VS V6 mis-firing ??

[peejay71]

1995 VS Acclaim V6

Upon acceleration engine jerks repeatledy several times.

Also does it when the cruise control tries to pull the car up a slope at 100kmh

Sometimes the car behaves for a couple of days, but then the "jerking" re-appears.

Getting frustrated and annoyed. Any ideas? Anyone?

Someone had mentioned the fuel filter?? But the car idles fine, and cruises fine, just when accelerating.

[kopper69]

Almost certainly the spark plug leads. Under load they break down through the insulation and short out, which means the cylinder doesnt fire and you get the jerk. Start by replacing the spark plug leads, full set will set you back about $50. You might as well do the spark plugs while you are there for around $12 for a full set (of 6, assuming we are talking about a V6). Do one lead at a time (so you dont get them mixed up) and you should be purring again in no time.

Not going to be anything to do with the fuel filter.

[immortality]

also double check the spark plug gaps on the old plugs. a gap that is to big causes the spark to "blow out" under load

[LowVp]

coils also do the same thing

[raywise]

Yep, mine does exactly the same thing. I've so far --
Replaced leads
Replaced plugs
Cleaned Throttle body
Cleaned injectors
Replaced fuel filter.

This is driving me mad. My mechanic said nothing shows up on diagnostics, but sure enough, under load while doing around 80-100ks, miss miss miss miss.

Someone in another thread mentioned the crank angle sensor can sometimes be at fault. Its a recon engine that got put into my VS only 2 years ago, so it should be purring. But it still has this rotten high speed miss,

Hoo Roo

[immortality]

Yep, mine does exactly the same thing. I've so far --
Replaced leads
Replaced plugs
Cleaned Throttle body
Cleaned injectors
Replaced fuel filter.

This is driving me mad. My mechanic said nothing shows up on diagnostics, but sure enough, under load while doing around 80-100ks, miss miss miss miss.

Someone in another thread mentioned the crank angle sensor can sometimes be at fault. Its a recon engine that got put into my VS only 2 years ago, so it should be purring. But it still has this rotten high speed miss,

Hoo Roo

double check your plug gaps and see if any look different to the others (colouring, soot etc). if all are fine and look the same. try and borrow a known good set of coils and DFI to try on your car. a tired coil can cause this. if then it still does it the only thing really left is the CAS

[hako]

Yep, mine does exactly the same thing. I've so far --
Replaced leads
Replaced plugs
Cleaned Throttle body
Cleaned injectors
Replaced fuel filter.

This is driving me mad. My mechanic said nothing shows up on diagnostics, but sure enough, under load while doing around 80-100ks, miss miss miss miss.

Someone in another thread mentioned the crank angle sensor can sometimes be at fault. Its a recon engine that got put into my VS only 2 years ago, so it should be purring. But it still has this rotten high speed miss,

Hoo Roo

And check for logged codes - this will give you an idea. The speed you quote is the speed range where the TCC locks the convertor up....maybe there is a connection?

[raywise]

Thanks for the above replies. I'll check the error codes, and I might remove the coil pack and module and see if there is any evidence of tracking etc.

Will keep you updated with what I find, gees I hate these niggly things. The rest of the car is perfect.

Hoo Roo

[raywise]

Well, checked the error codes and in sequence I get 12, which means all ok, and then 43, which is the Knock Sensor circuit.

I don't think the knock sensor playing up (if it actually is) will cause misfiring, but I'll have to investigate further.

Hoo Roo

[Harvs82]

Well, checked the error codes and in sequence I get 12, which means all ok, and then 43, which is the Knock Sensor circuit.

I don't think the knock sensor playing up (if it actually is) will cause misfiring, but I'll have to investigate further.

Hoo Roo

If the knock sensor isn't working properly, it could be retarding the ignition unnecessarily, which would probably give the symptoms you describe. Have you tried running premium fuel for a few tanks to see if there is any difference?

Another thing could be fuel pressure, or injectors not firing properly under acceleration...

[immortality]

i'd go with some premium fuel and maybe some fuel injection cleaner. if oyu have a clogged injector causing a lean condition in one cylinder will trigger the knock sensor causeing your problems.

[DannyboyDS]

you could just check that the knock sensor is plugged in too. it should be on the drivers side of the engine from memory just above the engine mount.

Another thing to check is that all vacume hoses are plugged in, after these two quick checks go with what Kopper has said, replace those leads and pull the plugs out, you might get away with just cleaning (some sandpaper will do the trick) the plugs and re-gapping them to 1.5mm for a straight petrol car.

your not on gas are you?

[Harvs82]

you could just check that the knock sensor is plugged in too. it should be on the drivers side of the engine from memory just above the engine mount.

Another thing to check is that all vacume hoses are plugged in, after these two quick checks go with what Kopper has said, replace those leads and pull the plugs out, you might get away with just cleaning (some sandpaper will do the trick) the plugs and re-gapping them to 1.5mm for a straight petrol car.

your not on gas are you?

Pretty sure that the VS V6 has twin knock sensors.... from memory they are an absolute bugger to get at too...

[hako]

If the knock sensors and/or circuit fail, the ECU goes to a default setting which should not cause the fault as described.

[DannyboyDS]

for the top two replies cheers, I didn't know that, I only know of the one on the drivers side as the wire broke when I did that engine mount (don't ask it was a bad day)

Harvs82 that would make sense though one knock sensor on one side wouldn't do much for a V engine.

[Harvs82]

for the top two replies cheers, I didn't know that, I only know of the one on the drivers side as the wire broke when I did that engine mount (don't ask it was a bad day)

Harvs82 that would make sense though one knock sensor on one side wouldn't do much for a V engine.

One other thing you can do to check your knock sensors is to have the engine idling at normal running temperature, grab a hammer and give the alternator bracket arm (the one that goes from the back of the alternator to down near the rocker cover) a swift sharp hit, obviously don't belt the living daylights out of it though... If the engine momentarily faulters or the rpm drop, then your knock sensors are working. By hitting the bracket with the hammer, the metallic noise created is similar to what the knock sensor 'hears' inside the engine if you are pinging etc.

[vg_ute_mad]

1995 VS Acclaim V6

Upon acceleration engine jerks repeatledy several times.

Also does it when the cruise control tries to pull the car up a slope at 100kmh

Sometimes the car behaves for a couple of days, but then the "jerking" re-appears.

Getting frustrated and annoyed. Any ideas? Anyone?

Someone had mentioned the fuel filter?? But the car idles fine, and cruises fine, just when accelerating.

G'day mate, do you have any updates?