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Discussion Starter #1
Hi,
Was driving a 1994 3.0 24v 164 quite hard today and, just for a split second, engine power cut - was around 4,000 to 5,000rpm at the time.
It was so brief and brutal think it had to be electrical. Not done it before, that I know of, but concerned it could be a warning of something about to fail.

Possibly the crank sensor?

Anyone else had anything like this?
 

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Had similar symptoms with the LS after I first bought it. Was dirty ignition module contacts. Had to disconnect them and clean with electronics spray cleaner, then use dielectric grease to protect them, as they are in a pretty dirty area of the engine bay. The two modules are located down below the (car) rhs of the air filter box, below and to the (car) lhs of the cruise control actuator.

Got nothing to lose by cleaning and protecting all electrical connections in the engine bay, esp these two connectors and the big round one at the aft of the engine.
 

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Richard, yes, something similar and I will try to explain it here. Car was 1995 Auto LS and I never was able to figure out the cause.

Every day on my commute to work, about 6 miles from my house on 15 south, or, when I was driving north on the 15 freeway on Sunday to church, occasionally at other times, my car would very momentary suffer a full loss of motor power. Tach went from 3000 to near zero and back again in <1 second. then the rest of the drive was uneventful. I don't recall how it started but after a few times I would notice it was always when I was just right at 3K RPM (within a half needle). I eventually got to the point where I could make it happen (but only once per drive, always about 7 or 8 minutes into it, always exactly at 3K RPM). Radio not interrupted, lights not interrupted, etc. MOtor and tach only, speedo never dropped.

It occurred through most of the life of the car. A passenger would not have noticed, it was that quick. LIke it missed one crank signal and then picked it up again. Changed crank sensors due to frank failure ; problem persisted. Tried another CPU, no change. Etc etc.

In the end the tbelt broke, valves crashed, and it was history. But this weird problem lasted (once I noticed it, quite by accident) more than 6 years. I did some querying wondering if it had been reported previously but no joy.

In the end I believe that what was happening was a buffer overflow in the CPU or other software bug that caused a one-time dropout each time the CPU went active with crank sensor signals after an ignition switch power-off. I'll never be able to prove it tho, as I was not able to get the source code (I tried!). The Marelli tester I ran found no faults in real-time run/capture mode. It remains a mystery to me to this day.

On another note, anyone that saw my 'just got a new spider' message on this thread and is interested, go to spider forum and see 'my dream S2 spider' thread!
 

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Discussion Starter #4
Thanks Guys,

Del, I'll try cleaning up those ignition connectors - not hard to get to and worth the try. Been heavy rains and winds past few days so possible some moisture could have headed that way.

Goats, wish me luck. Hopefully more solveable issue than yours. All instruments and everything remains visibly fine on mine.

Update from today:
Today the 164 started jolting on tighter left turns, namely coming out of a roundabout. Just momentary losses of power that actually feel like fuel starvation.

Put some more fuel in the tank and now almost half full. Seemed to run better but exiting left from another roundabout I gave it an extra 'throw' to the left and almost immediately (split second later), same thing. One jolt, then another, as if fuel starvation.

No warning lights or any other sign of anything wrong. No fuel or odd smells.

Was only on light to medium throttle as very wet today. Not been able to test it on right turns for the same reason. Seems to be better behaved on the straights.

Was wondering if it could be the fuel pump but the response was so fast after throwing it left, on a fairly light throttle, think it has to be something closer to the engine. Fuel or ignition, I don't know.
Lifted the bonnet and couldn't find anything loose or visible amiss.

Wierd, or just Alfa – pretty much the same thing.

Although it feels like fuel starvation I'm returning to the original notion of an electrical fault. Can't think of anyway a fuel issue could be made to happen so quickly over all 6 cylinders. Happy to stand corrected just need to sort it. Noticeably more prone to doing it than yesterday and only covered 20 miles since then.
 

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Very sudden almost instantaneous cutouts are almost always an electrical problem, fuel problems taking just a little more time to show up. I had experienced a series of sharp cutouts in my LS, esp when it was wet and rainy, and indeed there were no fuel problems, but cleaning the electrical connections in the engine bay eliminated those sharp cutouts ever since.
 

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A similar problem is very often alfa 156. Crank sensor. More precisely its wire and contact. The primary symptoms are exactly appear when moving from the shaking of the engine. Then start the engine stops with excellent rotation starter.
I have a crank sensor is always carried with me.
 

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Richard, yes, something similar and I will try to explain it here. Car was 1995 Auto LS and I never was able to figure out the cause.

Every day on my commute to work, about 6 miles from my house on 15 south, or, when I was driving north on the 15 freeway on Sunday to church, occasionally at other times, my car would very momentary suffer a full loss of motor power. Tach went from 3000 to near zero and back again in <1 second. then the rest of the drive was uneventful. I don't recall how it started but after a few times I would notice it was always when I was just right at 3K RPM (within a half needle). I eventually got to the point where I could make it happen (but only once per drive, always about 7 or 8 minutes into it, always exactly at 3K RPM). Radio not interrupted, lights not interrupted, etc. MOtor and tach only, speedo never dropped.

