1995 FZJ80 not running smooth / minor sputtering?

[MOcruisin]

The time has come to go from forum lurker, to a contributing member of the land cruiser society. (I know I'm here asking a question, but trust me, I have stuff to provide I haven't seen here yet!) Anyways, the rig in question is a 1995 FZJ80R, UK import and my ownership has just made 1 year last month. From as early as I can remember in my ownership it has not idled or run 100% smooth like a straight-6 should and I would like to try and get a collective input on this as I have already done lots of troubleshooting (detailed below). The best description I have for the problem is the engine is kinda puttering, most noticeably from the exhaust. It can just barely be felt with a hand on the valve cover. The only possible clue I have is a rare CEL for codes 24 and 31 IIRC. Those are IAT and VAF circuit codes, checked connector on airflow meter as it contains both sensors and found nothing wrong. It comes on from time to time but clears when the truck is shut off for a small length of time. Doesn't return for days or weeks, haven't identified any conditions causing CEL, and nor do the operating characteristics change when its illuminated either. The truck does this warm and cold, and throughout almost all of the RPM range from what I can tell. Probably is happening under-way at speed too, but its not noticeable when driving so I can't say.

Lastly, a quick piece on what the PO messed up before I bought it, just in case this carries any significance... PO said he tried to replace the plugs and wires but had problems with #5 and there's "something wrong with that plug." Turns out he just yanked the end of the plug wire off and it stayed on the #5 plug, but instead of going down to HF and getting long pliers to fix it, he just put it back together misfiring on #5. This persisted until I drove it home and figured out the problem in 10 minutes.

Troubleshooting I have tried:
-New Plugs & Wires
-All vacuum lines replaced
-Throttle Body cleaned (with new gasket)
-new Aisin coolant temp sensor
-IAC "reset" by cycling key from off to on 14x (noticeable effect, but not fixing my issue)
-EGR disabled (modulator was broken by PO, capped vac source lines to disable. UK ecu has no EGR check sensor anyway)
-Tried "unsticking" EGR by rapping on it with screwdriver handle while applying vacuum to the actuator, no change
-mechanics stethoscope on all injectors and nothing seemed to be suspect (4,5,6 are hard to get to, clicking was weaker but I was in quite a position and could be the reason)
-Checked engine wiring harness for common rub thru near supporting bracket, and heat damage from EGR (RHD wiring goes a different path away from EGR.)
I could have incorrectly checked this, or checked at a wrong location as it is mostly known on LHD models. A RHD weak point could still exist?

Other work done that's probably not related but could be:
-New Fusible Links
-CDL Switch
-New Intake Boot
-New Fuel filter on block (by PO, looks new)
-New Cap and Rotor (by PO, checked by me, seems fine)

I've done quite a bit of work to this rig in the year I've had it, but this non-smooth running issue and a weird squeak in the rear are going to drive me crazy, the squeak I can live with eventually but I do want to know what the engine problem is before I head out on a trip to MOAB later this summer. My dad recently picked up a LX450 and says it also exhibits this behavior, but I haven't seen it in person yet to truly confirm this. If anyone has any ideas at all I would love to hear them, please get some suggestions flowing and maybe we can figure this out and get my straight-6 running like one!

 

[Malleus]

First, what month was your truck made? It matters because the January '95 trucks have '94 parts in them, depending on when in the month they were assembled. The 2nd gen IACs are common failure points and are NLA. The 3rd gen IACs are direct replacements... and expensive.

Second, does this happen only when the engine is cold, only after it's warm, or all the time (when it happens)?

Lastly, where did you get the idea that "cycling" the IAC did anything? There are a pair of function checks, in the service manual, which have to be performed in order to validate the operation. I'd start there, if it was me.

 

[MOcruisin]

1. So, I'm not sure precisely how to determine this on my rig, there's no stickers in any of the door jambs and the only ID plate found is riveted to the firewall under the hood. I will insert a picture of it.

2. This DOES seem to happen both warm and cold. When I first start the truck it's noticeable when the idle begins to lower after a second or two, and If I take note of this RPM and use the hand throttle to set high idle to that RPM when warm, it does still do it. I got the idea to try and replace the ECT sensor from this thread, post #49.

3. I got this idea from this thread, post #5.

First, what month was your truck made? It matters because the January '95 trucks have '94 parts in them, depending on when in the month they were assembled. The 2nd gen IACs are common failure points and are NLA. The 3rd gen IACs are direct replacements... and expensive.

Second, does this happen only when the engine is cold, only after it's warm, or all the time (when it happens)?

