Engine dies - but why?

[Chris Mosher]

Clean the throttle body and MAF then take it on the freeway and do high speed run to clear everything out.

 

[Jobi-Wan Kenobi]

I picked up a fuel pressure gauge kit on my way home tonight. At idle it seems to be maintaining about 42 psi. I did also clean out the throttle body. After I did that and started the engine it ran for maybe 15 seconds or so and shut off but started fine again. Not sure if it was anything related or not.

 

[Jobi-Wan Kenobi]

Still seems like we got something going on here. No issue for the whole week then just dropped off the fuel pressure kit now and had trouble starting in the parking lot. Doesn't seem like the fuel pump was the issue. The one time it died at home after cleaning the throttle body it maintained pressure. MAF sensor was also cleaned.

Maybe a bit of an out of the box question, but here goes. I do have a fault code for a knock sensor. Is it possible that the sensor stops reading and the timing gets messed up causing the engine to shutdown?

 

[iamdub]

Still seems like we got something going on here. No issue for the whole week then just dropped off the fuel pressure kit now and had trouble starting in the parking lot. Doesn't seem like the fuel pump was the issue. The one time it died at home after cleaning the throttle body it maintained pressure. MAF sensor was also cleaned.

Maybe a bit of an out of the box question, but here goes. I do have a fault code for a knock sensor. Is it possible that the sensor stops reading and the timing gets messed up causing the engine to shutdown?

I think you'd get a knock sensor circuit code.

With the way it abruptly shuts off the same way it would when you turn the key off, I'm still leaning toward a circuit opening. Maybe at or in the PCM, maybe the BCM, maybe within the key switch or harness from there, along the column and into the abyss under the dash. Have you tried shaking harnesses and tapping on the connectors and the actual components (PCM, BCM, etc.) with a rubber mallet or plastic hammer? Remove the battery hold-down cleat and try rocking and bumping the battery around to test for an intermittent open circuit.

 

[Jobi-Wan Kenobi]

@iamdub the code i have is P0327.

I haven't tried any of that yet. I've only tried jiggling the ignition switch around. Was just going to look up the schematic for the ignition circuit.

 

[Fless]

A long shot, but in order to rule it out, remove both PCM connectors and inspect for water migration and pin fitment. Also, the moisture gaskets might need to be replaced if they're not in good shape.

EDIT: It also wouldn't hurt to unplug all the connectors on the BCM and at least reseat them. Also use a little contact cleaner.

 

[iamdub]

@iamdub the code i have is P0327.

I haven't tried any of that yet. I've only tried jiggling the ignition switch around. Was just going to look up the schematic for the ignition circuit.

The low voltage code would usually just cause that MIL and maybe, at most, marginally reduced power due to retarded timing. I don't even see an open circuit (something like a P0325) causing it to shut off. But, I can't say it couldn't happen. Still, it's the knock sensor circuit- there shouldn't be any knock at all under the very low load conditions such as when idling or even idling in gear. Even still, the response should be to retard timing and not shut the engine off.

Or, maybe it's suddenly and erroneously reporting an obscene amount of knock that the PCM retards the timing so much that the engine dies because it's at low RPM? I'd still replace the knock sensors and the harness because there's a problem here even if it's not the cause of the subject at hand. They're a critical component and are known to be problematic due to their location.

Did you replace the alternator as part of troubleshooting this issue or did the issue start after replacing the alternator? New and refurbished parts can be faulty.

I wouldn't worry so much with tracing the ignition circuit specifically. It's not necessary to trace an intermittent open (wiring or solder joint) that might happen from movement or temperature swings.

 

[Jobi-Wan Kenobi]

So was just out messing with it. I pounded, pulled and twisted on pretty much anything under the hood I could get at. It never missed a beat. I pulled one of the PCM connectors off and noticed something I've never seen before. There's some kind of oil in here. To me that's not normal.

 

[iamdub]

So was just out messing with it. I pounded, pulled and twisted on pretty much anything under the hood I could get at. It never missed a beat. I pulled one of the PCM connectors off and noticed something I've never seen before. There's some kind of oil in here. To me that's not normal.

How da hell?!

 

[Jobi-Wan Kenobi]

@iamdub ok that was my understanding of the sensor too. Yea it was to change timing when the engine is under load.

The alternator was changed because the bearing was on its way out and starting to squeak. It had been over a month when this started.

 

[Jobi-Wan Kenobi]

But I suppose start with cleaning up the connector cavities and see what happens. To me that's like filling it full of dielectric grease which I know shouldn't be done.

 

[Jobi-Wan Kenobi]

They both have oil in them.

 

[Tonyrodz]

They both have oil in them.

Weird. Was there any other oil staining in or around the area?

 

[Jobi-Wan Kenobi]

@Tonyrodz no there wasn't. Not a clue how it would have even gotten in there with being covered.

 

[Tonyrodz]

@Tonyrodz no there wasn't. Not a clue how it would have even gotten in there with being covered.

Very strange. Is it motor oil? Power steering fluid? I know it's hard to tell, but that might give you some kind of clue.

 

[Jobi-Wan Kenobi]

@Tonyrodz the color was dark like something that was used. I did have a power steering leak on the pressure hose right after I started driving it. I don't see how that would have gotten in there though with the cover in place. And the connectors weren't full of oil on the outside either.

 

[Tonyrodz]

@Tonyrodz the color was dark like something that was used. I did have a power steering leak on the pressure hose right after I started driving it. I don't see how that would have gotten in there though with the cover in place. And the connectors weren't full of oil on the outside either.

Was the leak on a high pressure hose? If it was could've just shot out while the hood was closed, and over time the oil got washed off the outer pcm case but stayed inside.
Hey, you never know.

 

[Jobi-Wan Kenobi]

@Tonyrodz yea it was the high pressure hose. Where it was leaking I never noticed oil being sprayed at the shield. But if this fixes it, great!

 

[iamdub]

So was just out messing with it. I pounded, pulled and twisted on pretty much anything under the hood I could get at. It never missed a beat. I pulled one of the PCM connectors off and noticed something I've never seen before. There's some kind of oil in here. To me that's not normal.

Smell it- Is it engine oil? Is it as runny as it looks in the pics or is it like an epoxy that might be melting at higher temps?


Maybe the oil pressure sensor is leaking and the pressure is pushing oil through the wiring like a tiny pipeline and dumping it inside the connector. Try a tiny catch can on the sensor's wires? Since the oil pressure and knock sensors are located in close proximity, maybe their wires are close to each other in the PCM plug and the oil dripped out of the oil pressure wire and hit the knock sensor wires below them?

Still, the knock sensor circuit might not be what's shutting off the engine. Could be the PCM killing it from what it thinks is low oil pressure from the intermittently failing oil pressure sensor. It may be cracked or just leaking and you have two problems.

 

[Jobi-Wan Kenobi]

@iamdub it was runny. I poured most of it out of there. I did change out the oil pressure sensor a couple weeks ago too because the other one stopped reading.