Engine misfire

Good afternoon,

If you have a misfire on number 4, you need to do some testing.

https://www.2carpros.com/articles/engine-misfires-or-runs-rough

Check for power to the injector. You should have 12 volts with the key on.

Check the compression as well. Low compression will cause this.

https://www.2carpros.com/articles/how-to-test-engine-compression

Do you have spark at the plug?

https://www.2carpros.com/articles/how-to-test-an-ignition-system

I attached a wiring diagram of the injectors for you as well.

https://www.2carpros.com/articles/how-to-check-wiring

Roy

12.2 and 3.8 volts #4 connector, good spark and compression on #4. Any thoughts about the MAF and coolant temperature sensors? Thanks for your help.

You should have battery voltage on one side and 0 on the other with it disconnected.

With the key on and the connector attached, you should have battery voltage on both sides.

No to the other sensors. If they were an issue, it would affect all cylinders.

Roy

Any ideas on why I'm getting 12.2 and 3.8 disconnected?

12.2 is good but the 3.8 is not.

What about the other check I suggested?

Roy

I'll have to get to it tomorrow. Dark now here. Thanks for your help.

You are welcome.

Keep me updated.

Always glad to help.

Roy

#2,#4,#6 injector connectors all read 12.2 and 3.8 with key on?

Is that disconnected? Or is that with the injector connected?

Roy

That's with all disconnected. I found an ECU fuse on the engine fuse block that was 12V on one leg and 0 on the other. Replaced it and now #4 is firing. Running better, but still not a great idle in drive. Tries to cut off. Could the other trouble codes be at fault? MAF and coolant temperature sensors?

What other codes? There were no codes listed in your question.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

Roy

Mass air flow sensor shows 0 volts on a SnapOn engine analyzer, along with a coolant temperature sensor. I replaced the MAF sensor and still no change in idle with plugged in or unplugged.

Please tell me the codes.

Did you check the compression and fuel pressure as I suggested?

Roy

I went to a guy I know who has a speed shop to use his scanner, will have to get to a auto parts store to get scanned. Drove vehicle 500 miles last week. #6 cylinder now missing. No effect when I pulled injector wire or spark plug wire. Have spark though. All ECU fuses are 12 v on both legs. Gas mileage is of course way down. Any thoughts appreciated.

As I suggested, check the compression and let me know the results.

https://www.2carpros.com/articles/how-to-test-engine-compression

Roy

Compression on 2,4, and 6 are all around 200.

Okay, put your voltmeter in the connector for the injector. Red lead to the power side of the injector and black to the other terminal. Tell me the volts with the key on.

Roy

0 volts at 2,4, and 6.

Any thought about the 0 volts reading? Get 12 on 1 pin 3.8 on the other with ground lead on negative battery, but 0 on both injector pins, also reversed get 0.

Did it read 0.00 or did it read nothing at all?

Roy

0.00.

That indicates the 2 wires you are testing are shorted together.

Inspect the harness carefully for any damage.

Roy

With engine running, dmm connected to #6 injector connector, i am getting voltage readings?

I suggested doing the test with the key on engine off.

With it running, you will not and cannot see the ECM grounding the return wire.

Roy

Also did that. I'm getting 0.00 on #2, #4, and #6 injector connectors with key to on (not running). Any ideas? #2 and #4 are working, #6 is not?

Put the black lead on a good machine ground and make sure you have 12 volts to the injector.

Roy

Have 12 volts on 1 pin, 3.8 on the other pin of injector #6 connector with dmm black lead to ground.

Okay, I would get a noid light and put it on the connector and crank the engine and see if it flashes while cranking.

You can rent one at a parts store.

Roy

Noid light shows #6 is firing.

Did you replace the injector? If the compression is good then it could be a bad injector.

https://www.2carpros.com/articles/how-to-replace-a-fuel-injector

Roy

REMOVAL
1. Release residual pressure from the fuel line to prevent fuel from spilling.

CAUTION: Cover the hose connection with rags to prevent splashing of fuel from residual pressure in the fuel line.


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2. Remove the delivery pipe with the fuel injector and pressure regulator.

INSTALLATION
1. Install a new grommet and O-ring to the injector.
2. Apply a coating of solvent, spindle oil or gasoline to the injector O-ring.
3. While turning the injector left and right, install it onto the delivery pipe.


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4. Be sure the injector turns smoothly.

NOTE: If injector does not turn smoothly, the O-ring may be jammed. Remove the injector and re-insert it into the delivery pipe and recheck.