When E34 code 1221 occurs, engine immediately stumbles!

[frstevec]

Greetings, ​
This is a follow up to my previous thread on e34 525it engine bogging down with 1254 and 1221 codes.
My new/old issue is that after replacing with new Bosch o2 sensor, the car starts and runs fine with no codes for 20 min highway driving, then throws the 1221 code; immediately the engine begins missing, stumbling and only intermittently responsive to throttle input. If I then unplug the MAF, restart the engine, it now has 2 codes-- 1215 and 1221 However, it runs great, no missing or issues. I have driven the car over 150 miles in this condition and the gas mileage is 18.5. It pulls to 6000rpm in 4th gear, singing.
My efforts to fix it include checking for fuelly plugs, weak coils, used starter fluid on cold engine checking for vac leaks, swapped out 2 different MAFs, swapped out TPS, ran seafoam through intake, replaced fuel pump, and fuel pressure regulator, used half tank of fresh 91 octane gasoline-- even unplugged the anti skid traction control sensor. NADA .
I still have not done a smoke test nor have I tried replacing the o2 sensor again (the original one acted the same as the replacement except it took longer before the code occured.) Any thoughts or suggestions? thanks

[demetk]

I'd backprobe the O2 sensor signal wire and see what voltage you're getting with and without the code. It should dither between .2 and .8 volts every second or so. Have you tried disconnecting the O2 sensor and see if it runs better when the code is thrown?

[Honolulu]

It seems you have an intermittent fault. I hate intermittent faults. That said, I would think your issues result from a physical fault such as a wire making/not making connection, or hose that's sometimes opened, perhaps by a bump in the road or (if you rev it to redline occasionally) a bad motor or trans mount. But unless you get lucky, a smoke test should be in your near future. I read that smoke machines aren't all that expensive any more. Also that someone using an e-cigarette (vaping) can blow smoke for the test.

[frstevec]

Great ideas-- I had not thought of disconnecting the o2 sensor while the fault is active. I can do the voltage chk at the same time when it is in the air. Next step . THANKS

[frstevec]

Yes, Intermittent fault -- I found a pinched wire to ECU to clear a code 1283 a few weeks ago. I tried to make sure I have good contact, have recent new motor and trans mounts-- looks more like leaky hose. I found a diy PVC smoke tester so I'll try that soon.

The big question is why it takes a long time to set off the code -- very random, no bumps, no acceleration, no apparent cause, suddenly on. It doesn't seem connected to engine temp either.
Thanks for your feedback.

[frstevec]

todays test-- connected MAF, disconnected o2 sensor= started and ran with some stumbling, after driving about 2-3 miles, the code 1221 o2 sensor came on even though it was not connected.
Next, I disconnected the MAF and the engine reved, quieted then ran 80+ % of normal, no stumbling but lower power.
So, I have 3 MAFs to check for proper operation; although I have tried them before in place - little or no difference. IDEAS?
Getting the smoke tester made tomorrow. Thanks for your thoughts, suggestions . Steve

[frstevec]

Well, smoke test did not reveal any leaks; I still get a 1221 code after driving for 1/2 hour or more. Engine stumbles, but will return to normal operation by disconnecting the MAF.
So I did a vacuum test. With engine cold or hot, the idling vacuum is steady 21Hg, when I connect the MAF, the vacuum drops to 17Hg. Is this normal? I have 3 MAF; all work ok although one is slightly better. I don't get a 1215 code but a 1221 code eventually when MAF is connected. Is the MAF bad?
Thanks for your input/help or solution.
Steve

[whiskychaser]

You wont always get a 1215 code because the MAF sometimes tells lies. It may under-report the amount of air and then sit there laughing when the O2 sensor is screaming for more fuel. In the end, the ECU says to you, 'I've done what I can, you sort it out'. Had a similar problem a few days ago. I had lean codes and misfires on 4 cylinders - all caused by a bad connection at the MAF plug. So try giving that a clean. Then move on to checking the O2 sensor voltages as Demetk suggests. And check your fuel pressure to rule that out too.

[jehu]

I recently had this exact same problem coming up repeatedly in a got worse over time I had a scan done and I posted about this in another thread the scan showed a fault with the control unit that's the DME and she turns out it appears to me that the problem was the unit was not secured in its slot that there was missing one of the tabs you insert at the ends of the Box and after replacing 1 that had been missing there's only 1 in there now the problem with this as you described if you did not reappear the entire day and I drove it about 2:50 miles where for the last several days it had been happening repeatedly

This can result directed my attention to the ECU I had been thinking it was just overheating and so I was occasionly replacing them and it just slipped my mind since the vehicle came without either of those tabs in place so I took one that I had from another 540 I and crammed it in there and that appears to have been the problem the computer brain was not keeping contacts

[frstevec]

jehu
I swapped out DME a few weeks ago from a 12/95 build date for the 12/94 build date one in the car. No difference but I changed back to the original one and had a hard time getting those clips in place to secure the DME. They are secure. I sympathize with your problem-- I keep finding other things that could be the answer -- but no joy. The scan you had done-- is your car obd 1? if so what equipment did you use to do the scan?

