- Thread starter
- #21
Hey! All suggestions are helpful. It seems like the rough idle/driving but barely is a common symptom of many different underlying problems
Help: 3FE Terrible Idle and Misfires after dead battery (1 Viewer)
- Thread starter junglehaole
- Start date
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Your throttle cable is too tight. Idle speed should be 650 at normal operating temp.
The correct way to adjust the throttle cable is to have someone push the pedal to the floor. The throttle plate should just touch the end stop. With the pedal released there should be some slack in the cable. Idle speed is set by the ECU and ISC valve.
Getting the factory service manual would be a great first step for you, as everything you've mentioned is explained in agonizing detail.
Maybe check the vac diagram under the hood?
Check that your hoses are going to the right places. When I was replacing mine I found most were cracked or hardly snug to the hard line nipples.
If your PO was messing with something he may have got too much air- needed more fuel- tightened the cable- and bypassed the efi to get as much fuel in the cyl as possible?
Just a thought- I do not know nearly as much as Jonheld so take this with a grain of salt.
Check that your hoses are going to the right places. When I was replacing mine I found most were cracked or hardly snug to the hard line nipples.
If your PO was messing with something he may have got too much air- needed more fuel- tightened the cable- and bypassed the efi to get as much fuel in the cyl as possible?
Just a thought- I do not know nearly as much as Jonheld so take this with a grain of salt.
- Thread starter
- #24
Thanks! The vacuum lines are right and I have the service manual, but I think the egr is clogged and I’m deleting it. The intake is bad and replacing that too.
Can you link the engine fsm for the fj80? I can only find chassis....not engine. Trying to solve rough idle and cannot find what factory idle is in my searching. Thanks
I second the agonizing part that jonheld mentioned, but well worth it. I am using the FSM to troubleshoot my MAF. Absolutely priceless since a reman MAF is pricey. Get a FSM.
- Thread starter
- #27
Ive been chasing this for a while now. Misfires are still terrible. No power, especially from a start or going uphill. Misfires like crazy. Once on a flat it can get up to 60 or 70. Flooring the pedal it stutters. Seems to have trouble shifting—it surges but seems to struggle to
It starts up but shudders, and I have to give it gas for it to stay running. Once it warms a little it maintains idle in neutral, but no matter what idles high—about 1100-1200. It can shudder and die if I put it in gear before the engine is warm.
What Ive done:
1. replaced thermostat—engine now gets warm
2. Replaced spark plugs and wires. I didn’t set the gap, and haven’t yet replaced distributor cap and rotor. The timing could be a problem—and will have to set that when I do cap and rotor.
3. replaced air intake and all vacuum hoses
4. Deleted EGR
5. Fuel filter (PO recently did fuel pump)
6. adjusted throttle and kickdown cables (didn’t seem to change transmission issue—seems like it’s just not getting the torque or power needed?)
7. Replaced EFI relay.
8. replaced O2 sensor closest to the driver side of the vehicle (#1?) The other won’t come off.
I pulled engine code 28- O2 sensor #2.
Im assuming the issue must be the timing and/or the fuel injectors. Or coolant sensor? I have these parts and will try them. But am I missing something? Im going through the FSM and the diagnostic flow charts but some of it is a little beyond my ability.
(How do I check if there is specified voltage between ECU terminal VF1/VF2 and body ground?)
I’m wondering if the ECU is fried from the EFI bypass? Or having the bypass pulled and changing the battery ran a current and fouled the already old injectors?
I’m in too deep to cut bait with the truck, but I also can’t keep putting time, money and energy into it if it won’t run.
And again returning to the point: it ran great before the fateful day the battery was completely drained by the EFI relay bypass being left out. So I’m generally confused and wondering if I’m just chasing my tail here, and potentially messing other stuff up with my banana mechanic game.
It starts up but shudders, and I have to give it gas for it to stay running. Once it warms a little it maintains idle in neutral, but no matter what idles high—about 1100-1200. It can shudder and die if I put it in gear before the engine is warm.
What Ive done:
1. replaced thermostat—engine now gets warm
2. Replaced spark plugs and wires. I didn’t set the gap, and haven’t yet replaced distributor cap and rotor. The timing could be a problem—and will have to set that when I do cap and rotor.
3. replaced air intake and all vacuum hoses
4. Deleted EGR
5. Fuel filter (PO recently did fuel pump)
6. adjusted throttle and kickdown cables (didn’t seem to change transmission issue—seems like it’s just not getting the torque or power needed?)
7. Replaced EFI relay.
8. replaced O2 sensor closest to the driver side of the vehicle (#1?) The other won’t come off.
I pulled engine code 28- O2 sensor #2.
Im assuming the issue must be the timing and/or the fuel injectors. Or coolant sensor? I have these parts and will try them. But am I missing something? Im going through the FSM and the diagnostic flow charts but some of it is a little beyond my ability.
(How do I check if there is specified voltage between ECU terminal VF1/VF2 and body ground?)
I’m wondering if the ECU is fried from the EFI bypass? Or having the bypass pulled and changing the battery ran a current and fouled the already old injectors?
I’m in too deep to cut bait with the truck, but I also can’t keep putting time, money and energy into it if it won’t run.
And again returning to the point: it ran great before the fateful day the battery was completely drained by the EFI relay bypass being left out. So I’m generally confused and wondering if I’m just chasing my tail here, and potentially messing other stuff up with my banana mechanic game.
Do valves and then check timing (or at the very least check timing). You don't need to wait for the new cap and rotor but when they come in it won't affect your timing necessarily. You can also use FSM to check the coolant sensor if I recall correctly.
The ECU told you that there's a problem with an O2 sensor. Why are you not listening to what it said?
This engine will not run correctly until you clear the codes that it's complaining about.
The O2 sensors are the primary feedback mechanism to the ECU that controls fuel delivery. FIX THE PROBLEM FIRST.
And why are you waiting to replace the cap and rotor? They stay in place when adjusting timing.
I'll repeat myself once more. Get a FSM and stop dicking around.
This engine will not run correctly until you clear the codes that it's complaining about.
The O2 sensors are the primary feedback mechanism to the ECU that controls fuel delivery. FIX THE PROBLEM FIRST.
And why are you waiting to replace the cap and rotor? They stay in place when adjusting timing.
I'll repeat myself once more. Get a FSM and stop dicking around.
- Thread starter
- #30
I have an FSM. The FSM lists about a dozen things to repair or replace before saying to replace the 02 sensor.
it ran fine before, code can’t be just the o2 sensor.
I replaced o2 sensor #1. I left it with a mechanic for some weeks with an OEM O2 sensor #2. He was unable to get it off without breaking the studs off.
Ive messed up not doing the timing snd valve adjustment FIRST. But im reaching out on this forum to tap the collective experience of others who know these vehicles and can help me understand how leaving a EFI bypass powered drained my battery and made a truck that otherwise ran great have a cascade of issues that do not seem to respond to adjustments.
The O2 sensor is downstream from everything that happens in the engine. Something happening in there is messed up.
It seems unlikely that the EFI bypass draining the battery caused the issue you are having. It could be that letting the ECU reset (by battery dying) is causing it to relearn everything and because something is not working right it can't adjust properly to what is being presented. As Jon says the ECU is 1980's tech so not terribly sophisticated by today's standards. If you can't get the #2 oxygen sensor off by yourself an exhaust shop could do it or make another bung to put it in.
The challenge with getting an old 80, and in particular a 3FE, is figuring out how badly neglected different parts of the truck are. Take it one problem at a time (there are probably multiple problems that need addressed).
In addition to doing and working on things already mentioned an easy thing to check and replace is the fuel sock at the fuel pump. In addition to the usual FAQs for 80s here are some 3FE specific things that I put together: 1991 1992 3FE Specific MUD References - https://forum.ih8mud.com/threads/1991-1992-3fe-specific-mud-references.1252728/
The challenge with getting an old 80, and in particular a 3FE, is figuring out how badly neglected different parts of the truck are. Take it one problem at a time (there are probably multiple problems that need addressed).
