The Classic FJ60 "Stumbling/Hesitating Acceleration/Running Problem (2 Viewers)

[FJStan]

Have you pulled it and taken a magnifying glass to the o-ring?

Negative - I have not touched the ICS.

I’ve been assessing all the other variables discussed on this thread and hoping to better understand the logic behind the “golf T” fix and the unplugging of the Tach. I honestly didn’t expect the ICS to play role in this whole hesitation/stumbling issue because I figured the ICS was more of an idle/decel related component - so...the plot thickens here.

However, interested enough - during this whole assessment journey I noticed the my dizzy was at full adjustment (advance) and while I could not designer the marking on the fly wheel, logic would say to bring it a little bit and wow - more power and much less hesitation. Talk about thickening plot... now what does that mean , but better is better so...

Lastly, my bottom vacuum at the HAC is unplugged - what the...

My search for perfection continues, but I couldn't have gotten this far without the help of this community - you guys rock

 

[Spike Strip]

Thx for the guidance here. If I’m following your logic correctly - regardless of what is going on throughout the various valves and sensors, the ultimate culprit of this classic stumble/hesitation is the Idle Control Solenoid, yes? ...and by keeping it in active mode permanently (by grounding it and thus completing the circuit) the issue goes away? It’s that simple?

I can be. It's the function of the ICS that is usually critical for this stumble/hesitation issue. Things that effect its function are all suspect.

The bottom tube on the HAC is open to atmosphere.

I would suggest you read the Emission FSM if you want a better understanding of what's going on.

You *might* want to try some of the things suggested here, then ask further questions.

 

[FJStan]

The bottom tube on the HAC is open to atmosphere.

Can’t be - it has vacuum. What is open to atmosphere is the entire bottom which has a filter. BTW, It was just an observation on the extent of issues making for a complicated situation. It ultimately goes to the distributor advance - when I get to it.

I would suggest you read the Emission FSM if you want a better understanding of what's going on.

I have been and that’s where I saw the diagram for that bottom tube. Again it was simply an observation of the current landscape.

You *might* want to try some of the things suggested here, then ask further questions.

I have! However, I’m not looking to simply resolve a symptom, I’m interested in resolving the problem at its origin.

All the suggestions mentioned here are incredibly helpful and food for thought. Obviously there is no clear solution, so trial and error are a given.

Thanks.

 

[mattressking]

Can’t be - it has vacuum. What is open to atmosphere is the entire bottom which has a filter. BTW, It was just an observation on the extent of issues making for a complicated situation. It ultimately goes to the distributor advance - when I get to it.



I have been and that’s where I saw the diagram for that bottom tube. Again it was simply an observation of the current landscape.



I have! However, I’m not looking to simply resolve a symptom, I’m interested in resolving the problem at its origin.

All the suggestions mentioned here are incredibly helpful and food for thought. Obviously there is no clear solution, so trial and error are a given.

Thanks.

You're saying that the top 4 tubes off the HAC are hooked up except for the bottom center hose? If so, its supposed to connect to the vacuum hardline assy, the vac diagram shows where.

The bottom most port on HAC is atmospheric, and clips onto the main body of the HAC which has the filter, that might be missing based on your description.

 

[NeverGiveUpYota]

[QUOTEFJStan, post: 11263450, member: 134547"]Negative - I have not touched the ICS.

I’ve been assessing all the other variables discussed on this thread and hoping to better understand the logic behind the “golf T” fix and the unplugging of the Tach. I honestly didn’t expect the ICS to play role in this whole hesitation/stumbling issue because I figured the ICS was more of an idle/decel related component - so...the plot thickens here.

However, interested enough - during this whole assessment journey I noticed the my dizzy was at full adjustment (advance) and while I could not designer the marking on the fly wheel, logic would say to bring it a little bit and wow - more power and much less hesitation. Talk about thickening plot... now what does that mean , but better is better so...

Lastly, my bottom vacuum at the HAC is unplugged - what the...

