[Diy_efi] rich/lean and O2.

Wed Nov 24 18:57:50 GMT 2004

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Have a problem I just can't get a handle on! Just installed 5.7L =
TBinjected chevy into my Cherokee and can't get the engine to run =
"closed loop". O2 sensor appears ok, but output at idle is .800+ volts, =
steady, and rapidly drops to .o25v, steady, above idle. I'm experiencing =
"lean stumble" until engine is completely warmed up. My O2 readings are =
the same at 140* engine temp as well as at 195* temp. My temp sensor =
(CTS) reads 1v at 190*. My fuel pressure holds steady across the rpm =
test range (625rpm to 2000rpm).
My throttle position sensor reads .65 at idle and 4.8v at WOT. I can =
drive the O2 reading up from .025 to .8+ by injecting propane into the =
TB, and can get the .8+ reading at idle to drop to.45v by pulling the =
pwr brake booster hose loose. The O2 signal from the ECM is .39v with =
the O2 sensor disconnected. The ECM and PROM are new and appropriate for =
the application (entirely stock).

What have I overlooked? Any thoughts would be appreciated.

Roger
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<DIV><FONT face=3DArial size=3D2>Have a problem I just can't get a =
handle on! Just=20
installed 5.7L TBinjected&nbsp;chevy into my Cherokee and can't get the =
engine=20
to run "closed loop". O2 sensor appears ok, but output at idle is .800+ =
volts,=20
steady, and rapidly drops to .o25v, steady, above idle. I'm experiencing =
"lean=20
stumble" until engine is completely warmed up. My O2 readings are the =
same at=20
140* engine temp as well as at 195* temp. My temp sensor (CTS) reads 1v =
at 190*.=20
My fuel pressure holds steady across the rpm test range (625rpm to=20
2000rpm).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>My throttle position sensor reads .65 =
at idle and=20
4.8v at WOT. I can drive the O2 reading up from .025 to .8+ by injecting =
propane=20
into the TB, and can get the .8+ reading at idle to drop to.45v by =
pulling the=20
pwr brake booster hose loose. The O2 signal from the ECM is .39v with =
the O2=20
sensor disconnected. The ECM and PROM are new and appropriate for the=20
application (entirely stock).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>What have I overlooked? Any thoughts =
would be=20
appreciated.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Roger</FONT></DIV></BODY></HTML>

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