stumble at cruising speed

dallen341

 
 
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Jan 28, 2004
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Claremont, CA
Need your help!

1987 FJ60, Jim C carb, new plugs, cap and rotor in clean condition, Decel fuel cut vacuum switch working properly, HAC circuit working properly., fuel level in carb proper at idle and at high rpms. At idle, purrs like a kitten.

However, accelerating this is an occasional stumble and there is an intermittent stumble at 2,000 rpms and higher.

Any thoughts?

Don
 

dallen341

 
 
Joined
Jan 28, 2004
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Claremont, CA
timing is spot on and valves adjusted less than 1,000 miles ago. Fuel filter newer but can't recall exactly when replaced. i suppose a new fuel filter is in order.

Don
 

MDH33

 
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Jul 5, 2005
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Ames, IA
the 2000 RPM stumble / hesitation was discussed in an earlier post. Try a search.

Is all of your emissions equipment in place? Someone had good luck correcting the problem by disconnecting the EGR. I'm having exactly the same problem so I'll follow this thread and post anything if I figure it out.
 

MDH33

 
Joined
Jul 5, 2005
Messages
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Location
Ames, IA
Figured out the hesitation / stumble problem on my 85 FJ60, stock 2F with all emissions gear in place. There is a vacuum splitter that comes up out of the intake manifold right in front of the carb. It's called a Gas Filter (not to be confussed with fuel filter). This splitter / filter was clogged. After cleaning it out and replacing a few cracked/dried vacuum lines my 2F is running great with no hesitation.

This was after a carb rebuild, checking all the main emissions valves, new PCV, fuel filter, air cleaner, valve adjust, tune up, cap and rotor, new wires, plugs... and it still hesitated. If I could get rid of all the emissions stuff I would. Seems like it is the cause of most poor running 2F's. Unfortunately I have to pass the strict emissions tests here in Denver, so it stays. I'm glad it is finally running and hopefully will pass its next test.

:cheers:
 

dallen341

 
 
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Location
Claremont, CA
I just figured mine out also. It's the EGR system. Since all of the components are newer, I suspect that the 2-1/2" flowmaster exhaust system does not provide enough back pressure in the exhauste system to cause the egr modulator to work properly. Just a theory and don't plan to verify it. However, I do know this is a common cause of egr faults on Chevy TBI applications that run exhaust systems with low back pressure. On Chevy's, according to Turbo City, the computer performs a EGR system test (very quickly) and if egr back pressure is too low, it throws a code.

Don
 
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Jul 21, 2004
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Colorado
I've had a similar problem where the the engine stumbles for a split second on my 60 and a buddy's 40. New vacuum lines throughout cured both of them.
 

MDH33

 
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Jul 5, 2005
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Ames, IA
I'm tempted to replace all the vacuum lines, valves and check valves, but without an emissions FSM I'm hesitant to rip out completely that spiderwebbed mess under my hood.
 

loeky

 
Joined
Mar 24, 2005
Messages
753
Location
Boulder
i've got what you need. i think i've posted the emissions pdfs before which have all the routing info you'll need in nice, zoomable pdf style:

http://www.sweetillusions.org/toyota/6.pdf
http://www.sweetillusions.org/toyota/7.pdf

here's a couple pics for good measure. red bling!
http://www.sweetillusions.org/toyota/fj60_vacuum_2.jpg
http://www.sweetillusions.org/toyota/fj60_vacuum_1.jpg
http://www.sweetillusions.org/toyota/fj60_vacuum_routing.gif

it's super easy and a cheapie fix that makes a large difference in overall running.
 
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Take one off, cut a new line the same length, install, & then move to the next one. I learned the hard way not to try taking a few off at a time and then go off memory. The FSM diagram is good to go through anyway since lots of 20 year old Cruisers have misplaced lines from previous owners.
 
Joined
Feb 7, 2005
Messages
361
Location
Leucadia (San Diego)
gulp3000 said:
Take one off, cut a new line the same length, install, & then move to the next one. I learned the hard way not to try taking a few off at a time and then go off memory. The FSM diagram is good to go through anyway since lots of 20 year old Cruisers have misplaced lines from previous owners.
Is the tube length important?

Bob

1977 FJ40 "MuMU"
1982 FJ60 "Clifford"
1992 FJ80 "Tubbs"
 
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