Help: 3FE Terrible Idle and Misfires after dead battery (1 Viewer)

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Mar 11, 2021
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big island, hawaii
I have a 92 FJ80 that I picked up a couple months ago. It has 314k on the chassis, and was told engine was replaced at 150k. PO was... I think a worst-case scenario PO. Missing, capped, and jerryrigged hoses under the hood. One jerryrigged fix was an EFI bypass with a pull switch inside the cab. Switch needs to be pulled to start the truck; I was told it could kill the battery if I left it open too long.

Well, I didn't drive the truck for a few days and left it open. The battery was completely dead when I next had to use it. I used a battery charger to charge the battery, and since then the truck has had the following problems:

*SUPER rough idle, steadies at ~500 and shakes the whole truck and makes a bunch of noise
*Major hesitation at a standstill--like need to floor the pedal to get it moving and it's a 3 second delay
*Truck is cold until it really has to work. Temp is bottomed out until it's been driven for a while on the highway. Seems to drive okay once it's going. But when idling, almost no pressure in main radiator hose to engine--you can squeeze it.
*When driving slowly or moving from standstill, the engine seems to pop and misfire
*Gas smell

When I first got the truck, it didn't run great but ran okay. I got a fresh oil change (oil was sooty and black), and replaced the leaking/shot 02 Sensor and then it ran great until the EFI bypass-dead battery.

I'm waiting on a tune-up kit to arrive from the mainland still with OEM plugs, wireset, air filter, fuel filter etc. Been waiting a month because it got mailed on the slow boat. (I'm in Hawaii).
I just replaced all the small vacuum lines today, but to no noticeable effect. I tightened the clamps on the jerryrigged air intake hose and it idled better at the next start up, then bottomed out again after a minute. I've put in a couple cans of seafoam. Should I put in Cataclear on the next tank?

If I had another vehicle, I would just let it sit until I get the tune-up kit. But it's my DD and I need it to get around the Big Island--I live in a remote area at the top of a 3 mile 4WD road.

Questions:
1. How would the dead battery have caused this? What could have gone wrong? What should I specifically try to do to remedy it to decent working order with what I may have on hand?
2. Is it safe to drive? Will I harm the engine?
3. Besides a full tune-up, and an EGR delete I just ordered, and new fusible link and belts (to replace stretched out, likely incorrect belts currently running slack), what else should I do to get this truck purring? Do I need to delete or replace the cats? I'm going to order a new set of OEM 02 sensors (the one I replaced was a Delphi from RockAuto...before I really had any understanding how important it is to go OEM with these trucks).

I've read as much as I can here... and can't seem to get a clear idea what the hell is up with my rig.
 
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A few thoughts.
A dead flooded cell battery should be replaced with a new battery.
Once it is fully discharged it will never come back 100%. Your 29 year old alternator is doing its best to try to keep up, but if the battery is compromised your system voltage will be low. Especially if your 29 year old alternator is not running 100%.

By itself, a battery failure/replacement will not cause any of the issues you are describing.

The fact that the engine temperature stays cold tells me that the thermostat is stuck open. In any case, since you are replacing hoses the thermostat AND GASKET should be replaced. Be certain to use OEM parts.
However, if all the gauges in the cluster are reading low, this could also be a low voltage issue.

Thermostat 90916-03052
Thermostat gasket 90430-43002
Thermostat housing gasket 16341-61030
 
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Joined
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Canyon Lake, TX
You have a long road ahead of you in getting the truck to run well. The best thing you can do is make sure you KNOW that parts are working correctly before moving on to other problems. I would get the battery load tested at your local parts store to make sure it is in spec. Then move on.

You really need to think this one through. You are describing a car that has been neglected for a long time. It maybe better in the long run to wash your hands with this one and move on. The repairs may cost so much money that you are better off with a different car. Black sooty oil means it either wasn't changed for a very long time, or that the rings and cylinder bore is so worn out you have a huge amount of blow-by in the engine. That messed up intake hose could have been sucking in dirt/dust for a long time. Meaning the engine is worn out. Get a compression test to see where you are at. You really need good solid information of the current condition of the engine to make the next decision. Sorry , Amigo. Not great words to read. I hope the best outcome for you.

While you're waiting for parts, and you feel like you want to do something, pull the spark plugs and post a picture of each one for people to give you some insight on how well the engine is running. Pay attention to what cylinder each one came from so you can put them back in the same place.
 
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Mar 14, 2008
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1,171
Check your battery voltage engine off and engine on. Minimum of 13 volts running, 12.2 engine off. If that switch powered the ignition then it might have cooked your ignitor box, distributor pickup or the coil being powered on with no airflow. If your voltage while running at fast idle isn't at least 13 volts, your systems won't be doing their proper job. Fuel pump could also have suffered damage if it ran till the voltage died.

