade
- new charcoal canister
- new fuel filter cap
- new knock sensors (2x)
- temp sensor (aftermarket unknown brand)

Now you can see my frustration why this thing isn't running like a top... Everything I can think of has been checked against the FSM. Because it runs good when it's cold I assume it's a sensor... But no CEL so I'm running in circles.

Known issues:
- front exhaust manifold middle bolts are slightly stripped and aren't as tight as the rest
- possible issue with the VSV (THIS WAS THE ISSUE)

Issues listed in the comments (condensed for viewers ease)

- Vacuum leak, cracked tube, wrong size (THIS WAS THE ISSUE - replaced entire vac system)
-Oil filler cap o-ring rock hard (replaced due to age, wasn't an issue)
- PCV valve grommet brittle (was replaced not an issue)
- Dipstick o-ring (didn't have time to check before issue was resolved, will be switching it out)
- Intake air tube not cracked (mine was in good condition)
- Timing off a gear (checked and moved, but wasn't the issue)
- IAC (idle air control valve) - ( checked against FSM was bad, but didn't solve my issue)
- Fuel Octane rating too low (didn't check due to gas prices)


Fixing the Issue: $320.53 (from Partsouq and Toyota parts deal not including IAC approx $400)

I replaced all the Vac lines, switches, couplers, everything that was still on the market in one go. Solved the issue and now runs extremely smoothly.

Parts replaced: FOR 1995 1FZ-FE
9099992002 - Vac line (you'll need about 4 of these)
2582013020 - valve bi-metal
9091710049 - gas filter #1
9091005212 - Large vac hose
9613251100 - larger vac clamps
9092503192 - Valve vac control (the thing with the blue cap)
9533306010 - Evap hose
9091012079 - VSV #1
9091012079 - VSV #2
9033903002 - plug

List does not include:
- intake manifold "gas" valve
- any egr components
-intake manifold gaskets (THESE ARE NEEDED)

 

[The Moose Trophy]

New year new update:

Swapped in some new spark plug leads (OEM) and it seems to have less of a consistent miss. Cleaned the distributor with electronic cleaner just to ensure no gunk was in there. I've also noticed the car runs significantly better if I warm it up to operating temp and then drive vs letting it warm up to 100°.
Miss is really noticable at ~800 rpm. Runs smooth at high rpm and ok at idle, but in that area it's pretty rough.
Let me know if a video would help with diagnosis.

 

[powderpig]

I once had a vehicle that was rebuilt (not by me) and the shop tried shave the Valve shims. Needless to say, they were not truly flat. what would
happen is the thick side of the shim would keep the valve open, and the thin side would allow the valve to stay closed. Now this was not on one Valve, but on many, the valves would sometimes sound like a heavy clicking(like a diesel). And sometimes sound and run smooth as silk. Drove me nuts for a few days. I found this out by doing a compression test on the cylinders, and finding odd reading showing up. Some strokes would build compression, other would not. Pulled the valve cover and check out the shims by pulling a couple and found the course grind marks and measured them to be not
flat. Crasy stuff. Replaced the shims with new, proper sizes, and all was good.
So, are you using good shims, or something you tried to flatten?
Have you tried swapping in a different distributor?
The negative 54.X degress of ignition advance is interesting, I would think the only way one would see that, is with a problem in the distributor, or computer.

 

[The Moose Trophy]

I once had a vehicle that was rebuilt (not by me) and the shop tried shave the Valve shims. Needless to say, they were not truly flat. what would
happen is the thick side of the shim would keep the valve open, and the thin side would allow the valve to stay closed. Now this was not on one Valve, but on many, the valves would sometimes sound like a heavy clicking(like a diesel). And sometimes sound and run smooth as silk. Drove me nuts for a few days. I found this out by doing a compression test on the cylinders, and finding odd reading showing up. Some strokes would build compression, other would not. Pulled the valve cover and check out the shims by pulling a couple and found the course grind marks and measured them to be not
flat. Crasy stuff. Replaced the shims with new, proper sizes, and all was good.
So, are you using good shims, or something you tried to flatten?
Have you tried swapping in a different distributor?
The negative 54.X degress of ignition advance is interesting, I would think the only way one would see that, is with a problem in the distributor, or computer.

I don't believe the shop ground down any shims, because I know the had to order some. Definitely sounds like what I have going on, I may go ahead and re-check the valves.

I had an aftermarket cardone distributor in for 15k miles or so and swapped it with a used OEM one think this was the issue. I may swap it back just to test what's going on. ECM was also swapped and have a new wiring harness, so I doubt it's anything within those electrics.

 

[Malleus]

 

[The Moose Trophy]

Alright swapped in the a cardone distributor, it was my spare. And no real change, seems to have less misfires at idle, and none noticed at higher rpm. However at ~850 rpm I can get a consistent miss, held if there for a few seconds to see if I could pop a code, nothing. Plugs and wires are new OEM and cap/rotor are less than 15k and don't show any cracks/issues. Checked the coil a few months ago against the FSM and that was fine.

Note: before I swapped the old distributor I noticed that a couple times the car had no power, I would hold my foot the the floor and only after a few seconds would it either change down or increase in power. The timing also would only go to 14 degrees at that point. Usually at 60mph and 2000 rpm I'll see 20-30 degrees and it'll have a lot of pep. I've had this happen before but usually it just goes away, no idea what's causing/caused it.

 

[The Moose Trophy]

See video for sound reference, can't tell a misfire by sound, just engine feel/diagnostic tool.

 

[The Moose Trophy]

Checked my valve clearances this past weekend, all within spec, some high and low on the range but nothing out.
Still a slight misfire at idle but after slapping everything together and taking it on an 8 hour road trip it is running a lot quieter. I'm going to retorque everything to make sure the heat cycles didn't loosen anything up.

