1984 FJ60 2F Won't Idle (1 Viewer)

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Jan 27, 2019
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I'm in need of some help with my 60. I got home from an hour long trip with my kids about a week ago, and as I was getting off the interstate I noticed that the engine started dropping RPMs and trying to die. It would still run smooth at 1700-2000 RPM, but as soon as I took my foot off the gas, it tried to die. I'm not sure what's relevant, so I'll provide details of recent maintenance and troubleshooting I've performed below.

I got the truck about a year ago. It ran rough and idle speed was set to about 1400, likely because the AC idle up vacuum port was snapped off and the PO had turned it up this far to get the AC to turn on. I replaced the broken switch and turned the idle screw down to around 800 during a carb tune (it ran rough any lower). It still hard starts, taking 15-20 seconds of cranking to get running and occasionally just shut off a minute or so after starting as if the engine got choked down. Since that time I've replaced spark plugs and wires, distributor cap and rotor (10 months ago). I replaced the fuel pump (8 months ago) due to a fuel starvation issue, and got a rebuilt carb (6 months ago). I replaced all vacuum lines 3 months ago. In the last 2 weeks before she stopped idling, my smog pump seized, and I devaned it and started using it as a dummy pulley. I then found my violet BVSV was snapped clean off and vacuum lines were to atmosphere. I replaced the BVSV, and retuned the carb because things were then wayyy off. After this, I had it idling at startup around 700 rpm, and after warming up around 900 rpm. I didn't check vacuum again but the hard starting persisted. Despite everything.

After the engine stopped idling I thought the issue might be a massive vacuum leak that wasn't pulling fuel through the idle circuit. I first exchanged the carb for my old one to see if that was the issue. Same problem. My next thought was maybe the intake manifold had cracked on me. I spent the last 3-4 days soaking old seized bolts in order to get down to it. I finally removed it today, and although my heat riser was in pieces, I failed to identify a crack. Although the manifold gasket is rough, it doesn't look like it had any through and through violations. I also just got done checking the idle cut solenoid using the 12V method and am hearing a distinctive click when I hotwire it off the battery. I'm planning to start reassembling everything when I finally get the exhaust manifold off, but I don't feel like I've identified the problem and am wondering if any one can give me some advice on what else might be the issue. Thanks for reading if you made it this far.
 

Dr. John

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Just musing here.....Vac leaks usually raise idle speed....First check would be for a stuck-on choke. Hmmm...Loose distributor could have timing off just enough to affect idle but not higher rpms. I'll keep thinking...
 

NeverGiveUpYota

Dare me.
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Vacuum leaks do not raise an idle. If your checking for a vacuum leak w/ carb spray you will find it because the spray will be sucked in and bring the idle up and steady it out. Vacuum leaks cause poor idling.
 
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Thanks guys. I’ll check the distributor tomorrow. The choke is good, not stuck and same problem persisted with both old and new carb when I changed them out.

Just musing here.....Vac leaks usually raise idle speed....First check would be for a stuck-on choke. Hmmm...Loose distributor could have timing off just enough to affect idle but not higher rpms. I'll keep thinking...
 
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Reno
Had something similar happen to mine today. Would run fine but it would die at idle. Symptoms started at the stoplight right when I pulled off the freeway, was idling totally fine before then. Tested vacuum and found a huge leak. Turned out my EGR valve stuck open on a short rip down the freeway, knocked it with a hammer lightly a couple times and the valve shut, idled perfect after that and got good vacuum back.

Not saying that’s what is happening to you, but your symptoms do sound like a vacuum leak of some sort.
 
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Alabama
I’ll try looking into this tomorrow. I bet I’ll have to get everything back together first before testing it but I’ll see if there’s another way. Thank you guys for the responses. I’m learning bit by bit
as @teamreno mentioned- check the function of the egr valve. They can intermittently not shut tight, creating a big vacuum leak. You can see it with a vacuum gauge.
Had something similar happen to mine today. Would run fine but it would die at idle. Tested vacuum and found a huge leak. Turned out my EGR valve stuck open on a short rip down the freeway, knocked it with a hammer lightly a couple times and the valve shut, idled perfect after that and got good vacuum back.

Not saying that’s what is happening to you, but your symptoms do sound like a vacuum leak of some sort.
 
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Check the pcv hoses too because if one of those breaks you will have a massive engine killing leak.
 
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I wanted to return to this now that I’ve had a few months to make sure I’ve got everything sorted. I completed my desmog, rerouted vacuum lines, replaced a rotten carb insulator plate and intake/exhaust manifold gasket. I tuned the carb, then set timing, then rinsed and repeated until I maximized vacuum. I now pull 19 on the vacuum at ~600 rpm idle. I still need to do a valve job on it, but it’s singing and is my daily again. The EGR was almost certainly the culprit, and I’m ever grateful to @teamreno for the suggestion.
 

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