Simple checks. Look at your plug wires, coil, ignitor and distributor pickup under the cap. If you see anything melted or obviously cracked / broken, start there. Once that passes inspection, pull the plugs and make sure none are fouled out. Clean or replace any that are bad, check resistance of plug wires that are on any fouled plugs. If that checks out, you can check the quality of the spark by using a tester or pulling a plug wire off and watching the spark quality. Don't shock yourself or do it in the presence of flammable fluids. Good sparks are blue and steady rythym.

If you can check fuel pressure, I'd do that as well.

You may not even have a thermostat, lots get thrown out to address overheating but fuel injected motors need proper temp or they stay in fail-safe or open loop operation which causes problems.
 
Joined
Mar 11, 2021
Messages
40
Location
big island, hawaii
A few thoughts.
A dead flooded cell battery should be replaced with a new battery.
Once it is fully discharged it will never come back 100%. Your 29 year old alternator is doing its best to try to keep up, but if the battery is compromised your system voltage will be low. Especially if your 29 year old alternator is not running 100%.

By itself, a battery failure/replacement will not cause any of the issues you are describing.

The fact that the engine temperature stays cold tells me that the thermostat is stuck open. In any case, since you are replacing hoses the thermostat AND GASKET should be replaced. Be certain to use OEM parts.
However, if all the gauges in the cluster are reading low, this could also be a low voltage issue.

Thermostat 90916-03052
Thermostat gasket 90430-43002
Thermostat housing gasket 16341-61030
Hi Jon, I was hoping to get your input on this.

I think you're right. I ordered all parts you listed after reading your message.

There is no pressure in the hose, and the engine is cold until I really make it work. And that the truck suddenly runs terrible after purring just before. There may be other issues (which I will also address ASAP) but the thermostat must be stuck open. All gauges work--battery shows always above half charge, temp gauge is floored cold until I've driven highway speed up a hill, etc.

One more specific question:
Would a bypass switch on the relay being pulled be running the fuel injection until the battery died or just sending power to the circuit? Would that have reasonably caused any damage?

Thank you! Very grateful to have an expert so generous with his time on this.
 
Joined
Mar 11, 2021
Messages
40
Location
big island, hawaii
You have a long road ahead of you in getting the truck to run well. The best thing you can do is make sure you KNOW that parts are working correctly before moving on to other problems. I would get the battery load tested at your local parts store to make sure it is in spec. Then move on.

You really need to think this one through. You are describing a car that has been neglected for a long time. It maybe better in the long run to wash your hands with this one and move on. The repairs may cost so much money that you are better off with a different car. Black sooty oil means it either wasn't changed for a very long time, or that the rings and cylinder bore is so worn out you have a huge amount of blow-by in the engine. That messed up intake hose could have been sucking in dirt/dust for a long time. Meaning the engine is worn out. Get a compression test to see where you are at. You really need good solid information of the current condition of the engine to make the next decision. Sorry , Amigo. Not great words to read. I hope the best outcome for you.

While you're waiting for parts, and you feel like you want to do something, pull the spark plugs and post a picture of each one for people to give you some insight on how well the engine is running. Pay attention to what cylinder each one came from so you can put them back in the same place.
Hombre,

On one hand, I agree with you. This truck needs a lot of maintenance, and I'm about 1/8 of the way through it. (along with all this engine stuff, change ALL fluids then front end rebuild). When I realized the extent of what I would have to do about two weeks after buying the truck, my heart sank.

I'll take your advice on getting pressure tests etc on the engine. That's smart, no doubt.

But at the same time: I'm on the Big Island of Hawaii. 4x4's are at a premium here. Toyota 4x4s especially (an old tacoma or 4runner runs for what 80 series run for on the mainland). But somehow, these trucks are undervalued. I bought this one for $2300 + some back taxes. Not a bargain given the deferred maintenance, but the frame and everything is rust-free, with very slight reparable rust where there's a couple dents on the body.

And I need a 4x4 to get up to my house. It's a gnarly ass road; it shakes the hell out of a brand new jeep or 4runner. This truck takes it, even if its running like s***.

This truck has been abused, but you know what? It has a f***ing WILL TO LIVE.

When it's running good, man, I love the beast. It will take a while, but it won't take forever to get this thing running good enough that I can use it to explore some of the cuttiest places on the Island.

And if it's better to move on, I need to get it running decent and then I can sell it for roughly what I got into it. While if I keep it and the engine doesn't recover from the abuse, worst case I buy a 1-HDT from alibaba and ship it to Hawaii.

In the meantime, I'm about to buy a 93 FZJ80 with 213k for $2k. It's not perfect, but I'm buying it from a mechanic who put a lot more than that into it. So I'll have one to drive while the other one gives me hell and hopefully over time I'll learn something.

