CEL 254 and 62 random stall WTF ?!

[318iM44]

Would these 2 codes causing random stall and misfire??

The CEL has been on for awhile, and when the engine randomly stall and misfire, either at a red light or on the freeway, the CEL would rapidly flash like a police strobe light.

According to CarSoft 6.5 it says DME MS41.0
The car is stock '98 318i 5speed with ASC.

These are two codes:
- 62 Secondary Air Injection System : Switching Valve
- 254 Tank Ventilation System : Large Volume Air Leak

The SAP and the Switch Valve attached to exhaust manifold are new and working great.

I've check the Fuel Expansion Tank (rear passenger fender), and Canister / Purge, located in the trunk under the spare tire.
They all are in good shape, no leak, no crack or broken nipples or hoses.

I also did the infamous "use brake cleaner to find vacuum leak hoses" with zero leak result, and all the vacuum hoses are tight and newly replaced.

Not to mention all kind of under the hood parts total of ~ $1,000 (parts only) that you can think of have been replaced. You name it.

The car runs great except when it randomly stall and misfire.

Would those code 62 and 254 really the cause of random stall and misfire??

[Michael_M]

Hard to go with that without proper information, does it happen at certain occasions or randomly ? does it change with surrounding environment such as heat, cold, humidity, etc or not?

My mind would go for the Intake Air resonance change-over valve.. but again without proper diagnosis I won't be sure!

[318iM44]

Originally Posted by Michael_M

Hard to go with that without proper information, does it happen at certain occasions or randomly ? does it change with surrounding environment such as heat, cold, humidity, etc or not? My mind would go for the Intake Air resonance change-over valve.. but again without proper diagnosis I won't be sure!

It happens randomly; regardless of temperature, elevation, speed, idle, rpm, daytime, night time, etc.
Such as idling at red light, or cruising around 30mph, or on a highway around 60mph. Other than random stall and cutting out, the car runs great.

Did you mean DISA is Intake Air Resonance Change-Over Valve?
I did swap that with a good working one, from my friend's m44.

Like the first post, when this happens, the CEL rapidly flash like a police strobe light without any sequence, until the stalling and misfiring are mysteriously over, which usually last for 15 to 30 seconds.
Even if i push the gas pedal all the way, it's still cutting out, jerking and missing.
Then the CEL stay on solid afterward.

The alternator is tested good.

It smells like fresh gasoline when idling, but all of the spark plugs are new and all have grayish tan tips, and not wet.

Now, based on CarSOft 6.5 Live Data reading:
- 0 Volt @ Tank Pressure Sensor
- 150 Celcius @ Air Intake Temp Sensor (after 1 minute idling from dead cold start)
- ASC @ ON (the button is not ON)

I think i'm very close of finding the gremlin, after all that new parts, yet i'm loosing hope to go forward without being broke.

[Michael_M]

Just out of curiosity, is it Standard tranny or Automatic?

So actually every time you car do that it throws different DTCs? not the same as the previous ones!

It is somehow complicated for me to diagnose that without diving in there and see what's going on.. but it seems you have like a bad splice connection.. Apparently it is splice no. X6821.. That splice distribute a lot of power to many systems you just mentioned like the Air Pump, DME, MAF, Fuel Pump, Knock Sensor, Camshaft sensor, etc.. that will cause those kind of weird and odd DTCs.

Attached is the picture for where that splice located.. make sure that it is properly connected with no signs of rust and definitely out of water reach!

[318iM44]

Thanks a lot for your help!

It's stock 5 speed manual transmission.

All of those codes and Live Data have been going on consistently the same, at every scanning process using CarSoft 6.5

I reset the CEL so many times, and also erase the "adaptation value". But those exact same codes are always coming back after a few miles of driving.

What is DTC? Is it the same as ASC+T ( Electronic Traction System) ?

Did you mean that sensor or the DTC or ASC+T throttle flapper is randomly stuck closed ? Thus prompts the rapid strobe of CEL plus misfire, cutting out?

If so, would it eliminate the misfire and cutting out issues by deleting / bypassing the ASC+T throttle/flapper body all together?

[Michael_M]

DTC stands for Diagnostic trouble code which is the same as the CEL.. Sorry but I got used to say DTC other than CEL as DTC is more common!

CEL/DTC 254 Large Volume air leak that might be triggered from just the fuel cap.. It might be leaking vacuum causing disturbance in the fuel system and thus causing the misfire and hassling.

