2004 Laredo electrical problem

I've had my Laredo for two years, and it's had this problem since day 1 (yes, I knew about the problem when I bought the car): the engine randomly cuts out. And I mean randomly; I've been completely unable to establish any sort of pattern. Usually it does it for an instant, and recovers. Occasionally it'll do it several times in a row. Rarely, it'll do it repeatedly for a mile or two, and be backfiring by the time it straightens itself out. It might cut out momentarily every five or ten minutes for a while, then go a hundred miles without doing it once. It doesn't matter what the weather's like, or how bumpy the road is. And of course, if it happens while I'm stopped it usually kills the engine.

The car's been a total work horse, and it's never quit on me. I've pulled heavy trailers, meandered down dirt roads, run freeways and threaded my way through city streets. But it seems to be having the multiple cut-out episodes more often than it used to, and that worrie me.

It has a 4.0 liter engine, with about 240,000 miles on it. Everything on the vehicle seems to work normally, with the exception of the seat belt and air bag lights staying on all the time. I've replaced the battery harness with another used one, and the computer with a rebuilt one; neither made any difference. When the engine cuts out the car drops out of cruise control and the speedometer needle nosedives; otherwise there doesn't seem to be any effect on the lights, gauges, etc.

It has me stumped. Anyone have any ideas?

 

If you still have your original PCM (computer) keep it.
Did you opt for a PCM with any modification or changes ie delete SKIS.

"When the engine cuts out the car drops out of cruise control and the speedometer needle nosedives"
What about warning lights - ABS, SRS, CEL, do the come on or stay out? RADIO drops out or continues?

Do you have ANY codes - yes check even if CEL is off. Ideally a SCANNER is preferred.

Do you have a REMOTE STARTER, added alarm, kill switch?

 

I have the original computer somewhere, but Lord knows where. I worked out of town for twenty years, was there more than I was home, rented a shop there too, and just retired. So I've been packing up and ferrying stuff back to California for a month. But I don't see any point in concentrating on the computer, because replacing it made no difference at all.

No warning lights come on or go off. The previous owner removed the radio, and I've never gotten around to replacing it.

I have a scanner somewhere. Like the old computer, Lord knows which box or tub it's in.

No remote starter, added alarm or kill switch. To the best of my knowledge, the car is completely original except for the stereo the previous owner removed, and the problem existed before he took it. I'm sure he'd have told me if it had been acting up, because the problem puzzled him too. He's a close friend and sold me the car for $800.00 as a favor, after my existing ride quit on me unexpectedly. Coming up on retirement, I was in no mood to suddenly take on car payments...

 

My thoughts:

the cutting out/stalling is not clear in my mind.
Thinking is - does it have a power interruption- All questions about dash lights
and radio.
OR is there a problem with engine management - sensors, fuel pump, ASD.

Getting a scanner on it would be my first step, codes and freeze frame might
offer a clue.

NOW a SWAG for the intermittent nature of engine shutting down as other items
remain operating (radio, fan etc) I would think of replacing the CKP sensor.
As always this CKP is a component where OEM is suggested.

 

The CKP sensor has occurred to me. Unfortunately it's a bear to access, or I'd have tried replacing it just on the off chance. If I can find my scanner, would a CKP problem show up when I used it? And would the CKP sensor malfunctioning affect the cruise control and the speedometer? Those seem to be the only things affected when the engine cuts out...

 

As I mentioned I am confused what happens - Am i reading the issue right?
engine stays running and cruise control and speedometer go off?
Obviously with no speedo the cruise would go out -
The cruise control get speed reading from ABS system over the bus.

 

The engine cuts out momentarily and comes back on, almost like a backfire. Usually just once, but occasionally multiple times: cut out, fire; cut out, fire; cut out, fire; etc. The speedometer drops out and returns with the engine...

As far as I've been able to see, it doesn't affect anything else. Except that when I was pulling a heavy load into a headwind yesterday and had pushed the button on the shifter to take it out of overdrive, the overdrive may have come back on when the engine cut out. Can't guarantee it though; I may have just bumped the button without realizing it.

 

I would still want to get a SCANNER on the system.

With the engine off no RPM seams likely things will shut off.
Again is it power or system shutting down. ie ASD.

 

Again: if I'm parked or at a light and the engine cuts out, it dies and I have to restart it. If I'm in gear and moving, it comes back on its own. I assume that's because the engine is getting rolled. The gauges, headlights, dash lights, etc., don't go out; just the speedometer and cruise control.

When I find my scanner, or feel rich enough to buy another one, I'll post what it says.

 

Im thinking CKP - they are a PIA can fail and no code would set.
That and the quick on off you describe would reinforce that 'guess'.

The speedo is having me think a separate issue as its tied to ABS. BUT I would correct stall before spending $$$ or
putting in a lot of time on this. MAYBE look at wiring diagram for something in common.

I think you are planning to find beg borrow steel a scanner and see if anything stored that may help.
I would suggest looking for a good price on a CKP - and picking one up.

 

Tks for the input. I figure I should either buy another scanner, or buy a CKP. I'm leaning towards the CKP...

 

Update: I still haven't unburied my scanner. But I took a shot in the dark and replaced the crankshaft sensor, mostly because it's so easy to do. No, it didn't fix the cutting out problem. But the car idles more smoothly, accelerates better, and has noticeably more power going up hills. So apparently it needed to be done... I think next week when I have a little more money in my pocket, I'll go ahead and replace the CKP. Can't hurt, might help.

 

OK... I just checked my bank accounts, and Social Security dropped $378.00 into my checking account today. I have no idea why, but I'll take it... looks like I'll be buying that CKP. They're predicting rain this afternoon, but I'll try installing it tomorrow. Not looking forward to the experience.

 

Oops; meant to say, replaced the 'CAMshaft position sensor.'

But I did finally get around to installing a new crankshaft position sensor/CKP this week, and it cured the problem. The wiring was kinked at a right angle coming out the back of the old one, and there's bare copper showing through cracks in the insulation. Someone must've yanked hard on it, for some reason.

I guarantee if this new CKP ever goes bad, I'm dropping the vehicle off at a repair shop and telling them, 'fix it.' That was a completely miserable job. There's probably a special room in purgatory (at least) for design engineers who stuff replaceable components into such an inaccessible place.

Many thanks to everyone for their input on the problem.