How slow are you going when it stumbles?

My very first repair on e53 was from a bad CPS. Symptom: stumble when turning into a parking space.

That said i don't think that would affect fuel mix.

Do you have a scanner that can watch/graph realtime?

O₂ sensor graph will be pretty helpful.


–awr–

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the stumbles happen at different speeds and directions of travel
 

Ok, there have been four stumbles so far, enough to make me not want to test drive, fearing a stumble/stall far from home, in traffic.

• 1) backing out of my driveway (backed up, turned 90 degrees to the right, and drove forward 100 feet, then made a 90 degree turn the left, and drove forward at moderate acceleration, with a short stumble,
  
  
• 2) when leaving the gas station onto a 2-lane secondary highway...a 90 degree turn to the right, and rapid acceleration to pull away from rapidly approaching traffic...causing a longer stumble, and near stall,
  
  
• 3 & 4) on an uphill left 90-degree curve, it seemed about to stall or go into limp mode for about 10 seconds following the curve, but it regained power just in time to do the same thing, on a flat 90-degree right curve that immediately followed, at about 45-50mph,
  
  
• 5) conversely: on four successive turns following that, on two left turns, onto short streets at moderate speed 30+mph, then another two right turns, first into my driveway and after 100 feet, further downhill to my parking area, also probably driving a bit too fast, there was no stumble.

And, there is the incident on the first test drive where the transmissin hung in gear going uphill on the first curve mentioned in "3 & 4", above, but without any stumbles on those curves & turns, during that first test drive.

And, WTF is a rich condition being reported if there is a fuel cut-off happening (obviously there is one, onhard curves and turns). It got worse after I reset adaptations.

I don't remember how I used to record/graph my O2 sensors using Torque Pro, but I did at least once previously, and I've no idea how to do it on my Foxwell. But, watching the realtime display on my dashboard tablet, I can see the O2 sensors working fine.

I ordered Tee-fittings from Amazon so I can use a hand-held vacuum pump (I have two: one in a brake bleeder kit, another in a cooling system test kit) to vary the vacuum to the FPR, to see if the fuel pressure to the engine varies. And, i'll have to wait for the wife (out of town) to drive behind me, in case of stalling away from home (so I can tow it home, just in case the system fails entirely, way out in the sticks). This might take awhile to diagnose, so I'll be missing the inspection deadline, by a lot.

At what point does the "sudden change in performance and going from lean to rich" lead back to the simple, single act of replacing the fuel pump, and touching nothing else? I'm tempted to let the X5 sit, until I save enough to afford an INDY to repair it (flat-tow expense to the other side of the county, who knows what parts they'll throw at it, and exorbitant technician's fees once there). Sorry for that, but this problem just makes no sense to me.

Did the inspection station plugging into my OBD port damage my DME??, and why would even that cause 90 degree turn stumbles??

Oh, I already mentioned that I added a bottle of Cataclean to my fuel two days prior to going for inspection. Possible link to my problem? i'm trying to cover all possibilities, though I doubt that Cataclean could screw up the fuel system ON TURNS, especially since I've been using fuel injector cleaners in increasing amounts, for 4.5 years (any tank or fuel line deposits surely have broken loose long before now).

But, if there were deposits knocked loose by the Cataclean, and were sucked up by the siphon pump (partially clogging it) and/or fuel pump (clogging it enough to burn it out, after 20 years of service), how would I clean the system to go back to a normal state?

You don't need a Tee to put the vacuum pump on.
If it's all on turns then there might be something going on in the tank causing starving and not even related to the rich problem. It just takes a few minutes to take the pump out and have a look at what's going on and get a look at the fuel sender problem while you're there. Having trouble installing the pump increases the chance something went wrong.
To take the pump out lift the seat bottom and tilt it ahead, stand it upright in the foot well and there is tons of room, no need to take off seat belts, cut a square of the sound proof material away over the pump if you haven't already, take the cover off, pry off the hose with a bit of care, the nipple has a metal tube but it's still plastic ;) use a small prybar and hammer to tap the retaining ring working a bit at a time on opposite sides. Really shouldn't take long at all.

sort of a "plan of action" to follow
 

I'm thinking that the problem MUST lie in the new pump install. If my conjecture about Cataclean-dissolved deposits creating blockages was true, why would there be good fuel pressure most of the time, and wouldn't the injectors run lean?

Perhaps the base of the pump is out of the deepwell , causing fuel shortages on cornering, or somehow I crushed the intake, or damaged the siphon pump assembly. But none of those thoughts explain a rich condition.

I'm going to try graphing the O2 sensors during a drive under load (avoiding the hard turns), before I dive into the fuel pump itself, again.

Don't use a tee, put the vacuum pump on the regulator line and see what that does, that will rule some things out, but more so give you some insight on how things work with fuel injection vs carburetor. Let us know what you find and I will explain it to you.
If you haven't already check the air filter, it's very easy to forget the basics when you have so much and probably multiple problems going on ;)

back to the beginning
 

I looked up the Google AI answer to the simple question: If a car stumbles or stalls when cornering, after installing a new in-tank fuel pump, what could be the cause?

answer: "Incorrect Installation/Kinked Lines: The act of turning or cornering shifts the fuel in the tank, which can cause issues if the new pump assembly (especially the internal "bucket" or reservoir lines) is not sitting correctly, a fuel line is kinked, or a "sock" filter isn't properly submerged.
Action: Recheck the installation in the fuel tank, ensuring all internal lines and the pump assembly are correctly seated and not kinked, and that the fuel pickup is not hitting the tank sides or picking up air on curves."

