OBDI Chevy tech question...

[jtdesigns]

OK.. This is the deal.. My best bud got a DD for free.. Its a 1991 Chevy Lumina with a 3.1L V6..

No CEL but is storing a code 13 when pulled.. O2 sensor. Now.................

 

This car runs like a top up until it warms up.. You can actully hear it switch over to running real rough. (shakes, power loss, sputtering kinda, like a spark plug wire arcing)

 

Would you say the O2 sensor has everything to do with this??

 

So far we have installed a fuel pump (40psi), new fuel filter, new wires, plugs, air filter, cleaned the egr and ports, and did a seafoam treatment through the intake.

 

 

O2 sensor is going on either tomorrow, or Sat. I hope this would be our next step seeming how there is a DTC for it.

 

Why isnt the CEL staying on if the O2 is bad?? Cleared the code (removed batt power, sat overnight, reconnected) let it idle and still got code, but as stated no CEL.

 

I was hoping to check the injectors, only if I could without pulling the intake plenum :wall:

 

:waving: I'm hoping there is someone here, in the vast knowledge of knowers, that can direct us to keep from throwing parts at this thing till the problem is solved. :waving:

[CEThomas]

Sounds like it's the O2 sensor. I do not recall all the codes that the PCM will store w/o a light :hmm: but I know a few will store. Same with ODBII, I will hook up my scaner to see all the codes stored from time to time that do not set off the light. Also a good way to see how fast my daughter has been driving :banana:

[jtdesigns]

Sounds like it's the O2 sensor. I do not recall all the codes that the PCM will store w/o a light :hmm: but I know a few will store. Same with ODBII, I will hook up my scaner to see all the codes stored from time to time that do not set off the light. Also a good way to see how fast my daughter has been driving :banana:

 

 

OK Thanks Charles. I didnt know ODBII had a top speed record..

[CEThomas]

Her car has a vac problem and I can pull the data from when it recorded the problems which also has the speed when the code was sent, which is always when she takes her foot off the gas :yes:

[watchamakalit]

I would be 99% positive its an O2 sensor issue. Sounds to me like it is running fine when its in open loop but when it warms up and goes to closed loop you have issuse. (I might be incorrect as to when its open loop and when its closed haven't dealt with OBDI in a while)

[86FUBAR]

This what i got off alldata , hope it helps

 

 

CIRCUIT DESCRIPTION

 

The ECM supplies a voltage of about 0.45 volt between terminals "A16" and "A22". (If measured with a 10 megohm digital voltmeter, this may read as low as 0.32 volts). The O2 sensor varies the voltage within a range of about 1 volt if the exhaust is rich, down through about 0.10 volts if exhaust is lean. The sensor is like an open circuit and produces no voltage when it is below 316~C (600~F). An open sensor circuit or cold sensor causes "Open Loop" operation.

 

NOTE: Because of all the possible color code combinations used on electrical wiring diagrams, always refer to SCHEMATIC DIAGRAMS/ELECTRICAL AND ELECTRONIC WIRING DIAGRAMS/ECM CONNECTOR IDENTIFICATION for correct color code identification of circuit.

 

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

 

 

 

Code 13 will set underthe following conditions:

Engine running at least 2 minutes after start.

Coolant temperature at least 50~C (122~F).

No Code 21 or 22.

02 signal voltage steady between 0.35 and 0.55 volts.

Throttle position sensor signal above 4% for more time than TPS was below 4%. (About 0.3 volts above closed throttle voltage)

All conditions must be met and held for at least 25 seconds. If the conditions for a Code 13 exist the system will not go "Closed Loop".

This will determine if the sensor is at fault or the wiring or ECM is the cause of the Code 13.

In doing this test use only a high impedance digital volt ohmmeter. This test checks the continuity of CKTs 412 and 413 because if CKT 413 is open the ECM voltage on CKT 412 will be over 0.6 volts (600 mV).

DIAGNOSTIC AIDS:

 

Normal "Scan" voltage varies between 100 mV to 999 mV (0.1 and 1.0 volt) while in "Closed Loop". Code 13 sets in one minute if voltage remains between 0.35 and 0.55 volts, but the system will go "Open Loop" in about 15 seconds. Refer to TESTING PROCEDURES/DIAGNOSIS BY SYMPTOM/INTERMITTENTS

[jtdesigns]

Thaks for your replies!!! We fix'd er right up.. The cuprit was a bad ingnition module.. :banana: :banana: