What exactly is wrong with my 3200GT?

[onlinesys]

Morning gents,

Recently car stowed from time to time if the air-con is on when I press the clutch.
Doesn't matter if the engine is cold or hot. No such issue if aircon is not being
switched-on.

Knock sensors changed one year ago. Checked with data cable with the computer and
there is no error code.

Any insight?

 

[jluis]

What do you mean with stowed?
If the AC causes the engine to drop the engine speed considerably, you might have a shot AC compressor that is putting too much load on the crank.

 

[onlinesys]

What do you mean with stowed?
If the AC causes the engine to drop the engine speed considerably, you might have a shot AC compressor that is putting too much load on the crank.

When I press on the clutch with aircon on, Sometime I could see red-light on at the oil pressure-guage and engine just died.
How could I check if there is a shot AC compressor since it is only intermittent?
Thanks

 

[conaero]

Hum, have you had the endfloat checked?

Seems odd that it only does it when the AC is on?

It could be that the extra strain of turning the AC pump is what is causing it, how is your battery and alternator?

 

[CatmanV2]

I think he means stalled. So what's the idle speed currently?

C

 

[davy83]

well you have a few things possible here. Certainly whats happening is not right. what rpm does the engine idle at when the AC is off? does it idle evenly? does the engine or oil pressure change when you put your foot on the clutch with the AC off. I am wondering if the engine seems totally normal and runs well other than when the AC is on then it does point to the AC compressor. however if the engine is not happy and its just the load making it stall then you may have more serious problems.

 

[Contigo]

Sounds like end float as they say when you dip the clutch the oil pressure can drop!

 

[jluis]

If it's endfloat and if the clutch pressing is already stalling the engine, than an urgent engine rebuild is required and might already be too late to salvage the crankshaft.
You should get the endfloat measured ASAP

 

[onlinesys]

well you have a few things possible here. Certainly whats happening is not right. what rpm does the engine idle at when the AC is off? does it idle evenly? does the engine or oil pressure change when you put your foot on the clutch with the AC off. I am wondering if the engine seems totally normal and runs well other than when the AC is on then it does point to the AC compressor. however if the engine is not happy and its just the load making it stall then you may have more serious problems.

I guess it is around 800rpm on idle when the AC is off.
Yes, oil pressure lower when food on the clutch but won't stall the car.

 

[onlinesys]

Hum, have you had the endfloat checked?

Seems odd that it only does it when the AC is on?

It could be that the extra strain of turning the AC pump is what is causing it, how is your battery and alternator?

Battery and alternator seem fine to me.

 

[allandwf]

Oil pressure could be a red herring, as it will drop if revs drop off considerably. Try revving it when dipping the clutch and see if the aircon belt squeels.

 

[onlinesys]

Oil pressure could be a red herring, as it will drop if revs drop off considerably. Try revving it when dipping the clutch and see if the aircon belt squeels.

Thanks for the advice. I remember the fuse which controlled the air-con was blown after I filled up the refrigerant and things worked fine after fuse replaced

 

[alfatwo]

Yea but why would that cause the engine to stall,re gassing the aircon wouldn't make any difference..
Sounds like something in the engine internals is partially seizing..

Dave

 

[davy83]

Ah ok 800 rpm is wrong the engine should idle at 1000rpm at least and should never go as low as 800 rpm. So have you tried replacing the crank sensor? this is how the ECU measures engine speed?

 

[Contigo]

Agree with Davy, the idle rpm is too low and should be about 1k rpm. The oil pressure sensor dropping and flashing red is when the car is at near stall point as this is when the oil pressure drops. The Air con is probably a red herring but first thing to check is rpm/crank sensor. The other issue could be the Throttle body failing.

 

[onlinesys]

Agree with Davy, the idle rpm is too low and should be about 1k rpm. The oil pressure sensor dropping and flashing red is when the car is at near stall point as this is when the oil pressure drops. The Air con is probably a red herring but first thing to check is rpm/crank sensor. The other issue could be the Throttle body failing.

Frankly, I am not 100% sure if it is actually idle at 800rpm and really need to check first.
All I could remember was that if the aircon is off, depress the clutch will make the oil pressure drop to something like
half to 3/4 but could be flashing red if the aircon is on hence sometime car will stall.

I had the throttle body and knock sensors changed half a year ago but didn't change the crank sensor though

 

[jluis]

Depressing the clutch and having oil pressure drop is a sign of excessive endfloat from what I read.
Mine always maintains the oil pressure when pressing the clutch.

 

[davy83]

Equally if the revs are too low and the ECU is unable to maintain the idle speed, this would cause the oil pressure to drop just because the RPM is low, and would also explain why it stalls since the ECU does not see the speed drop without the crank sensor? Not sure if its quite that simple, but for the £30 it costs to replace the cranks sensor i would give it a shot?

Depressing the clutch and having oil pressure drop is a sign of excessive endfloat from what I read.
Mine always maintains the oil pressure when pressing the clutch.

 

[Contigo]

Yes it is too easy to dismiss for the price of a part and let's face it end float is not that common!

 

[CatmanV2]

Yes it is too easy to dismiss for the price of a part and let's face it end float is not that common!

I think it's worth checking the end float, but indeed to be careful not to get ever excited. If the engine is bogging down due to low idle + additional load, then I'd fully expect the oil pressure light to come on.

Not to say it *doesn't* have an end float issue, though
C