Misfire?

[atkinson40]

Truck seems to missfire....sometimes?

 

Starts fine and idles, but...If I look at the tailpipe, I hear a slight Pffft, Pfft and a tiny puff of white smoke coming out to corespond to this.

 

Engine has a slight tremble indicating a kinda?? miss??

 

Does not go away if I increase the throttle.  I've hooked the timing light to all wires, and no sign of a miss.  Pulling the wires off one at a time causes the engine to run worse.

 

Is there any way to isolate the cylinder?  Thanks kevin

[datzenmike]

Take the plugs out and compare?

[banzai510(hainz)]

ck spark plugs. reck the valave lash.

adjust the mixture

 

these re all best guess on my part

[racerx]

also check sprak plug wires, cap...

[banzai510(hainz)]

also check sprak plug wires, cap...

 

 

He had rebuilt this motor so I assume all this stuff is new already. Plus if it runs worse when the wire is pulled shows that its working. Unless a really old plug wire and its shorting to ground or to another wire. This can bee seen at night is a spark crosses wires

 

water under dizzy cap?
 

[racerx]

sounds similar to exp. I had before and noticed that one of my spark plug wires that goes to cap was corroded and was greenish in color.

[atkinson40]

Take the plugs out and compare?

 

Thanks Mike,

 

Left To Right.  1-4.  I think OK?  Kevin

[atkinson40]

ck spark plugs. reck the valave lash.

adjust the mixture

 

these re all best guess on my part

 

Plugs shown above. Mixture adjusted. New Cap/Wires. Need to reck lash.

 

Thanks Hainz,   Kevin

[atkinson40]

sounds similar to exp. I had before and noticed that one of my spark plug wires that goes to cap was corroded and was greenish in color.

 

I was thinking this morning....If it was particular to one cylinder,  at 700RPM, it should happen more than 10 times a second.

 

I don't think that's happening.  Maybe once a second, or less.  Maybe it's something intermitant?

 

Thanks Racerx,  Kevin

[atkinson40]

I'm bored waiting for the power booster to come in.

 

Found a couple of air cleaner lids at the JY and made me an old school cleaner. :w00t:

 

[banzai510(hainz)]

I had a pumped up L20 and in 1st gear 7K rpm it would start cutting out.

 

spark plugs look perfect to me. alot better than mine.

 

That OCD is gonna kill you!!!!!!!!!!!!!

[atkinson40]

That OCD is gonna kill you!!!!!!!!!!!!!

 

Thanks hainz, :w00t:

 

I hope not, :rofl:   Checked the vale lash.  Set to 8/10 cold.  Now they seem to be making way too much racket.

 

When I get the power boster, I'm going to put it in and drive it for awhile....see what's up.

 

Thanks kevin

[banzai510(hainz)]

this is just me but I do my lash .006 and .008 cold

[racerx]

atkinson40..like your filter set-up.  Have you adjusted your carb to base setting..as far as white smoke is this during intial start up and/or when cold.  Cars will blow white smoke specially if very cold.  Did your car ever overheat?  You may want to check your oil dipstick or oild cap, just to be sure..that your headgasket is okay.  If color of oild is choc. milk then good indication of bad HG also you can smell coolant coming out of exhaust. Did you do a compr. check?

[atkinson40]

this is just me but I do my lash .006 and .008 cold

 

Yesterday I went back and readjusted to a really, really tight 8/10.  Maybe 7/9.  Sounds much quieter. Thanks kevin

[atkinson40]

atkinson40..like your filter set-up.  Have you adjusted your carb to base setting..as far as white smoke is this during intial start up and/or when cold.  Cars will blow white smoke specially if very cold.  Did your car ever overheat?  You may want to check your oil dipstick or oild cap, just to be sure..that your headgasket is okay.  If color of oild is choc. milk then good indication of bad HG also you can smell coolant coming out of exhaust. Did you do a compr. check?

 

 

Just rebuilt the motor.  Less than 10 miles.  Maybe just needs to break in.  I'm going to relax. 

 

Run it for awhile and see what's up. 

 

Maybe the slight tremble is normal and  I'm just plumb LOCO!! :w00t:  

 

When I get the booster in,  I'll see if I can run it by someone else to see what they think.

 

Thanks kevin

[banzai510(hainz)]

dont expect a 2012 motor out of a 1960s tech.

[atkinson40]

dont expect a 2012 motor out of a 1960s tech.

Thanks Hainz,

 

Got the booster and sucked on the vacumm.....it holds.

 

Drove it to the carb man to show him where the 32/36 he sold me ended up.

 

Without me asking he said "running a little rough" 

 

He went into his shop and dug out a tool he could pull the wires with at the cap.

 

After pulling them one by one, his diagnosis was "#3 ain't happy".

