Intermittent shutting off?

Hello Joe,

Let me clarify about it shutting off at the stoplight. The engine didn't have time to warm up. The stoplight is approximately 4.5 blocks from my house. It ran until the light turned green and before I could hit the accelerator, it died. The temperature gauge was still on the cold mark.

I thought it could be the fuel pump, but this problem has been so intermittent that it threw me off about it possibly being the fuel pump. Sometimes it will go for a couple of weeks before having a stumbling or shutting off issue.

If it is the crankshaft position sensor, where would it be located? I might just try replacing it before doing the fuel pump to see if it fixes the issue.

Althea

Hello Joe,

I have some more trouble shooting info for you. The other day I was driving the truck and waiting to turn into a parking lot. As I waited for passing traffic, I thought I had been hit from behind. However, the truck had actually stumbled and the lurched. My friend, who actually owns the truck, said that the stumbling and lurching had also happened to him a few times, but he forgot to mention it to me.

As we were contemplating, for several days, of what could cause the stumbling and lurching; my friend had discovered that the truck is equipped with a fly-by-wire system instead of accelerator linkage/cable. Could the fly-by-wire be malfunctioning and making it appear to be either the fuel pump or the Crank Position Sensor? If so, how can we test it?

It just seems that as time goes by, the truck is throwing more symptoms at us.

Yes, he has ran his code tool several times and there were no codes.

Hi Joe, here's the latest on this Chevy truck. My friend decided to get a new code reader because he thought the one he had was out of date. The new code reader is able to provide live data. Recently, the truck has not been able to start when it's very cold outside. However, one cold day after trying and trying it finally started. He had the code reader hooked up on live data, and even though it was not throwing a code, on live data the throttle body was jumping all over the place. He ordered a new throttle body, but still hasn't replaced the crank position sensor or the fuel pump although He has the parts.

Well, it's confirmed. It was the throttle body. We've been driving the truck every day since the 21st and haven't had an issue with it. Thanks for the help.

Hello Joe,

Well, we're very frustrated with this truck. Putting in a new throttle body did not last long, only a couple of weeks. We drove it to Amarillo, and it started acting up again. Now it's even worse and it's still not throwing codes. We did, however, replace the crank position sensor which is what was thought was wrong with it previously. But now it's doing something new.

When we drove it to Amarillo and back, approximately a 220-mile round trip, Marty engaged the cruise control and it was having intermittent issues, then it did throw a code and said it was the CPS, so we replaced it. The truck ran fine for a couple of weeks and then began acting up again.

Now it's doing something new. It won't start at all when it's cold outside. So, we did some more investigating and came up with an ambient temperature sensor. However, information on where it says it's located seems to be false. It says it's located between the front bumper and the bottom of the radiator. We can manage to get it started when it's warm outside, but if we attempt to drive it then it dies on us. But we're afraid to drive it in case it won't start again.

Here's another new thing it's doing. With the key in the run position, engine not running, but all the relays under the hood are clicking, snapping, and popping. He attempts to start the engine and it won't start. It is cold outside. Also, the check engine light on the dash blinks, but it's still not throwing any codes.

I think the ECU/ECM has gone out. It makes sense because the poor truck has gone crazy. Either it has lost its mind or poor old Pop is possessing it. I have provided a short video for you to see what it's doing.

Althea

Okay, thanks Joe, I'll let him know and we'll try that. But if it's warm outside the truck starts right up. It only doesn't start when it's cold outside and that's when the relays start doing their thing.

"If you have a live data scan tool, go to live data and see what the engine coolant temperature sensor (ECT) is signaling to the PCM. It should be very close to ambient temperature." Live data says ambient temp is 16*C = 60.8*F, right now it is 68*F outside.

Funny that you would mention the fuel pump because one of the relays that was doing the crazy clicking is for the fuel pump. He mentioned that his father had the fuel pump replaced in 2022, the year before he died. The other relay that was going nuts is for the power train. So, I'm guessing that those need to be replaced? I'll let him know what you said in your previous post.

Thea