What's the difference between MAF sensor and MAP sensor as they relate to starter issues?
I have an '88 Corolla FX with 145k and have to pump gas lightly and turn key briefly perhaps 3 or more times after not running car for a few days. Issue becomes worse with rain and humidity to the point where stalling when running occurs especially after not running for several days after heavy rains. A low amount of gas in tank seems to make it worse.
Thanks for your help.
MAF = Mass Air Flow - measures the amount of air flowing into the engine. At that time, I think there were 3 types of air flow meters. One was a hinged door or flap that got pushed open as more air entered, the second was a heated wire that was cooled as more air flowed past the wire, and the third was a light source and detector with a mirror mounted on a ilament. - as more air flowed past the mirror, it would vibrate more and light detector would count how fast the mirror twitched.
MAP = Manifold Absolute Presure - measures manifold intake vacuum
Generally, neither a MAF or MAP sensor affects starting without affecting driveability as well. If the car runs OK once it is started, these sensors are not likely causes of the hard starting condition.
There are several possibilities which should be checked before replacing.
If it is fuel-injected, measure fuel pressure when the condition occurs to see if the fuel pressure regulator is not maintaining fuel pressure.
I think this vintage had a cold start injection system. If so, check cold start injector function and cold start injector timer function.
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