The Classic FJ60 "Stumbling/Hesitating Acceleration/Running Problem

[FirstFJ60]

I’ll definitely look into it. I wasn’t aware there was a meet around here - THX

Resurrection to a thread that helped me. I was getting hesitation in 1st 2nd berween 2000 and 2500 rpm. I plugged that EGR line and the symptoms are GONE like the other great success they have had in the thread. I have more power and its running smooth. Im good since Va dont do smog test and Im not selling it....sooooo

 

[rlocke49]

Hey all!
Wanted to share my experience with the same hesitation issue. My 86 Fj60 would have a pretty noticeable hesitation only once warmed up at 1800 RPM. Like clockwork, any gear, varying load same nasty misfire/hesitation. I had rebuilt the carb, had the engine rebuilt (high blow by and low compression) and still had the issue. I figured unplugging the tach was worth a shot...turns out it was! hesitation is completely gone. I was pleasantly surprised that it was such a simple fix, now comes the challenge of finding a good replacement tach. Hope that helps someone!

 

[RodrigzCrzr]

Hey all!
Wanted to share my experience with the same hesitation issue. My 86 Fj60 would have a pretty noticeable hesitation only once warmed up at 1800 RPM. Like clockwork, any gear, varying load same nasty misfire/hesitation. I had rebuilt the carb, had the engine rebuilt (high blow by and low compression) and still had the issue. I figured unplugging the tach was worth a shot...turns out it was! hesitation is completely gone. I was pleasantly surprised that it was such a simple fix, now comes the challenge of finding a good replacement tach. Hope that helps someone!

It’s most likely your Emissions computer.
located behined the drivers side kick panel.
sometime the main connections gets loose. You could open it up and re solder the pins. my Tach would also not work and my truck would cut out and not hold a la idle. I replaced the computer and it went away.

 

[LETSROLLEM]

It’s most likely your Emissions computer.
located behined the drivers side kick panel.
sometime the main connections gets loose. You could open it up and re solder the pins. my Tach would also not work and my truck would cut out and not hold a la idle. I replaced the computer and it went away.

Having the same issues. Do you happen to have a picture of the exact part you changed out? Thanks

 

[Gretsch]

Do you happen to have a picture of the exact part you changed out?

 

[LETSROLLEM]

View attachment 2718787View attachment 2718788

Thanks! I was pretty sure that was it, just wanted to make sure. So you just pull the entire “circuit board” or just unplug the connection in the green?

 

[LETSROLLEM]

Thanks! I was pretty sure that was it, just wanted to make sure. So you just pull the entire “circuit board” or just unplug the connection in the green?

Btw, I see you’re in Plano, I’m in Old Lake Highlands, right by White Rock Lake. I love your 60. I looked for a brown one forever, but never could find a decent one. Settled on white. May reach out to you after I try this and let you know how it turns out

 

[cheeese]

Anyone know if there's a way to delete the emissions computer on a desmogged truck? Seems like if you have removed all the components it wants to run, the computer itself isn't needed.

 

[Gretsch]

So you just pull the entire “circuit board” or just unplug the connection in the green?

There is a harness that plugs into the green bit you see in the photo under the dash. The circuit board itself is just mounted to the body under the dash driver side kick panel. To replace it you would just unplug and unbolt from the body and then do the reverse to put it back. I actually had to reflow the solder on the plug on the circuit board for mine to make the ICS function properly to get the truck to idle. To gain access to the circuit board itself you unplug/unbolt the black box off the truck, then you can open up the black box to reveal the IC board contained inside. Just sort of lays in the black case if memory serves. Been awhile since I did the soldering. But got the truck to idle again. HTH.

 

[Gretsch]

May reach out to you after I try this and let you know how it turns out

Reach out anytime.

 

[LETSROLLEM]

There is a harness that plugs into the green bit you see in the photo under the dash. The circuit board itself is just mounted to the body under the dash driver side kick panel. To replace it you would just unplug and unbolt from the body and then do the reverse to put it back. I actually had to reflow the solder on the plug on the circuit board for mine to make the ICS function properly to get the truck to idle. To gain access to the circuit board itself you unplug/unbolt the black box off the truck, then you can open up the black box to reveal the IC board contained inside. Just sort of lays in the black case if memory serves. Been awhile since I did the soldering. But got the truck to idle again. HTH.

Thanks!!

 

[DFXR]

1985 FJ60, stock CA-smogged 2F. My Stumble always comes back, no matter how much I clean the EGR valve or throw "good used" vacuum modulators or VSVs at it.

Small, easy and cheap fix that I have been running - a Vacuum Delay Valve between the EGR Vacuum Modulator and the EGR valve. It slows down the vacuum signal between the Modulator and the EGR valve. Once it opens (ideally 4-5 seconds) the EGR functions as normal and keeps your NOx in check.

I have seen this mentioned once or twice over the years but never with details.

With this in place, no stumble, and it passes smog. Both the visual and the actual sniffer test. I don't think it's kosher to "alter" the EGR system like this, but the result is kosher for me and the Black/White valve looks like it belongs there.