Thanks for the advice, and thanks to this community pretty much any of these trucks can be salvaged if they're not rusted out.
 
Joined
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Messages
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Location
big island, hawaii
Check your battery voltage engine off and engine on. Minimum of 13 volts running, 12.2 engine off. If that switch powered the ignition then it might have cooked your ignitor box, distributor pickup or the coil being powered on with no airflow. If your voltage while running at fast idle isn't at least 13 volts, your systems won't be doing their proper job. Fuel pump could also have suffered damage if it ran till the voltage died.

Simple checks. Look at your plug wires, coil, ignitor and distributor pickup under the cap. If you see anything melted or obviously cracked / broken, start there. Once that passes inspection, pull the plugs and make sure none are fouled out. Clean or replace any that are bad, check resistance of plug wires that are on any fouled plugs. If that checks out, you can check the quality of the spark by using a tester or pulling a plug wire off and watching the spark quality. Don't shock yourself or do it in the presence of flammable fluids. Good sparks are blue and steady rythym.

If you can check fuel pressure, I'd do that as well.

You may not even have a thermostat, lots get thrown out to address overheating but fuel injected motors need proper temp or they stay in fail-safe or open loop operation which causes problems.
Okay--so good advice here. It's hard to tell because everything already looks like s*** in the engine bay. I'll send a photo. The plastic coating on the lines going from the starter to the engine looked a little cooked, so I wrapped them in electrical tape. Starter still works fine and the engine cranks right up.

Battery voltage gauge shows above halfway (probably hanging at 2/3) while running and while not.

I really hope the fuel pump is chill.

More symptoms:
The truck if its been sitting for a few hours it will start up and idle correctly and smoothly (1000rpm) then over two minutes deteriorate (500rpm) and get all shaky and rattle the whole vehicle.

I think the thermostat must be a problem (in addition to other things) because previously the truck's temp was always right in the center of the gauge, pretty much never fluctuating. Now it's buried unless I make it work hard.

I'm going to replace the plugs, wireset, fuel and air filter as soon as they arrive. Belts, thermostat, and EGR delete too. Hopefully all by the end of next week.
 
Joined
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The factory gauges suck. Verify things with a decent voltmeter, not a Harbor Freight $5.99 model and temps with a infra-red thermometer.
 
Joined
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Would a bypass switch on the relay being pulled be running the fuel injection until the battery died or just sending power to the circuit? Would that have reasonably caused any damage?
From your description I can only guess that this mystery switch simply bypasses the EFI relay. If that's the case, it will drain the battery in 2 days but not cause any damage. It is powering sensors and VSVs and control systems. The igniter/ignition coil/injectors do not get powered from the EFI relay, but rather the ignition switch.

In an unmolested configuration, the fuel pump will only run when cranking the starter or when the flap in the AFM opens when the engine starts sucking air. However, the fuel pump logic can be easily bypassed with a jumper in the diagnostic connector mounted on the right side of the firewall. If that's the case, then the fuel pump WILL RUN with that mystery switch.

I would STRONGLY suggest that the EFI wiring be brought back to stock or at least documented as to what the PO did. Right now we're all just throwing darts.
 
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With the key in the ON/RUN position, before cranking the starter, does the CHECK ENGINE light illuminate?
With the engine running does it show any error codes?
 
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big island, hawaii
With the key in the ON/RUN position, before cranking the starter, does the CHECK ENGINE light illuminate?
With the engine running does it show any error codes?
CEL always illuminates when the switch is pulled and then turning ignition. If the switch isn’t pulled, then no CEL and it won’t start. Then when running, CEL is always illuminated. How do I check the error codes?

The switch is just a wire running from the socket where the EFI fuse is supposed to be into the cab. Nothing else.

I imagine fixing the wiring or returning to stock would require getting a new fuse box at the minimum, and possibly new wiring loom for entire engine. It’s on the ever-growing list.
 
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CEL always illuminates when the switch is pulled and then turning ignition. If the switch isn’t pulled, then no CEL and it won’t start. Then when running, CEL is always illuminated. How do I check the error codes?

The switch is just a wire running from the socket where the EFI fuse is supposed to be into the cab. Nothing else.

I imagine fixing the wiring or returning to stock would require getting a new fuse box at the minimum, and possibly new wiring loom for entire engine. It’s on the ever-growing list.
If the CEL is on while running, there is an error condition. Connecting pin 6 to pin 3 in the diagnostic connector will flash the CEL with a 2 digit code.

Is the switch in place of the 15 amp ECU-IG fuse in the fuse box by the driver's left knee OR the 15 amp EFI MAIN fuse in the fuse box under the hood OR the EFI MAIN relay in the fuse box under the hood?
Putting a switch in place of a fuse is an incredibly stupid thing to do, unless that same circuit is fused downstream. Fuses are there for a reason.