My search for perfection continues, but I couldn't have gotten this far without the help of this community - you guys rock[/QUOTE]
Again, pull your emissions computer and grab a magnifying glass. Read the thread I started on 'reflowing solder points' and maybe you'll find some issues. Tach is connected to the computer. I remember at one point I had crazy spikes in my tach upon startup after work in the cold. It would creep right up to 3k and stay there but listening and feel I knew it wasn't reallyat 3k. All I read pointed toward the computer. I'm very much a novice, quitecluelessso really never figured it out and eventually have done a full top end... still working on getting it 'right' but it's something to investigate.
@mwebfj60 have you read up on this? Sorry can't read back now if you have.... this guy often has another way of seeing issues. He is another of the smart ones I turn too fairly often.

 

[FJStan]

The bottom most port on HAC is atmospheric, and clips onto the main body of the HAC which has the filter, that might be missing based on your description.

Not to divert from the point of this thread but upon closer inspection (not much time spent on this) it does look like the bottom filter port (black part) that is open (that hose is open to atmosphere), but why does it have vacuum?

 

[FJStan]

@mwebfj60 have you read up on this? Sorry can't read back now if you have.... this guy often has another way of seeing issues. He is another of the smart ones I turn too fairly often.

I will certainly take a look. Open to all suggestions. I’m keeping a checklist of things to verify and test.

I know that the Tach disconnect works so I’m going to try to ground the ICS as my next quick fix while I hunt down the root cause.

 

[Gretsch]

I will certainly take a look. Open to all suggestions. I’m keeping a checklist of things to verify and test.

I know that the Tach disconnect works so I’m going to try to ground the ICS as my next quick fix while I hunt down the root cause.

Fixed a similar issue on mine. Engine wouldn't idle periodically, cut out during highway speeds. Grounded the ICS to the carb and its never run better. Been running two full weeks and not a single issue. Like a new truck.

 

[Spike Strip]

The HAC bleeds air into the carb at altitude to lean out the mix. That's the vacuum you feel. That's why there's a crummy air filter. Your HAC may be stuck open if you're below 4000 ft elevation .

 

[FJStan]

The HAC bleeds air into the carb at altitude to lean out the mix. That's the vacuum you feel. That's why there's a crummy air filter. Your HAC may be stuck open if you're below 4000 ft elevation .

I will check the state of the HAC this weekend to confirm. I’ll also look for an explanation re each of the four ports and the bottom filter port. I have a need to know...

 

[NeverGiveUpYota]

I will check the state of the HAC this weekend to confirm. I’ll also look for an explanation re each of the four ports and the bottom filter port. I have a need to know...

That's a good attitude. Also if you don't have them in hand already the fsm link is in my signature. You can pick up the books on eBay as well. Prices range drastically tho.

 

[mwebfj60]

[QUOTEFJStan, post: 11263450, member: 134547"]Negative - I have not touched the ICS.

@mwebfj60 have you read up on this? Sorry can't read back now if you have.... this guy often has another way of seeing issues. He is another of the smart ones I turn too fairly often.

I haven't read through this post yet, I will give it a read soon. I have been hooking up a T to various vacuum systems lately with a gauge in the cab and logging the vacuum state at different driving conditions...
For example, the vacuum switch for the FCS system, I wanted to see if the FCS closed during times other than on decel and at shutoff. The vacuum is manifold equivalent at idle. Under all acceleration types, I can't get the vacuum above 5" no matter how light or heavy I am with the throttle. Makes sense if you look at where the port is in relation to the butterfly. In 1st and 2nd gear cruising at 1500 RPMs, I can get the vacuum up to a level where it would trigger the FCS ..all other gears and RPMs the vacuum is too low. So....
If you want to remove the FCS system entirely from the equation for testing purposes, you can remove the FCS from the carb and replace it with a 8mmx12mm fine thread 1.0 pitch bolt, use the washer from the FCS. You'll have to stall it out when you shut it off and your idle will be rich and rough for a few moments after decel but at least you will know if there's a problem with the FCS system components or not...and you don't have to hack up your wiring.

 

[mwebfj60]

View attachment 1556312

Not to divert from the point of this thread but upon closer inspection (not much time spent on this) it does look like the bottom filter port (black part) that is open (that hose is open to atmosphere), but why does it have vacuum?

OSS broke it all the way down in this thread..
Chasing a vacuum leak

 

[IS2SPICY4U]

My two cents...

