ECM Fault - could be TPS

[Akselrud, Boris]

I think I did scope the TPS signal, found no problems, but I'll do it again
since you say there were incidents like that.

-----Original Message-----
From: KasaRyan at aol.com [mailto:KasaRyan at aol.com]
Sent: Monday, December 06, 1999 6:22 PM
To: gmecm at efi332.eng.ohio-state.edu
Subject: Re: ECM Fault - could be TPS


My 93 chevy truck with the same TBI engine would do the same thing sometimes

after washing the engine.  It turned out to be the water messing up the 
Throttle Position Sensor.  If you have really hosed one good you have about
a 
30% failure rate on it!  The computer sees the changing TPS value as you 
moving the throttle and incorrectly alters the a/f ratio to compensate.
Then 
it sees that that messes up the idle speed and o2 reading and alters the 
injector pulse and IAC position to account for things.  The result is that 
the engine may run crappy at anything less than 75% throttle for no apparent

good reason when the problem is just the TPS.  Use a scantool or a good 
voltmeter and make sure the voltage is linear with motion and unchanging at
a 
fixed throttle setting

Ryan Hampl