 

When I told him about about the pfft,  pfft misfire/noise coming out the tail pipe he said "lean misfire"

 

This is an old grizzly geezer that's been working these engines for about a billion years.

 

Kinda gotta lend some credance to his advise.  "Chase what's wrong with 3"

 

Good compression.  Spark almost big enough to weld with.  Timing good.  Plugs look as shown above.  Has gas.

 

Gonna revisit a vacumm leak in #3 intake runner.  Maybe the manifold/head mating surface is fail.  Dunno.

 

At least now I feel OK it's not just me thinking #3 is fail.    Thanks kevin

[datzenmike]

 

Thanks Mike,

 

Left To Right.  1-4.  I think OK?  Kevin

 

Plug #3 does look darker.

 

 

Just rebuilt the motor.  Less than 10 miles.  Maybe just needs to break in.  I'm going to relax. 

 

Ten miles is not near enough. Check the oil and water and take it out on the highway and hammer it!!! Keep between 2,500 and 4K revs. Accelerate in 3rd from 40-60 full throttle and let slow down by itself. Repeat 15 - 20 times. Keep eye on temp (it should be ok) You want to force the rings hard against the newly honed bore. This quickly wears the high points off and provides a better seal for the rings. Make it work hard! Constantly change the RPMs. In town accelerate quickly where it is convenient and don't lug the motor... keep revved up slightly. Try not to run at a steady RPM, keep changing it. At 50 miles change the oil and filter to get rid of the microscopic metal debris. Use ordinary motor oil do NOT use additives or a 'break in oil'

 

After a few hundred miles check the plugs during an outing when they give a fresh reading..

[atkinson40]

Plug #3 does look darker.

 

 

 

Ten miles is not near enough. Check the oil and water and take it out on the highway and hammer it!!! Keep between 2,500 and 4K revs. Accelerate in 3rd from 40-60 full throttle and let slow down by itself. Repeat 15 - 20 times. Keep eye on temp (it should be ok) You want to force the rings hard against the newly honed bore. This quickly wears the high points off and provides a better seal for the rings. Make it work hard! Constantly change the RPMs. In town accelerate quickly where it is convenient and don't lug the motor... keep revved up slightly. Try not to run at a steady RPM, keep changing it. At 50 miles change the oil and filter to get rid of the microscopic metal debris. Use ordinary motor oil do NOT use additives or a 'break in oil'

 

After a few hundred miles check the plugs during an outing when they give a fresh reading..

Thanks Mike

 

I've put a few more miles on it since that post.  I read your prior responses on breakin and I'm leaning on it hard.

 

I've had it up over 80MPH on the freeway and cruise it about 70MPH.  Streets are up to 50 like you said.

 

Next up is oil change.

 

What is suspect to me is that I've been fighting #3 cylinder since before the rebuild. 

 

The only common items are the dizzy base,  head(been rebuilt),  Intake/exhaust manifold.

 

I didn't break the intake manifold/head apart when I rebuilt.  I'd done that shortly before and had both mating surfaces resurfaced.

 

I looked at the plug wires in the dark this morning to see if I could see a short to ground.  Nadda. 

 

I've been pondering how to dribble a bit of gas in #3 intake runner to verify a lean problem/vacumm leak, but short of drilling a hole in the runner, I'm stumped.

 

I've squirted carb cleaner all around the runner to head junction, and got zip, but this doesn't check hidden exhaust to intake port leak possibility. 

 

I could pull the intake manifold off and inspect around #3 runner, but that means a new gasket, and I'd like to break my brain a little more seeing if I can prove that's it.

 

I could also pull #3 wire, let it run a few seconds, shut it off and pull #3 plug.  I think it should be wet.  If it's not, then that will kinda point in the lean mixture direction.  I think.

 

Thanks kevin

[datzenmike]

Lean mis fire, if at all, is only at idle. Once revved it doesn't do it does it?.

[atkinson40]

Lean mis fire, if at all, is only at idle. Once revved it doesn't do it does it?.

 

 

No Mike

 

Thanks,  Kevin

[atkinson40]

No Mike

 

Thanks,  Kevin

 

Retraction. :blush:   Yes it does.   I changed the oil and ran it. 

 

If I put my hand on the motor I can still feel the misfire as I rev it up.

 

It's a small periodic tremble, but still there.

 

Please help me understand Mike, Why wouldn't a lean miss be there as I rev it up?

 

If #3 runner is sucking air, wouldn't it still suck air as it's rev'd?

 

I did figure out a way to get a bit of gas in #3 runner as my brain was waking up in bed.

 

There's a vacumm port at the appex of the runners.  It used to go to the old air cleaner.  I plugged it.

 

I think I can pull the plug and fit a tiny tube of some sort in that hole and into #3 runner.  Then gas down the tube.

 

See what effect this has.  Thanks kevin