Lastly, where did you get the idea that "cycling" the IAC did anything? There are a pair of function checks, in the service manual, which have to be performed in order to validate the operation. I'd start there, if it was me.

 

[Malleus]

 

[Malleus]

So this is a diesel? 1PZ engine?

 

[MOcruisin]

So this is a diesel? 1PZ engine?

1FZ gasser, yes.
February of 1995, noted. Wasn't sure it was as simple as trusting a vin lookup, been mislead on that in the past a time or two

 

[Malleus]

OK, I have no idea where you can snatch a service manual for that, unless someone in the UK has one under their mattress. Use the '95 service manual in the Resources forum, 80 section, and run through both operational checks, the mechanical and electrical. I would be surprised if the IAC doesn't fail one or both.

 

[Malleus]

1FZ gasser, yes.
February of 1995, noted. Wasn't sure it was as simple as trusting a vin lookup, been mislead on that in the past a time or two

You also appear to have an A442F transmission, unless someone's swapped that out. LMK if you have problems with that.

 

[MOcruisin]

OK, I have no idea where you can snatch a service manual for that, unless someone in the UK has one under their mattress. Use the '95 service manual in the Resources forum, 80 section, and run through both operational checks, the mechanical and electrical. I would be surprised if the IAC doesn't fail one or both.

I'm still looking for a service manual myself, but I will absolutely be following the specified tests after work this afternoon. One thing to note on my IAC though, when I get my stethoscope on it and mess with the engine rpm somehow, I can hear little ticks of what I assumed was the stepper motor stepping.

You also appear to have an A442F transmission, unless someone's swapped that out. LMK if you have problems with that.

AFAIK this isn't a bad thing, but I also do not believe it has been swapped at all. The only remark I have about my trans is the 2nd gear shift seems slow, I can hear the solenoid click 0.5-1.0 seconds before the shift occurs. With 230k miles I simply attributed it to age and wearing clutch packs.

 

[LongDuck]

How many miles was it driven with no spark on #5? Any idea?

 

[MOcruisin]

How many miles was it driven with no spark on #5? Any idea?

Considering I did the driving, roughly a 4 hour total trip to get it home. Also to clarify, it wasn't NO spark, but more unreliable/inconsistent spark. It ran mostly smooth and on all 6 cylinders for probably 70% of the total mileage. I can't say for certain how long it was operated in this condition before I bought it though. Guy never really used it much after he purchased it though, he was in the army and not frequently with the truck. I've always been slightly concerned about a mechanical issue with cylinder 5, but it runs so strong and smooth under load. No hot start issues either.

 

[Malleus]

I'm still looking for a service manual myself, but I will absolutely be following the specified tests after work this afternoon. One thing to note on my IAC though, when I get my stethoscope on it and mess with the engine rpm somehow, I can hear little ticks of what I assumed was the stepper motor stepping.


AFAIK this isn't a bad thing, but I also do not believe it has been swapped at all. The only remark I have about my trans is the 2nd gear shift seems slow, I can hear the solenoid click 0.5-1.0 seconds before the shift occurs. With 230k miles I simply attributed it to age and wearing clutch packs.

You'll hear the stepper, whether it moves the plunger or not. That's one of the checks: you have to physically observe the movement.

Nothing at all wrong with the A442F. Your slipping may be the cable; I'd check that first. FWIW, the first gear clutches wear first, if it's been used hard. If it's been driven by a grandmother, it's the third gear that goes first. Either way, 2nd gear usually lasts longest; least torque of the low gears and least use of the high gears.

 

[petegangies]

Have you tried resetting the ecu by pulling the efi fuse?
o2 sensor original?
smoke test and eyeballed all vacuum hoses in and around the intake manifold?
checked timing with a timing light?
does it look like the 2 screws on the VAF plug have ever had a screw driver on them?
injectors ever been cleaned? If a true miss, you can also disconnect one at a time to see if one of them makes no difference to the idle.
also might be worth popping off the vacuum hose on the fuel pressure regulator and checking if any petrol in it.

p.s my idle is not dead smooth.. and a few others have said the same. However, when I blip the throttle and when driving, the engine is smooth. At idle, it sounds like it has a very mild cam. I've never been able to sort that and the cars sensors and spec are all within all within range on the electrajet diagnosing software. There's not much I haven't done or replaced on my truck, so I eventually gave up and just accepted thats how it is. It's more of an OCD thing for me, then anything.

