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VT V6 , VERY rough noisy idle, won't run/rev

gohrdrgomad

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You're basically right.
But I haven't done a comp test....because if the head comes off it all get s too expensive :(

The mechanic I had the car at for initial diagnoses, said all other cylinders had good compression, but none on number 4.
The car had 'run badly' , at IDLE, for a total of two to three minutes, including roadside assist diagnoses, and not say, at 100kph on the freeway.
And so, when I replaced the #4 intake spring, I also pulled out the pushrod and it had suffered NO damage, so I can assume the lifter is also not externally damaged, although there's no saying if it is fecked internally. The spark plug from number 4 is also fine, not damaged.
So, to summarise:
Car will NOT start, but:
Car has fuel, fuel pump, fuel injection, good spark, good coils, NO fault codes whatsoever, a new CAS, a good battery, no water in oil ( although a little in water, as per normal)
and an engine with dodgey compression on ONE cylinder but it still won't even cough, when I turn it over.
In fact since being to the mechanic, the starter sounds weak or like it's trying too hard to turn the engine over.
Perhaps it's on the way to being seized, or all the main bearings are spun.....?
It could be the DFI, the MAF, the IAC, the Cam Angle Sensor, the Oil Pressure Switch/Sender, the O2 sensors, the this the that.....
I might try a fuel filter, but really, I've already spent nearly $800 of my time and money on a car that still doesn't run and was barely worth $1500 before it broke. I think the writing is on the bin for this VT......
If it was running before you started what you have, it is unlikely you have other worries about anything else yet. Your battery could be low on cc.amps and it sitting cold no oil up top does put load if you just keep cranking it. I assume it wont show any codes until it is actualy running. Weather or not you have dash warnings or not? Call a auto elec is my best advise to you. You can do a comp test now....
 

Tree cutter

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If it was an intake valve spring that broke then it could have fired back through the intake and blown a vacuum hose off or damaged the air flow meter. I would be checking for vacuum leaks first
 

sticksicks

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If it was an intake valve spring that broke then it could have fired back through the intake and blown a vacuum hose off or damaged the air flow meter. I would be checking for vacuum leaks first
Well, no.
Any bits of spring would end up either in the rocker cover area or maybe down in a near by oil gallery passage.
A bit of valve, on the other hand, would either exit the exhaust port or jam down the side of the piston.
For a bit of spring to end up in the intake manifold, I reckon the rest of the engine would be in bits too :))
 

Tree cutter

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I didn't mean a bit of spring could go back through the intake. I meant air pressure from the cylinder could fire back through the intake if the valve stays open because of a broken spring.
 

sticksicks

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So, I don't have an engine bore-scope to peer into my cylinder or any air-compressors in my workshop ( my workshop consists of a
pleasantly sloping piece of rapidly growing lawn in the full sun).
I also really want to avoid taking the head off, as it won't make the car easier to start or sell....
To check if pressure is blowing back past the intake valve, I need to have all the other spark plugs out, the # 4 one in, and
as I turn the motor-that-won't-start over by hand-wrench, I'll somehow get my ear up to the throttle body to listen for back-blow-by-whatever, which I really think I'll get....
Genius level acheived :cool:
 

gohrdrgomad

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So, I don't have an engine bore-scope to peer into my cylinder or any air-compressors in my workshop ( my workshop consists of a
pleasantly sloping piece of rapidly growing lawn in the full sun).
I also really want to avoid taking the head off, as it won't make the car easier to start or sell....
To check if pressure is blowing back past the intake valve, I need to have all the other spark plugs out, the # 4 one in, and
as I turn the motor-that-won't-start over by hand-wrench, I'll somehow get my ear up to the throttle body to listen for back-blow-by-whatever, which I really think I'll get....
Genius level acheived :cool:
ln your own mind.
 

Tree cutter

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If you haven't got a compression gauge you could always hold your thumb over the spark plug hole while someone winds the engine over on the starter. This way will at least tell you if you have some compression or not. You could compare it to other cylinders to see if it feels about the same. It wont hurt your thumb but will just push your thumb away from the plug hole and make a hissing noise if you have compression.
I would be charging the battery or getting a jump start before going any further and then checking that the air intake hose between the throttle body and air flow meter has not blown off at one end or split. You also need to check the vacuum hoses at the throttle body to make sure they haven't blown off. I really don't think there is much wrong with your engine if it now has compression on all cylinders.
 

sticksicks

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Finally did a compression test.
Engine was cold, as it won't run. Wants to start, but won't run, starter seems to work too hard and engine backfires once through manifold or EGR. At least it makes sure there's no blockage....
I cleaned the throttle body and IAC plunger. Cleaned MAF elements with MAF cleaner. Checked vaccum hoses, charged battery, checked wind direction, scratched me a...
Anyway, here's the readings for those still reading ( first number dry, second number after I added a squirt of engine oil and
turned engine over a few times) I tested each cylinder four times, two dry and twice 'wet' and was very careful to tighten the tester in the plug hole firmly:
1: 135/150 psi 3 : 110/125 5: 90/120
2: 85/50 4: 0/0 6: 85/100
That, my friends, is a cactus engine.
If I have the inclination, I'll pull off the DS head and have a squiz.
 
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