1984 FJ60 with 2F purchased April 2016.. Did not have any hesitation/dying idle until late September that year.. since then it has been on/off.. after reading this thread almost a year ago I disconnected the tach.. that made a big difference that lasted a few weeks.. but left it disconnected anyway.. if I connect it back up then the hesitation increases in severity and frequency.. so no tach for me

The one thing I have noticed pretty much from day one is that when the issue is present, it can last for quite a few mins or miles, so having the choke open two clicks helps.. Here is an interesting explanation I found in the CCOT page:

Carb Needs Choke Pulled to Run, FJ40, Q/A
Answer: You may have a vacuum leak. Look to see if a vacuum hose fell off somewhere. Other causes of vacuum leaks include carb mounting bolts backing out or manifold not torqued down...

Jeff Zepp


Answer: Jeff Zepp is correct... I'll bet you it is a vacuum leak. You are describing a classic case of vacuum leak. A vacuum leak causes your carb to see a lean mixture because it is getting too much air (through mixture adjustment AND vacuum leak). Therefore your motor only wants to run if you choke it which is, in fact, making the mixture more rich by restricting air. They are sometimes hard to find but I'll guarantee you have one.

BIG​

Today my air pump seized! So once I replace it, I'll be checking the entire emissions system for leaks and following the Emissions FSM troubleshooting guide, as well as taking some clues from this thread.

I hope this info helps.

 

[FJStan]

I just realized that I never updated my situation on this thread.

I replaced the manifold gaskets, bolts, studs, nuts and vacuum lines. Had the manifolds resurfaced. I pulled the “non essentials” from the engine, but kept the HAC and rerouted vacuum lines with new set-up. I did not recurve the dizzy and no mods to carburetor.

The engine still needs to be retuned - carb settings and timing, since idle is at 1,200 rpm.

As I write this, the stumbling/hesitation has been completely eliminated.

Thank you all for your help and guidance.

 

[NeverGiveUpYota]

Idle at 1200? Which would mean if you disconnect your FCS at the carb then she probably won’t stall out?
I know I still have a leak as frustrating as that is to say... and I’ve got my idle set at about 1k... tach isn’t working accurately and I’ve tried disconnecting my FCS and she won’t stall.
Hoping this weekend to pull her apart and put her back together w/ two gaskets like I should have the last time.

 

[IS2SPICY4U]

One small addition to my post above... I forgot to mention that when the issue is present and I have to pull the choke a couple of clicks, I can feel that there is little to no resistance when pulling the choke nob. Which is interesting, because when the issue is not present, pulling on the choke knob during normal operation there is some level of resistance. Not sure what that relates to. Anyhow...

Update:
The plot thickens...

As I also said, my air/smog pump seized on me last week. I took the opportunity to put new belts in and I got a new (rebuilt) air pump as well. Once I put everything back together and started it up for the initial drive test, the LC started running very smooth, like way back on day one I got her. I even plug my tach back up! I took it for a test drive and had no hesitation/stall issues whatsoever. But that only lasted about an hour.

Although I have fixed the air pump issue, it seems that, now that I have a new air pump, the problem is more persistent. So I will definitely going to have to chase that vacuum leak.

 

[FJStan]

Idle at 1200? Which would mean if you disconnect your FCS at the carb then she probably won’t stall out?

I’ve tried disconnecting it and it DOES stall out.

I think the timing is still advanced too much. I noticed it knocking pretty bad this weekend. It’s odd because it doesn’t always knock, but it was pretty consistent this weekend.

I feel like it’s always something - I’m just going to start attributing everything to “character”

I really like my FJ (aka Stanley) - love driving this thing and the kids get a kick out of riding in it. They know that we can’t take Stanley when there’s salt on the road because it makes Stanley sick.

Mine has ~270k miles so things are bound to start breaking, regardless.

 

[NeverGiveUpYota]

Oooof! 270k is up there. Mines practically a baby at 190k.
Knocking scares me. I’ve not heard that one. If it truly is knocking.. shouldn’t you try to figure it out before you throw a rod?

 

[NeverGiveUpYota]

Hey @FJStan I see your in NJ. The Gotham City Cruisers winter meeting is coming up in Feb, they hold it in NJ. Check them out in the clubhouse section. I’ve never gone but met a bunch of them. Lots of great folks and a number of nice well used 60’s in the group.
@woytovich... pretty sure this guy is in it.