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4 Cylinders not working

Imesha

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hi ,
i posted earlier in regards to my SS (AFM) running like ****. Its lacking power and almost stalls when in gear.

Attached are the codes i got from a bluetooth scanner. Is there also a difference between a constant check engine light and also a flashing check engine light?

In regards to the purge solenoid i have replaced it and still no luck.

The car is a SS-V L76 (AFM) automatic with 1 7/8 pacemaker headers to no cats to walkinshaw catback.

The car reads that its in 8 cylinder mode however it dosnt feel like it and the codes indicate that the 4 cylinders are deactivated.

any information regarding this matter would be greatly appreciated.


 

lmoengnr

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Going by the codes and your descriptions, it looks like DOD is always on.
Cyls 1+7, 2+4 have collapsible lifters, they pump up with oil pressure controlled by solenoids.

Does it seem to be running on 4 cylinders?
 

Imesha

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Going by the codes and your descriptions, it looks like DOD is always on.
Cyls 1+7, 2+4 have collapsible lifters, they pump up with oil pressure controlled by solenoids.

Does it seem to be running on 4 cylinders?
It is very possible that it's running on just the 4 cylinders because of the lack of power.

My understanding is that the lifters are pumped with oil once the computer sends the signal to the solenoid. If I was to assume the solenoid is stuck would the computer pick up it's stuck in 4 cylinders mode ( because it's showing 8 cylider mode).
 

lmoengnr

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It is very possible that it's running on just the 4 cylinders because of the lack of power.

My understanding is that the lifters are pumped with oil once the computer sends the signal to the solenoid. If I was to assume the solenoid is stuck would the computer pick up it's stuck in 4 cylinders mode ( because it's showing 8 cylider mode).
I would be sure that the PCM would be commanding 8 cyl mode most of the time, it will only run in DOD mode under certain circumstances.
I don't have enough knowledge of the AFM/DOD oil circuit, but would assume that the oil flow would be connected to the lifters on cylinders 1+7, 4+6.
Fail safe would be to always pump up, I would think that a solenoid controls the outlet of this oil circuit, only opening when AFM mode is commanded.
I'm not sure what would happen if that failed to close...

Has the car been tuned?
 

Imesha

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The car hasnt been tuned, I called holden but they couldn't tell me anything on how the mechanics of it would fail without having the car there.

From what I've read when 4 cylinder mode is activated the cam still rotates but the valves for those certain cylinders remain shut. The computer also cuts fuel and spark to those cylinders, with the assumption mine are stuck closed but the computer still in 8 cylinder mode I feel like those cylinders are just being pumped with fuel and spark without the intake and exhaust valves operating. if so this can't be good.
 

426Cuda

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The car hasnt been tuned, I called holden but they couldn't tell me anything on how the mechanics of it would fail without having the car there.

From what I've read when 4 cylinder mode is activated the cam still rotates but the valves for those certain cylinders remain shut. The computer also cuts fuel and spark to those cylinders, with the assumption mine are stuck closed but the computer still in 8 cylinder mode I feel like those cylinders are just being pumped with fuel and spark without the intake and exhaust valves operating. if so this can't be good.
If it is running in 4cyl mode 100% of the time, I highly doubt those cylinders are still getting fuel and spark.
Best to take it to a mechanic. Otherwise you are risking serious engine damage while driving it.
 

Smashfist

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It's throwing control circuit codes for the AFM solenoid pack (the valley cover that has the AFM solenoids in it). Being all open circuit codes would make me think that either there is a wiring issue to the solenoid pack, the connector isn't plugged in or the solenoids are cactus. Given that it's unlikely all of the solenoids would go open circuit at the same time, I'd start with making sure it's plugged in and you haven't had mice etc chew the wiring to it. The AFM solenoid plate plugs in at the rear of the engine behind the inlet manifold (next to the oil pressure sensor). It's a cock to get to but that's where I'd start.
 

Imesha

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It's throwing control circuit codes for the AFM solenoid pack (the valley cover that has the AFM solenoids in it). Being all open circuit codes would make me think that either there is a wiring issue to the solenoid pack, the connector isn't plugged in or the solenoids are cactus. Given that it's unlikely all of the solenoids would go open circuit at the same time, I'd start with making sure it's plugged in and you haven't had mice etc chew the wiring to it. The AFM solenoid plate plugs in at the rear of the engine behind the inlet manifold (next to the oil pressure sensor). It's a cock to get to but that's where I'd start.
Yesterday i took off the manifold and took off the valley plate, the connector was plugged in and there didnt seem to be any problems with it from what i saw. I might have to trace the wires back to see if its spliced somewhere else.

Im thinking about using this issue as an excuse to just delete the AFM unit and cam the car while ive got it apart.

Just looking at my options for cams, is there much of a difference besides specs in the various companies that make cams ( VCM, Harrop and Crow cams).

Thanks again for everyones input
 

Kandhol

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Hi mate did you find the solution for that problem. My car is doing the same thing engine light flashing at idling and AFM cylinders not working car is running on 4 cylinder. Let me know if you found the issue. Thanks
 

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Paraphrased form the workshop manual, the AFM solenoids are hot (one side of the solenoid always has 12V) and the other side is connected to the ECU. When 4 cylinder mode is required, the ECU grounds the AFM solenoids. This ECU grounding energises the solenoids which then open and thus feed high pressure oil though the solenoids to the AFM lifters. This high pressure oil enters the AFM lifters and compresses the lifter lock pin within the AFM lifters and thus frees the two halves of the lifter from each other. As such, the lower half of the lifter follows the cam and slides into the upper half of the lifter which keeps enough pressure on the pushrod to stop noise but not enough to operate the pushrod and rocker. That way the associated valve remain closed. Whether the ECU also inhibits fuel and spark, isnt stated within the workshop section but I’d expect at-least fuel is cut in the AFM cylinders when commanded. Just couldn’t be faced searching for that clarify within the workshop manual.

When 8 cylinder mode is no longer required, the ECU removes the ground circuit and the hot solenoids can no longer be energised (as current can no longer flow). That way the AFM solenoids close and the high pressure oil stops flowing to the lifters. The high pressure oil within the passages and AFM lifters bleeds out and thus the lock spring within the AFM lifters push out. That way the lock pins can again lock the two half’s of the lifter together in a non collapsed position so they can operate the pushrods, rocker and the valves.

As the AFM system required really clean oil, there is a serviceable AFM oil screen filter that sits under the oil pressure sensor at the back passenger side of the AFM valley plate. But if this filter is blocked, all it means is that high pressure oil may not flow to the AFM solenoids so tne system may not be able to get into 4 cylinder mode when commanded by the ECU so it’s not a failure mode that would cause 4 cylinder activation… In any case, the AFM system requires clean oil is circulating the engine so it’s best to ensure factory oil change intervals are adhered to. Sloppy change intervals will bite owners. Ideally, for long engine life, doing more frequent oil and filter changes is a favourite of many jc members. Oddly the AFM screen filter isn’t mentioned in the service schedule but some have said helps if checked/cleaned and/or replaced at least every now and again.

My opinion, really the AFM system is somewhat robust… However, with AFM solenoids being hot, that means that if an earthing fault on the ground wires to the ECU occurs, the AFM solenoids will do their thing and your engine will operate in 4 cylinder mode without ECU intervention. Since it’s a non commanded situation, the ECU may continue to feed fuel to the cylinder which may not be a good thing :eek: As such, check your AFM connector plugs and particularly the earth part of the AFM wiring going to the ECU. How the wiring is routed and what colours are involved, I haven’t looked…

Good luck with it :cool:
 
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