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Strange problem with timing


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On my L28ET and 83 L28ET EFI powered S13 I having a strange issue while idling and then driving I can feel it in cruising so today I took the time to put a timing light on the engine and see if my timing shifted on me. I'm watching my timing for a few minute os so and one of the other guys at work came over to talk to me while I was in the middle of testing the timing. We both saw this next thing happen, the timing was a steady 20' BTC and then out fo the blue it would go advance a good 20' or so and go right back just as quick, if you blink you will miss it. It did this very erratic but intermittingly while we both watched it.

 

I had pulled the car in a few minutes before it was time for me to lock down the shop so I had to get out of there and go home even though the car was questionable, good thing I live close to work. On the ride home I noticed that the car would have a erratic/intermitting miss just like at the shop. I was thinking about it the whole way home (A good 15 minutes) and this is what I think is going on.

 

I think I have a "F"ed up CAS unit. I had some things to do this evening when I got home from work so I didn't get to test anything further. I have some CAS units in the garage and tomorrow after work I will swap it out to see what it runs like after that.

 

Any thoughs?

 

BTW if anyone followed my other thread where I was trying to get my mixture straight, I have it almost dead on and she was running real strong till this started.

 

Thanks

pallnet

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On my L28ET and 83 L28ET EFI powered S13 I having a strange issue while idling and then driving I can feel it in cruising so today I took the time to put a timing light on the engine and see if my timing shifted on me. I'm watching my timing for a few minute os so and one of the other guys at work came over to talk to me while I was in the middle of testing the timing. We both saw this next thing happen, the timing was a steady 20' BTC and then out fo the blue it would go advance a good 20' or so and go right back just as quick, if you blink you will miss it. It did this very erratic but intermittingly while we both watched it.

 

I had pulled the car in a few minutes before it was time for me to lock down the shop so I had to get out of there and go home even though the car was questionable, good thing I live close to work. On the ride home I noticed that the car would have a erratic/intermitting miss just like at the shop. I was thinking about it the whole way home (A good 15 minutes) and this is what I think is going on.

 

I think I have a "F"ed up CAS unit. I had some things to do this evening when I got home from work so I didn't get to test anything further. I have some CAS units in the garage and tomorrow after work I will swap it out to see what it runs like after that.

 

Any thoughs?

 

BTW if anyone followed my other thread where I was trying to get my mixture straight, I have it almost dead on and she was running real strong till this started.

 

Thanks

pallnet

 

Sounds like you are on the right path. Don't overlook the connectors themselves. In an engine (and harness) of that age, it could also be oxidized connectors, loose connections, brittle wiring, etc. Try jiggling and tugging everywhere while one of the guys keeps the timing light on it.

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I assume you have good plug wires and that cross arcing isn't an issue? also the rotor and cap in good condition? it always puzzeled me how any engine can be so sensetive to a 1 or 2 degree rotation of the cao in relation to a rotor than has a half inch wide electrode at the end, just wondering is the car can be originating form off center due to damage or wear or whatever

 

from my experience when the cas fails it's intermitant for a very short time befor ecomplete failure

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This problem just started so the CAS could be on it's way out and then again there could be another issue such as cross arching but I will know more tomorrow evening.

I will be taking the truck into for for sure, I don't want to play auto tech on the side of the road and being late for work is not an option.

Thanks for the info fellas.

pallnet

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Tonight I replaced the CAS and timed the dizzy. While watching the timing mark, it appears to be fixed. I watched the timing mark for a good half hour while reving the motor and stuff and it looks good. Tomorrow during the day I will take her out for a drive to make sure all is well (I will have a spare dizzy in the car just in case). I sure as he11 hope I don't have to go any further with it, not that it's a major problem, I just can't wait to install my oil cooler, intercooler and reinstall the AC system.

Thanks

pallnet

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