Weird "stalling" problem

Well, it seems my reputation for always getting stuck with the weird problems continues to live up to it's name.

Here's the deal. The last couple of days, while driving on the highway, the engine will just suddenly cut out. Like, just totally shut off like it stalled. It's identical to if I would shut the ignition off while moving. So of course, I'm gliding along with no power and then about 1 to 2 seconds later, the engine suddenly starts firing again and continues running like absolutely nothing happened. Then a mile or two down the road, it'll do the exact same thing again.

When this happens, I don't actually lose electrical power. All my lights and gauges still work just fine except for one exception: the tach. When the engine cuts out, the tach almost immediately drops to zero and when the engine starts running again, it shoots back up to where it was.

So any idea where the hell I should start? Try as I might, I cannot replicate the problem. There doesn't seem to be any condition that causes it to happen, it just happens at complete random.

Are there any codes? The tach instantly dropping to zero is normal. All that means is the crank sensor is seeing the engine stop quickly. Which is normal for an engine that is shut off with the key. The problem now, is what's causing it.

If there is a code, that will help immensely. Otherwise you are just going to have to start testing things. Since its completely random, i'm inclined to believe it is an electrical problem not a mechanical one. Unfortunately, these are some of the hardest problems to fix.

Ohm check coil. If that's good I'd suspect crank sensor. Actually i already suspect an intermittent crank sensor issue

No codes, not even a pending one.

I'll try and check the coil after work today. After mulling over it, the coil was my first suspicion followed by the crank sensor. I just figured I'd post in case I missed something obvious.

Check before driving it and after you get home so it's both hot and cold. Internal windings can expand with heat slightly and it can affect operation in some cases

Checked the coil. Pin to pin was 1.4 ohms, pin to terminal read a bit over 13,000 ohms. This was when the coil was "cold."

As a further development, the engine is randomly not starting first pull. Leaving for work, it took two turns before the engine fired. Leaving work, it started first turn, then leaving Wal-Mart, it took four tries.

I'm still thinking intermittent crank sensor

Yeah, that's about the only thing that I can think of as well. Crawling around underneath, replacing it looks like it'll be an...awkward task.

It's not a whole lot of money and I'm certain that it's the original one, so I might just roll the dice and replace it.

A bit. I've done 3 and i like to go over the top of the passenger side with a ratchet and extension. 1/2" socket or 1/4" allen

Finished replacing the CPS. As far as difficulty vs pain in the ass goes, it was definitely more of a pain in the ass, LOL, but now if I ever have to do it again, it'll probably take half the time anyway. Plenty of beer cans and cuss words were tossed. Good time, LOL.

First turn fired no problemo. Gotta give her a proper road test of course to verify if the problem has actually been fixed but it's nice to know that I didn't screw anything up especially after wresting blindly around the many many wires, vacuum lines and convolutes to do the job. Will report.

Yeret said:

Finished replacing the CPS. As far as difficulty vs pain in the ass goes, it was definitely more of a pain in the ass, LOL, but now if I ever have to do it again, it'll probably take half the time anyway. Plenty of beer cans and cuss words were tossed. Good time, LOL.

First turn fired no problemo. Gotta give her a proper road test of course to verify if the problem has actually been fixed but it's nice to know that I didn't screw anything up especially after wresting blindly around the many many wires, vacuum lines and convolutes to do the job. Will report.

Click to expand...

I got a proper non cheap one and replaced it when I did the plenum. Definately a lot easier. For future reference, I found it easier to lean across from the driver side, gave my left hand a fighting chance.

Hopefully it stays fixed for you. Cant tell you how many times i've had to screw with the one on my dad's suburban. That one is harder to get to than ours.

Went out for a drive and everything seems fine. No cutting out on the highway and three starts in a row fired first try no problem. So, I'm happy again.

I'm getting to the point now where I've replaced so many sensors that I might as well just replace the last few that I haven't. Hopefully I can be done with drivetrain electronics for a while afterwards.

Good 'ole trucks. Seems no matter how much money ya throw at 'em, you always find something else to fix, LOL.