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post #1 of 19 (permalink) Old 08-13-2017, 03:28 AM Thread Starter
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sudden loss of power

Experienced a sudden loss of power whilst cruising on the highway yesterday, about 70 mph, accelerating. Looked to see the battery indicator light on. The engine was off but I was able to downshift (out of habit?) in preparation to pull over. When my foot came off the clutch, the engine started again. I regained power and continued to drive. I drove for about twenty more minutes without incident. I had fueled up just before the drive with high test, gas cap tight. Seems to me I lost fuel for about twenty seconds. Any ideas about what caused this? Advice much appreciated.

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post #2 of 19 (permalink) Old 08-13-2017, 07:15 AM
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Did you notice if the tach was reading or did the needle drop to its rest? The tach gets its signal from the ignition/coil. So, if the tach needle dropped then you had a loss of ignition. If the tach continued to read you likely had a loss of fuel delivery. This doesn't exactly diagnose the issue but it might tell you where to start looking.

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post #3 of 19 (permalink) Old 08-13-2017, 09:34 AM Thread Starter
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Good to know. The tach did drop as I recall. That's probably why I instinctively downshifted. I'll check that.

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post #4 of 19 (permalink) Old 08-13-2017, 09:57 AM
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carbs? spica? L-Jet? Motronic?

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #5 of 19 (permalink) Old 08-13-2017, 10:29 AM
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carbs? spica? L-Jet? Motronic?
What color is your car? Was the top up or down? Was there a pretty girl in the passenger seat? (got a photo?)
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post #6 of 19 (permalink) Old 08-13-2017, 10:51 AM Thread Starter
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L-jet, top down, no girl. I ran it to Montreal and back with no problems but shook up a lot of stuff. Found loose connectors on the coil and starter, both fixed. A hole in the intake air hose, fixed. Wondering what else got "road tested."

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post #7 of 19 (permalink) Old 08-13-2017, 11:01 AM
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loose flywheel sensor maybe on bellhousing?
obvious perhaps, but check battery leads are on tight (you might have removed battery ground to work on the car and then just slipped it on the pole forgetting to tighten it.....can happen!)
main lead into top of coil not pressed down fully?

Dom - Alfa Spider 1990 S4 - formerly: Alfa 101 Sprint, 2600 Sprint, Montreal - family classics: Jensen Interceptor II, '58 Hooper RR Silver Cloud I, Shadow II, '60 Corvette.
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post #8 of 19 (permalink) Old 08-13-2017, 11:12 AM
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Check the air duct that goes across the top of the engine very carefully. They often split in the accordion shaped section near the Air Flow Meter (AFM). This split can open up (often while accelerating) and the resultant 'false air' (unmetered by the AFM) will mess up the fuel injection (the computer thinks the engine is decelerating or at idle). Then, when the acceleration stops the split closes up and it runs OK.

If you do find a loose connection or split, also check the motor mounts. When they get old and saggy they let the engine move more than it should which is stretches the air ducts.

No pretty girl, huh? Too bad...

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post #9 of 19 (permalink) Old 08-13-2017, 01:14 PM
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If the tach did drop to zero and you lost ignition then also check grounds on the engine especially since other connections because loose. Check main positive terminal block on drivers side inner fender for tightness as well.
It also could be the start of a bad ignition switch. I lost power on the highway very much like you described when my switch was starting to go bad.
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post #10 of 19 (permalink) Old 08-13-2017, 05:28 PM Thread Starter
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The air duct was just replaced as a hole developed. Motor mounts are new. Engine was rebuilt top to bottom over the winter. Engine ground and other electrical connections are probably a good place to start although now I'm fixated on the girl.
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post #11 of 19 (permalink) Old 08-19-2017, 09:55 AM
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My most recent cut off issue was caused by the red stripe relay behind the seat, but I have an S4 and I am not sure you even have one of those.

It is a fierce, piercing shade of yellow, aglow with passion and defiance,
vibrating with the energy of a thousand suns, of thunder at dawn.

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post #12 of 19 (permalink) Old 12-27-2017, 01:58 PM Thread Starter
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The intermittent loss of power gremlin has started up again, this time with more frequency, at least once on every drive. Same condition, cuts out for a few secs and then starts itself back up. I have checked the places mentioned but to no avail. Everything seems tight. Also, I noticed this relay screwed into the right wheel well, one leg to the main power block, the other to the starter motor. Anyone know what this relay does? Factory or PO installed? Is this a hard start to give relief to the ignition? Can it fail? Guessing it may be the source of my problem.

Here's a video of the problem. Not the batt indicator on the tach goes out and then brake oil and sensor lights come on as the car restarts. And yes, the tach did drop to zero.

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Last edited by Sfizio; 12-27-2017 at 02:01 PM.
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post #13 of 19 (permalink) Old 12-27-2017, 05:38 PM
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I would check the Relays under the rear shelf.
I had a relay cutting off intermittently over a period of weeks with a long cranking time and failure to fire up.
It would always start after a 2nd or 3rd try and run OK until one day it cut off on an exit ramp.
The mechanical relay arm cracked for either the Fuel or Ignition.
It's easy to remove the plastic relay cover to inspect.
It could also be an ignition switch.
Do any other accessories cut out when this happens??
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post #14 of 19 (permalink) Old 12-27-2017, 05:46 PM
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Quote:
Originally Posted by ghnl View Post
What color is your car? Was the top up or down? Was there a pretty girl in the passenger seat? (got a photo?)
It's funny because it's true...
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'84 Spider Veloce...Why do I have a feeling this is going to be more expensive than my dog showing hobby was...
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post #15 of 19 (permalink) Old 12-28-2017, 11:33 AM
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Your mystery relay is a starter relay, like you surmised, added by some prev owner. Maybe as a stop gap to solve your current (no pun intended) issue! Maybe.

Check simple things like the ground strap under the car, ECU grounds under the hood. Ignition switch might be suspect, also.

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