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Category: RV
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Looking for ignition timing specs for 1990 chevy P30 454.

Customer Question

Looking for ignition timing specs for 1990 chevy P30 454. And the voltage parameters for the throttle position sensor for same.
Submitted: 9 years ago.
Category: RV
Expert:  ebrock63 replied 9 years ago.



Ignition timing is 4degrees BTDC(before top dead center), and TPS output voltage range is 1.25 - 5.0v




Customer: replied 9 years ago.
Any ideas on the rough idle, stalling?
Expert:  ebrock63 replied 9 years ago.



You definitely want to change the TPS as it is below minumum output voltage.


Check for a vacuum or air intake leak as well. Replace any vacuum lines that are cracked, swollen, collapsed, or broken.


With engine idling, spray around base of intake manifold with carb cleaner. IF idle changes, replace intake manifold gasket.


Check egr valve for vacuum, make sure egr ports are carbon clogged.


Customer: replied 9 years ago.
One more question, my problem seems to be related to the IAC not opening. I have no vacuum leaks. In fact the engine idles good with the IAC removed! A big old hole in the side of the throttle body. Huge vacuum leak there. As soon as I put in the IAC it wants to stall. Smells rich. Could the passage way from the IAC be clogged? Plunger makes it too rich? And with it removed it gets enough air? Thanx.