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Discussion Starter #1
Hi All,

I hace recently swapped out my 305 TBI for 383 TBI and have yet to get the timing down. Car will not stay running long enought to check timing. After disconnecting the EST bypass, the car stalls. I have tried advacing and retarding the timing prior to starting the carin bypass mode, as well as tried disconnecting while it is running (poorly) and still connected to the timing components. I have replaced the igntion module once due to it testing bad, but accoriding to the azone tester, this one is good. Distributor and pick up coil are new. Help! I have been troubleshooting for about 10 weeks now and have only gone backwards it seems. Any help would be greatly appreciated!
 

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Re: Troubles Setting Timming/Running

OBD I?
Attach vacuum gauge to manifold/full vacuum.
Ensure EGR valve is fully seated and in good repair - no leakage.
Ensure MAP sensor has good vacuum source and sensor itself works good and is getting 5VDC reference voltage.
Short Pins A & B together at ALDL connector.
Key on, eng off for about 10 seconds, key off.
Unplug IAC and bypass ignition, remove Pins A & B short.
Pull out welch plug at TBI curb idle screw and crank in about two-three turns to open throttle plates.
Set up timing light and ensure spark, crank engine to start.
Adjust timing as needed to keep vacuum high and engine to run smoothly.
Lower rpms once engine up to operating temperature to say 600 rpm, base rpm - non-ECM controlled, or whatever RPM is needed to keep engine running.
You may have to loosen and adjust TPS sensor to adjust smoothness, only after reaching oper temp base rpm.
Vacuum gauge should read above 16 inches for stock spec running.
Stop engine and reconnect EST and IAC and disconnect ECM power or battery to erase diagnostic codes, then reconnect battery/ECM power.
Turn ign key on for 10 seconds then off to set initial ECM idle.
Attempt to start, should run. ECM controlled idle should be around 750-850 rpm and ECM controlling ign timing.

Engine should run with some normalcy if you lifted TBI and swapped out 305 for a 383 and 383 camshaft has less than 220°@0.050" duration and wider than 112° LSA.
Otherwise, you'll need a reprogram.
 

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Discussion Starter #3
Re: Troubles Setting Timming/Running

Thanks for the walk through. I followed your steps and was able to get the car running again without the EST bypass plugged in. I noticed though I was having 1-2 in Hg of vacuum fluctuation (from 17 to 15 in Hg). Also, when i hooked back up the EST bypass and IAC, car wouldn't run very well, actually backfiring up through the intake. Anotehr note, after shutting off the car, I notice that occasionally I will have some smoke built up in the throttlebody. If I open the butterflys on the throttle body. the smoke is cleared. The interesting part to me is when I pop my oil cap, I will have smoke there as well. Is this indicitive of an Intake manifold leak? This could be the cause of alot of problems if so. Thanks again for the help!
 

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Could be an intake leak.
Could also be residual smoke from the backfire, not enough advanced timing.
 

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Discussion Starter #5
I have moved the distributor one end to the other trying to find the "sweet spot" and once i hook back up the bypass wire it struggles. I think I may need to pursue changing out the intake manifold gaskets, though they have less than 100 miles on them (may have goofed up on the install).

Would you expect to see smoke in the valve cover upon a backfire (this may be a very rookie question...)?
 

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The smoke in the valve cover could be condensation and maybe the PCV system is not working.

Another trick, take a hand vacuum pump and place it onto the MAP sensor and plug the hose pulled off from the sensor.
Pump in 20" of vacuum and see/hear if the engine runs better.
You want the EST disabled and does the timing mark move with the dist body rotation? 8°-10° BTDC would be a good place to start.
The charcoal cannister and its plumbing is in good order? You could plug the inlet hose to the manifold.
 
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