1984 FJ60 Engine Sputtering, Bucking - FIXED!!!

[Landpimp]

AC, 1st set your normal idle to 650-700 rpms(wait till warmed up). Now turn on the AC, and adjust the screw so the with the AC on the idle is about 1000rpm's, turn AC off and it should go back to 650-700. with AC on idle will go from 650-1000 fairly often, depending on demand.. There is a selnoid that controlls the vacume to the AC idle up, if its gone bad it will cause the idle to stay higher than what the ac idle.is set at

 

[Gretsch]

What is your vacuum at idle? Intermittent dying definitely sounds like Fuel Cut/EGR/Computer issues, I myself have had two hiccups but they seem to disappear before I can actually diagnose.

1. Check the Fuel Cut Solenoid by turning ignition on, but truck not running and unplug the solenoid. Touch the connectors together for connectivity and listen for the solenoid click. If no noise, that is your idle issue. This is ideally done when the issue is present. If it fails, the FCS bypass needs to be done by grounding the white wire that comes off the solenoid, as seen below.

2. Next would be verifying the fuel cut solenoid vacuum lines. Check the vacuum diagram and make sure its routed correctly to the vacuum switch. I'd post the diagram, but my work comp is blocking all the good diagrams.

3. Remove the emissions computer, this is a tricky one. It's under the driver kick panel and the only way to really inspect is check for broken solder joints on the board. Normally there are some broken ones on the points for the connector on the board, so a quick reflow and/or additional dab of solder does the trick. If you can get your hands on a known good unit, that helps for testing as well.

4. EGR. With truck running, unhook vacuum feed (top vacuum line on valve) apply vacuum to the valve manually with a piece of hose and suck lightly (only time I'll tell someone to do that). If the engine starts to stumble, the valve is functional. It would also help to clean the valve out, so hit it with some pb blaster at all the connections and hope it comes off easy. You can also cap the vacuum line off the modulator to egr valve and see how the truck runs with it disconnected.

5. Is fuel level center in the site glass on carb? Try and verify when the truck is fine and running and also when it won't idle.

OK thanks here. If I continue to have issues I'll use this checklist to rule out other possibilities.

Another silly question here. I just thought of this and feel dumb not thinking about this before. PO told me that he would sometimes get in the truck to start it, and would get no power anywhere. He would then go 'jiggle' the negative battery cable and the truck would then come to life. I have not experienced this myself, but he seemed to think it happened with regularity. I planned on replacing the terminals on the battery posts, but have not gotten to it yet. Now I assume, if the truck is running (started), these battery cables are unused other than to charge the battery via the alternator. If a ground strap on the battery was intermittently losing connection to the post, while driving, that would have no effect on engine idle or cutout right? Meaning if while driving the cable was bouncing along and losing connection to the post due to a bad connection, it would have no effect on the solenoid we have been talking about, correct? I am pretty sure it wouldn't but wanted to be sure. Thanks and sorry for the noob stuff.

 

[Landpimp]

The wire(you said was a ground) that is spliced that goes to the exhaust manifold is the temp sensor for the carb cooling fan. It tells the fan when to turn on, which will only happen when the key is off.

 

[Gretsch]

The wire(you said was a ground) that is spliced that goes to the exhaust manifold is the temp sensor for the carb cooling fan. It tells the fan when to turn on, which will only happen when the key is off.

OK thanks. Fan is still coming on so I assume I did not mess anything up by replacing this lead.

 

[NeverGiveUpYota]

Also correct me if I'm wrong folks (@mwebfj60), disconnecting the emissions computer won't simply disengage the ICS it also affects the tach wire from the coil. So I don't believe it's something you want to just go pulling. Get the ICS fixed, buy a new one tho JimC says the CCOT one is chimcon (china made) and isn't very reliable or source a good used one. @JustinJawbreaker was selling off a bunch of stuff as was another guy @CaptClose told me about. Could be the little o-ring is worn... when I just put my carb back together I took a maginifying glass to mine and it was totally dry rotted. Luckily I had a new one kicking around or hardware stores sometimes have assortment boxes. Check the wiring... I replaced my green wire which was cracked and ready to break and added new female ends in the clip too.
I had mine hard wired too for a bit but then it started acting wonky so I clipped it back in and that seemed to reboot it. Zero clue if that's right or not. Some folks have had success pulling their emissions computer and reflowing the solder points too. There are old school amp rebuilders that could do it.
So just saying. Try to fix the issue before jimmying it.
Work in progress all the way w/ these old beauties!
Felicity

 

[NeverGiveUpYota]

OK thanks here. If I continue to have issues I'll use this checklist to rule out other possibilities.

Another silly question here. I just thought of this and feel dumb not thinking about this before. PO told me that he would sometimes get in the truck to start it, and would get no power anywhere. He would then go 'jiggle' the negative battery cable and the truck would then come to life. I have not experienced this myself, but he seemed to think it happened with regularity. I planned on replacing the terminals on the battery posts, but have not gotten to it yet. Now I assume, if the truck is running (started), these battery cables are unused other than to charge the battery via the alternator. If a ground strap on the battery was intermittently losing connection to the post, while driving, that would have no effect on engine idle or cutout right? Meaning if while driving the cable was bouncing along and losing connection to the post due to a bad connection, it would have no effect on the solenoid we have been talking about, correct? I am pretty sure it wouldn't but wanted to be sure. Thanks and sorry for the noob stuff.

