1995 Monte Carlo running rough

Tiny
CZR1760
  • MEMBER
  • 1995 CHEVROLET MONTE CARLO
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 120,000 MILES
I just bought a 1995 Monte Carlo with a 3100 V6 120K miles. The car ran & ideled fine with no problems. I drove the car to work today, no problems & as soon as I started to come home today the car started idling rough, accelerating sluggish with a noticable "hollow popping" sound from the engine when accelerating. The check engine light came on and stayed on. I am not able to check the flash codes because I have a 12 pin plug with only two wires at A & M. Is there a way to "jumper" this connector to check for flash codes. The car previous owner didn't know much about the car, but had a new battery, radiator, thermostat and hoses put in as well as a new serp belt. The cooling fan was loose, which I tightened. I changed the oil and installed a new tesioner pulley. I didn't pay much for the car and can't afford to put much more into it. Please help.
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Friday, March 11th, 2011 AT 3:02 AM

7 Replies

Tiny
FIXITMR
  • MEMBER
Might be a weak fuel pump. You'll have to pressure test it. This is gotta be why they sold it(problems)? I've had similar purchase experiences. Car drives fine for a day or 2 then crapola!
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Friday, March 11th, 2011 AT 3:16 AM
Tiny
CZR1760
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I can check the fuel pressure when I get home today. What is the fuel pressure supposed to be? I've had simaliar symptoms (loose of power, popping, missing)with other vehicles, when a bad cap or rotor were involved, but this car has coil packs.I do not know how to check if they are functioning properly. Thanks.
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Friday, March 11th, 2011 AT 1:03 PM
Tiny
FIXITMR
  • MEMBER
I think you can get the coils and ignition module checked at the chain auto stores. I had a similar problem and it was the ignition module.
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Saturday, March 12th, 2011 AT 5:36 AM
Tiny
CZR1760
  • MEMBER
I have not been able to check fuel pressure or coil yet, but the coil pack is loose at the mounting point. The bolts that are holding it down are bottoming out and tight. They just seem as though they are too long, leaving aprox 3/8" gap. I know that the previous owner was a younger kid and I have found several things, with the wiring, that have not been correct. The car previously had an alarm system installed, but it is no longer functional. I have found several "rats nest" with the wiring. I don't know if the coil pack being loose will cause a miss or not, but I plan to change bolts, if necessary and tighten while checking to see if the coil & ignition module are functional.
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Tuesday, March 15th, 2011 AT 3:51 AM
Tiny
CZR1760
  • MEMBER
I called and none of the local auto stores test coils and I still don't have a way to check for flash codes, since the only wires in the ALDL are A & M. Since I need to check this myself, what is the acceptable voltage for the coil, using a voltmeter? And what is acceptable fuel pressure? Again this is a GM 3100 V6. Thanks.
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Tuesday, March 15th, 2011 AT 3:55 AM
Tiny
FIXITMR
  • MEMBER
I have some family emergency issues came up so I have to let this go you might want to start a new question.
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Wednesday, March 16th, 2011 AT 11:48 AM
Tiny
GLENN66
  • MEMBER
I own a Z34 monte carlo 3.1 Litre The 3.1/3.4 coil packs must maintain GROUND so clean, sandpaper base of coil that mounts to engine block and tighten in place using correct bolt length. All GM early prior to 1996 coil / magneto had ground contamination issues caused by Galvanic corrosion [ metal base against Aluminum Block or opposing types of materials in contact], vaseline or anti-seize product eleminates this, plus oil/grease is factor. If still running rough Be sure wires R plugged into coil pack in proper Firing order #1 is closest to curb on coil pack [located above starter below front exhaust header] when U R standing in front of car looking at Motor. GM order is Left To Right-Clockwise same as in Old Dist. Days GM fires clockwise 146325 is 3.1/3.4 coil order. THIS info is important since previous owner replaced all cooling/overheating parts meaning incorrect firing order motor will run hot/rough N in cold surge between 2000 rpm back to 500 then erratically jump 500,1200, to 2000 at idle IT WILL cause U to spend needlessly On mass airflow, Idle air control solenoid etc. Books Do not allows say we define wiring order by sitting behind steering wheel OR standing in front of car.U May Have Leftover problem of Temp Guage to High this will Trigger Check Engine Light. Replace Engine Coolant Temp Sensor near Thermostat Housing Then when Key is turned ON disconnect negative leave 24 hours this reset is too clear codes N reset ECM main engine computer to restart motor must turn key to ON--20 seconds OFF 20 seconds Do this 2 cycles THIS Programs ECM Then U can Start/Test drive. Good Luck.
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Saturday, April 23rd, 2011 AT 4:44 PM

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