bouncing idle / slight misfire - FJ62 (1 Viewer)

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Had plugs changed on my 1990 62 recently (along with new exhaust). What came out we’re not stock plugs bpr5es-11 (gap is wider than FSM) put in by PO. Replaced with Denso W16EXR-U stock ones. But I developed a very very slight bouncing / low idle and I think tiny misfire. I can hear the tiny misfire out exhaust. (Video Attached)

To rule out the plug gap, I switched in NGK BPR5EY-11... didn’t help, now back to running stock NGK BPR5EY. Still has the ever so slight bounce idle / and I think misfire. I did reset ECU and have run enough miles through it.

I tried searching for a vacuum leak using brake cleaner but didn’t find one.

Am I being anal or is this idle a bit rough and there’s a misfire that should be solved or ignored.

Link to Video:
Link to FJ62 idle bounce / misfire.

UPDATE1
- Found some slight sparking going on on the spark plug wires in the dark. Replaced with OEM wires. (Gonna confirm tonight that there’s no arching anywhere else)
- disconnected battery / reset ecu
- everything is working but the bouncing idle and slight miss is still there.
- still figuring it out...

UPDATE2
- replaced my fuel filter because it hadn’t been replaced since I owned the vehicle.
- looks like the old one on there was for an fj80
- no change in my idle issue

UPDATE3
- pulled off the black ISVC and cleaned the plunger.
- replaces fuel pulsation dampener
- no change. Still slight misfire / bouncing low idle.

UPDATE3
- mechanic replaced:
- 02 sensors
- distributor cap
- set timing
- improved slightly but still noticeable especially once warm and idle drops. Still slight misfire / bouncing low idle. 🤷🏼‍♂️

(I may try the fuel pressure regulator at some point in future as @slcfj62 had mentioned in one of his posts that this in conjunction with the dampener and fuel filter fixed all hi rough idling issues. As of now I’m just living with it.)
 
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Does the 62 use a distributor? Maybe it’s a battery thing and just happens to have reared its head now when you changed plugs. Perhaps the timing and other adjustments were set to compensate for the non-stock plugs? Do you have the service manual? I’d go through the whole tune up process and see if that settles it. If it persists, just drive it as long as it’s running okay.
 
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Idle should be higher... probably hunting cause it’s trying to get to 650 but can’t... maybe a fuel pump sock is getting clogged or maybe the return is clogged... the fuel pressure test sounds like a pain in the but, but I think is easy enough to do.. at least, I’ll keep telling myself till I actually do it...
 
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Need to check all the wires for resistance or cracking. Easiest to do after dark in a place without a lot of ambient light. Check the distributor for corrosion too. Most likely a wire issue. Easy to pull the metal off the conductor core when changing plugs.
 

red66toy

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The fj62 EFI is very basic but needs very clear and accurate instructions from its sensors to work correctly. I would check your idle air control valve, throttle position sensor, and make sure there are no vacuum leaks and the egr system is working. I have had all sort of crazy issues with my 3FE and working my way through the FSM has helped a ton. Idle should definitely be at 650 so check your throttle position sensor first.
 
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Need to check all the wires for resistance or cracking. Easiest to do after dark in a place without a lot of ambient light. Check the distributor for corrosion too. Most likely a wire issue. Easy to pull the metal off the conductor core when changing plugs.

Interesting... you say easiest to do after dark... not an issue, but how exactly do you go about that? Am I just looking to see if I see any sparks coming out of places they shouldn’t on the plug wires?
 
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Interesting... you say easiest to do after dark... not an issue, but how exactly do you go about that? Am I just looking to see if I see any sparks coming out of places they shouldn’t on the plug wires?

Well I figured this out and I can definitely see some tiny sparks from a few different spots in the dark so I’ll start by replacing all the wires and go from there. Great advice w the inspection in the dark tip!
 
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Small update as I am still tracking down this slight bouncing / low idle. Checked wires in the dark thanks to @WILLD420. Saw some sparking so replaced the wires with new ome ones. No sparking now, but issue still there.

Also replaced my fuel filter because it hadn’t been replaced since I owned the vehicle. The one I pulled off was from an fj80. So both the plugs and the fuel filter I took off were from an FJ80 so I’m wondering if the timing has been set to accommodate for all that.

Next steps I’ll probably check again for any vacuum leaks I might have missed, might pull or check ISC, and then probably head to mechanic for them to check timing if I can’t tie it to a leak or ISC.

Oh and part of why I’ll check ISC... the entire reason I had the plugs changed in the first place (besides never being done) the truck had been cranking longer and longer. After this low idle issue I noticed the FSM points to the ISC as a potential cause. But it also points to ISC as a cause for slow starts especially if you press the gas peddle when starting it starts up faster. And yeah I’m pretty sure mine starts up first or second crank if I press the gas. So I’ll try to check ISC before bringing it to mechanic for timing. I didn’t quite understand the FSM test for the ISC but I’ll dig a bit deeper and see if I can understand it and report back.
 
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The iscv test consists of measuring winding resistance, and proving the actuator is functional by simulating the voltage flashes the ecu sends it to make it go open or closed and exactly how much... you will tease the valve by pulsing dc voltage at its windings in a specific order... hth.
 

red66toy

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The iscv test consists of measuring winding resistance, and proving the actuator is functional by simulating the voltage flashes the ecu sends it to make it go open or closed and exactly how much... you will tease the valve by pulsing dc voltage at its windings in a specific order... hth.
Ah the old “teasing the valve” trick. Never fails.
 
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The iscv test consists of measuring winding resistance, and proving the actuator is functional by simulating the voltage flashes the ecu sends it to make it go open or closed and exactly how much... you will tease the valve by pulsing dc voltage at its windings in a specific order... hth.

Right, I’m looking at the FSM now. You have to conduct this resistance test and valve operation check with the actual ISV pulled all the way off correct not just disconnected?

And assuming pulled off do you actually have drain the engine coolant like the FSM says or I can just pop it off?
 

red66toy

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Right, I’m looking at the FSM now. You have to conduct this resistance test and valve operation check with the actual ISV pulled all the way off correct not just disconnected?

And assuming pulled off do you actually have drain the engine coolant like the FSM says or I can just pop it off?
Not much coolant drains out of you take the whole assembly off. Be prepared to make or buy a new gasket if your old one gets torn or something. The black electrical part can be simply unscrewed from its metal base with those three screws. If you need to replace just the valve.
 
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Not much coolant drains out of you take the whole assembly off. Be prepared to make or buy a new gasket if your old one gets torn or something. The black electrical part can be simply unscrewed from its metal base with those three screws. If you need to replace just the valve.

So if I just unscrew the black part with the three screws I don’t have to worry about the gasket and fluid? I could just take that off and clean it up and see what happens? That seems fairly painless.
 
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I unbolted mine all the way from the manifold. Not a lot of coolant comes out/ and those hoses are likely shagged anyway. I capped off my water bypass altogether...
 

brownbear

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One 3Fe thing I did to my FJ80. It also had a bouncing idle.

I think it's an EGR thing. So there are two vacuum lines coming out of the manifold at the top. Pull them both off and put BB's into the hose to block the flow. It won't let vacuum control the EGR.

When I did this my idle improved dramatically and my fuel mileage went up. But what it showed was probably my EGR was not so healthy. I ran my cruiser with the EGR vacuum blocked for the whole time I owned it and it ran good. The BB's cannot be sucked down the hose or into the engine, as the fitting that the vacuum line attaches to is too small for BB to fit. I used those .177 BB's. You know from a pellet gun. I saw this tip on here somewhere.
 

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