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Discussion Starter #1
My 1988 Alfa Spider has a unusual ignition timing problem. The car was running then began to run worse over a period of less than a week. Now it doesn't run much at all. It will only start cold and as it warms it starts to run very erratic then will quit running, not to start again until it has sat over night. And it may not start then.

During the standard checks for troubleshooting a puzzling problem was found. During cranking of the engine, the ignition timing is dead on the mark using a timing light. When the engine starts and is running the timing mark on the crank pulley disappears and cannot be seen with the timing light. If the timing light pickup is moved to #3 spark plug, the ignition timing is back in the correct position.

I'm not crazy, two other people who are familiar with engines saw this. None of us have never seen this problem before. I am at a loss as to the problem. Both the Ignition and Fuel ECU's have been replaced along with the main and Drive relays.

Any help or an opinion would be greatly appreciated. If other info is necessary to form some sort of opinion then I will gladly give it.
 

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Trained (ex)Professional, , 1953-2018 RIP,
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Sounds like the reference point transmitter could be suspect. This is the lower of the two flywheel sensors and it sends a TDC signal to the ignition ECU. It could also be a faulty sensor connection. Both sensor connectors are by the w/washer reservoir. The reference point connector is the gray one; engine RPM is the black connector.
Do you have an ohmmeter with which to check the sensors as outlined here?
 

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"I'm not crazy..."

Chief,

Thanks for clearing that up :).

Timing marks, not apparent on the crank pulley when triggered from plug one, then mysteriously appearing in the proper place when triggered from #3 seems odd. Although, come to think of it, is there a commonality between spark timing on #1 and #3? Not too many of us have made an opportunity to check and I may do that tomorrow. Perhaps spark is OK on wire #1 at start up, but then vanishes. You did not mention check-out of the distributor cap or plug wires. Does the problem move with a plug wire swap?

Will ponder further.

All the best and remember, this too shall pass.
 

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As postulated the sensor could be bad or have a bad connection that gets worse with heat. You don't know if the timing was working as you described before the problem. To me, your problem sounds like a O2 sensor problem. The only mark on the timing is TDC, so it will move with advance, you do not adjust/set the timing with a timing light on an S3.
 

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Don't make me get off the couch!

As postulated the sensor could be bad or have a bad connection that gets worse with heat. You don't know if the timing was working as you described before the problem. To me, your problem sounds like a O2 sensor problem. The only mark on the timing is TDC, so it will move with advance, you do not adjust/set the timing with a timing light on an S3.
I get very cranky when I have to get off the couch :).

Went to the garage and found my timing light down in a box under my dwell-tach...I never throw anything away. Discovered that triggering the lamp from plug wire #3 results in no visible marks on the pulley, however, moving the pick-up sensor to plug wire #4 shows the marks right where they should be!

And although, as rogerspeed noted, you don't use a lamp to time S3, L-Jets, they are very helpful in regard to verifying timing advance via action of the ignition computer, and to a small extent the VSD.

As an additional confabulating factor, I reviewed Papajam's (?) excellent schematics and confirmed the O2 sensor does not talk to our totally stand-alone ignition ECU and therefore, has no effect on ignition timing. Of course a bad O2 sensor may have effects on the Injection ECU that would cause the symptoms noted by the Chief (who has adamantly declared himself to be "not crazy", you may recall).

Corrections welcome!

A stumper, upon which I, and no doubt many others, will continue to cogitate.

What's the latest, Chief?

All the best.
 

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My 1988 Alfa Spider has a unusual ignition timing problem.
Have you done any recent work on the engine/ignition system?

Is the rotor firmly attached to the distributor drive shaft? There is supposed to be a nub inside the rotor to locate it on the distributor drive shaft. If that nub has broken/worn off or if the rotor is not fully seated onto the distributor's drive shaft the timing will go all kinds of wacky. If you are not already crazy (I think that is still a consideration) it'll drive you crazy.

...however, moving the pick-up sensor to plug wire #4 shows the marks right where they should be!
That sounds like your distributor is 180 degrees off. I suspect about 50% of Spider engines that have been rebuilt end up 180 degrees off. The engine won't care as long as the timing is right.
 

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Trained (ex)Professional, , 1953-2018 RIP,
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... moving the pick-up sensor to plug wire #4 shows the marks right where they should be!
Exactly as it should be. Cylinders 1 & 4 fire 360 degrees apart so the timing marks will appear in the same position when the timing light is triggered by either cylinder.
If the light is triggered with cyls 2 or 3, the pulley marks will be 180 degrees away from the timing pointer. This is the thought behind the TDC sensor on the flywheel being suspect.
 

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jim may have the correct diagnosis. the timing light is a great diagnostic tool, but it helps to have known references, comparisons. S-3 distributors have eccentric dawg, they will only fit one way, you can turn it 180, but it will not be fully seated, you can observe at the mounting. Have you looked at the plug deposits upon the engine failing, another good diagnostic tool. The O2 sensor problem can make an S-3 run rich and die, having not laid eyes and hands on this car, I can't conclude it is purely an ignition problem
 

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Discussion Starter #9
Hello to all and thanks for the info.
I'll do my best to respond to everyone in order.
As to the Reference point transmitter, the ohms reading is 987, as well ,as the RPM transmitter. This reading has been verified more than once just to make sure.

On the commonality between #1 and #3 spark timing, I know of none, that's what makes this so weird. The distributor is in it's original position when the engine was running fine. It has not moved. The distributor cap, rotor and wires have all been replaced after the engine started running very badly. They had no effect on the problem. I did swap the plug wire positions from the norm and encountered a backfire of huge proportion. Won't do that again.

The Reference point transmitter could be bad even if ohm's ck is OK. The terminals in the connector were checked but could go bad with heat. I only use a timing light for verification of idle timing and the advance of timing during engine acceleration.

No engine or Ignition work was performed prior to problem. All work has been after this problem showed up.

After reading what everyone has written, it seems that my next best step would be to replace to O2 sensor and the reference point transmitter. I do agree, there may be more than one problem here.

Thank you gentlemen for everything. Sometimes one gets lost without help.
 

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I have experienced a flywheel sensor that tested OK with the ohmeter but, when removed from the bellhousing, evidence of some physical damage was noted. Replacing it with a used but known good sensor solved a no-start issue.

Also, the sensor is attached to the bellhousing by a single allen-head bolt into the aluminum casting. It'd be easy to strip out the threads and have it move out of position (loose) or even fall right off (and be left dangling by the cable). It could thus test OK but not function (sense) properly.
 
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