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

[hank14]

Hey !!! I know what's wrong w/ mine now-I don't have a hose on the end of that pot to the right of the red " Circle" . Where does that hose go to . ? This thread is crucial . I'm going to get hose RIGHT NOW !

If you mean the brass colored vacuum valve- it's the a/c idle up system. The hose goes to a vacuum switching valve to the right of the headlight washer reservoir. It applies vacuum to the carbureator, which increases idle speed to around 1000 RPM if adjusted properly, for when your a/c compressor is running. It's non functional if you don't have a/c.

 

[hank14]

I measured the vacuum while driving on the different ports coming off the EGR modulator today- it's only getting about 4 inches at any point. The VSV is opening at 1500 RPM like the FSM says it should.

I also measured the vacuum at the primary advance on the distributor- only about 8 or so.

Vacuum at the "Gas Filter" on the intake manifold in front (grill side) of the carburetor- only 8-9 inches.

Something's not right.

 

[hank14]

Might as well update this.
After taking my EGR valve off and cleaning it thoroughly with carb cleaner, the bucking and suging has been gone. It's been about 6 months, and I'm starting to get some mild bucking again, so I'm going to pull it and clean it again and see if that helps.

 

[MDH33]

I just read through this old thread and I thought I would add something.

I had the same issues with my '85 FJ60 and did all the checks on the emissions as suggested. It ended up being the TACHOMETER that was causing the hesitation. I disconnected it at the Igniter and problem solved.

Try that first before diving into the emissions stuff and disconnecting your EGR.

 

[x15glla]

Killer!

My 87 FJ60 has the same trouble. Been driving me crazy. I was about to drop $300 on a new carb, Ill try this first. THANKS

 

[BillNoy]

My 86 FJ60 has had a miss or stutter from about 1200 to 2000 rpm since I bought it.

Tried :
Another carb ( it had a Weber on it, went stock)
Desmog, per Jim
Another dizzy
Disconnected tach
Disconnected speedo ( speed sensor within works with "computer"
Disconnected computer
Checked compression, ( all 150-160)

It still stutter/misses
It idles smooth and pulls well above 2000, ( to the 2500 rpm redline )

Can the intake manifold be my last possibility ?

 

[Butt Ugly Chuck]

Can the intake manifold be my last possibility ?

You may have a vacuum leak and intake manifold is one possible source. Spray carb cleaner on mating surfaces and see if rpm's change. Base of carb is another common spot for a leak.
Good luck!
Butt

 

[BillNoy]

Butt

Using WD40 I couldnt detect a change in idle speed spraying around carb base etc. , hooked up a vac guage and went for a drive.

Vac at idle, 19.5....smooth

vac at about 35mph with the engine stuttering....about 15 or 16 with a light peddle ( the terrain was flat), needle steady.

It seems to me that if there was a crack in the manifold I would not see almost 20 inches of vacum at idle, make sense ?

I dont know where to look next, is it possible that the coil/igniter are the cause of the miss ?
Bill

 

[VETTE60]

sounds like the dashpot on the carb. i had the same problem a number of years ago. changed the dashpot, and voila!

check it out and let me know.

 

[Butt Ugly Chuck]

Vac at idle, 19.5....smooth

vac at about 35mph with the engine stuttering....about 15 or 16 with a light peddle ( the terrain was flat), needle steady.

Those seem like solid vacuum numbers. I've got 21" Hg at idle, and 18-19" running in third gear at 2,000 rpm on flat ground with my EGR bypassed and running smooth (more like 12-13" with EGR hooked up properly). Not sure where to send you next, you seem to have covered lots of ground already.

Tried :
Another carb ( it had a Weber on it, went stock)
Desmog, per Jim
Another dizzy
Disconnected tach
Disconnected speedo ( speed sensor within works with "computer"
Disconnected computer
Checked compression, ( all 150-160)

Wish I was smart enough to help, but no doubt someone on here is.

Best of luck
Butt

 

[BlackPanzer]

- Chiming in from the cheap seats here... I had the intermittent stumbling problem and went through a parts replacement endeavor that did not seem to work; new cap and rotor, sparkplugs, inspection and replacement of all vacuum hoses, fuel filter, adjust timing, etc. Nothing seemed to work definitively although the intermittence of stumbling did seem to occur less frequently. The clue came when I noticed it only seemed to do this when it sat after running for a little while (10-15 minutes) and became hard to start. The problem would go away after driving for a bit and then reappear.

I remembered reading something in the forums way back about old intake manifold gaskets creating the similar problem. Sure enough, I replaced the intake manifold gasket and it worked! Apparently the expansion and ultimate contraction of the gasket at cooling was allowing just enough air into the system to cause hesitation. It has not had the issue since.



-Just my twosents for what its worth.

 

[MDH33]

Cracked intake manifold possibly. If you pull your carb and look straight down into the intake, you can usually see where they crack.

 

[jeremiahm]

I just read through this old thread and I thought I would add something.

I had the same issues with my '85 FJ60 and did all the checks on the emissions as suggested. It ended up being the TACHOMETER that was causing the hesitation. I disconnected it at the Igniter and problem solved.

Try that first before diving into the emissions stuff and disconnecting your EGR.

I am always into the quick and easy and have owned enough different vehicles to know the crazy stuff usually fixes the problem.

So I have an 85 FJ60 that is about a week old and has these symptoms real bad. Disconnected the TACH at work today and drove home GOLDEN!!! Very unnoticeable stutter in the 2200 rmp range (assuming since I didn't have a tach!) and no backfire when letting off the gas or down shifting! Later in the evening I was at the store and hooked it back up to see if there really was a difference and it was night and day, barely driveable. Pulled the plug on the tach and all better again.

This is a great tip, try it.

So, what is the Tach doing to cause all of this meyham???? Is it a wicked ground issue somewhere between the coil and Tach this is giving some low voltage feedback to something? That's all I can think of unless the Tach has some other attachments along the way to the gauge. Any ideas?

Thanks for a great Tip,

Jeremiah

 

[TexasAgFJ60]

Chiming in to keep track. Going to start tracing next weekend.

 

[randers32]

hi to all you cruisers and hope i don't waste anyone's time,but my HAC valve has the the larger of the tubes on the bottom just hanging down by my driver side shock....can this be right...i definitely need a vacuum diagram...thanks for any help.... o yah...my stubbles all the way through the lower bands...real bad...just have to feather the pedal into movement..

 

[hank14]

hi to all you cruisers and hope i don't waste anyone's time,but my HAC valve has the the larger of the tubes on the bottom just hanging down by my driver side shock....can this be right...i definitely need a vacuum diagram...thanks for any help.... o yah...my stubbles all the way through the lower bands...real bad...just have to feather the pedal into movement..

The dangling big hose is right- it should be open to the atmosphere.
Buy the factory emissions manual and study it like the Gospels.

 

[Softride62]

Anyone ever consider it could be a clogged (bad) Cat. I have the same issues when cold, and hard to start. Then when engine is running pretty smooth the exhaust is still sputtering

 

[econcepts]

FJ-60 Vaccum Diagram

wow, what a post - covers years - well I have a reproduction of the original 1982 FJ-60 vaccum diagram and this seems like a good place to post it. Enjoy!

 

[Spike Strip]

That's a nice version of that diagram... Thanks for sharing.

 

[rover67]

great post, gonna check more stuff tonight!