Constant Jerking

Hi,

Has the CAN-bus system been scanned? CAN stands for controller area network. Basically, all the computers/modules are tied together via a few wires. If you scan the entire system, it will identify codes regardless of the module they are stored in.

Here is a video showing how it's done:

https://youtu.be/InIlnsjOVFA

Let me know if that was done and if codes were found.

Next, when you feel the jerking, is it when you are sitting at idle or when you try to accelerate and the engine is under a load? Also, at this point, has it only happened when the engine is cold? What is the temperature of your location?

Let me know as much as you can.

Take care,

Joe

When you say valves, are you referring to the intake and exhaust valves? Basically, was the cylinder head overhauled?

By any chance, can you get your hands on a live data scan tool? If you can, the short-term fuel trims are important for me to know. Also, I would like to know if the engine coolant temperature sensor is sending a signal similar to ambient temperatures when the engine sits overnight.

One other question. Is the check engine light staying on when the engine is running? If so, you really need to have it scanned again to see if there are diagnostic trouble codes stored.

Let me know. The idea that it seems to do it when it's cold or nearly cold is making me think it is either a fuel pressure-related issue or something with the temp sensor. The fuel trims will help me determine if it is a low fuel pressure issue. Otherwise, you could check the fuel pressure after the vehicle sits overnight and hasn't been started.

Here is a link that shows how it is done:

https://www.2carpros.com/articles/how-to-replace-an-electric-fuel-pump

You will need a fuel pressure gauge, but most parts stores will lend one to you.

Let me know.

Joe

Hi,

If the engine is getting too much fuel, that is the problem. Since the light is on, I do suggest having the computer scanned. I'm not sure where you are located, but most parts stores will do it free of charge.

Next, we need to check fuel pressure. Here is a link that shows in general how it's done:

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

Pic 1 below shows the manufacturer's specifications for fuel pressure. The remaining pics show how to test pressure specific to your vehicle. You will need a fuel pressure gauge, but most parts stores will lend one to you.

If the pressure is too high, the fuel pressure regulator is likely bad. It is located in the fuel tank. The very last pic below shows its location.

I do suggest having the computer scanned so we know exactly what diagnostic trouble codes are stored. If you do, let me know what codes are found.

Let me know if I can help or if you have other questions.

Take care,

Joe

See pics below.

Hi,

There are a couple of things there that can cause the issue. The mass airflow sensor (MAF) is higher than 4.5v which is beyond where it should be. That can certainly cause an issue. Also, the coolant temp sensor is exactly the same. The voltage is higher than 4.5v. And also can cause the problem.

Here is what needs to be done: Since they are both showing high voltage (MAF and ECT), I don't think the sensors are bad. Instead, I have a feeling there is a short to power.

The first thing I would check is the reference voltage to both. Each should have a 5v reference from the PCM. I suspect they will be a good bit higher. If they are, then the tech needs to determine where the short is located.

Do you know if that has been checked?

Let me know.

Joe

Hi,

That will do it. Something internal must have shorted. If you have a chance, let me know if that takes care of your problem.

Take care,

Joe

Hi,

The ECU, if bad, usually would need to be sent out to be repaired. However, there are sites you can purchase a rebuilt one online. I purchased one from a place called car computer exchange for my own vehicle. It was already programmed based on the info I sent. It was under $200.00 and basically, all I did was remove my old one and install what they sent and it worked perfectly. They already had it programmed so there was no need for me to update or change anything. You may consider checking if one is available for your vehicle. I can help you replace it yourself if you would like.

Also, please understand that the site I mentioned is not affiliated in any way with the site or myself. I just had a good experience with them. I'm not trying to sell anything. LOL

And yes, the ECU is sometimes referred to as the main computer. An ECU is a small electronic control unit. Basically, it controls different functions in the vehicle. There are different control units on today's vehicles. When the mechanic mentioned ECU, I suspect is referring to the PCM or powertrain control module which could be responsible for the problems you are experiencing.

You take care of yourself and let me know if there is anything I can do to help you.

Joe