Rare hiccup/stall while idling

[guy48065]

*very* rare-- idling at a light about 1x per week the engine will shudder and usually continue to run. About three times in 6 months it has stalled.
Anyone else have experience with or know the cause? I really don't want to just start throwing parts in it hoping to get lucky. No codes.

4.0 with under 100k.

[plato442]

This sounds similar to another thread in which it is a rough idle but more of a misfire. Mine does what he explains in that thread, yet also is sooo similar to yours. I'm almost wondering if its a sticking valve?

[Paulaurora]

Crank sensors common issue. If you scan your car with tech 2 or other good scaner it will give u the code for them or will give you code for engine near stall detected. it will not show u cel light. I had same issue changed the sensors no problem after it.

[guy48065]

About a month ago paid the Cadillac dealer to run diagnostics and there were no codes other than the vacuum leak ones I could see with my ELM327/Torque.

I thought codes are saved only if the ecu detects out of spec condition for some period of time. IOW a single - cylinder misfire one time would be ignored. Is that wrong?

[Paulaurora]

some codes are reset after 40 successful test passes in a row if something fail even once during the 40 times ignition cycles it will stay in memory and not all codes will give u cel lights. There is possible that will be no codes for crank sensors but they still on its way out.

[guy48065]

So is one cylinder misfiring a common symptom of a filing crank sensor, or a more plausible guess than some of the other possibilities?

I'm hoping there's some history here. Like I said I really don't want to just start throwing parts at it like in that other misfire thread.

[Paulaurora]

Well if u still have vacuum leak it might cause same issue.

[tigger]

I can understand about not wanting to just throw parts at it.

When my CKP sensor(s) started flaking out, symptoms were identical to yours; occasional stumble while idling and a much less frequent stall with no codes. I went though everything; plugs, smoke test, fuel filter, fpr, injector cleaning, throttle body cleaning, maf cleaning, etc., etc., ad nauseam. I even switched coil packs with a Caddy, ...no dice. It finally threw a P0386 a few months later. For what it's worth, I had already ordered the new A and B sensors because the stall had become an almost daily event and I couldn't think of anything else it could be, haha!

Good luck!

[guy48065]

Oct 23, 2014 18:43:58 GMT -6 tigger said:

I can understand about not wanting to just throw parts at it.

When my CKP sensor(s) started flaking out, symptoms were identical to yours; occasional stumble while idling and a much less frequent stall with no codes. I went though everything; plugs, smoke test, fuel filter, fpr, injector cleaning, throttle body cleaning, maf cleaning, etc., etc., ad nauseam. I even switched coil packs with a Caddy, ...no dice. It finally threw a P0386 a few months later. For what it's worth, I had already ordered the new A and B sensors because the stall had become an almost daily event and I couldn't think of anything else it could be, haha!

Good luck!

Now that's what I've been hoping for! I can swap parts & chase my tail with the best--but I'm here to learn from others who've already been there.

Oct 23, 2014 15:43:19 GMT -6 Paulaurora said:

Well if u still have vacuum leak it might cause same issue.

Nope--fixed that.

[plato442]

It's not really 'throwing' parts at it when you're trying to pinpoint the problem! You have to start narrowing it down somehow. Usually start with with the simplest of things. Vaccum leak, clean the TB and mass etc, plugs and boots, until you find the problem!

[Paulaurora]

well for most of us this was issue with CKP sensor(s).

[plato442]

And I'll be replacing one or both of them shortly! I know at least one of them is new if not both, because I ordered a new one when I did my 4.6 swap 2 years ago.

[Paulaurora]

Best to do Both since u might have issue with 1 but other will fail shortly after.

[genedjr]

Question: is this another one of those sensitive parts that needs to be OEM or can I use cheaper ones?

And - does anyone know the code details (PID#, formula)?

And - to change them, I saw one guy pull the oil filter adapter, is that necessary?  I do have big hands but I also have alot of long reach tools.

...gene

[Paulaurora]

AC delco for CKP other wise will have issues.

[plato442]

in case anyone is looking through this thread, here are the GM Original Equipment ACDELCO part numbers

ACDELCO 2131578 UPPER SENSOR (associated PN 12559529, 12575481, 213806)
ACDELCO 2131579 LOWER SENSOR (associated PN 12559530, 12575482, 213807)

[98redaurora]

My Aurora has been randomly stalling at traffic lights. Usually 1 time once a week. Ordered new crank sensors, but it has been so cold in Michigan. Hopefully I can get them in soon!

[irlfan82]

not to high jack the thread but rather then starting another one with almost the same symptoms. the last few days when i would go out to start the car before work or heading home from work, it would run for about ten minutes then dye. It will start right up and run fine. Could it be the crank sensor ?

[98redaurora]

Possibly yes. (Unless someone thinks otherwise?).

I would check and clean your throttle body, IAC, and MAF first. If it still stalls then most likely your crank sensors.
When was the last time you had a tune-up with spark plugs, and wires?

Hope that helps,
98redaurora

[98redaurora]

Also not to hijack the thread lol.
But I bought two of these off Rockauto as it lists this part fits. Will this even work? www.amazon.com/Delphi-SS10090-Engine-Crankshaft-Position/dp/B000CGM6JU/ref=sr_1_1?s=automotive&ie=UTF8&qid=1420586577&sr=1-1&keywords=SS10090

[98redaurora]

Okay. I think I figured out my confusion. 1st gen and 2nd gen CKPs are not the same.