2003 ex v6 engine issue

[morrisme]

My wife's vehicle, 160k very well maintained.
It started with driving 70mph on a road trip, the engine stopped, and started within 1 sec time and repeated this randomly for the next 10 seconds. We slowed down to about 60, checking Guage's and listening for any signs. Problem was gone. Drive to the next gas station and checked everything over. No obvious problem
We drove 3000 miles this event occurred 12 times over 3 days.
No dtc's no codes no computer stored history.
I am a mechanic, I custom build hot rods, full fabrication, and have no issues programming tuning modern vehicles. This one has me stumped.
The problem is slowly getting more and more frequent to the point it is now happening every time it runs and at any speed and any load, but still totally random. Some drives it will not do it at all and the next (10 min later) every second it's running.
I hate replacing parts for no reason however.
Replaced plugs, wires, coils, injectors, fuel pump, cam sensor.
Thinking about crank sensor next.
Any thoughts or help would be appreciated.

 

[G-466290]

camshaft sensor is bad. mine did same symptoms. you can do it with out removing timing cover. but its tricky

 

[morrisme]

Cam shaft sensor was good. I replaced it anyways and measured exactly the same.
Problem is still there, it is not the sensor.

 

[Victor Rusk]

My wife's vehicle, 160k very well maintained.
It started with driving 70mph on a road trip, the engine stopped, and started within 1 sec time and repeated this randomly for the next 10 seconds. We slowed down to about 60, checking Guage's and listening for any signs. Problem was gone. Drive to the next gas station and checked everything over. No obvious problem
We drove 3000 miles this event occurred 12 times over 3 days.
No dtc's no codes no computer stored history.
I am a mechanic, I custom build hot rods, full fabrication, and have no issues programming tuning modern vehicles. This one has me stumped.
The problem is slowly getting more and more frequent to the point it is now happening every time it runs and at any speed and any load, but still totally random. Some drives it will not do it at all and the next (10 min later) every second it's running.
I hate replacing parts for no reason however.
Replaced plugs, wires, coils, injectors, fuel pump, cam sensor.
Thinking about crank sensor next.
Any thoughts or help would be appreciated.

That is a truly baffling problem, and I can appreciate how frustrating it is, especially for someone with your experience. The fact that it's so intermittent and doesn't throw a code makes it a real challenge to diagnose. Based on everything you've described, particularly the "engine stopped and started within 1 second" and the increasing frequency, there are a few possibilities that are more likely than others. The fact that you've already replaced so many key components is a testament to the difficulty of this issue.

You're on the right track with the crankshaft position sensor. This sensor is absolutely critical for the engine's timing. If it's giving an intermittent signal, even for a split second, the engine's computer will lose its mind and kill the ignition and fuel. This would perfectly explain the engine "stopping and starting within 1 second." The problem with this type of intermittent failure is that it may not be long enough for the computer to register a trouble code.

Another possibility is a bad electrical connection. This is a very common issue on older vehicles. A faulty ground wire, a corroded battery cable, or a bad connection to the engine's computer can cause an intermittent loss of power to the entire system.

You can try checking the main ground strap from the engine to the chassis. A loose or corroded connection here could cause a momentary loss of electrical power, which would stop the engine. You should also check the main power wire from the battery to the fuse box and from the battery to the alternator.

Another thing to consider is the engine's computer itself. While a bad computer is rare, a faulty power or ground pin on the computer's connector can cause a lot of the problems you are seeing. You could try carefully inspecting the connector for any signs of corrosion or damage.

Lastly, have you looked into the throttle position sensor? This sensor also works with the computer to determine the air/fuel mixture, and an intermittent signal could cause the engine to shut down.

Given that you've replaced so many parts, a diagnostic tool with live data logging might be your best bet. If you can monitor the crankshaft position sensor's signal, you might be able to see the drop-out when the problem occurs. It's a bit like looking for a needle in a haystack, but it may be the only way to catch the problem in the act.

 

[morrisme]

Thanks for the input.
I have been live scanning and recording, with trigger points when the problem occurs...
Checked all grounds and leads, so far no issues.
Throttle position checks out good.
As of now there are two problems that keep me from gaining ground.
1). Kia ECU data is slow processing with low speed communication meaning that sensor failure response is almost 2 full seconds behind.
2). I am unable to test the ECU. If it is a bad prong or electrical component it could go undetected, and I won't know until it finally fails.

The problem is continuing to get worse so I will eventually find a fail point or at least the results of a failure.
Ie: the violent nature has me worried that it will strip or break a timing belt.
May not point to the actual problem or cause, but may just destroy the engine.... requireing replacement.
I actually took it to a dealer and they have been looking at it for a couple of weeks now. They are frustrated as much as I am. Lol, although it makes me feel better that they didn't find a bad fuse. Ha ha.
We will see if they can find a real issue or not.

 

[Victor Rusk]

Thanks for the input.
I have been live scanning and recording, with trigger points when the problem occurs...
Checked all grounds and leads, so far no issues.
Throttle position checks out good.
As of now there are two problems that keep me from gaining ground.
1). Kia ECU data is slow processing with low speed communication meaning that sensor failure response is almost 2 full seconds behind.
2). I am unable to test the ECU. If it is a bad prong or electrical component it could go undetected, and I won't know until it finally fails.

The problem is continuing to get worse so I will eventually find a fail point or at least the results of a failure.
Ie: the violent nature has me worried that it will strip or break a timing belt.
May not point to the actual problem or cause, but may just destroy the engine.... requireing replacement.
I actually took it to a dealer and they have been looking at it for a couple of weeks now. They are frustrated as much as I am. Lol, although it makes me feel better that they didn't find a bad fuse. Ha ha.
We will see if they can find a real issue or not.

Thanks for the update. It's good to hear that you're making progress, even if it's slow. It's also reassuring that you've got the dealer involved. The fact that they're also struggling with it tells you just how difficult and unique this problem is. You've brought up two very good points that are likely a big part of the issue.

First, you're absolutely right about the ECU's data being slow. A 2-second delay is an eternity in a modern engine, and it would explain why you're not seeing a real-time fault on your scanner. By the time the scanner registers the problem, the engine has already recovered. This makes a live-data log very difficult to work with.

Second, your concern about the ECU is also valid. An intermittent fault with a specific pin or component on the circuit board is a nightmare to diagnose. A dealer can perform a "wiggle test" on the wiring harness to see if they can recreate the problem, but if it's an internal fault, they won't find it until it completely fails.

It's a testament to your diagnostic skills that you're already considering these things. The violent nature of the problem is indeed a major concern, and your worry about it destroying the engine is completely justified. A violent hesitation like that can put a huge amount of stress on the timing belt, and you're right that it could eventually cause a catastrophic failure.

It sounds like you're at the point where you have a few options:

You can keep driving it and wait for the problem to become so frequent that it finally throws a hard code, or you can consider replacing the ECU as a last resort. This is a very expensive gamble, but it might be the only way to solve the problem if all other avenues have been exhausted.

I hope the dealer is able to find a real issue for you. It's rare for them to be stumped, and it's a good sign that they're taking the time to really look at it...