 

[MOcruisin]

Have you tried resetting the ecu by pulling the efi fuse?
o2 sensor original?
smoke test and eyeballed all vacuum hoses in and around the intake manifold?
checked timing with a timing light?
does it look like the 2 screws on the VAF plug have ever had a screw driver on them?
injectors ever been cleaned? If a true miss, you can also disconnect one at a time to see if one of them makes no difference to the idle.
also might be worth popping off the vacuum hose on the fuel pressure regulator and checking if any petrol in it.

p.s my idle is not dead smooth.. and a few others have said the same. However, when I blip the throttle and when driving, the engine is smooth. At idle, it sounds like it has a very mild cam. I've never been able to sort that and the cars sensors and spec are all within all within range on the electrajet diagnosing software. There's not much I haven't done or replaced on my truck, so I eventually gave up and just accepted thats how it is. It's more of an OCD thing for me, then anything.

Have you tried resetting the ecu by pulling the efi fuse?
Yes, no notable change. Also had battery disconnected a lot in my repairs.

o2 sensor original?
It has one single o2 sensor, before the cat. Seemingly quite old but probably not original. It does constantly flop between lean and rich on my toyobd1 reader I managed to pick up. It's one of the threaded styles into an adapter plate. AFAIK original sensors are not threaded and are one piece with just the 2-hole flange?

smoke test and eyeballed all vacuum hoses in and around the intake manifold?
Yes, have done. Poor man's test without a "real" smoke machine, but it yielded no observable leaks.

checked timing with a timing light?
Not yet, will do this afternoon as well.

does it look like the 2 screws on the VAF plug have ever had a screw driver on them?
I don't see two screws on mine. Are you referring to the flapper type VAF? I have the black cylindrical type.

injectors ever been cleaned? If a true miss, you can also disconnect one at a time to see if one of them makes no difference to the idle.
Not to my knowledge. I don't think it's a true miss and down a cylinder though.

also might be worth popping off the vacuum hose on the fuel pressure regulator and checking if any petrol in it.
Have checked this, no petrol inside vac line. No observable change with unplugged as well.

 

[petegangies]

Have you tried resetting the ecu by pulling the efi fuse?
Yes, no notable change. Also had battery disconnected a lot in my repairs.

o2 sensor original?
It has one single o2 sensor, before the cat. Seemingly quite old but probably not original. It does constantly flop between lean and rich on my toyobd1 reader I managed to pick up. It's one of the threaded styles into an adapter plate. AFAIK original sensors are not threaded and are one piece with just the 2-hole flange?

smoke test and eyeballed all vacuum hoses in and around the intake manifold?
Yes, have done. Poor man's test without a "real" smoke machine, but it yielded no observable leaks.

checked timing with a timing light?
Not yet, will do this afternoon as well.

does it look like the 2 screws on the VAF plug have ever had a screw driver on them?
I don't see two screws on mine. Are you referring to the flapper type VAF? I have the black cylindrical type.

injectors ever been cleaned? If a true miss, you can also disconnect one at a time to see if one of them makes no difference to the idle.
Not to my knowledge. I don't think it's a true miss and down a cylinder though.

also might be worth popping off the vacuum hose on the fuel pressure regulator and checking if any petrol in it.
Have checked this, no petrol inside vac line. No observable change with unplugged as well.

correct! mine also had this.. changed the exhaust pipe and installed one with the factory o2 mount and put a new OEM Denso o2 sensor in it. I'm in Australia, so have the same configuration as you. Changing the o2 sensor with a brand new genuine Denso one made a big difference. I also had issues with the plug on the loom side for the o2 which was causing intermittent connections. If I were you, this is where I would start. Btw, at no stage did I ever get a code or engine light for the oxygen sensor, but it was still an issue and not working correctly.

re the VAF, sounds like you have the MAF style, not the old flapper, so ignore my comments re: screw. Could still have issues with your MAF too, but I'd start at the o2 sensor first. They don't tend to love aftermarket sensors and they are an item that need replacing periodically, not often, but don't last forever before they start to transmit unreliable data to the ecu.

 

[MOcruisin]

OK, I have no idea where you can snatch a service manual for that, unless someone in the UK has one under their mattress. Use the '95 service manual in the Resources forum, 80 section, and run through both operational checks, the mechanical and electrical. I would be surprised if the IAC doesn't fail one or both.

