Rough Idle After Timing Adjust (Solved) (1 Viewer)

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Hello all,

I am doing a little tune-up on my FJ60. There’s been a few things that the PO had done incorrectly, so I figured I better check the timing.

The 60 has a really hard time starting when cold. Had to pump the accelerator pedal multiple times and the whole starting process takes 5mins or so. There is a very small knock once started, but it leaves as the engine warms. I am at 8,500’ elevation and the current temperature is about 20-30* F. Once warmed up, the 60 idles very nicely.

I went out and drove until the engine was warm. I set my timing light to 7* advance, connected it to the #1 spark plug wire (closest to radiator), closed off the 2 vac lines, and shot the light at the timing window. My timing was so retarded that I could not even see the BB in the window. I rotated the distributor CCW until it was lined up on the BB. I tightened down the distributor, rechecked the timing (looked good) and reinstalled the vac lines. The engine sounded great the whole time (albeit with a slightly higher idle)

I shut off the engine and then restarted. Upon restarting, the 60 was severely hesitating/missing and I had to baby the throttle to keep it idling. I realized that I hadn’t set the timing while idling at 950RPM (It was closer to 700-800RPM at setting) so I retarded the timing a bit. With the use of a helper, I got it as close to 7* at 950RPM as I could.

The engine sounded a little more rough than normal, but I went out and drove it around for 6-7 miles. When I get home it was no longer idling at 700-800RPM, but was closer to 950-1000RPM. The engine sounded very smooth and I felt good about it. I went to check the timing one more time (removed the vac hoses) and it was on the money at the BB. Reconnected the vac lines and restarted the engine, and again it was idling rough when restarted. I’ve attached a video of the rough idle, and a photo showing how much “gap” I have on my distributor bolt.

What could be going on? Does it take a while to build vacuum, or should it be instant? Does it matter that I’m at high altitude? I’m going to go out with a water spray bottle and start looking for a vac leak. I’m perplexed that it could be idling so well with retarded timing, but begin having idling issues after the only change I made was “fixing” the timing. This was my first time using a timing light, but the whole job seemed so straightforward, I can’t wrap my head around what I could have done. It seems odd that suddenly a vac leak appears after adjusting timing.

Thanks for the help, M

Video Link:
B3731590-A520-4271-A167-1FD69C377036.jpeg
 

OSS

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Test the HAC system.
Optimum timing can be set without a timing light.
Set the timing by noting engine torque and absence of pinging when under load at 1800-2300 RPMs. Basically, advance it until it pings at any rpm or load then retard it a bit from there until there's zero pinging. - Then check the timing with a timing light if you want to see where it ended up. 7° BTDC is a starting point, not the final word from heaven.
 

mattressking

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Make sure you are timing with all accessories off and vacuum lines disconnected from vacuum advance. Then like @OSS said, test HAC.

My guess is the timing was bumped to mask a vacuum leak. Check your vacuum when cold and hot and see what the variation is. You'll read lower at your altitude so calculate according to elevation. Once you know where you stand with vacuum, make sure you have a good valve adjustment and idle mixture/speed. Also make sure you are adjusting mixture/idle speed once the truck is warmed up and hot. Usually 15min of driving or so will do the trick.
 

Chad717

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Good advice above. I am no expert, and I am just learning as well, so I’m not much help, but I am at 6500 ft elevation and I have been able to bump my timing up to about 10 degrees. I have a timing light that you set the advance on and then shoot the 0 degree mark. If you don’t have that, you can just advance a bit past the BB. This is all after taking care of what was suggested above.
 

MoaByte

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The BB is at 7°. So if you set your light to 7° you are at 14° advance?
 
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Chad717

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Correct. If you time it to the BB at 7*. If you set the light to 7* and time it to the TDC line then you are at 7*. If i was using the BB I would just leave the light at 0. Otherwise I put the light on whatever degree I want and time it to the TDC line.
 

2mbb

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^^this. You shouldn't set any advance on your timing light and then align the pointer with the "BB". Also make sure you put the two vacuum tubes back onto the correct advance diaphragms (inner diaphragm is from carburetor vacuum, outer diaphragm comes from the HAC).

The HAC advances the distributor an additional 6degrees. Once you set the timing with the HAC disconnected, you can connect it back, and use the setting on your timing light to dial back to strobe to see the actual advance you are getting from the HAC.
 

mattressking

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Leave the gun at 0, time to the dot/bb which will put you at 7 degrees. With HAC connected and functioning, that bumps you 6*. If you are adding timing, make sure it’s with everything disconnected.

1611701952533.jpeg
 
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Thank you all so much for the assistance. I was using the timing gun incorrectly, and was indeed setting the timing to 14* advanced.

I re-timed it, correctly this time, and then added the vacuum lines. Total timing advance increased to what looked like 13-14* based on my timing gun dial. This leads me to believe the HAC is working!

It idles better but may be just a hair rough still. I do believe the PO could have had it retarded to mask some other issue. I plan on buying a vacuum gauge tomorrow and will tackle the valve adjustment when we get a warm spell on Thursday.

Thank you all again for the help. This forum amazes me yet again!

M
 

2mbb

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Retarding the timing is a fix for pre-ignition (engine ping). So listen for that as you drive around especially under load. But since you had your timing light set incorrectly on your first attempt do you really know the PO had retarded the timing?

a slightly rough idle could be many things: spark plugs, wires, vacuum leaks, carburetor, valve adjustment.
 

MoaByte

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If you haven't checked your valve lash, do so. A burned exhaust valve can be prevented and you might make it run better. Better get a valve cover gasket before.
At your altitude, you should be able to advance your timing to 9-10° with low or mid octane. Only way to know is try it.
 

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