Here's the valve I use. You can find NOS around the web, eBay, etc. Around $10-20 depending on who has it. Toyota makes delay valves as well, but they are harder to find and usually cost 3x as much.

Ford/Motorcraft
Distributor Delay Valve
D3FZ-12A091-A or D32E-AA

Here's where I put it. Black side towards the vacuum source:

Here are my smog numbers with it in place. Everything else about this 2F is stock and intact:

I found an old Ford shop manual online with a chart showing the specs of their various delay valves. Black/White should start opening up between 3 and 9 seconds depending on the strength of the vacuum signal. Watching in real time on the smog shop dyno, mine is/was around 4-5 seconds. You could easily test this with a Mityvac if you wanted.

I got a Black/Yellow VDV (D3AZ-12A091-A) while I was messing around with all this and it works just as well, maybe even better through the 1200-2500 range, but the yellow stands out quite a bit and could bring out the b1tch in a petty smog tech. I wouldn't go for much longer of a delay because you could end up running high NOx/lean for longer than you want.

Note that the chart is for Ford/Motorcraft valves only - color combos and specs don't necessarily sync up across manufacturers. So a Black/Yellow Ford valve could be very different from a Black/Yellow Toyota valve.

Hope this helps someone-


From the Ford shop manual:

 

[jeremiahm]

@DFXR thanks for keeping good info coming to this old thread! Someday I will have a 60 again and I know I will need it.

 

[Winkz]

Lots of good info here, still chasing my stuttering/hesitation issue.

I have an 85 FJ60, de-smogged with the City Race carb. 169k

I am able to set the timing, idle speeds, and vacuum is 18in of Hg.

The stuttering/engine stall occurs with sudden accel, or when accelerating in 3rd gear or higher.

The only issue I am able to identify is that the engine is running rich. The float bowl is about 75% full, piston heads and all 6 plugs are black as well as the inside of the carb. I also have white (faint) smoke when idling. If I adjust the fuel mixture screw, I lose vacuum.

I did some investigating found this crack inside the manifold:

Would this be enough of a crack to cause issues? Other pictures I've seen show a much more pronounced crack. I haven't had a chance to pull it to check the other side. I didn't notice the crack last time the manifold was pulled.

 

[Webster]

Old post , but hope some still watching,
The tach disconnect only works with those running stock ( Asian) carb, correct?
It is somehow effecting fuel cutoff solenoid on carb?

I have a Weber so don’t expect the tach fix will help me?
Or is the tach messing with ignition system?

I should mention I’m desmogged. Thanks!

 

[cps432]

Lots of good info here, still chasing my stuttering/hesitation issue.

I have an 85 FJ60, de-smogged with the City Race carb. 169k

I am able to set the timing, idle speeds, and vacuum is 18in of Hg.

The stuttering/engine stall occurs with sudden accel, or when accelerating in 3rd gear or higher.

The only issue I am able to identify is that the engine is running rich. The float bowl is about 75% full, piston heads and all 6 plugs are black as well as the inside of the carb. I also have white (faint) smoke when idling. If I adjust the fuel mixture screw, I lose vacuum.

I did some investigating found this crack inside the manifold:


View attachment 2778151

Would this be enough of a crack to cause issues? Other pictures I've seen show a much more pronounced crack. I haven't had a chance to pull it to check the other side. I didn't notice the crack last time the manifold was pulled.

That’ll cause issues...

 

[cps432]

Old post , but hope some still watching,
The tach disconnect only works with those running stock ( Asian) carb, correct?
It is somehow effecting fuel cutoff solenoid on carb?

I have a Weber so don’t expect the tach fix will help me?
Or is the tach messing with ignition system?

I should mention I’m desmogged. Thanks!

Try it and report back. You may be the first to try it.

 

[Webster]

Try it and report back. You may be the first to try it.

Will do tomorrow, pretty easy to try.

 

[g-man]

Just adding to this thread. I had the same EGR hesitation. Don't forget to test the EGR VSV (vacuum switching valve) follow the vacuum line from port R on the modulator over to it. Test it like this:

Mine failed this test. So I replaced it with this:

Amazon product ASIN B0814MPNFB
Here is how I did it:

See post #15...https://forum.ih8mud.com/threads/bogging-down-issue.1282751/#post-14438005

 

[bcolvin]

Bringing this one back from the dead. I had the same stumbling issue. My 60 is desmogged so much of the EGR suggestions did not apply to my scenario. So I thought I post another item to try if you are having these issues.

In the past I had a manifold gasket need tightening so I assumed this was the same problem since I had stumbling like before. Stumbling from 1.5 - 2k rpm’s. When the cruiser stalled the sight windows on the carb was 1/2 full so gas was making it to the carb. Checked the manifold and no issues. Checked distributed cap looked good, opening the screws to the carb.

Blew compressed air back through the jets and lo and behold that fixed the issue. Something else to try if you are searching