I already had surmised that it was the most likely cause, so the only thing I did on my X today (after moving my wife's Halloween stuff to the shed, and bring in her extensive Xmas decorations (including Santas of every sort and description). Took all day. She's skipping Thanksgiving decor, since it just doesn't yet feel like Fall.

Well, anyway, I skipped the vacuum test of the FPR, and checked air box and MAF, instead. Both OK, then un-installed the fuel pump. Once out, I checked the sender for proper operation using a multimeter, and it is OK, too (I'll need to use OBC test 21 to reset the gauge, if I ever put it back on the road.

I took a picture looking inside the tank after I removed the pump, and saw the three hoses that I might've been crushing when i did the first installation. I took my time, and made sure I felt the pump drop into the deep well.
Attachment 85133

we'll see tomorrow if it made a difference.

more of the same
 

I tested the X on my 10 mile course around the house, then followed that by taking vieos of my dashboard display.

The X never stalled out, but stumbled four times, this time only on right turns and curves. I intentionally over-accelerated and whipped around them, just for maximum effect.

The STFTs at some points were as high as -28.5, again, while the LTFTs were between -7.03 and -8.59 (they were both at -8.59 when I started the drive). I took two videos of the display when i first returned to the driveway, and after awhile, I reset the MAF, and took two more. i don't understand the patterns shown by the O2 sensors, but when i graphed (and lost the graph) them on the drive, they looked better.
https://drive.google.com/file/d/1t1H0O_RWlMctlTFndLeEVYnGmQEWBmOI/view?usp=sharing
https://drive.google.com/file/d/1PvfjK_tS9LvAsc0x-y-7ggptoDl432Y3/view?usp=drive_link

https://drive.google.com/file/d/1WqaZFVs7dAIWNGdcyhTJwZgjeoFwNEY0/view?usp=sharing
https://drive.google.com/file/d/1G3F...ew?usp=sharing
The first video had throttle% on the left, but the other three had RPMS in that space. i hope they'll open for y'all.

finally, I took a pic of the emission monitors, and there are still three incomplete (before I reset the MAF). If only one had remained, then I'd take it in for inspection and to heck witth the stumbles. The wife is going out of town tomorrow, so I won't be test driving until she gets back, so i have time to sit, think, and curse my fate.
Attachment 85134

Tomorrow I'm going to install one of the cheap old $20 MAF sensors, just in case the Siemens MAF went bad, when the inspector plugged his machine into the OBD port. Not likely, but I'm grasping at straws. I see no reason that the new fuel pump makes my X run rich, now.

I'm also looking at the stumble/stall situation as a separate problem. Since fuel pressure is
a steady 50 psi when the body is stable and only happens when on curves and corners, then I have to rig up my fuel pressure tester to the windshield so I can read it while maneuvering. My kit doesn't have the 3ft long extension I need, so I'm shopping for one.


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"grasping at straws" but it "feels like" a new ≠ fixed situation and there's a problem with the pump or wiring that is affected by the g-force of the turning. The gauge with the long hose to read while driving will help determine this situation.

Have you done the tap on MAF test? Sometimes a wire or trace gets loose and they will be affected by vibration. Tapping with a screwdriver handle will cause a stumble when they go bad.


–awr–

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Anyone know where to buy a 3-ft fuel pressure tester hose extension?
 

Haven't tried the tap test on this MAF, yet, but why would it have been damaged COINCIDENTALLY simultaneously at the same time the fuel pump failed, or just by (gently) removing it, to try a different one at the inspection station, when the X5 first quit running? I'll tap test it before I try one of the two $20 MAFs I carry as emergency spares.

If/when I find an extension hose for my pressure tester, and see that the pressure is dropping on turns, how does that reconcile with running rich all the time, now?
Does anyone know where to buy a 3-ft fuel pressure tester hose extension?

If, for some reason the new pump is varying flow, dropping the pressure way below 50psi, causing the stumble, any idea how I damaged the pump when first installing it? I found no apparent damage when I pulled the pump out to check the sender (with a multimeter), and loked it over for anything amiss, then carefully re-installed the pump in the deep well, with minimal effort, this time. Should I get a cheap replacement just to see? I just ordered a "free to me" pump, and will try it if necessary (or keep it as an emergency spare, or at least for components).

Obviously, I missed the inspection deadline 10-31-2025 (and 7-day grace period), so I'm now aiming for a solution that works well enough just to drive it to the "safety inspection" (sans emissions!) next October. I had a problem with my '09 HHR Panel, back in Dec. '15, when it was due for inspection, and it took me until Nov.'16 to get it inspectable, again. That's one of the reasons why I keep spare vehicles around (plus, different niche usages assigned to each one)