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Improvised oscilloscope probe for Automotive ignition analysis.
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dardosordi:
Hi, I had a similar issue in my Ford EcoSport. The mechanic replaced sparkplugs, leads, carburetor an the failure persisted. I scoped it, used OBD scanner and could not figure it out.  :-BROKE  :horse:  :scared:

The mechanic suggested changing the oil the manufacturer recommended for a thicker one. All fixed.   :-//

Edison:

--- Quote from: dardosordi on January 11, 2019, 09:51:52 am ---Hi, I had a similar issue in my Ford EcoSport.
--- End quote ---
Ford ekosport had so-called hydroshells to control the clearance of the valves - there was an absolute need for oil with a specific viscous number. Other oil = other dynamic pressure = malfunction hydra = changing valve clearance = irregular operation.
Gregg:
Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit.  As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.
An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms.   Not that triple side draft carbs don’t have their advantages; multiple SUs need a lot of fiddling to tune properly and to keep in tune.  Jaguar certainly liked multiple SUs and they ran quite well when in tune.   Single carburetors on inline sixes have always had issues with cylinders 1 and 6 getting a proper fuel mixture at all RPM and engine load conditions due to the longer runner length; generally this is overcome by running a richer mixture to the other cylinders to compensate. 
Next on my list of possibilities would be valve train problems.  Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart.  Are the lifters solid or hydraulic and matched to the cam profile? The oil pump and distributor are driven off of the back portion of the camshaft and wear, misalignment or loose timing chain are possibilities. 
Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.
Jim-0000:

--- Quote from: Gregg on January 12, 2019, 04:45:18 am ---Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit.  As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.........
--- End quote ---
I am glad you agree!

--- Quote ---An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms.   .................
--- End quote ---
The carburettor is a Holley. The intake manifold was fabricated from two manifolds to suit the carb and the head. It was professionally welded and machined flat etc. New gasket fitted. Zero chance of leak, all who have looked at it agree.


--- Quote ---Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart.  ..............
--- End quote ---
Brand new roller rocker gear is fitted (at great expense!). Problem here? Most unlikely I suspect.


--- Quote ---Are the lifters solid or hydraulic and matched to the cam profile? ......
--- End quote ---
I don't know. I would assume the lifter are solid, but not at all sure. I will find out later this week.


--- Quote --- 
Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.

--- End quote ---

Cooling system pressure test has been done a couple of times. The head stud layout tip is one worth some consideration.

Current prospects and plan:

1. Fit solid core ignition leads (plug leads) when they arrive in the mail.
2. If problem persists, do a full oscilloscope investigation of the ignition system. Now we have the equipment available.

Thanks for the posting.
vk6zgo:

--- Quote from: Jim-0000 on January 12, 2019, 09:41:06 pm ---
--- Quote from: Gregg on January 12, 2019, 04:45:18 am ---Now that we know more about the engine being a vintage Holden Grey, we may be able to narrow things down a bit.  As far as “taking it elsewhere” is concerned, that is hardly in the spirit of the EEV blog forum even if it turns out not electrically related.........
--- End quote ---
I am glad you agree!

--- Quote ---An intake manifold modified from the horrors of triple SU carbs to an unknown single carb is certainly suspect for vacuum leaks; which would fit the description of symptoms.   .................
--- End quote ---
The carburettor is a Holley. The intake manifold was fabricated from two manifolds to suit the carb and the head. It was professionally welded and machined flat etc. New gasket fitted. Zero chance of leak, all who have looked at it agree.


--- Quote ---Rocker arm wear and misalignment are particularly hard to diagnose without taking it all apart.  ..............
--- End quote ---
Brand new roller rocker gear is fitted (at great expense!). Problem here? Most unlikely I suspect.


--- Quote ---Are the lifters solid or hydraulic and matched to the cam profile? ......
--- End quote ---
I don't know. I would assume the lifter are solid, but not at all sure. I will find out later this week.


--- Quote --- 
Another possibility, although remote, is head gasket sealing; the head stud layout in the Holden isn’t optimal for keeping a good head gasket seal in performance engines.

--- End quote ---

Cooling system pressure test has been done a couple of times. The head stud layout tip is one worth some consideration.

Current prospects and plan:

1. Fit solid core ignition leads (plug leads) when they arrive in the mail.
2. If problem persists, do a full oscilloscope investigation of the ignition system. Now we have the equipment available.

Thanks for the posting.

--- End quote ---

If it is a grey motor it will almost certainly have solid lifters.
The modifications necessary to fit hydraulic lifters would be so profound that most people would just ditch the "grey" & go for a "red" motor.
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