[my328ibimmer08]

Hello there!!

I currently have a 2008 328i BMW convertible with an N52 engine. It's now at about 140,000 miles, and it's been stumbling for a while.

My car stumbles every time I start it, as I have to give it some gas to get it back to a non-stumbling state at around 1k rpm, but after it warms up, it goes back to stumbling between 500 rpm and 1k rpm. The car stays on still, but just stumbles as it's in neutral, and even in drive when I'm at stoplights/signs. But when I turn my A/C on, the stumbling stops, but as soon as I turn it off, it goes back to the stumbling. Plus, when I'm driving my car for about 40-60 mins, its highest temperature it has gone to is 240 degrees, which is within the normal range of 215-240 degrees.

Back in December, I took it to a dealership for an oil change, recall, and inspection, and they gave me an estimate to remove the valve cover and inspect the timing and camshaft journals for the stumbling. My valve cover is leaking oil as well, but not a significant amount. For the recall, it was for the Positive crankcase ventilation (PCV) valve heater. After that, my stumbling wasn't as bad, but still there when I started the car.

As of last week, I got another oil change over at Belle Tire. During my oil change, they showed me the filter, and it had very little metallic glitter in it. After taking it to another place to check it over for codes and the new filter, there was no glitter in it this time.

The reason why I think there was glitter was that about two months ago, my lower radiator hose popped off and spilled out all the coolant. I tried to fill it with water for a temporary fix to get it home, but hitting every red light made it worse by the second. So, since there was no coolant, the cars temperature didn't go above the middle tick (250 degrees), so I didn't think there was any major damage. But regardless, the glitter was most likely a result of that. Every other time I have changed oil, I have never had any metallic glitter!

So sorry for this long post! But, I really need to figure out what could be the cause! I've replaced the VANOS solenoids, the spark plugs, and coils are from Oct 2023. Please, if you have any idea on how to test for a specific problem, or what it could possibly be, please let me know!!

(My dad is thinking it's a blown head gasket; I think it could be a possible vacuum leak or timing issue.)

[TunafishE93]

Codes, we need codes!

[gbalthrop]

Originally Posted by my328ibimmer08

... 2008 328i BMW convertible with an N52 engine. It's now at about 140,000 miles, and it's been stumbling for a while. My car stumbles every time I start it, as I have to give it some gas to get it back to a non-stumbling state at around 1k rpm... But when I turn my A/C on, the stumbling stops, but as soon as I turn it off, it goes back to the stumbling. Plus, when I'm driving my car for about 40-60 mins, its highest temperature it has gone to is 240 degrees, which is within the normal range of 215-240 degrees...
about two months ago, my lower radiator hose popped off and spilled out all the coolant. I tried to fill it with water for a temporary fix to get it home... the cars temperature didn't go above the middle tick (250 degrees), so I didn't think there was any major damage...

Welcome to the Forum!

Hopefully we are all here for the same reason: to learn something & help others. Can't learn anything if we don't admit we don't know it all (NOBODY knows it all).

I hope you realize the two things that can ruin an engine most are:
1) NOT shutting it OFF (trying to get home) when you have a major coolant leak;
2) NOT shutting it OFF when you have LOW/NO oil pressure.

If your lower radiator hose burst in Jan/Feb in Illinois, I HOPE you fixed the hose & added antifreeze (any Ethylene Glycol base, such as Prestone) within several hours. Otherwise, plain water will freeze & damage things. Continuing to "try to get home" without proper cooling can also 'damage things'. I confess I've "been there, done that". In my case, I thought I shut it off (1989 Jag XJ-6) in time (at shopping center lot), but had head gasket failure 11 months later.

You have warning lights for BOTH Coolant Temp & Oil Pressure. NO Gauge for either. You don't mention EITHER warning light. Instead, you talk about the OIL TEMPERATURE, in the 240-250 range. That is normal oil temperature (measured by the OZS or Oil Level/Temp sensor on the sump) for a fully-warm engine that has been run for at least 10 to 15 minutes.

Your Coolant Temperature is "sensed" by the ECTS (Engine Coolant Temp Sensor) on the front of the Oil Filter Housing. That sends a voltage signal to the DME (Engine ECU) and the DME will cause a Yellow Coolant Temp warning light on Instrument Cluster if Coolant Temp rises to ~ 215 F. If Coolant Temp rises to ~ 220 F, the DME should light a RED Coolant Temp warning light. The DME MAY also shut down spark/injector pulse, turning off engine at that Temp. Do NOT depend on that however. In your case, with NO coolant to Coolant Pump, due to "popped off" lower hose, no coolant is pumped to the head where ECTS is located, so Temp signal from ECTS is unreliable.

Rather than "Fear the Worst", try to think of this as a 'Learning Experience', & DIAGNOSE the issue as if it were a car belonging to someone else (hard to do if YOUR "daily driver"). Suggested "Next Steps":

1) Try to recall, & accurately report, what warning lights (Icon & Color) appeared & when, on your Instrument Cluster 2 months ago.

1a) How soon after bottom hose "popped off" did you fix the hose & fill system with 50% Ethylene Glycol? What was lowest ambient temp engine was exposed to, BEFORE doing that?

2) Get/borrow a Scan Tool, at least a $30 P-code reader that can also show "Live Data", such as the Autel 319 linked below, & read/report ALL DME Fault Codes to this Forum:
https://www.amazon.com/Autel-AutoLin...s%2C181&sr=8-1
That Autel Scan Tool will ONLY give data from DME (& possibly Transmission/EGS Module), & NOT the other ~ 19 Modules in your 328i. It WILL provide basic data for Engine ECU on any vehicle sold in US since 1996.

2a) If you are near an AutoZone, Advance Auto, or other large parts chain that provides FREE code-reading service, try that & report fault codes here.

3) Since your "stumbling" goes away with A/C compressor activated, that suggests the cause of stumbling is NOT a mechanical engine issue, such as compression/head gasket, but rather fueling, vacuum leak, or idle speed. Compressor activation is ONE of the inputs to DME which controls fueling & idle speed. Fault Codes & their "Freeze Frame Data ('Snapshot' of system conditions at moment fault code was saved) may provide clues. If NOT, viewing "Live Data", such as MAF Rate & RPM will help.

3a) Try disconnecting the MAF Sensor connector, on firewall side of the Air Cleaner Housing (if NOT sure where that connector is, please ask). See if engine Starts & Idles better with that connector DIS-connected (fueling is "mapped" rather than per sensor input). If so, you have an issue with connector, wiring, or sensor. Running engine with Sensor DIS-connected will set Fault Code for MAF sensor. Don't throw any parts at this time.

Generally, Scan Tool Data provides CLUES. It does NOT tell you to replace "Part X". You/we need to get as many clues as possible in order to diagnose. Although other tests, such as Compression Test, may be indicated in the future, I would NOT take things apart or change anything, UNTIL after doing Scan Tool Diagnosis, & analyzing that data.

There are folks on this Forum who will help if YOU try to learn & supply the FACTS/DATA.
George