Alright, got some results here. First test, the clicking noise when the engine is shut off. This noise is present. Electrical test, 22 ohms each pair, all ok within spec. Mechanical test removed from vehicle, also tests okay. Moves in and out slowly following FSM procedure, no one coil pulls any more current than another. So, IAC all within spec as far as I can tell?

correct! mine also had this.. changed the exhaust pipe and installed one with the factory o2 mount and put a new OEM Denso o2 sensor in it. I'm in Australia, so have the same configuration as you. Changing the o2 sensor with a brand new genuine Denso one made a big difference. I also had issues with the plug on the loom side for the o2 which was causing intermittent connections. If I were you, this is where I would start. Btw, at no stage did I ever get a code or engine light for the oxygen sensor, but it was still an issue and not working correctly.

View attachment 4113345

re the VAF, sounds like you have the MAF style, not the old flapper, so ignore my comments re: screw. Could still have issues with your MAF too, but I'd start at the o2 sensor first. They don't tend to love aftermarket sensors and they are an item that need replacing periodically, not often, but don't last forever before they start to transmit unreliable data to the ecu.

This route sounds likely. The O2 sensor installed when I bought the vehicle had powder metallurgy adapter flange plate thing and it was cracked in two. My new exhaust system has a proper Toyota flange, and I bummed an adaptor flange from a friend made of actual homogenous steel and have been running it ever since. I imagine the sensor can't be of fantastic quality if it came with a super cheapo adapter flange. Where did you pick up your real Denso O2 sensor at?

Also checked the timing. It was a half a timing mark off of the 3° specified in the FSM, adjusted slightly to be perfect and no change.

 

[petegangies]

Alright, got some results here. First test, the clicking noise when the engine is shut off. This noise is present. Electrical test, 22 ohms each pair, all ok within spec. Mechanical test removed from vehicle, also tests okay. Moves in and out slowly following FSM procedure, no one coil pulls any more current than another. So, IAC all within spec as far as I can tell?



This route sounds likely. The O2 sensor installed when I bought the vehicle had powder metallurgy adapter flange plate thing and it was cracked in two. My new exhaust system has a proper Toyota flange, and I bummed an adaptor flange from a friend made of actual homogenous steel and have been running it ever since. I imagine the sensor can't be of fantastic quality if it came with a super cheapo adapter flange. Where did you pick up your real Denso O2 sensor at?

Also checked the timing. It was a half a timing mark off of the 3° specified in the FSM, adjusted slightly to be perfect and no change.

I actually sourced a genuine Toyota Denso one off Amazon, I think it was shipped from Amazon Japan though. You can also purchase them off amayama.com, partsouq.com and megazip.net (my local toyota parts dealership had them but double the price). I'm not 100% sure if yours has the same part number as mine, but you can check for your specific part number on any of those 3 sites I shared. The new sensor will come with a new gasket. If your 2 nuts are overly rusted or rounded and need replacing, I suggest doing them at the same time.

 

[Malleus]

Your IAC sounds good; lucky you!

Pete's recommendations are all good, but Dave Stedman has the best prices, Toyota's recent price increase (today) notwithstanding.

 

[MOcruisin]

I've sent Dave an email and got that ball rolling, otherwise they seem available from a Denso distributor for ~$75, and from Toyota for ~$115, so it's not a huge price to pay even if it doesn't end up fixing the problem. However, I feel we are now going down a likely path now and a wonky O2 sensor reading sounds highly likely to make the engine run poorly without actually throwing a code. Who knows when my suspicious O2 sensor was installed, most likely in the UK long before import as it looks quite weathered.

Another thing to note, my tailpipe has a light soot buildup on the inner surface as if running rich? I replaced the exhaust system with an off the shelf y-pipe/cat thing and then fabricated all the rest myself from 2.5" stainless about a year ago. So, I know the tailpipe is clean metal underneath and not old and crummy.

 

[petegangies]

I've sent Dave an email and got that ball rolling, otherwise they seem available from a Denso distributor for ~$75, and from Toyota for ~$115, so it's not a huge price to pay even if it doesn't end up fixing the problem. However, I feel we are now going down a likely path now and a wonky O2 sensor reading sounds highly likely to make the engine run poorly without actually throwing a code. Who knows when my suspicious O2 sensor was installed, most likely in the UK long before import as it looks quite weathered.

Another thing to note, my tailpipe has a light soot buildup on the inner surface as if running rich? I replaced the exhaust system with an off the shelf y-pipe/cat thing and then fabricated all the rest myself from 2.5" stainless about a year ago. So, I know the tailpipe is clean metal underneath and not old and crummy.

That's cheap! Here from a dealer they're about $380 AUD, I ended up getting mine off Amazon for about $156 AUD. Given how often Toyota loves discontinuing parts, I bought 2 to have a spare!