It occurred through most of the life of the car. A passenger would not have noticed, it was that quick. LIke it missed one crank signal and then picked it up again. Changed crank sensors due to frank failure ; problem persisted. Tried another CPU, no change. Etc etc.

In the end the tbelt broke, valves crashed, and it was history. But this weird problem lasted (once I noticed it, quite by accident) more than 6 years. I did some querying wondering if it had been reported previously but no joy.

In the end I believe that what was happening was a buffer overflow in the CPU or other software bug that caused a one-time dropout each time the CPU went active with crank sensor signals after an ignition switch power-off. I'll never be able to prove it tho, as I was not able to get the source code (I tried!). The Marelli tester I ran found no faults in real-time run/capture mode. It remains a mystery to me to this day.

On another note, anyone that saw my 'just got a new spider' message on this thread and is interested, go to spider forum and see 'my dream S2 spider' thread!
Exact same issue on mine. Has been doing this for some years. It does it once, not always but usually the same distance on the same route from home in the morning. Will never do it any other time. Of course now I have a non starter but I don't believe it's related.
 

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YEA! Someone else noticed this too. V6 does it happen exactly at 3K RPM? IS your car an automatic ?
 

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Discussion Starter #9
Hi,
Mine is a manual. Checked the two ignition connectors near the air filter and both are fine. Can't find any other connector loose or dirty.
Drove fine today but yesterday it cut twice while idling when a bit cold.

Probably not related as also have an unstable idling issue. Reckon that is due to some leak on the rear exhaust manifold or bit further down - can smell exhaust slightly, especially when accelerating quickly from stationary. Just can't pin down where it is coming from. Changed gaskets between head and rear manifold (pig of a job) and been under the car with the engine running to listen for leaks. Found one at the lambda sensor (sensor body broken!) and replaced that but still an issue, somewhere. Driving me crazy.

Alfas...
 

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check the EGR valve (if you have one) where the vertical tube attaches to the header. The banjo bolt there always loosens up over time and starts leaking exhaust gas
 

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check the EGR valve (if you have one) where the vertical tube attaches to the header. The banjo bolt there always loosens up over time and starts leaking exhaust gas
Thanks, Goats.

This has indeed come loose in the past. Was fine when I was checking the lambda sensor but will look again, just in case.

Cheers.
 

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"Checked the two ignition connectors near the air filter and both are fine"

Did you actually pull them apart and clean them? Mine looked ok but only when I actually cleaned them with electronics spray (use a lot of it, it just evaporates away anyway) did the problem go away. Also pull apart and clean that big round connector at the rear end of the engine above the clutch housing.

I found through the years that inspection only of electrical connections doesn't do it in many cases.
 

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Discussion Starter #13
"Checked the two ignition connectors near the air filter and both are fine"

Did you actually pull them apart and clean them? Mine looked ok but only when I actually cleaned them with electronics spray (use a lot of it, it just evaporates away anyway) did the problem go away. Also pull apart and clean that big round connector at the rear end of the engine above the clutch housing.

I found through the years that inspection only of electrical connections doesn't do it in many cases.
OK, Del, I'll spray them with cleaner too. Have only pulled them apart for a visual check and all looked fine from that.

Thanks and will post results shortly :)
 

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Just trying to be sure, of course.

I just hate electrical connection problems in cars, and if I have one apart, I clean the dickens out of it just to be paranoid about it. Doesn't mean it always cures the problem but since it's such a simple thing to do to clean and lube the connection, why not, just to be sure.

These 164s had a reputation for problem connections for some reason, and Carlo told me Alfa paid the dealers so much a connection to clean and lube them to cut down on problems.
 

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Discussion Starter #15
check the EGR valve (if you have one) where the vertical tube attaches to the header. The banjo bolt there always loosens up over time and starts leaking exhaust gas
Spot on, Goats, thanks. Checked the banjo today and was loose. That's solved the exhaust leak. Will find out what effect that has on the idle issues, if any, tomorrow.
 

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Discussion Starter #16
Just trying to be sure, of course.

I just hate electrical connection problems in cars, and if I have one apart, I clean the dickens out of it just to be paranoid about it. Doesn't mean it always cures the problem but since it's such a simple thing to do to clean and lube the connection, why not, just to be sure.

These 164s had a reputation for problem connections for some reason, and Carlo told me Alfa paid the dealers so much a connection to clean and lube them to cut down on problems.
Will pick up dielectric grease this weekend and go through all the main connectors. Cheers.
 

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yah even a blind squirrel finds a nut every once in a while!

Check my post Dusty Rhodes Hard Times for some ideas on poorly running 24V car, these days the very first thing I do after being diligent to rule out a false air leak is to check fuel pressure. It takes 5 minutes and is such a good diagnostic tool ---
 

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"yah even a blind squirrel finds a nut every once in a while"

?
 

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yep I'm the blind squirrel and the nut I found was the loose banjo bolt causing exhaust leak!
 

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Discussion Starter #20
yah even a blind squirrel finds a nut every once in a while!

Check my post Dusty Rhodes Hard Times for some ideas on poorly running 24V car, these days the very first thing I do after being diligent to rule out a false air leak is to check fuel pressure. It takes 5 minutes and is such a good diagnostic tool ---
Will do, thanks.
 
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