 

[Malleus]

 

[The Moose Trophy]

After checking valve clearances I was pretty stumped. I didn't feel the need to check any deeper since the engine was rebuilt and this wasn't the shops first 1fz. Also the conditions of the idle and just general feeling of the engine weren't very consistent.
Being a little stumped I decided to leave it alone while I focused on other things, rebuild the front axle, rebuilding the AC, etc.
Long and short I ordered a new temp sensor since I was going to swap the other temp sensors. Car running improved a lot, misfire is all but gone, if not completely, the engine power is way more consistent and just feels way more smooth and happy.
When I had the engine redone I didn't replace the temp sensors, and the one in question was a random aftermarket that I had swapped in when I got the car. Tested out ok and the digital temp reading was the same as the OEM so not exactly sure why it would be part of or the whole issue.

If the misfire and rough idle issue comes back I'll make another post.

 

[jkeithw]

After checking valve clearances I was pretty stumped. I didn't feel the need to check any deeper since the engine was rebuilt and this wasn't the shops first 1fz. Also the conditions of the idle and just general feeling of the engine weren't very consistent.
Being a little stumped I decided to leave it alone while I focused on other things, rebuild the front axle, rebuilding the AC, etc.
Long and short I ordered a new temp sensor since I was going to swap the other temp sensors. Car running improved a lot, misfire is all but gone, if not completely, the engine power is way more consistent and just feels way more smooth and happy.
When I had the engine redone I didn't replace the temp sensors, and the one in question was a random aftermarket that I had swapped in when I got the car. Tested out ok and the digital temp reading was the same as the OEM so not exactly sure why it would be part of or the whole issue.

If the misfire and rough idle issue comes back I'll make another post.

what's the part number on that? I'm chasing a similar issue.

 

[jkeithw]

what's the part number on that? I'm chasing a similar issue.

also, I went to Brad Penn 20w50 in ours a few years ago - now the pressure gauge reads normally, and the engine is MUCH quieter. I like BP for the zinc for my air-cooled stuff; now I run it in all my 2000 and earlier Toyotas.

 

[The Moose Trophy]

what's the part number on that? I'm chasing a similar issue.

See below part number:
89422-35010

Also an honor to help out an awesome vendor.

 

[The Moose Trophy]

also, I went to Brad Penn 20w50 in ours a few years ago - now the pressure gauge reads normally, and the engine is MUCH quieter. I like BP for the zinc for my air-cooled stuff; now I run it in all my 2000 and earlier Toyotas.

Good to know, i definitely noticed it's quieter on 10w30, but Alaska gets too cold for it during the winter so I switch to 5w30. Noise level much reduced with the new temp sensor though, not whisper quiet but I shouldn't get people walking up and asking if it's a diesel anymore.

 

[The Moose Trophy]

Final update (unless things change)
- OEM temp sensor fixed the random misfire, loud idle, and general hesitation. The previous temp sensor checked out ohm wise, but must've been out of spec in a different way.
- it was single digits this week and I covered the grill to keep some heat in the engine. After driving around fkf a few days it produced the same symptoms as before, removed and now idles fine and is quite.
Engine is way smoother and finally enjoyable to drive, my notoriously smooth in line 6 wasn't for a long time and now is. I hate idling it before and now I have no concerns.

Thanks all for the comments and help along the way. Definitely an odd one.

 

[Jaketh3snake]

Final update (unless things change)
- OEM temp sensor fixed the random misfire, loud idle, and general hesitation. The previous temp sensor checked out ohm wise, but must've been out of spec in a different way.
- it was single digits this week and I covered the grill to keep some heat in the engine. After driving around fkf a few days it produced the same symptoms as before, removed and now idles fine and is quite.
Engine is way smoother and finally enjoyable to drive, my notoriously smooth in line 6 wasn't for a long time and now is. I hate idling it before and now I have no concerns.

Thanks all for the comments and help along the way. Definitely an odd one.

Has the coolant temperature sensor fix held up? I have been chasing something similar in my new to me 1995 FZJ80 (1FZFE). Identical clicking noise as your video, and more importantly inconsistent firing upon startup.

I went and inspected the sensor on my truck and noticed that the connector clip was cracked. Barely applied pressure with fingers and the connector came off and retaining clip portion disintegrated.

I reconnected it (pushed it back on, knowing it is now not properly attached) and for giggles turned the key to ACC and plugged in my scan gauge. The coolant temperature on the scan gauge was showing over 90 F, even tho the truck had not been driven today and last started about 8 hrs ago just to move in the driveway. Ambient is about 70 F today.

Obviously I need a new connector, but curious if this fix for you has held up with the sensor replacement. After reading some more in the FSM, and seeing the false high coolant temperature reading on the scan gauge leads me to believe this sensor is telling the ECU the engine is hot (or hotter than it truly is), and the VSV is working as it should to send exhaust/ more fuel to avoid vapor locking, resulting in my stumbling initial firing. Sounds a lot like it is being flooded on its first fire which would explain this.

Appreciate your post, and hopeful this is the trick for me too. This intermittent stumbling/ rough idle has been giving me fits for months.

 

[The Moose Trophy]

Sadly I can't comment on this as much as I wish because my car got totaled. From what I remember it definitely smoothed things out and didn't have the inconstant power feeling with the aftermarket sensor.

 

[Jaketh3snake]

Sadly I can't comment on this as much as I wish because my car got totaled. From what I remember it definitely smoothed things out and didn't have the inconstant power feeling with the aftermarket sensor.

I appreciate the reply. Sorry to hear about your truck. Hope everyone involved was ok.