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Engine has trouble starting

Tiny
MMPRINCE4000
  • MECHANIC
  • 8,548 POSTS
The 3X reference signal is produced by the ignition control module (ICM). The ICM calculates the 3X reference signal by dividing the crankshaft position (CKP) sensor 18X pulses by 3. This calculation is performed while the engine is running, and while the CKP sync pulses are being received. The powertrain control module (PCM) uses the following information:

The 3X reference signal in order to calculate the engine RPM, and the CKP at engine speeds above 1,200 RPM
The pulses on the circuit in order to initiate injector pulses
A constant monitoring of the number of pulses on the 3X reference circuit
A comparison to the number of 3X reference pulses to the number of 18 X reference pulses and CAM signal pulses being received
If the PCM receives an incorrect number of pulses on the 3X reference circuit, DTC P1374 will set and the PCM will use the 18X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 18X reference and camshaft position (CMP) PCM input signals only.

This would have to be checked by GM or competent garage as P1xxx codes are manufacturer specific.

P0xxx codes are generic OBDII codes applicable to all OBDII PCM's.
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Wednesday, February 3rd, 2021 AT 4:17 PM (Merged)
Tiny
1983_DUSTIN123
  • MEMBER
  • 2 POSTS
  • 1996 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 190,000 MILES
The car stats right up after it has sat over night, but after it has been driven and gotten warmed up it is hard to start. I was leaning towards a crankshaft positioning sensor, camshaft positioning sensor, or coil pack control module.
Thank Dustin
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Wednesday, February 3rd, 2021 AT 4:17 PM (Merged)
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
First meke sure the fuel pressure is being maintained after the engine is off.
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Wednesday, February 3rd, 2021 AT 4:17 PM (Merged)
Tiny
1983_DUSTIN123
  • MEMBER
  • 2 POSTS
And how do I make sure it is maintaing preasure after its off and if its not whats the problem
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Wednesday, February 3rd, 2021 AT 4:17 PM (Merged)
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
You will need a fuel pressure test guage to do so, measure up the pressure with the key on turn the vehicle on run it check the pressure turn it off, then turn the key back on then off, watch the pressure, it shoudl drop less than 1psi per 2mins.

If it does it is either a bad fuel pressure regulator, leaky injectors or a bad tank check valve.
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Wednesday, February 3rd, 2021 AT 4:17 PM (Merged)
Tiny
JMERLINA
  • MEMBER
  • 1 POST
  • 1995 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 139,000 MILES
As I'm driving my car, my RPMs fluctuate while my foot is on the gas. This causes my car to bog down and then it picks up again. If my foot is NOT on the gas, my car will stall. In addition, sometimes when I try to start my car, warm or cold, it will not start. It will crank, but will not start. I'm thinking fuel pump, but what do I know. I have just replaced the computer, but this did not help. Could this be 2 separate problems or just one? I have a 3.4L GTP.
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
MASTERTECHTIM
  • MECHANIC
  • 4,749 POSTS
Well you should probably install a fuel pressure gauge to be sure but it sounds like a weak fuel pump could be the problem. The fuel pressure should be about 38 psi
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
CHARLIEH59
  • MEMBER
  • 1 POST
  • PONTIAC GRAND PRIX
I have a 1992 Pontiac Grand Prix with a 3.1 Liter Engine and about 164,000 miles on it. I started the car one morning and it seemed to crank awhile before it finally started when it did start it seemed to be missing or running rich. It stalled on me a couple of times at a stoplight and now has a surging problem at idle. I checked the air filter and when I did I found raw fuel in the intake hose. The check engine light is not on so I am wondering what it could be any info or things I can check would be helpful. Thanks!
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
TBDK
  • MEMBER
  • 24 POSTS
First thing I would find out the code and problem of the check engine light. That could be the root of problem. Which type of fuel injection do you have? TBI(Throttle Body Injector, 1 injection point) or MPF(Multi Port Fuel Injection, 1 Injector at each cylinder) Make sure the injectors are clean and installed securly/ correctly. I can't really think of hand what would put fuel in the intake hose except MAYBE a dead cylinder flooding BADLY. Seems unlikely though. If you have the TBI then it may just be a dirty injector. If you have MPFI Then that's a bit tougher to figure out.
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
NATEROACH
  • MEMBER
  • 2 POSTS
  • PONTIAC GRAND PRIX
I have a 2000 Grand Prix GT 110,000 Miles. Lately it has been stubborn to start and often requires the gas peddle to be held to the floor to get it to start. When it finally starts it runs rich and spews gas rich exhaust fumes. It also will idle high ( 2000 RPM) randomly. When I check the ECM the only error codes that I have gotten are P0125, which is insufficient coolant temp for closed loop operation. The local shop said they could find nothing wrong, but suspected that the fuel pressure regulator was to blame. I would appreciate any help that you guys could give me.
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
You could have a Coolant Temp Sensor that is out of range, or if the thermostat is stuck open it will set that code. Does it run cool? Take a long time to get to operating temp? Does it get to normal operating temp?
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
NATEROACH
  • MEMBER
  • 2 POSTS
Actually I have replaced both the temp sensor and the thermostat in the past 4 months. The car does get up to normal operating temp and doesn't seem to take longer than normal. Every now and then it will run hot because it is idling at 2K-2.5K rpm. I should also mention that the service engine light also will turn off by its self after a while ( day or so, sometimes after only an hour or so). For the time the fuel system is my largest concern, being that the service engine light seems to be intermittent.

Thanks
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)
Tiny
2CARPRO JACK
  • MECHANIC
  • 11,533 POSTS
Ther is a vacuum line that goes from th epressure reg to the intake manifold. Remove it and look for raw fuel, if it is present then the reg is blown and needs to be replaced. The only other way for raw fuel to enter the engine is if one or more of the injectors are leaking down.
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Wednesday, February 3rd, 2021 AT 4:18 PM (Merged)

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