1994 1FZFE Bouncing/Surging Idle (2 Viewers)

[YotaVincent]

Recent head gasket replacement on 1994 OBD1 1FZFE land cruiser. When up to operating temperature, trucks idle will bounce at a stop. Doesnt matter if its in park, drive, etc, it will surge in RPM about 50-150. During the head gasket replacement, I deleted the pair system and placed new Denso 234-4153(late model downstream) o2s in the manifolds and switched the white and blue pins. Owner states this problem was not present before HG replacement. I am stumped at where to proceed with this rig. So far I have checked for vacuum leaks, swapped IAC, TPS(both from a late model truck), rotor, cap, large intake hose between AFM/TB, disconnected fuel pressure regulator vacuum line, with no change. This truck has the blue colored ECU.


Any guidance would be greatly appreciated at solving this Idle surging. Another note, when truck is warming up, acceleration is hesitant during a slight period in the warm up process. Cold is completely OK, 25%-40% warm slight hesitation, completely gone above 40%. 3k RPM and above truck comes alive and feels like VTEC engages.

 

[Fj80oregon]

Have you checked your injectors and associated clips? You can listen to each injector with a stethoscope or any long metal object.

 

[YotaVincent]

Have you checked your injectors and associated clips? You can listen to each injector with a stethoscope or any long metal object.

I have not, but will in the morning. All clips were ok, I replaced two of them with new harness side connectors.

 

[YotaVincent]

During HG replacement, fuel filter, spark plugs and wires replaced. I have also bypassed the EGR with a paperclip and looping vacuum lines. When resetting ECU via EFI 15A fuse, truck runs great for first 5 minutes until "learning" and hunting returns.

 

[Fj80oregon]

Coolant temp sensor maybe, test per FSM or replace they are cheep and can cause weird issues.

 

[YotaVincent]

Coolant temp sensor maybe, test per FSM or replace they are cheep and can cause weird issues.

I replaced the ECT when I did the HG, cheap amazon one. I suspected it might have been too cheap. I went ahead and replaced it today with a Toyota one. No change.
All injectors are firing and sound uniform via a long screw driver. I did notice today unplugging vacuum to the FPR did help my cause. The motor is still surging but very minimally. I'm not sure if that's because of the higher idle from unplugging the vacuum source. Giving vacuum did cause the surging to come back and produce a lower normal idle.

 

[YotaVincent]

Update, was able to source a known good condition AFM to test with, problem appears to be resolved. Now onto sourcing one I can keep!

 

[Fj80oregon]

@cruiserland has one I believe.

 

[CrabCake]

I've heard that these guys do a good job on servicing them...

Air Flow Meter Service

Bavarian Restoration refurbishes all Bosch Air Flow Meters to meet factory specifications. Let me tell you that this is one of the most important sensors for your engine. After 10 or so years, these...

www.bavrest.com

 

[YotaVincent]

I've heard that these guys do a good job on servicing them...

Air Flow Meter Service

Bavarian Restoration refurbishes all Bosch Air Flow Meters to meet factory specifications. Let me tell you that this is one of the most important sensors for your engine. After 10 or so years, these...

www.bavrest.com

I sent them an email earlier, also found the guy from eBay that rebuilds them. Repair is 3x more with BAV, with this item knowing to fail and NLA, get what you pay for rebuild wise?

I also want to add, when this truck came in, codes 21 and 28 were present. Perhaps the ECU running in fail safe mode masked the AFM problem to begin with hence making itself known now with good working O2s.

 

[CrabCake]

Interesting, thought that it was actually the same group. Heard good things about the eBay guy, or maybe there’s more than 1 on there?

 

[MileHigh80Guy]

I sent them an email earlier, also found the guy from eBay that rebuilds them. Repair is 3x more with BAV, with this item knowing to fail and NLA, get what you pay for rebuild wise?

I also want to add, when this truck came in, codes 21 and 28 were present. Perhaps the ECU running in fail safe mode masked the AFM problem to begin with hence making itself known now with good working O2s.

I went down (and still am) the 21/28 rabbit hole. Still digging in, but current inspections lead me to tear apart the upper intake manifold, replace the lines and check the wiring harness by the EGR, as the EGR wiring is already crispy and broken.

Maybe dive in there?

 

[YotaVincent]

Interesting, thought that it was actually the same group. Heard good things about the eBay guy, or maybe there’s more than 1 on there?

The eBay guy(South Carolina) appears to be a solo dude, whereas BAV(California) is an actual shop. We are going with BAV just based on the location and reviews.

I went down (and still am) the 21/28 rabbit hole. Still digging in, but current inspections lead me to tear apart the upper intake manifold, replace the lines and check the wiring harness by the EGR, as the EGR wiring is already crispy and broken.

Maybe dive in there?

I no longer have the 21/28 codes after replacing the O2s during the HG service. There are no codes present after 100 miles of road testing, 10x drive cycles. The harness wrap around the EGR was removed and thoroughly inspected while I had the harness removed. I replaced two injector clips and one knock sensor pigtail.
Before tearing into yours, I would check the pins for corrosion on the harness side O2s. One connector is down the passenger side inner apron fender, and the other crosses over the bellhousing. You can also check for continuity from all four pins to the ECU harness pins/grounds.

 

[Old Nick]

Recent head gasket replacement on 1994 OBD1 1FZFE land cruiser. When up to operating temperature, trucks idle will bounce at a stop. Doesnt matter if its in park, drive, etc, it will surge in RPM about 50-150. During the head gasket replacement, I deleted the pair system and placed new Denso 234-4153(late model downstream) o2s in the manifolds and switched the white and blue pins. Owner states this problem was not present before HG replacement. I am stumped at where to proceed with this rig. So far I have checked for vacuum leaks, swapped IAC, TPS(both from a late model truck), rotor, cap, large intake hose between AFM/TB, disconnected fuel pressure regulator vacuum line, with no change. This truck has the blue colored ECU.


Any guidance would be greatly appreciated at solving this Idle surging. Another note, when truck is warming up, acceleration is hesitant during a slight period in the warm up process. Cold is completely OK, 25%-40% warm slight hesitation, completely gone above 40%. 3k RPM and above truck comes alive and feels like VTEC engages.

My wife's rig (also a '94 FZJ80) was idling terribly. No codes. Cold starts: idle was dipping down to 250rpms and then bumping up to 650 and higher... all over the place. I didn't take it down to the head, but resealed the rest of the engine (new injectors, new spark plug wires, new hoses - phh, water and vacuum.

Went back through the FSM, which led me back to the throttle body. Pulled it... again. Tested the TPS and AIC valve... both were way out of spec. Just replaced them (the AIC valve for our '94s is NLA from Toyota... so I put a new one for the '95-'97 models on it... seems to be working fine ). Installed new gaskets too.

Started it up today... and it started and idled smoothly and consistently... initial idle 1200 rpms; dropped to 800 (still a little high... need a tweak to either the TPS or the throttle cable).

I don't mean to muddy the waters. Just sharing a recent experience getting rid of a crappy idling situation.

 

[ZackR]

My wife's rig (also a '94 FZJ80) was idling terribly. No codes. Cold starts: idle was dipping down to 250rpms and then bumping up to 650 and higher... all over the place. I didn't take it down to the head, but resealed the rest of the engine (new injectors, new spark plug wires, new hoses - phh, water and vacuum.

Went back through the FSM, which led me back to the throttle body. Pulled it... again. Tested the TPS and AIC valve... both were way out of spec. Just replaced them (the AIC valve for our '94s is NLA from Toyota... so I put a new one for the '95-'97 models on it... seems to be working fine ). Installed new gaskets too.

Started it up today... and it started and idled smoothly and consistently... initial idle 1200 rpms; dropped to 800 (still a little high... need a tweak to either the TPS or the throttle cable).

