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Author Topic: Missing Cylinder at idle  (Read 14380 times)

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NoobKevin

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Missing Cylinder at idle
« on: September 04, 2019, 09:43:15 pm »
I believe I have a cylinder that is not firing or I am so unfamiliar with a v6 at idle and I am chasing rabbits and squirrels. Timing light shows all 6 are getting coil voltage. Replaced all injectors. Do I pull plug wires like back in the day or is there a better way?

GTRS Fiero

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Re: Missing Cylinder at idle
« Reply #1 on: September 04, 2019, 09:46:12 pm »
Perhaps using an infrared temp sensor would help.  Check the temp of each cylinder.  A cylinder that isn't firing should be cooler.

Fierofool

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Re: Missing Cylinder at idle
« Reply #2 on: September 04, 2019, 11:23:07 pm »
Pulling wires would identify it, but it can also put a load on the ignition control module, causing it to fail.  Generally the V6 runs rather smoothly.  If there is a misfire, it would be pretty noticeable. 

Check the front bank to be sure you have the spark plug boots fully seated onto the plugs. 
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

NoobKevin

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Re: Missing Cylinder at idle
« Reply #3 on: September 07, 2019, 09:05:17 pm »
#1 cylinder is misfiring badly. Plug is wet and black. Can't tell if it's oil or fuel. New injectors all around. I swapped in a used plug and same misfire. Plenty of spark coming from the distributor. Trust me on this one.  :o

I read compression can be a factor. Could valve lash set improperly also be a factor? Could it cause a compression issue? Guess I should check compression instead of rambling.

GTRS Fiero

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Re: Missing Cylinder at idle
« Reply #4 on: September 07, 2019, 09:08:59 pm »
Yep, check compression.  That will test the seal of the piston/rings/cylinder, the head gasket, and any leak at the valves.

GTRS Fiero

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Re: Missing Cylinder at idle
« Reply #5 on: September 26, 2019, 07:28:21 pm »
What is the status on this?

NoobKevin

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Re: Missing Cylinder at idle
« Reply #6 on: September 30, 2019, 09:55:08 pm »
Hi All,

  I spent last week in Michigan where I worked alongside a car guy. We talked about valve lash and how it’s set. The nuance about setting lash escaped me. I was encouraged to set the base so the rocker just made contact with the pushrod and to not focus on the spinning sensation of the pushrod as the indicator. I used this approach as I rotated the motor one cylinder at a time, rolling the motor four complete rotations. I used the rotor cap as a visual and the increase in resistance to approximate cylinder position. I used the rocker arm movement to find the zero play point. Once satisfied with the zero lash, I set all valves by a 270 degree additional turn on each nut.

I fired it up tonight and it is purring with just a slight idle fluctuation. I haven’t even set the timing. I may have to pull the manifold apart again because the front valve cover may be leaking. But I have that process down to about an hour now. It sounds so cool.

GTRS Fiero

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Re: Missing Cylinder at idle
« Reply #7 on: September 30, 2019, 09:57:51 pm »
Glad to read the progress, and thanks for the update.

The slight fluctuation in idle is probably normal.

Fierofool

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Re: Missing Cylinder at idle
« Reply #8 on: September 30, 2019, 11:00:39 pm »
On a fresh startup after battery disconnect, my car runs horribly.  Runs rich, too, but it sounds like it's got a pretty mean cam in it.  It takes a little bit of driving at operating temperature before the ECM relearns and the engine smoothes out. 
There are three kinds of men:

1.    The ones that learn by reading.
2.    The few who learn by observation.
3.    The rest of them have to pee on the electric fence and find out for themselves.    Will Rogers

GTRS Fiero

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Re: Missing Cylinder at idle
« Reply #9 on: September 30, 2019, 11:02:20 pm »
That must've made for some good times during RFTH.

scottb

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Re: Missing Cylinder at idle
« Reply #10 on: October 01, 2019, 08:23:32 pm »
Charlie has the hotrod, didnt seem to bother my car at all