Intermittent shutting off?

Hi,

It could be a fuel pressure issue or even the crankshaft position sensor. When they start to fail, often heat adversely affects them.

Do me a favor. Take a look through this link and let me know if it mirrors what you experienced:

https://www.2carpros.com/articles/symptoms-of-a-bad-crankshaft-sensor

Let me know. Also, if it stalls when you are driving, it must not be fully stalling. You may be experiencing a power loss due to a loss of spark that restarts, and the engine then continues.

Let me know your thoughts.

Joe

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

The crankshaft position sensor is usually affected by heat. However, anything is possible. I have attached the removal instructions below. It is at the rear of the vehicle, close to the transmission bell housing on the driver's side.

Let me know if this helps.

Joe

See pics below.

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.

Hi,

The system has an accelerator pedal position sensor and a throttle body position sensor. Have you ever scanned it for diagnostic trouble codes?

As far as the CKP, it may or may not set a code.

Let me know if you checked for codes.

Joe

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

Hi,

Since there are no codes, the one thing that can cause it to stall is a faulty crankshaft position sensor. It can do this without setting a code.

Also, what you experienced, feeling like you were hit from the rear, could have been caused by it nearly stalling and then catching itself.

Have you ever checked the fuel pump pressure to ensure it is within specification? If you haven't, that may be a good idea. If it is good, I recommend trying the sensor to see if that resolves the issue.

Here is a link that shows how it's done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I have attached the manufacturer's fuel pressure specifications below.

Let me know your thoughts.

Joe

See pic below.

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.

JACOBANDNICKOLAS is one of our best! Sounds good, the throttle body issue will make the truck go into limp mode. Be sure to clear any codes once the throttle body has been replaced.

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.

Hi,

Thanks for the update. I'm glad you have resolved the problem.

Take care of yourself and feel free to come back anytime in the future.

Joe

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

Hi,

First, open the relay box and determine which relay is making the noise and let me know what you find. If you place a finger on one at a time, you will feel it.

Next, 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.

Note that the ECT is what communicates with the PCM, indicating the engine's temperature. If it is off far enough, it will cause a delayed start or no start. This sensor is located on the cylinder head. See pic below.

Let me know what you find.

Joe

See pic below.

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.

Okay so the engine coolant temperature sensor seems good. I would check the grounds and positive battery cable from the battery to the engine, if that is okay I would take the battery down to the auto parts store and have it load tested, it sounds like it might be bad. Also, the stalling problem sounds like a fuel pump in the tank, I would get a OEM unit. When the fuel pump goes bad it will not leave a trouble code.

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

I am sorry to hear about your dad. It could be the fuel pump has gone bad again, but I would swap out the relay and if it makes the same noise replace the fuel pump and check the fuel pump ground as well, have a nice weekend ;)

Hi. Thanks for the condolences about dad. Marty decided to do a kind of strange test on the relays. Being that they only act up when it is cold outside, and now it's not, he took the relays he thought were problematic and put them in the freezer for several hours and then installed them back onto the truck. However, the relays did not fault out and the truck started right up. Then he decided to put the whole relay box under ice. After several hours, he tried to start the truck. It would not start, but the relays began acting up again. How are we going to figure out what is wrong with this truck when the relays seem to only be raising a ruckus when it's cold outside?

Thea

It sounds like the relay box is bad, I would get another one and install it. Also, when the engine will not start using starting fluid to see if anything changes, it could still have a bad fuel pump.

Please go over this video:

https://www.youtube.com/watch?v=lXLJbuAZ4CE

Please go over this guide and get back to us.

Hello. Before I begin, I'd like you to know that Marty is a retired certified mechanic. His disability caused him to have to retire before all this new-fangled electronic stuff came into play, though he has always read up on it, we just haven't experienced it "personally" until recently. Up until recently we haven't owned anything any newer than a 1989 Isuzu Pickup. Then about 5 years ago his brother gave him a 2004 Ford Expedition, and last year he inherited the 2005 Chevy Colorado from his father. So, computerized vehicles is foreign waters for us. However, compared to the Ford, the Chevy has been a complete mystery for us. The Ford is good at throwing codes when there's something wrong with it, but the Chevy not!

Anyway, he drove it to the store yesterday and it started and ran without missing a beat. However, when he got back in the truck to go home, it started acting up again. After he got back home, he hooked up his code reader and it threw code 2610 which says it's the PCM. But then he began doing some more investigating on the internet and some sources say that just because it throws a 2610 code, it may not be the PCM.

If the diagnostic tool throws a specific code that relates to a specific part, then how can it not be the part the code is related to? That just does not make any sense! I thought that's what the code reader was for, to tell you when it's throwing a code that the part is bad which is related to that code. If that is not the case, then how is a mechanic at a shop to know which part to replace? Wouldn't that just make it that the mechanic is throwing parts at it until it doesn't throw a code anymore? We can do that here at home.

It is my belief that the code reader is supposed to tell you which part is bad, so you replace the part which is related to the code in order to prevent you from throwing parts at it until it stops acting up. I do understand that the code reader does not relate to certain parts such as the fuel pump. But isn't it supposed to tell you what is connected to the PCM? Then, what if the PCM is bad, could it cause all this mysterious stuff to be happening?

Thea

This code can be the PCM if you have not disconnected the battery recently.

P2610 - ECM/PCM Internal Engine Off Timer Performance.

The engine timer is an internal feature inside the PCM so it will need to be replaced. You can get a preprogrammed unit by searching Google or Ebay.

Well, something new is happening. Now we have the check engine light flickering and no key in the ignition. He says it flickers real fast, then stops for a bit, and then flickers real fast again. It keeps doing this, like its cycling or something. We're looking for a new PCM. We're going to try replacing it. If that don't work, then I guess we'll have to send it to a shop.

It sounds more and more like the PCM is bad.

That's what I have been thinking for a while, even without diagnostic testing. We are ordering a new PCM today. I'll let you know if it fixed the problem.

Sounds good have a great week!

Good news! It was a bad ECU. We ordered a new one for about $200, waited over a week for it to be programmed to our truck's vin no. After we installed it, we had to find someone to sensor relearns, which cost an extra $75. The truck is running great now. No engine lights, no relays going crazy. So, thanks guys for all your help.

Glad you could get it fixed, thanks for letting us know. Please use 2CarPros anytime we are here to help.