[Diy_efi] rich/lean and O2.

Wed Nov 24 19:12:30 GMT 2004

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double check the grounds...=0D
it's possible with a bad ground to the ECM that the ECM isn't truly seein=
g
the proper O2 sensor voltage... to it, .800v may be .450 at the O2 input.=
=2E.=20
can you pick up the sensor voltages etc via the ALDL? (scantool) that wil=
l
show you exactly what the ECM is seeing=0D
 =0D
 =0D
-------Original Message-------=0D
 =0D
From: RogeranCarol=0D
Date: 11/24/04 13:56:04=0D
To: diy_efi at diy-efi.org=0D
Subject: [Diy_efi] rich/lean and O2.=0D
 =0D
Have a problem I just can't get a handle on! Just installed 5.7L TBinject=
ed
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* engin=
e
temp as well as at 195* temp. My temp sensor (CTS) reads 1v at 190*. My f=
uel
pressure holds steady across the rpm test range (625rpm to 2000rpm).=0D
My throttle position sensor reads .65 at idle and 4.8v at WOT. I can driv=
e
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 boost=
er
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 applicatio=
n
(entirely stock).=0D
 =0D
What have I overlooked? Any thoughts would be appreciated.=0D
 =0D
Roger=0D
=20
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<DIV>double check the grounds...</DIV>
<DIV>it's possible with a bad ground to the ECM that the ECM isn't truly =
seeing the proper O2 sensor voltage... to it, .800v may be .450 at the O2=
 input...&nbsp; can you pick up the sensor voltages etc via the ALDL? (sc=
antool) that will show you exactly what the ECM is seeing</DIV>
<DIV>&nbsp;</DIV>
<DIV>&nbsp;</DIV>
<DIV id=3DIncrediOriginalMessage><I>-------Original Message-------</I></D=
IV>
<DIV>&nbsp;</DIV>
<DIV id=3Dreceivestrings>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>From:</B></I> <A href=3D"m=
ailto:rogerancarol at cox.net">RogeranCarol</A></DIV>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>Date:</B></I> 11/24/04 13:=
56:04</DIV>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>To:</B></I> <A href=3D"mai=
lto:diy_efi at diy-efi.org">diy_efi at diy-efi.org</A></DIV>
<DIV dir=3Dltr style=3D"FONT-SIZE: 11pt"><I><B>Subject:</B></I> [Diy_efi]=
 rich/lean and O2.</DIV></DIV>
<DIV>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Have a problem I just can't get a handle=
 on! Just installed 5.7L TBinjected&nbsp;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 i=
dle. I'm experiencing "lean stumble" until engine is completely warmed up=
=2E My O2 readings are the same at 140* engine temp as well as at 195* te=
mp. My temp sensor (CTS) reads 1v at 190*. My fuel pressure holds steady =
across the rpm test range (625rpm to 2000rpm).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>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 dro=
p 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).</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>What have I overlooked? Any thoughts wou=
ld be appreciated.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT>&nbsp;</DIV>
<DIV><FONT face=3DArial size=3D2>Roger</FONT></DIV>
<DIV>&nbsp;</DIV></TD></TR>
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