DTC or CEL 62 then you also might need to check the whole Secondary air pump system.. It doesn't really means that you need to change parts but might be a simple short circuit causing that issue which is labour intensive to run after each and every wire and try to know what is causing all that!

Sorry I thought it was throwing different codes every time that what made me think it won't be related to a specific system but then since it throws the same code every time then it must be something either affecting both systems or affect one system that affect the other.

Did it start to act up like that by itself or have you replaced or fixed something lately and then that issue started to happen?

My Suggestion is to replace the Fuel cap as it is the cheapest option, go for a run and see how things will go..

If the ASC is always on check Fuse no. 21(5A) and fuse no. 38(30A). ASC control or have control on the TPS (throttle position sensor), a power surge might happen triggering the ASC Control Module.

Sorry I know it is confusing but electrical diagnosis are way more hectic than mechanical diagnosis.

I have a feeling that is caused from a short circuit or corroded wire!

[xxxJohnBoyxxx]

Your car has a motronics 5.2 DME (DME number ending in 668). Check the DME for corrosion on the back of the circuit board. It will look like green mold. This can cause odd codes. Also I didn't read all threads...Do you have a consistant code for the SAP? If so I can help on that. Adaption value error is caused when the injectors have to have their code adapted over the normal acceptable values to make the car have a lambda A/F of 14.7. This can be caused by large vacuum leaks, low fuel pressure, dirty injector screens, etc.

[318iM44]

@ Michael M, is the x6821 physically coded in that wrapped wires?

@ John, the code 62 has been reset and back on for awhile. I replaced the mushroom valve and there's no leak at the new Air Pump or the plastic hose.

I took the DME out, and it is the original unit with matching VIN to the car.
It looks nice and clean. There's no visible sign of green, rust or mold all around the casing.

[Michael_M]

Yea it will be in a wrapped wires!, you don't really have to break in and get them out of the wrapping, but just make sure they're not wet and no signs or water leaks inside, mould, etc..

And the other important question, have you done anything lately in the vehicle before it started acting up like that r did it just started doing that by itself ? like evening changing oil, replacing mounts, etc..

[318iM44]

After this issue already happening, i did replace the fuel filter, both engine mounts - due to the engine shakes so bad when idling, and still shaking even with new stock engine mounts properly installed.

I also remove, clean/sand and reinstall that ground cable, the one attached to the passenger side engine's arm mount to the frame.

Opened the wiring case located below the wiper, and it looks nice and clean in there. There's no sign of moisture, rust, or mold.

Should i disassemble the DME casing to reach and look into the internal circuit board?

Thanks!

[Michael_M]

what about before that issue started to happen?

There is a ground terminal located just beneath the coil pack connector, make sure this one is also properly grounded.. (picture attached)

Try replacing the fuel cap if possible..

[318iM44]

Before these issues happened, the idle has always been steady around 700 rpm, BUT the engine has always been shaking (missing or vacuum?) while idling at any time, any temperature and any place.

I did replace the fuel cap and oem coil pack.
The ground cable that you showed me up here looks fine, but i will double check that again in the morning.

Thanks!

[Michael_M]

Ok so let me get things a little bit organized here, what you've replaced so far
Engine Mounts
Fuel Filter
Spark Plugs?
All Vacuum Hoses
Fuel cap
Coil Pack
DISA

Anything else has been replaced ?

Engine shaking before you replaced all the above can directly be connected to the bad engine mounts you used to have before replacing with new one.

Make sure that MAF connector is connected properly, disconnect and reconnect it same for the coil pack (disconnect and reconnect). Make sure to disconnect the -ve battery terminal just as a precautionary measure!

Also check splice no. X6461, it is directly connected to both Intake air temperature sensor and the tank pressure sensor. first picture I attached shows the location of it.

[bullmand]

This probably isn't going to help much, but the only time I've experienced anything like this with mine was when I had some fancy aftermarket plugs it it. It exhibited your original symptoms of a terrible idle and shaking. I replaced the plugs with OE parts and that resolved the problem. It sounds like your problem may be more complicated, but I thought I'd throw this out there.

[318iM44]

@ Michael M, the ground cable that you mentioned last time is actually nice and tight.
Other new parts were Air Filter, Plug Wires, PCV or CCV, SAP.

I can kinda hear a clicking noise (shorting?) whenever the CEL / DTC is rapidly flickering, right where the CEL located in the instrument cluster.

@ bullmand, all of the new spark plugs are stock OEM Bosch FR7LDC+