CheckConnector.jpg




DSKneeFuseblock.JPG


Relay Block Fender.jpg
 
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OK, so that is only 1 leg of the switch which is feeding +12 to what is the load side of the EFI relay. The other leg of the switch has to be +12 in order for this engine to run.
I'd be willing to bet that the PO couldn't figure out why the engine wasn't running and bypassed the relay in order to dump the vehicle.

If you look at the diagram I posted you will see what the correct voltages should be for each pin of the EFI relay.
Pin 1 should always be ground
Pin 2 should always be +12
Pin 3 should be a logic high (+12) when the key in in the ON/RUN position.
Pin 4 is the feed to the EFI system

It's also a possibility that the wiring under the EFI relay and 15 amp EFI main fuse is compromised. This was a common issue due to the heat of the exhaust manifold over 30 years.
All of this is repairable using OEM parts.

Fusebox Relay Contacts - 82998-12060
Fusebox Blade Fuse Contacts - 82998-12140
 
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He originally told me that the fuse kept blowing, and he didn’t want to keep buy fuses, so he installed that to bypass it.
Could this be a major source of my problems? Ie did this just finally catch up ti me after running okay for a while, or it just something that ought to be fixed sooner than later.

And to be clear, to remedy this cooked fuse, I would only need those two parts and a new EFI relay fuse?
 
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And a couple bits of info:

1. the vacuum pressure must be off because occasionally while driving the truck while it’s popping and stuttering, the brake pedal gets super firm.
2. These lines going from what I believe is the starter (I’m a noob, so could be wrong) were the only thing that looked recently damaged. The plastic was melted so I wrapped them in tape. I don’t know if this might be contributing to the truck running so roughly.

E7C40AB0-8CB6-408F-8C13-1CF9FBCF7440.jpeg


3. I have a strong feeling I need to change the spark plugs ASAP. I bought new denso copper oem ones today and already have the oem wire set, so I’ll change all that tonight. I can’t wait longer for the rest to come in the mail. Im forced to drive the truck and it’s sketchy the constant popping/misfire sound in the engine.
 
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He originally told me that the fuse kept blowing, and he didn’t want to keep buy fuses, so he installed that to bypass it.
Could this be a major source of my problems? Ie did this just finally catch up ti me after running okay for a while, or it just something that ought to be fixed sooner than later.

And to be clear, to remedy this cooked fuse, I would only need those two parts and a new EFI relay fuse?
So this guy sounds like a knucklehead. He bypassed the 15 amp EFI fuse and EFI relay. Obviously there is a issue in the EFI circuit that is popping fuses.
Find the issue and fix it. Then move on.
 
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Joined
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And a couple bits of info:

1. the vacuum pressure must be off because occasionally while driving the truck while it’s popping and stuttering, the brake pedal gets super firm.
2. These lines going from what I believe is the starter (I’m a noob, so could be wrong) were the only thing that looked recently damaged. The plastic was melted so I wrapped them in tape. I don’t know if this might be contributing to the truck running so roughly.
3. I have a strong feeling I need to change the spark plugs ASAP. I bought new denso copper oem ones today and already have the oem wire set, so I’ll change all that tonight. I can’t wait longer for the rest to come in the mail. Im forced to drive the truck and it’s sketchy the constant popping/misfire sound in the engine.
1. Likely a bad brake booster or check valve in the booster.
2. Those "lines" are throttle cables and that black plastic cover that they go into is the cruise control actuator. The starter is on the lower right side of the bellhousing.
3. OEM spark plugs - 90919-01091 or Denso part number W16EXRU11
 

RockDoc

I'll take Bruce Vilanch for the block.
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Post deleted.. on further thought, what I wrote seems extremely unlikely and probably more distracting from actual issues than helpful.
 
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Joined
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1. Likely a bad brake booster or check valve in the booster.
2. Those "lines" are throttle cables and that black plastic cover that they go into is the cruise control actuator. The starter is on the lower right side of the bellhousing.
3. OEM spark plugs - 90919-01091 or Denso part number W16EXRU11
I replaced the spark plugs and wires today. The old ones looked BAD.

I tightened the throttle cables and now have an idle in park at 1200. It drops to 700 in drive or reverse, but still has major issues transferring any power to the drive train. Doesn’t seem to be popping/misfiring like before, but I haven’t tried driving it so much. I’ll know soon.

I need to use the truck today to pick people up from the airport. Not sure exactly what to do or if I need to get a taxi and then rent something until I can get this figured out. I managed to do a 4 hour round trip drive yesterday (it was weaker than usual on the highway but still ran, in town it was SLOW), but the truck died when I got home. Started up this morning and I’ve been doing what I can do with what I have on hand.
 

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