FJ60 struggles to rev past 2500rpms

[callmeahab]

Hi all, newbie here and my first post - apologies in advance for forum learning curve. Located in St Petersburg Florida.

I recently purchased an 85 FJ60 (225kmi mostly NM and Texas driven) which was desmogged at some point by POs but sat for 2 yrs driven little.

It ran ok in test drives and very short drives after purchase. It had/has a rough idle and get worse after 20mins of driving to where it would stall at idle but at speed it had good power and acceleration. I checked the fuel filter (clean) and fuel pump (did not replace but looks newish) and gas is going to the carb.

I decided to have the carb rebuilt by Ron at Performance Carburetor in Clearwater FL. to rule out a gunked up carb. Ron said that the secondary diaphragm was in ok condition and did not replace it. Ron did replace the accelerator plunger. I reinstalled the carb which was challenge to get the linkages correct etc but I believe its installed correctly.

However now its struggles to rev past 2500rpms in neutral and drive. (The rough idle has not changed either - same symptoms but I can't test drive it due to rpm issue.)
I have tested w/ carb cleaner for vacuum leaks (initially there was

I have reviewed a few threads here but no clear resolutions.

Any advice and help would be greatly appreciated.

 

[MoaByte]

Firstly, how old is that fuel? Run a few tanks of quality gas from Texaco or Exxon. That did wonders for mine when I first got it

Then you need to verify your valve lash and adjust as needed. It isn't hard to do but very important. While you are in there, check your spark plugs, distributor cap, rotor and plug wires. Also verify that your vacuum advance is still working, might be stuck or your diaphragm was used to much when it was new.
Bring pictures and get back here if you need help.

Might want to order new grommets and gasket for the valve cover ASAP.

 

[callmeahab]

@MoaByte - Thanks for these pointers. Yes I added a full tank of non-ethanol gas.

@MoaByte when you say "diaphragm" are your referring to the 2ndary diaphragm on the carb?

Since the rev struggled right after carb rebuild and reinstall I was thinking it was related to the rebuild and the diaphragm was damaged/impacted.

 

[MoaByte]

I was referring to the diaphragm in the vac-advance. You can suck on the hose and feel it working, it shouldn't leak.
I am carb challenged. The carbs are a marvel of engineering and I struggle with even CVT motorcycle carbs. I'm sure someone will chime in to help.

 

[callmeahab]

Another symptom that I neglected to include: it does backfire a bit when revving.

 

[tmxmotorsports]

Another symptom that I neglected to include: it does backfire a bit when revving.

Verify timing is correct

 

[MoaByte]

Could be vacuum leak, partially clogged main jet or timing advance.

 

[MoaByte]

Or even that accelerator diaphragm.

 

[MoaByte]

Did you know that you can use a squirt bottle with soapy water to find vacuum leaks? Much safer than using carb cleaner or propane.

 

[CruiserTrash]

Baseline first, otherwise you'll chase your tail. Like @MoaByte says: spark plugs, valve lash, timing, make sure the distributor advance diaphragm is working. Add to that a new air filter & oil change - amazing what those two can do to a truck that's been sitting. Replacing the fuel filter already was a good move. Follow the factory service manual for all of this. It's available for free under the "Resources" tab at the top of ih8mud. I'd also thoroughly verify the "desmog" work. Lots of people rip out a bunch of vac lines and call it good, but are really creating more problems. the factory Emissions service manual is your friend here.

Couple other questions: Do you have a catalytic converter? After all of the above is done, you may find the cat is plugged partially or fully. Baselining will help drivability in the long run anyway, so it's not wasted time. I'd also verify that your carb is sealing to the intake manifold properly, and that you don't have any leaks between the intake/exhaust manifolds and the head.

 

[cruisermatt]

before anything, verify you have are achieving actual mechanical WOT. It is possible to swap the linkage rods with each other (they are different lengths) and only get about 60% throttle opening. Have someone depress the gas pedal while you watch (engine does not need to be running) and make sure the butterflies are fully opening

 

[LAMBCRUSHER]

verify no vacuum leaks first. check all vacuum lines for good connections/ no split ends, no cracked vacuum devices. one way to do this is to do an okie rebuild.

okie rebuild- cover your hand with a welding glove, get the rig running at high idle, then choke it with your gloved hand till it dies. do this several times. IF it does NOT die, you have unmetered air entering the system (vacuum leaks).

