FJ60 stumbling and bucking at highway speeds (2 Viewers)

[Chad717]

Hi all! Finally picked up an FJ60 on Friday and I am super pumped. I have pics that I will share when I get back from work on Monday. Meanwhile, a question.

I live in Colorado and the PO took the time to get it resmogged, but did not get it through emissions. In the process of doing this, the POs mechanic put smaller jets in the carb to try and lean it out. Every time I drove it when looking at it it ran great.

I picked it up and drove about 20 minutes down the highway and it rand and drove great. I then jumped back in it about an hour later and about 5 minutes into the drive at highway speed it started to stumble and buck. I would let off the gas, it would smooth out and then a few minutes later it would do it again. I could go through all 4 gears just fine, but around 2500 rpm it would start again.

I pulled over and called the POs mechanic, he was convinced it was the smaller jet and that it was to small. He suggested pulling out the choke, which I tried, but it didn't make any difference. I made it most of the way home on back roads cruising about 45 mph just fine, however the problem got progressively worse. The engine would start and idle just fine, but under a load it would stumble and buck. Didn't matter what gear I was in at this point. I gave up and called a tow and had them drop it off at my house.

I have a theory and you all can tell me whether it sounds right or wrong. I am willing to change the jet, but because it ran so well at the beginning I am wondering if it is something else. Maybe the fuel cutoff switch or whatever it is called? I figure maybe the wiring is bad and as it heats up the resistance increases and causes the problem. I am gone for work, so I haven't had a chance to get under the hood. I will on Tuesday.

I'm a novice mechanic, done a moderate amount of work on my other vehicles, I really would like to work in this cruiser myself and really get to know how it works. Any suggestions I will take. I also would love to desmog it, but because of where I live in Colorado, this isn't an option.

Thanks in advance, I appreciate the knowledge and help here!

 

[NeverGiveUpYota]

Acc pump is my first thought. Did he replace it w/ a new one after screwing w/ the carb? Could be you have crud blocking the jets too. @mwebfj60 this guy is generally spot on w/ carb issues.

 

[OSS]

When troubleshooting (anything) always start with the easiest & cheapest possibilities first. Even just to rule it out.

Replace the fuel filter even if it looks clean. It could be restricting fuel at higher flow rates.

Consider the possibility that the fuel pump isn't pumping enough fuel during high demand.

The 2F with its high altitude compensation system shouldn't need a smaller jet in the carb to run good at 6000 ft. The 2F can run fine at 8000 feet and higher with the stock jets. I used to live at a ski resort & the 60 ran great up there, though with less power than at sea level of course.

Make sure that the cool air intake hose that connects to the air cleaner neck is installed.
Definitely put the stock carb jet back in and give it a test drive. Then go from there.

 

[Landpimp]

Things I have found cause that

Vac lines hooked up wrong(pics of your engine bay will help)
Egr not working(bypass)
Any one of the vac switching valves(test)
Junk in the carb (do okie rebuild )
Idle.selnoid , don't think so in your case)
Fuel, filter, pump,maybe timing.

Seeing how it was re smoged something in all that junk not hooked up or working right would be where I would concentrate on.

 

[Chad717]

Thanks NeverGiveUp and OSS. OSS, that is pretty much my exact plan of action. When I get back on Tuesday I'll let you know how it goes. I don't even know if it is a Weber or what's the other one? I assume a package of jets will fit both?

 

[Chad717]

Thanks landpimp! Can I bypass EGR and still pass emissions? And secondly, forgive my ignorance but what is an "okie rebuild?"

Thanks again for the help

 

[Chad717]

Ok never mind it's an Aisin

 

[mattressking]

Thanks landpimp! Can I bypass EGR and still pass emissions? And secondly, forgive my ignorance but what is an "okie rebuild?"

Thanks again for the help

You can bypass by pulling the vacuum line and capping off the EGR. No parts removed. Doubt you'd pass emissions, that stranger things have happened.

Okie is probably carb rebuild. I've seen that mistake before.

 

[Chad717]

Thanks mattress king that makes sense. I'm at 6500 feet altitude and probably will be driving up to the mountains a lot with this FJ. I think the jet that is in it now is a 1.45 and I was gonna change it back to 1.47.

 

[Chad717]

Just got home from work and here is a quick pic of the engine stuff... I will get some better pics. I have the emissions manual and I'm going to start tmrw tracing each vacuum hose to make sure they are in the right place. just wanted to post this in case anyone saw a glaring problem. It seems to be pretty clean and well done so we will see!



oh and here is a gratuitous pic of the cruiser because i am so excited to join the club! Love this thing already!

 

[87CRUSR]

A 60....nice choice.

 

[Chad717]

Quick update for ya'll. Using the emissions FSM I traced most of the vacuum lines today. There were only a couple of problems I found, and i'm not sure if any of them are enough to cause my problem.

First, the vacuum lines to the distributor were switched. The one with the VTV On it was on the front, not the back... the pic is after I switched them. BTW it is hard to tell in the FSM which way the VTV is supposed to be, I mean for flow as far as the A and B side.

