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Greetings Alfisti,
Since my 166 was stolen a month ago my friend has been kind enough to lend me his 'spare' 1991 164 Q so I can get to work and back until the insurance company decides to pay up.
This car has numerous issues which have left me by the side of the road a few times in that month.
Currently I am having a problem that sounds quite similar to Richard Bradford's problem mentioned a few threads down. Driving on the freeway or at 2-3000rpm the car runs fine, however at idle when warm it starts to rev violently before stalling. The car will start again but needs to be revved using the accelerator to keep it running or it will stall again. This is not a problem when the motor is cold. I have noticed a correlation between this and the oil pressure guage (but being an Alfa who can say how accurate this is!). When the car is warm and stopped the oil pressure guage drops to zero and the car then eventually stalls. When running at warm temp the pressure sits on around '4' or half way across the guage. Today driving back from the shops the oil pressure warning light displayed for the first time, although the pressure was similar to what it has been all week without the lamp displaying.
From my limited understanding of engines, I think that a drop in oil pressure is caused by either a leak somewhere or a drop in compression (??). There is no evidence of oil leak on the floor in the garage and the level of oil in the engine is fine.
The car has recently been serviced and has had a new sump installed.
Any advice or suggestions would be greatly appreciated!
Thanks guys!
 

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It is my Understanding that "O" Oil Pressure at Hot Idle is Normal

When I first started looking at 164's I also noticed that some cars showed "zero" oil pressure at hot idle. I asked the BB about this, and everyone assured me that this is normal (actually, the pressure is low but there) as long as the oil pressure warning light doesn't come on at idle nad as soon as the rev's come up, the pressure returns to a readable value on the gage. I recently purchased a 1995 Q (US version) and have the same oil pressure results. It is near zero at hot idle and the warning light doesn't come on. As soon as the rev's pick up, the pressure climbs to about 55 psi.

Therefore, it appears that the stalling is not related to the oil pressure readings.
 

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..It is near zero at hot idle and the warning light doesn't come on. As soon as the rev's pick up, the pressure climbs to about 55 psi.

Therefore, it appears that the stalling is not related to the oil pressure readings.
I agree with this observation - near zero, not zero and it does climb up very nicely. If the Q starts to run too hot, you will see the oil pressure drop...

Best regards,
 

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Discussion Starter #4
Thanks for your (very prompt) response guys! So my question is if it's not the oil pressure that's causing this violent stalling....what is? :):confused:
 

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As suggested in other posts, clean and lube with dielectric grease ALL electrical connections in the engine compartment, paying SPECIAL attention to the ignition modules under the cruise control actuator above and ahead of the clutch housing and the large round multiconnector at the rear of the heads above the clutch housing. LS's and Q's are known for suffering this intermittent and "violent" hesitation at times. It is my personal experience that it is a cutout of the ignition due to poor conductivity at the connections.
 

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air leak!

Sounds like all the symptoms of the so called 'tramp air' coming into the system.

Best way to find this-- get the engine cold and start it. Spray electrical contact cleaner (aerosol) arounnd the AFM, intake tube, all intake runners, all around everywhere there are hoses and connections. See if the idle changes. If it does you have found the leak!

If no joy, get the engine hot and try it CAREFULLY!!! Spray minute amounts as it will ignite if truly hot and it is combustible. Have a Co2 fire extinguisher handy, or if it ignites hard, blow it out. But really, do be careful when doing this on a hot engine. It does work, but can be dangerous if you are careless

DO NOT LET THE FLAMING BEGIN (either real or BB type!)
 

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I would use WD-40 or carb cleaner before would use electrical contact cleaner to search for air leaks. I use these on the rubber carb mounts to find air leaks. Doesn't take but a small shot to hear the noticable difference in the engine when you find a leak. Spray around the bases of the air intakes as I had a bad manifold gasket that wasn't sealing. Only when I removed the manifold did I find out it was leaking almost from new.

I would get some DeOxit D-5 and go around to clean all the contacts as suggested. Especially the ground connectors. Poor grounds can wreak havoc.

I would also suggest that you check the idle air controller on the back of the manifold. The rubber seal shrinks and allows more air in and the controller can't keep up, as it shifts from rich to lean. Also the internals on the IAC gets grime inside and needs a periodic cleaning to loosen the movable vane.
 

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Rationale for contact cleaner

Leaves no residue! Evaporates completely! But yes it is combustible!
 

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My wife's L was stalling unexpectedly while idling. I couldn't identify the problem, as the hoses seemed to be intact. I thought that the crank sensor might be going, and replaced it with good results for a few days. Then the stalling started again, sudden stalling as if ignition or fuel was going away.

But I then remembered that the upper dogbone mount was getting chewed up, as was the radiator hose material job I did on it. So I looked at the right front motor mount and found it totally trashed. This lets more strain to the dogbone and kills them. So I replaced both mounts and all has been well since. (It's a Good Thing that I didn't throw away the crank sensor I swapped out.)

There is a rationale for using higher boiling point (less volatile) fluids for leak detection: they get a chance to be drawn into leaks as liquids, where they make their presence known IMMEDIATELY. But to each his own. I use brake cleaner (non-chlorinated) and try to put liquid directly onto suspeted leaks. If you want to know what the response to a leak would be, shoot a snort up into the air cleaner intake with the engine running. It gets her attention.

MIchael

edit: By the way, in spite of everything, it is a Good Thing to have a reliable oil pressure sensor. How about testing yours or just replacing the sensor head? If you want, a simple mechanical oil pressure gauge can be paralleled with yours with a little effort, even if only as a temporary measure to give you a calibration test for the Alfa gauge. Or make a comparison old vs. new.
 

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I saw that reference to "fire" in your post and fire to me under the hood is not a good thing. :( I had an Alfetta catch fire from an electrical short and fortunately the car was in the driveway when it happened. The fire extinguisher was with in arms reach and I minimized the damage. Brake cleaner, carb cleaner, starter fluid (ether-very volatile) and WD-40 are good things to spray as you get a good response to air leaks.

May I suggest that if you don't have a fire extinguisher at the garage door, you should invest in one. You never know when you might need it. Mine sits just inside the door where I am about 10 steps away.

The oil pressure question is something I asked about a while back. I invested in a good oil pressure guage and I have already used it several times. Just last weekend I used it on my wifes spider because I wasn't sure what the guage was telling me. I had good oil pressure and the guage was showing correctly. What was happening was I changed from 20w-50 dino oil to 5w-50 synthetic and the pressure fluctuation was showing a wider swing of the needle.
 
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