M20 wont start all of a sudden

[RobDog]

Unplugging the coolant temp sensor or the oxygen sensor will make the car run in open loop until the car is shut off and started again. Open loop is when the engine runs off of a pre programmed base tune on the ECU, that allows the engine to run when cold, until the oxygen sensor warms up. When the oxygen sensor warms up the ECU switches to closed loop. Closed loop uses live data from your oxygen sensor and coolant temp sensor to control the fuel mixture, giving the engine better fuel economy, power, and making it smoother running. Maybe your oxygen sensor, coolant temp sensor, related wiring, or ECU are bad and causing an incorrect fuel mixture. But it sounds like a closed loop problem from my understanding

[Jaxx_]

My apologies Jaxx but I have been corrected, what gets unplugged while running is the temp sensor.

unbolt it and test the resistance (ohms) of the sensor at room temperature (~70F), ice water bath (32F), and boiling water(212F). Post the results.

The part should be pretty cheap if you want to replace it. If it is reading extremely cold the motor may think that the air is very dense, causing the car to run rich. Can you start the car with it unplugged? Does the condition change at all if the engine gets up to temperature?

[ezlnh8u]

the c191?

My apologies Jaxx but I have been corrected, what gets unplugged while running is the temp sensor.

[Jaxx_]

We hold the throttle down for the few seconds it takes to unplug and replug back in.

the c191?

[ezlnh8u]

how do you keep the car running if you unplug power to the injectors? What are you doing?

We hold the throttle down for the few seconds it takes to unplug and replug back in.

[Jaxx_]

Replaced the injectors, but no change. When I unplug the power to the injectors while the car is running bad plug it back in, it goes back to normal, drives good, but when I turn the car off and back on, the issue comes back. It seems as when I do that it's by passing something.

how do you keep the car running if you unplug power to the injectors? What are you doing?

[ezlnh8u]

Replaced the injectors, but no change. When I unplug the power to the injectors while the car is running bad plug it back in, it goes back to normal, drives good, but when I turn the car off and back on, the issue comes back. It seems as when I do that it's by passing something.

[Jaxx_]

Does your car have the c101 connector? Checked for corrosion?

Perhaps I am incorrect, but there is nothing on the C101 connector that would have an effect on fuel injectors stuck open.

[e30onBBSs]

I have to check if its not the harness like you mentioned. After turning the car off, and turning back on, the issue came back. Replicated what we did earlier unplugging the power to the injectors then back in. the car idled fine.

Does your car have the c101 connector? Checked for corrosion?

[ezlnh8u]

You need to confirm the problem is not in the harness.

Stuck fuel injectors usually just need a proper cleaning: flow cleaning the body, not just an ultrasonic bath. Replacing pintle caps and filters would be good too. It'll be cheaper than replacing all of the injectors and they will probably come back just fine. Worst case you have to buy a couple, but you'll at least know which ones are good.

I have to check if its not the harness like you mentioned. After turning the car off, and turning back on, the issue came back. Replicated what we did earlier unplugging the power to the injectors then back in. the car idled fine.

[Jaxx_]

We unplugged the power to the injectors while the car was running.for about 20 seconds. After plugging power back in, the car idled smooth and no back fire. The car has been on now for 5 minutes with smooth idle. I am assuming it's time for new injectors? Anyone have a good reseller?

You need to confirm the problem is not in the harness.

Stuck fuel injectors usually just need a proper cleaning: flow cleaning the body, not just an ultrasonic bath. Replacing pintle caps and filters would be good too. It'll be cheaper than replacing all of the injectors and they will probably come back just fine. Worst case you have to buy a couple, but you'll at least know which ones are good.

[ezlnh8u]

I think you found your issue... as I posted before for diagnosing your injectors....

We unplugged the power to the injectors while the car was running.for about 20 seconds. After plugging power back in, the car idled smooth and no back fire. The car has been on now for 5 minutes with smooth idle. I am assuming it's time for new injectors? Anyone have a good reseller?

[Jaxx_]

Checked all the injectors. Took them out, all of them read 16 OHM, did a thermal cleaning on them, started the car, same symptoms. Left it running for about 2 minutes. And the car started idleling smooth. Took the car out around the block, it pulled strong and smooth, on the way back to the house. It reverted back to the surging symptoms. At this point I think I Should dive into the timing?...

I think you found your issue... as I posted before for diagnosing your injectors....

It likely means that some of your injectors are stuck open. You can test them by running the car and listening to the injectors. They should be clicking/ticking clearly at idle. Do not mistake the valvetrain noise for this clicking. You can use a vacuum hose or a screwdriver on the injector to listen to it.

[ezlnh8u]

https://youtu.be/pOgXzB3bMLo

Link to a small video of my car shot by cars on board.

[ezlnh8u]

Wait - so it runs but drives like crap? This thread is so confusing. Kill it and start a new one. Thread or car. :)

I have been reporting everything that has happened since the issue started.

How it all started.

From one day to another the car would crank but not turn over, it ended.up being the main relay, the car then started but with surging and and rough idle, and rich.
replaced the following.

1: 02 sensor.
2: coolant temp sensor.
3: ICV
4: AFM
5: plugs and wires.
5: cap & rotor
6: FPR
6: cleaned injectors.

After doing all this, the car still ran with the same.sirging issies, I let it warm up for 2-3 minutes, the idle went back to normal, drove it for 2 blocks, it ran good, on the way back to the house it reverted back to the same symptoms. (Surging, rough idle and rich). The thread explains it all from start to present. I don't see how starting a new thread will help?