 

[tmxmotorsports]

before anything, verify you have are achieving actual mechanical WOT. It is possible to swap the linkage rods with each other (they are different lengths) and only get about 60% throttle opening. Have someone depress the gas pedal while you watch (engine does not need to be running) and make sure the butterflies are fully opening

Been waiting for you to respond to this thread was going to recommend your shop to take a look if that is in op budget or if your shop was even close to him.

 

[klinetime574]

If the struggling to get over 2,500rpm started after the carb rebuild it sounds more likely the linkage may have been installed incorrectly. Also check the pedal stop bolt inside the cab (although unlikely the issue).

Rough idle in your situation shouldn’t be the carbs fault unless something was done incorrectly or it needs adjustment. To elaborate, if the rough idle was present before and after rebuild it’s probably not the carb. I will say it is interesting that the screws on the air horn are hex head black. Factory would have been JIS phillips hardware.

Another note: the wires for the fuel cut off solenoid look like they might be interfering with the throttle linkage. Factory routing ran it under the air cleaner and around to the driver front of the carb. Also make sure it is plugged in (can’t see in pics).

My vote: verify mechanical WOT and check timing.

HTH

 

[callmeahab]

Thanks all for your guys great feedback.

@cruisermatt @klinetime574 - I was thinking this too, that I reinstalled incorrectly.

re: idle solenoid circuit, I did route it the other way b/c it was hanging close to heat shield. - will put back to orgi.

Can someone post a photo of how the carb linkages should look?

 

[callmeahab]

To be more specific about throttle issue: from 1st to 2nd gear it struggles to pass 2500rpms, then if I push gas pedal down all the way it will rev to over 3k rpms, from 2nd to 3rd it will oscillate from 2500k rpms to well over 3.5k rpms, in 3rd it will tug tug to 3k rpms but it won't decelerate, meaning it will keep rpms high even taking foot off gas pedal.

 

[WartHog73]

Thanks all for your guys great feedback.

@cruisermatt @klinetime574 - I was thinking this too, that I reinstalled incorrectly.

re: idle solenoid circuit, I did route it the other way b/c it was hanging close to heat shield. - will put back to orgi.

Can someone post a photo of how the carb linkages should look?

This link has some pics and helped me diagnose my rig. To this day I don’t know how the rods got switched (maybe someone messed with it when it got painted but it wasn’t me). It was like night and day once fixed. However I didn’t have any of the other issues you are having nor the decel backfire. I would keep looking for a exhaust leak and vacuum leak once you verify correct rod positions.

82 fj60 looses power going up hills

i'll take a photo this evening and post it here for you with the part circled for ease of use.

forum.ih8mud.com

 

[callmeahab]

This link has some pics and helped me diagnose my rig. To this day I don’t know how the rods got switched (maybe someone messed with it when it got painted but it wasn’t me). It was like night and day once fixed. However I didn’t have any of the other issues you are having nor the decel backfire. I would keep looking for a exhaust leak and vacuum leak once you verify correct rod positions.

82 fj60 looses power going up hills

i'll take a photo this evening and post it here for you with the part circled for ease of use.

forum.ih8mud.com

@WartHog73 Thank you! I will review and compare ASAP.
Even when rods were incorrectly switch did it seem like the throttle was opening etc?

 

[WartHog73]

Unfortunately, I didn’t have @cruisermatt for guidance initially so I basically got everything else up to par before I realized the real issue but the rig ran great. It was just I had no power especially on hills - it was embarrassing lol.

I can now hit 80 and that is with a RTT, bowfin rack, drawers, and 4plus bumper. I need the right incline and wind assistance too but you know what I’m saying!

 

[WartHog73]

@callmeahab - here is another link with some good pics in case you need additional. Hope it’s an easy fix and PO’s didn’t do too many ‘odd’ things…!

1987 FJ60 throttle linkage

So, I had some down time and installed my JimC Aisan carb. I cruised through the reinstall with numerous beer breaks and I got cocky. I got it all buttoned up and notice the pedal is almost all the way on the floor. What gives? Is this system adjustable at all? I will post photos as soon as I...

forum.ih8mud.com