[Gmecm] 93 CHEVY g20 VAN

[David Allen]

  CTS fault very common and will not set a code until it gets VERY bad. ECM
will continue to beleive the faulty sensor signal and operate accordingly
until the sensor completely fails.
  With the engine running, disconnect the CTS sensor.  The check engine
light will come on and the ECM will substitute an "average" temp reading for
the disconnected sensor. If a bad CTS is the cause, the rich-running symptom
will go away within a few seconds of unplugging the bad CTS sensor.
  Cold starting may not be possible without this sensor so replace it if it
is  bad - don't leave it unplugged.
David


-------

Common faults.

CTS (coolant temp sensor--at manifold, not head). Scan will verify this one
quick.
Leaking exhaust manifolds...system will command rich.
Leaking EGR valve...runs richer at lower speeds and idle, due to lower MAP
vacuum signal.
Worn distributor bushings...cracked magnet--can double trigger the RPM
signal to the ECM.
Bad MAP sensor or vacuum leak to sensor--various TSB's on this failure.
Incorrect spark plug reach (least likely).

Lyndon.



----- Original Message ----- 
From: michael b
To: gmecm at diy-efi.org
Sent: Friday, December 30, 2005 11:22 AM
Subject: [Gmecm] 93 CHEVY g20 VAN


93 CHEVY G20 VAN 5.0L  RUNS TOO RICH, I REPLACED PLUGS, CAP,ROTOR,WIRES, O2
SENSOR,THROTLE BODY GASCKET,MAP SENSOR, I EVEN CUT THE CAT OUT TO SEE IF WAS
CLOGGED ALOT OF PARTS AND HAD THE CODES CHECKED ( NO FAULT CODES FOUND)
BLACK SMOKE , RUNS ROUGH, STALLS. ANY HINTS?



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