Whiskeychaser
I replaced FPR recently and tested it as well as replacing fuel pump. Because I get an instant change in idle speed when connecting or disconnecting the MAF plug, I assume that it is ok but I will clean and use dielectric grease on the connector to be sure.
Remind me what voltage values I am checking at the o2 sensor connector and when to check it - hot engine?
Thanks

[jehu]

My car is OBD1 it's a 95 5 40 I went to a BMW specialist shop not a dealership and he used an Autologic unit

[shogun]

Remind me what voltage values I am checking at the o2 sensor connector and when to check it - hot engine? Thanks

Of course the engine + cat must be at operating temperature, because the O2 sensor signal is coming with hot cat and engine running.
Testing: https://www.hella.com/techworld/us/T...a-sensor-4379/
After the engine is started, a value between 0.4 – 0.6 V appears on the display (reference voltage). If the operating temperature of the engine or lambda sensor is reached, the fixed voltage begins to alternate between 0.1 V and 0.9 V.
Check the sensor output signal to the DME. I once posted how to test the oxy sensor on top of the DME for M60 and M70 and M30 engines, then we can make sure that the signal arrives there, here
http://www.bimmerboard.com/forums/posts/472541/
http://www.bimmerboard.com/forums/posts/622383/
Check the ETM which pins it is on your DME
I have made my own oxy sensor tester, actually a exhaust, gas, oxygen monitor usually installed in the dash, modified it, added oxy sensor plugs and installed inline, here in action https://www.youtube.com/watch?v=K8miz_1aHYw

1221 Lambda (O2) Sensor 1
This code is stored when the engine temperature is >70C and the Oxygen Sensor value is out of range or not present. Check the Oxygen Sensor wiring and the operation of the sensor. The value should fluctuate. Slow fluctuation indicates a polluted Oxygen sensor and negative values indicate a damaged sensor.
https://www.engine-codes.com/p1221.html

Fault Code description
Error Description
1211 - DME, Motronic computer, related fault - which may indicate problem with car computer itself. Delete any stored codes and perform following test: Start the car and let it run for 30 seconds; Turn off car and let it sit for another 30 seconds; Perform diagnostic test again; If the same flash code re-appears DME should be replaced
1215 - Indicates problem relating to Air / Mass Flow Meter - AFM or MAF depending on your e30 model. Causes could be cable wire damage, short circuit in the unit, or air / vacuum leak (check air intake hose - big L-shaped one
1216 - Designates error with potentiometer in Throttle Position sensor. Some later model cars have potentiometer, as opposed to switch (TPS) found on majority of e30 s. This code will be active if inappropriate sensor values are read by control unit, and although presence of this fault code may indicate bad potentiometer, wire harness connection at the sensor is common issue (corroded, loose connection, or broken).
1221 - Fault related to Oxygen ( O2 ) sensor is present if the sensor is unplugged, bad / not-operational, or sensor values are out of range. Test the O2 sensor for proper operation, as well as check harness connections by the sensor + in engine compartment.
1222 - Lambda control fault code is produced when Motronic system in Bosch control unit receives signal indicating that air/fuel mixture is either excessively rich or excessively lean for period of time loner then 10 seconds. Majority of the causes that affect drivability of the car can be responsible for DME flashing this error:
•air leak
•defective Air Flow Meter ( AFM)
•bad engine temperature sensor
•incorrect fuel pressure
•problem with injector(s)
•defective evaporation system
•empty gas tank
•issue with spark plugs
•problem with valves
•etc.
1223 - This fault code indicates problem relating to Coolant Temperature Sensor (CTS). Test the CTS sensor for proper functionality and check sensor wiring and connections
1224 - Fault with Air Temperature Sensor , which can indicate bad sensor, break or short in wires
1231 - Battery Voltage / DME Main Relay error code can mean that battery voltage is out of range (either too high or too low), or that battery was disconnected. Test charging system and /or battery to find problem cause.
1232 - Error associated with "idle" portion of Throttle Position Switch. Test TPS for proper operation.


1233 - Error associated with "WOT" (Wide Open Throttle) portion of Throttle Position Switch. Test TPS for proper operation
1251 - Fuel Injectors (group #1) fault can indicate problem with either individual injector or first group of injectors. Solution is to check fuel injector connectors, wiring from DME to injectors, and to test injector(s) for proper spray pattern. Additionally, fault code 1283 could be set in conjunction with this one.
1252 - Same as 1251
1261 - Fuel Pump Relay Control code indicates break or short circuit associated with fuel pump relay. Test for proper signal on number 3 pin on DME. It can also mean that output stage of DME is faulty (Motronic version 1.3 only)
1262 - Possible causes for Idle Speed Control fault are:
•damaged wiring to the idle speed actuator
•wire from DME is defective
•output stage of DME is damaged
Also if engine stalls while it is above 600 RPM, code 1262 will be set
1263 - Purge Valve fault can indicate that Evaporative Control Valve is faulty, that wire from DME to the valve is damaged, or problem with output stage of DME (Motronic version 1.3 only)
1264 - EGO Heater error code is stored if there is fault with Oxygen Sensor Heather or it's relay , Air Pump relay, supply wiring, or wire from DME
1444 - No errors

[frstevec]

WOW
shogun!
Thank you. You are the best. Thank God, I only have 2 of these codes (just reading the others narrows the focus toward my solution). Now I have a path to follow.
Thanks again.