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What might cause my engine to act like it's going to stall

I have a 2011 Cadillac CTS4 with a 3.0 engine with about 85,000 miles on it.Over the past 3 months on four different occasions the engine has acted like it was going to stall out. Two of the times occurred when I first started the car in the morning and the morning the engine light would come on and blink a few times and go off, the car would not stall out and run just fine the rest of the day. The other two times were as I was slowing down to a stop light, as the engine reved down it felt like it was going to stall out again and again the engine light would blink a couple of times but then stop. After the first two times I took the car to a Auto Zone for a code read, and it came back with no code.
I followed that up going to my local car place I ususally have work done and they said they got the always fun P0300 code and advised to go with new spark plugs and coils. They said the spark plugs looked worn but not bad but that the coils were needed to be replaced. I had that done back on black Friday and for the next 5 plus weeks nothing, but then this week the other two times happened. Went back to auto zone and still no code.
Overall the car runs great, starts right up idles just fine, gets the gas milage a car of this type should get and such.
So what might cause these random “stalling” events on the engine and what should be my next step?

Random misfire. I’m predicting if you take it to a shop with a sufficient scanner the p0300 code returned. Assuming that plugs, and coils are all good, you need to start looking at fuel issues. Too much fuel pressure from faulty regulator, 2 or more bad fuel injectors. Then to compression check. Compression test is the lsst check but is quick and easy might want to do it anytime.

If it ain’t spark… its gotta be fuel! Old mechanics memes.

Id suggest low fuel pressure may be the issue. Failing fuel pump, maybe, or fuel pump relay. I’d swap out the relay with a new one because they are cheap and easy to reach. You owners manual should show where it is. If it persists, a pressure gauge needs to be hooked up so that is can be read while driving.

In any event, it most likely won’t get better, only worse, making it easier to find.

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Is there a way a shop and or the dealership can check something like the fuel pump issue? I have a scheduled oil change coming up and wondering if I should have them check the fuel pump/relay.

Just describe what the vehicle has done as clear as you can . Now if this place is a quick change place don’t let them do anything but change the oil and filter . If the dealer be prepared to pay for the diagnostic 's.

How do you check to see if either of those are the problem? I see that the relay is just a fuse somewhere in the car, but as for the pump how do you check to see it’s operating as it should?

Your engine has an electronic throttle body.

The electronic throttle body is what controls the engines idle speed.

If the throttle body is dirty, it can cause a rough idle and the engine to almost stall.

And if not enough air is able to enter the engine, it can cause a misfire at idle.

Try having the throttle body cleaned.


A relay is not a fuse but it does live in the fuse box. It is a high current switch driven by a low current signal. Plugs in, un-plugs. So simple even a dealership can do it (tongue in cheek here, any mechanic knows this)

You test the pressure of the fuel pump with a pressure gauge that is teed into the fuel line, and yes, any mechanic can handle that as well. Making sure the pressure is high enough but not too high idling and when driving.

Do NOT let a quickie lube place even attempt this! They are NOT mechanics.

That type of intermittent misfire is usually caused by dirty/sticking valves in engines with direct fuel injection. Your GM dealer has an upper engine cleaning process to remove the carbon.

I actually had them clean that when they replaced the plugs and coil and the guy said it was kinda dirty and needed cleaning. What baffles me is it went for more then like 6-7 weeks after that work before acting up again.

Not sure what’s causing the stalls, but suggest going forward to replace the plugs per Caddy’s maintenance intervals or even more often. Driving with worn spark plugs is false economy. As the plugs wear from all the sparking the gaps tend to grow wider. The computerized ignition system knows this is occurring b/c it discovers the spark voltage that used to work ok now won’t produce a spark unless the voltage is increased. So it raises the voltage in the coils. Produces a good spark, car runs well, but the higher voltage causes the coils to overheat and burn out. Spark plugs are cheaper than coils.

If I had that problem here’s what I’d do beyond the obvious like checking diagnostic codes and visually inspecting the throttle body area.

  • bring all the routine engine maintenance up to date
  • measure fuel pressure
  • measure compression
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I’m with tester here. My first thought was electronic throttle body or MAF sensor (if this engine is still equipped). Be sure not to open the butterfly when cleaning it, though.

I’m not sure how you’d test an electronic TB, to make sure it isn’t faulty. This may be an issue you have to wait until the engine gives another code, assuming the cleaning doesn’t help.

Back in November (on black Friday) I had all the spark plugs replaced, the coils replaced and they did a full cleaning of the throttle body. After that it ran great for the next 5-6 weeks right up until this week. I bought the car used back in February of last year. It has always started and ran without issue. I personally have always felt that from time to time when I would be waiting at a stop light or such that the car was not idiling at the right speed and that it “felt” like to me it might stall. No lights ever came on, it only happened on occasion and never at back to back stop lights. My friend when riding in the car couldn’t tell but it just felt that way to me. At this point I am just baffled.