Your fusible link has three main wires into it. Alt, Ignition and Lights (gurus, if I'm wrong speak now). You tell me if those would affect startup or even driving if something is loose or corroded inside the insulation. Cut them and rewire now. You can redo the fusible link too. Can even source half of it still unless they're gone now (I bought one half end last year this time). The rest of it I pulled apart and rebuilt.

 

[mwebfj60]

You're getting good advice from Landpimp, Yota and others so I'm just going to respond to the computer question. If you are desmogged, the emissions computer is only controlling the idle cut solenoid by the tach input and the vacuum switch from the decel vacuum port on the carb base. Vacuum above 14" and RPMs greater than 1800 cause the ICS to cut off fuel to the primary slow (idle) circuit of the carb. So when you are decelerating, you don't suck an excess of fuel into the cylinders. If you have the ICS grounded, which should only be a temporary thing for troubleshooting IMO, then the computer isn't doing anything.

 

[Gretsch]

So I drove "Beast Mode" around last night for a half hour and decided to drive her in to work (32 miles one way). I cannot get it to do what it was doing before with rough idle and bucking. I drove in this morning and it drove vey smooth the whole way. No shuddering and did not buck on me once. Had good power and was easily able to keep up with traffic. Got stuck in traffic but it never tried to shut off or had a rough idle while stopped. I just paid $1600 to have this same sort of drivability issue fixed on an 06 Jeep I have. $4 and a little time and this 60 drives like new. That's the sort of thing I am looking for with this vehicle. If this really handles my issue, I am truly amazed. I am going to keep watching this week to see if any more issues crop up, but man, many thanks to all the members posting solutions. Its truly appreciated.

 

[SuperDuperCruizer]

When I was in college, I blew out my clutch about 1-hour north of my destination. It was a 500 mile trip, and I was hoping I could limp it the way there.

A total stranger in a Defender 90 stopped and offered to use a tow strap to get me to the nearest NPS ranger station (My summer job was lifeguarding on the National Seashore). The guy once owned an FJ40 and was kind enough to assist.

You're a part of the community and you probably haven't met the guy that's going to get you out of the next pinch. Just remember to pay it forward When the shoe is on the other foot.

 

[wngrog]

I read up on this on Mud last week and @beno and I went through all the things mentioned here that it could be yesterday.

Took it on highway 45 miles and it Drove great. 1/2 way home it started sputtering bad and only ran smooth with accelerator on the floor.

I'm gonna toss a new CityRacer carb on it. My current one has about 9 years on it so I guess it's time.

I love the idea of getting the rest of this vacuum out of the bay too.

 

[Gretsch]

500 is pretty darn low for a normal idle. I'd set it to at least 700 if not 800. That could be causing it to try to stall out when the high idle kicks down.

So I confirmed that the idle is at around 6/700. Not 500 like I said.

 

[wngrog]

On a second note,

My truck idles at 800 then drops to 600 when the AC is on.

I have a new Denso AC vacuum switch.

It is getting good vacuum and power to the switch.

It's not working.

 

[Gretsch]

So have driven this truck about 100 miles this week. No bucking while driving. It has not bucked once at speed since doing this fix. Worked great all day Wednesday and Thursday. Stuck in traffic and it handled it no problem. On Thursday however, it worked great all day and then about a minute from my house as I was turning into my neighborhood after the work day was over, it just totally cut off. Made it the 32 mile drive home and then a minute from the house problems. Guess if it had to shut off thats a good place to do it. Running along and then slowed down to make a turn and as I put my foot on the clutch, engine went dead. I was able to get the truck turned and restarted it. It fired right up like nothing happened. Worked flawlessly the whole week until last night. Now I am getting low on fuel, and as I mentioned the fuel gauge reading is not yet known to be accurate so its possible I am about out of gas and just don't know it. Gauge still shows 1/4 left. Can someone please confirm the size of the fuel tanks on an 1984 FJ60? 23 gallons?

 

[NeverGiveUpYota]

Yeah that's about right. I always had it in my head 22. Rarely have I been able to fill over 19. My gauge is working but wasn't till I opened up the sender cover and PB'd the snot out of the connections. But I go by my trip and just always fill at no more than 200.

 

[Gretsch]

Yeah that's about right. I always had it in my head 22. Rarely have I been able to fill over 19. My gauge is working but wasn't till I opened up the sender cover and PB'd the snot out of the connections. But I go by my trip and just always fill at no more than 200.

I am closing in on 200 miles on the trip. Wonder if I am just out of gas?

 

[NeverGiveUpYota]

Could be. I might even fill at 160/180. Not sure it's been awhile since I drive her for a length of time.

 

[wngrog]

24 gallons.

My truck gets from 10 to 14 mpg depending on use.

I'd fill it every 200 miles to be safe.

 

[Gretsch]

OK so I just checked. Trip is at 183 miles. If 200 miles is the magic number then it would seem the gauge is correct at showing a quarter tank and this shut off last night was from something else.

 

[wngrog]

Having a carbureted motor quit on you while stopping and hanging a 90* turn is not a totally bazarre concurrence.

Since it cranked right up just keep on trucking

 

[Gretsch]

So ran to lunch today and sort of chickened out and got gas. Had my wife in the car and still working through the WAF (wife approval factor) so did not want anything to happen to the 60 that would undermine that process (like running out of gas). With the gauge at a quarter tank and trip at 190 it took 15 gallons. I think the gauge is good. ran solid the whole way. No bucking or shutdowns. Not sure what last night was.