In addition to doing and working on things already mentioned an easy thing to check and replace is the fuel sock at the fuel pump. In addition to the usual FAQs for 80s here are some 3FE specific things that I put together: 1991 1992 3FE Specific MUD References - https://forum.ih8mud.com/threads/1991-1992-3fe-specific-mud-references.1252728/
When you say things like, "code can’t be just the o2 sensor" when the ECU is telling you that it IS the O2 sensor, it makes me bang my head on the desk.
This is a tractor motor from 1986 with 1st generation fuel injection. It is the most basic EFI/ECU combination. Any error code that is thrown needs to be addressed because the ECU has a VERY limited window of error correction. 1986 technology.
"The O2 sensor is downstream from everything that happens in the engine"
This statement is 100% incorrect. The O2 sensors are the PRIMARY FEEDBACK TO THE ECU FOR FUEL DELIVERY. If the O2 sensors are not working correctly, the ECU will not be delivering fuel correctly.
- Thread starter
- #33
Thank you— I get it and I’m calling around to find a shop that will handle it.
I only objected because FSM has a full page flow chart of things to check, repair or replace, before it says to replace o2 sensor, which I’ve tried to do myself, and left with a mechanic who essentially gave up on it or just plain bullshitted me
- Thread starter
- #34
Thank you, this is what I needed to hear to stop squirreling out on WTF happened when this all started.
essentially the entire truck was badly neglected though. So doing as much as I can afford is probably good, especially realizing that the system will work better once the o2 sensor actually works.
I your O2 sensors are 29 years old, then it's a good bet that they're well past their prime. Page FI-44 of the FSM gives you step by step diagnostics of the 2 O2 sensors.
Ignition timing and valve adjustments will NOT change due to a dead battery. Most likely scenario is that the heating coils in the O2 sensors burned out.
Once the CEL is cleared and the ECU is happy, you can resume troubleshooting any issues that remain.
Ignition timing and valve adjustments will NOT change due to a dead battery. Most likely scenario is that the heating coils in the O2 sensors burned out.
Once the CEL is cleared and the ECU is happy, you can resume troubleshooting any issues that remain.
- Thread starter
- #36
I got it--and I got the 02 sensor in question and am on getting that fixed. But would a bad 02 sensor cause such a cascade of problems? The constant misfires? Something else must be up. The mechanic I took it to assumed that the bypass ran a current to the fuel injectors and fouled them, or the coolant temp sensor is bad. He's worked on many land cruisers but is of course no expert on them. But at the same time, he wasn't able to replace 02 sensor #2 without breaking the studs, and I'll have to take that to an exhaust shop.
But to actually get to one (50 miles away), the truck needs to run better.
I'll try again on the 02 sensor myself, because maybe he was bullshitting me. Is it ridiculous to try unbolting that part of the exhaust that they are on and taking it in somewhere?
Meanwhile, I have on hand what is needed to do the timing, valve adjustment, and replace the injectors, and figure I gotta do that. Even if they're not the acute problem, they're probably all bad.
As mentioned in an earlier post, the fuel injectors are not fed from the EFI relay circuit, but rather the ignition circuit. They are pulsed from the ECU and the ignition circuit side of the injectors is constant +12. So even if the injectors were fed +12 with the truck off, the injectors would remain inoperative until the engine was running.
I understand you're kinda new here........
I also want you to understand that the guy that's TRYING to help you is one of (if not THE one) the MOST knowledgeable people on this forum about troubleshooting the 3FE and getting you good answers.
Long and short of things:
Listen to what Jon says.
Do what Jon says.
Report back with facts of what took place.
Ask bullet point questions.
State facts about results, not "feelz" if at all possible
If you don't start listening and doing, he's going to go away because he can only take so much.......
Soooo, did you get your truck fixed? The nut on that O2 sensor should be a 12mm or 13mm, put some penetrating oil on it and use what's called a "12 pt box end wrench" , dont use one that's a ratchet because it will be too wide. Find one thats 10-12" long so you have some leverage and just apply constant steady pressure until that nut gives. Order a new OEM O2 sensor, a local dealership might can order one, or CruiserCorps has them, also other websites in the Vendors section at the top of the page.
The brake booster remark hits home with me! I never knew a brake booster effected anything but the brakes until I replaced one on my 92 3fe.
