1992 Chevy Blazer Vortec No Start

BLAZERSC

MEMBER
1992 CHEVROLET BLAZER
6 CYL
2WD
AUTOMATIC
218,000 MILES

Hello, I have a 92 Chevy s10 Blazer w/ vortec engine and auto trans (2Wheel Drive). Yesterday when my wife was driving it, it started stumbling and bogging down on her. She pulled off of the interstate into the E-lane and started it back up. It would immediately start as normal but as soon as she would hit the gas it would bog down, and either lope or cut off.I had it towed to our house, and once I got it home, I tried to start it, it started right up, but as soon as you hit the throttle it would bog down and die. This morning I went out to start it and now it wont start.I have checked the exhaust to make sure there is pressure coming out, and from what I can tell the cat is not stopped up.I have also checked for spark and it has tested good also. As far as the fuel, I took the line loose at the filter and turned the key to on and it sprayed fuel everywhere, I did not check the pressure for I dont have a pressure gauge, but I also checked it at the fuel rail and it seemed to have quite a bit off pressure there also. Could the timing have jumped or is there something I am missing?Any help would be greatly appreciated. Thanks in advance. Hope you can help me.

And I forgot to menton, when did start it yesterday, it would sometimes back fire through the intake, I am thinking it is the timing but just wanna get a second opinion.

3 Replies

RASMATAZ

MECHANIC
75,992 POSTS

Its a must that you check the fuel pressure it should read 60-66psi if okay test the TPS, MAP and knock sensor.

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Friday, January 29th, 2021 AT 2:06 PM

BLAZERSC

MEMBER
2 POSTS

Ok, fuel pressure is 62 psi.I found the map sensor on it, do you know anyway I can check it?Thanks

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Friday, January 29th, 2021 AT 2:06 PM

RASMATAZ

MECHANIC
75,992 POSTS

Testing the MAP sensor:

Step 1. Locate the MAP sensor along the firewall or to the right-passenger side of the engine compartment.

Step 2. Check the vacuum hose attached to the sensor and make sure is in good condition and free of obstructions. Also make sure there are no loose wires and the sensor's electrical connector is in good shape.

Step 3. Determine what type of MAP sensor is installed in your vehicle--voltage or frequency type. If you have a voltage type, you will use a voltmeter for this test; if it is a frequency type, you will use a tachometer. Consult your vehicle service manual if you're not sure what type you have.

Step 4. Unplug the electrical connector from the MAP sensor and turn the ignition key on, but do not start the engine. With a voltmeter, measure the reference voltage by touching the reference wire with the meter's positive lead and the negative lead to ground-black wire, which is at the connector's end coming from the computer. If the reference voltage--about 5 volts--is out of specification, you have found the source of the problem. Reconnect the MAP sensor and turn off the ignition key. Take your vehicle to a professional auto electrical shop for further testing.

Step 5. Attach the voltmeter or tachometer negative probe to the ground (black) wire and the positive probe to the signal wire. The sensor's connector should be plugged in. The third wire--the reference wire--produces a steady 5-volt signal only. Consult the wiring diagram in your vehicle's service manual if necessary. You might want to insert pins into the wires to attach the probes to for this test.

Step 6. Disconnect the vacuum hose from the MAP sensor and attach a hand vacuum pump.

Step 7. Turn the ignition key on, but do not start the engine.

Step 8. Read the voltage or rpm. With 0 inches of Mercury (in-Hg) vacuum, you should get between 4.5 and 5 volts, or between 300 and 320 rpm.

Step 9Apply 5 in-Hg of vacuum. You should be reading now about 3.75 volts, or between 275 and 295 rpm.

Step 10. Apply 20 in-Hg of vacuum now. This time you should be reading about 1.1 volts, or between 200 and 215 rpm. Compare your readings with those specified in your vehicle service manual. If the values are out of specification, replace the MAP sensor.

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Friday, January 29th, 2021 AT 2:06 PM