As I worked my way through the emissions manual I found that they had not replaced the BVSV's when they resmogged it. I am tempted to leave it this way if I can get away with it, unless it could cause some issues, I guess they are just temp sensors basically, opening and closing the vacuum for hot or cold engine? Anyway the PO just routed the vacuum lines like this if you can see from the pic

basically just bypassing the BVSV's and so I guess the engine operates as if those are always open...

Lastly the bottom hose on the ABV was disconnected

So I reconnected it.

I also found a really dirty EGR Vacuum Modulator filter...are these easy to procure or no? Local parts shop type of thing?

Thats all I found for today, but it seems to me that these are minor problems, probably not causing my issue.... HOWEVER, I did take it out for a short drive tonight because I am to scared to get to far away. It started and ran great, even at Highway speeds...there was one moment of slight hesitation, but it could have been mental on my part. I'm still not sure how to tell if it is fixed, because the problem showed up after 30 minutes plus of driving when I picked it up...so I guess I'll have to risk getting stuck again.

Thanks for looking at my pics and all the help!

 

[CaptClose]

Kudos to you Chad, for actually taking the time to read through the emissions manual and figure out your emissions system.

 

[Chad717]

Ok quick update. Last friday before I left for work I ran the truck through the emissions station where it failed with high HC and high CO, so I have kind of combined my two problems into one. I understand the gas tank tricks (sorta), but i'm hoping in the course of working through the emissions, I can also fix my stumble.

Today after a long 4 days of work I finally got a chance to fiddle around a bit, although I didn't have a ton of time. I started the truck and took the air hoses off the air cleaner, the driver's side hose had some suction, although not much, but it was sucking air. I then unhooked the air bypass hose and confirmed it was not blowing air.

I also just out of curiosity turned the truck off and disconnected the green plug by the carb, the FCS? if i'm not mistaken. I turned the power back on and the confirmed that when i plugged it back in I heard a clicking. So that seems to work, I was kind of hoping that that would help my stumbling issue, but on to the next.

I plan on starting with the AI system and walking through that using the FSM, after that, I am going to remove the EGR valve and inspect it, although I should probably plug the vacuum lines to the EGR and run it to see if that corrects my stumble.

I'll let you guys know how that goes, and I'll gladly take any suggestions! Thanks again for all the help.

chad

 

[DFXR]

To bypass the EGR, pull the vac line that runs from the EGR vacuum modulator to the top of the EGR valve. I plug both the open vac line and the open nipple, though I'm not sure it's necessary. Then swap the two vac lines at the distributor sub-diaphragm - basically you'll be going back to the incorrect orientation that you discovered and pointed out a few posts back. I (and many others) have run like this for fairly long periods. If you get any pinging, upgrade to a higher octane gas.

FWIW, it's possible to pass emissions testing with a bypassed EGR. It depends on how engaged or lazy the tech is with regards to the visual inspection, and checking the timing. Of course the prudent thing would be to diagnose and fix it...

 

[mwebfj60]

Do you have a mighty vac? If so, check all your vcvs and vtvs, advance diaghragms, HAC, All diaghragms on the carb, and the list goes on. You have the advance VTV in corrctly, the flow is restricted from colored side (blue in this case) to black side and free flowing from black to blue. Slows down the vacuum advance curve. Maybe it was switched because the primary diaphragm (inside one) is bad..pretty common fail point. Sounds like you're going about it right, just be methodical and step through the emissions manual testing each system. If you look at each system individually it's not really that complicated.

On a side note, with the BVSVs bypassed, you won't have a choke in the Winter. You will have the fast idle but as soon as you start up, the vacuum from the fuel filter should pull the choke opener diaghragm (bottom right on carb).

 

[rustybucket]

Possibility the inside of the distributor is arcing across the terminals from moisture build up or from carbon tracking. That will cause backfiring. Jet inside carb could be another problem. Put a vacume guage and run at highway speeds tell us the readings. Also, put a 5 psi pressure guage on exaust to see if its partially plugged. Should read no more then 1 or 2 psi pressure.

 

[Chad717]

Thanks all, @mwebfj60 I did not know that about the BVSV bypass. Interesting. Well today I bypassed the EGR and took it out for a drive, ran great, until I was shifting into third going up a hill and got into the gas a bit, it started to stumble around 2000 rpm, I let of the gas and gently pushed back in and kept going. It stumbled a few more times after that, so I guess the stumbling problem is not related to the EGR, although I guess the emissions problem could still be. I still feel like it is a carb issue, PO said it was rebuilt recently, professionally, but who knows...

 

[rustybucket]

So is the truck shifting at the right shift points for the right speed of the truck? Take off the distributor cap and look inside the cap for arcing between terminals. EGT would not cause this because it opened up under maximum load. It introduces some exhaust into intake to suppress NOX

 

[Chad717]

Well I'm shifting it and it works pretty well, it just seems to hesitate occasionally. That makes sense about the EGR, and it is a good suggestion about the distributor cap. I got to be honest I'm such a newb that I'm worried about taking the distributor cap off and messing up the timing, I still havent figured out how to set the timing on this truck yet. One of the many things on my list.