I don't mean to muddy the waters. Just sharing a recent experience getting rid of a crappy idling situation.

The throttle cable shouldn't have any tension at idle so it won't be part of the idle adjustment unless its currently pulling the throttle open.

Have you had a few stop start cycles since the ECU was reset? Also be sure to unplug the battery and reset the ECU if you haven't already.

I also have a 94' and went through all of the same issues you are describing, once it's dialed in the idle will be right at 650 per spec.

 

[Old Nick]

The throttle cable shouldn't have any tension at idle so it won't be part of the idle adjustment unless its currently pulling the throttle open.

Have you had a few stop start cycles since the ECU was reset? Also be sure to unplug the battery and reset the ECU if you haven't already.

I also have a 94' and went through all of the same issues you are describing, once it's dialed in the idle will be right at 650 per spec.

I need to double check the throttle cable, just to be sure.

Only 2-3 stop start cycles.

And, I'll be darned if I didn't unplug the positive side of the battery for a full reset. Thank you for reminder. I appreciate it!

 

[MileHigh80Guy]

The eBay guy(South Carolina) appears to be a solo dude, whereas BAV(California) is an actual shop. We are going with BAV just based on the location and reviews.

I no longer have the 21/28 codes after replacing the O2s during the HG service. There are no codes present after 100 miles of road testing, 10x drive cycles. The harness wrap around the EGR was removed and thoroughly inspected while I had the harness removed. I replaced two injector clips and one knock sensor pigtail.
Before tearing into yours, I would check the pins for corrosion on the harness side O2s. One connector is down the passenger side inner apron fender, and the other crosses over the bellhousing. You can also check for continuity from all four pins to the ECU harness pins/grounds.

Thanks, yea, they were were both crusty and corroded through. Reran the wires from the drivers side/bellhousing cat directly to the O2 sensors, got rid of 28, but still hanging on to 21 and all the connectors have continuity. EGR Temp harness is cut, the crusty O2 sensor wire were spliced in poorly ( I repinned them properly) so I suspect further ****ery in my future. Little bread crumbs of past repairs I keep finding from the PO.

Good luck!!`

 

[petegangies]

do you have the part number for the 95-97 model IACV?

Thanks,
Pete

My wife's rig (also a '94 FZJ80) was idling terribly. No codes. Cold starts: idle was dipping down to 250rpms and then bumping up to 650 and higher... all over the place. I didn't take it down to the head, but resealed the rest of the engine (new injectors, new spark plug wires, new hoses - phh, water and vacuum.

Went back through the FSM, which led me back to the throttle body. Pulled it... again. Tested the TPS and AIC valve... both were way out of spec. Just replaced them (the AIC valve for our '94s is NLA from Toyota... so I put a new one for the '95-'97 models on it... seems to be working fine ). Installed new gaskets too.

Started it up today... and it started and idled smoothly and consistently... initial idle 1200 rpms; dropped to 800 (still a little high... need a tweak to either the TPS or the throttle cable).

I don't mean to muddy the waters. Just sharing a recent experience getting rid of a crappy idling situation.

 

[Old Nick]

The throttle cable shouldn't have any tension at idle so it won't be part of the idle adjustment unless its currently pulling the throttle open.

Have you had a few stop start cycles since the ECU was reset? Also be sure to unplug the battery and reset the ECU if you haven't already.

I also have a 94' and went through all of the same issues you are describing, once it's dialed in the idle will be right at 650 per spec.

Worked like a charm. Unplugged the battery. Killed a little time. Did a few other things. Then, Hooked the battery back up. Idled at 1250rpms… then, slowly but surely the rpm’s dropped to 650. Took it out to run some errands. Several on/off cycles. Settled to 650 every time. Fixed! Thank you for the reminder.

 

[Old Nick]

do you have the part number for the 95-97 model IACV?

Thanks,
Pete

22270-66011

Can confirm that it’s plug and play on a ‘94.

Don’t forget to buy a new o-ring too