RHewitt

So I have a 2010 EX Sedan automatic with just over 150,000 miles on it. On my way in to work, the engine stalled on me twice while driving straight down the road, and there was another moment where it didn't stall but for a few seconds the revs dropped below 500 and no matter how hard I pushed the pedal I got no throttle response. While doing my bulk drops later in the night(a 50-mile drive), I had no issues whatsoever. All three incidents occurred right when the transmission shifted up.

That was two nights ago and I've had no further incidents. Everything I've looked up points to a faulty fuel pump, but the fact that it's gone so long without further trouble and that the issue only happened when the transmission upshifts makes me want to cover all bases - I've never seen any talk of something like this happening on upshifts only so I wanted to make sure I haven't overlooked a possibility. At 150K miles, I might as well do the fuel pump as preventative maintenance even if it ISN'T the issue anyway.

Other potentially relevant details: It was a cold night(sub-40F) and the engine hadn't quite completely come up to temperature(it was only completely cold on the FIRST stall, though), but it had sat long enough(four hours) to completely cool down before being driven again. The fuel tank was about 1/4-1/3 full, and was topped off about a mile into being driven for the bulk drops. It has been allowed to drop below 1/4 tank once in a great while, but this does not happen as course of habit(I know doing so is a bad idea and I avoid it as much as possible).

Thank you in advance for any information you can provide.

RHewitt

The stalling just happened again, and even worse this time: It stalled repeatedly, and continuously, unlike last time where there was several minutes in between the two stalls. Moreover, if I revved the engine in neutral, it went fine, but as soon as I put it in Drive, no throttle response, and the engine would stall before long.

I am getting NO warning lights whatsoever.

Colin42

That doesn't sound like fuel pump to me

FRSam

Almost sounds like a vacuum issue to me. Next step would probably be to get some live data to see what's happening leading up to the stalling. Most Bluetooth OBD2 readers have that function now.

RHewitt

Okay, this morning's occurrence happened on the way in to drop the car off for ball joint replacement. The mechanic there does not do engine transmission or electrical(just suspension, brakes, and muffler), but I picked his brain anyway when I picked it up. He advised checking the battery first. That seems unlikely since I got a new battery in February while tracking the flickering lights issue, and alternator even less likely since I replaced that just a few months ago to SOLVE the flickering lights issue. But you got to start somewhere, and Autozone does battery testing for free.

Battery and alternator were okay, BUT the tech did notice something odd: The comptuer let him run the alternator test with the engine OFF, which it shouldn't do, and that indicates some sort of draw from the battery. Should I be chasing this, or should I look elsewhere first?

Another possibility: A while back while chasing a rough idle issue I changed the MAF due to it being a possible cause of the issue. As the issue turned out to be oil contamination(not from any leaks in the engine, just an error by the dealership during the previous oil change), I kept the original MAF sitting around since I couldn't be certain of it being an issue and I am considering switching out the MAF as a troubleshooting step. Should I bother? (I'm asking instead of just doing since I prefer to wait for the engine to cool down before I do stuff like that anyway, so I got a couple hours)

RHewitt

Nevermind.

RHewitt

So after much annoyance with screws I did test the old MAF, and it does seem to have confirmed it is not working properly. I had no stalls, BUT nearly every time I started rolling from a complete stop there was a hesitation and brief rev drop on initial acceleration. No discernible issues once moving - one instance of a possible throttle hesitation, but it was so mild it could have been normal and I just noticed it this time because I'm paying such close attention. I will probably put the MAF I had been using back in before I go to work tonight. Had my phone connected to the BT OBD-II reader and it didn't catch anything odd with the vacuum pressure - bouncing between 22 and 17 while driving, dropped to 9-12 on light acceleration, dropped to 6 if I accelerated more forcefully.

Another thought occurs. A week ago I had the oil changed. When I had the rough idle it was due to oil contamination due to an error on the dealership's part. Could a similar error cause the type of issue I'm having now? It took me a month to notice the rough idle because it was only an issue in colder weather. This issue is far from consistent, but seems not to be related to weather.

Since we're leaning away from fuel pump, I am considering opening a new thread more accurately titled to address the wider issue in order to hopefully attract more attention and possible advice..

FRSam

I'll retitle it now and we can edit further as necessary. Let me know what you'd like it changed to in future.

RHewitt

A better retitle would be something along the lines of, "engine stalling while driving" - we don't yet know if the MAF is the issue, it's just a potential cause that I'm in a position to try and work with.

RHewitt

Another possibility has been brought to my attention: EGR valve. But from what I can find this seems to be an issue at idle revs, and while my issues haven't occurred at HIGH revs, it has certainly not been at idle. And there's still the issue of it not stalling when the car was in Neutral last time around.

Colin42

Could try unplugging the egr to eliminate it as a suspect

RHewitt

What should I expect in terms of normal behavior if I do that?

And forgot to mention: Last night at the last minute before heading into work it hit me how easily the MAF is to replace, so I opted to leave the old one in for further testing - if it causes TOO much trouble I can stop quickly and swap it out in two minutes. So I've got the newer MAF in my car and will drive for a few days on the old one to see if I have a recurrence of the original issue. The hesitation to start from a complete stop is not a constant thing, but happens frequently enough to tell me that this older MAF is not good(I did spray it with MAF cleaner before putting it in just to be sure), but if I don't have a recurrence of the stalling issue then we have a likely culprit. I will of course put the newer one back in after a few days to see what happens just to make sure.

Colin42

If the egr is the issue it should behave normally with it disconnected

RHewitt

Okay, got something new: About an hour ago when I was heading out, the car wouldn't start when I tried at first. There was a rapid clicking sound when I turned the key, but the starter did not turn at all. The very next time I tried to start the car, only seconds after, it started up like nothing went wrong.

So now I'm thinking something in the ignition system.

Colin42

Bad ground, check battery connections and other grounds very carefully.

RHewitt

The battery connections appear fine(and are plenty tight). The chassis ground behind the battery appears to be fine(cell phone images attached for your analysis). I do not know the location of any other grounds to check - image searching bring up almost entirely images of modded engines, so it is less than helpful. Could really use a clear resource on this.




New battery was installed in February, alternator in June, so I doubt these parts are themselves are at fault. If it's not a ground I'm thinking possibly ignition switch.

Colin42

The one on the trans looks pretty green, as long as it isn't crispy it should be ok

RHewitt

So now I just need to find where the other ones to check are.

RHewitt

So after nearly a week of driving with the old MAF installed I have had no stalling. I will be switching back to the new one sometime soon for further testing. Why not right away? Because Mother Nature decided to dump nearly a foot of snow(during a storm that was predicted to only get 3 inches) on my area and conditions are not conducive to using my car for the time being.

It occurs to me that if a loose ground is at fault, the repair of the ball joints(which was literally done IMMEDIATELY AFTER the last stalling issue - it happened on my way to drop the car off) will have reduced vibration enough to make the issue less likely to recur.

RHewitt

So even after putting the new MAF back in, I have still had no recurrences of the issue. This obviously points to an electrical issue, but without the issue recurring tracking it down is nearly impossible.