engin light flickers with engine miss. what gives?

[cobb 535]

My check engine light flickers with a miss in the engine. This happens at idle and all the way up through acceleration. The miss goes away on harder acceleration but the light glows solid during this time. No codes are being set other than the 1222 that has been there for a while.
A little history. This is a 1989 535i. I had an occasional high speed miss that I thought would be corrected after I peplaced the crankshaft pully/harmonic balancer yesterday. I installed a unit from my donor car as the old one had a cracked bore and broken keyway. This showed up as no spark last week due to the pulley not moving with the motor. I replaced the cap and rotor before I discovered the pulley problem.
The repair was finished yesterday afternoon and at the end of an otherwise uneventful 20 minute test drive the missing started. Cruising seems Ok. this shows up at idle and acceleration. I have checked the crankshaft position sensor clerance (0.40 ) and resistence (545 ohms) with no changes when moving the wires.
Does anyone have suggestions where to look next

[2DYE4]

1211 DME Control Unit
1215 Air Mass Sensor
1216 Throttle Potentiometer
1218 Output Stage, Group 1
1219 Output Stage, Group 2
1221 Oxygen Sensor 1
1212 Oxygen Sensor 2
1222 Lambda Control 1
1213 Lambda Control 2
1223 Coolant Temperature Sensor
1224 Intake Air Temperature Sensor
1225 Knock Sensor 1
1226 Knock Sensor 2
1227 Knock Sensor 3
1228 Knock Sensor 4
1231 Battery Voltage/DME Main Relay
1232 Throttle Idle Switch
1233 Throttle Wide Open Throttle Switch
1234 Speedometer A Signal
1237 A/C Compressor Cut Off
1242 A/C Compressor
1243 Crankshaft Pulse Sensor
1244 Camshaft Sensor
1245 Intervention AEGS
1247 Ignition Secondary Monitor
1251 Fuel Injector 1 (or group 1)
1252 Fuel Injector 2 (or group 2)
1253 Fuel Injector 3
1254 Fuel Injector 4
1255 Fuel Injector 5
1256 Fuel Injector 6
1257 Fuel Injector 7
1258 Fuel Injector 8
1261 Fuel Pump Relay Control
1262 Idle Speed Actuator
1263 Purge Valve
1264 EGO Heater
1265 Fault Lamp (check engine light)
1266 VANOS
1267 Air Pump Relay Control
1271 Ignition Coil 1
1272 Ignition Coil 2
1273 Ignition Coil 3
1274 Ignition Coil 4
1275 Ignition Coil 5
1276 Ignition Coil 6
1277 Ignition Coil 7
1278 Ignition Coil 8
1281 Control Unit Memory Supply
1282 Fault Code Memory
1283 Fuel Injector Output Stage
1286 Knock Control Test Pulse
1444 No Fault Codes

[cobb 535]

Would the lambda control cause these symptoms? The code 1222 has been there for quite a while before the miss showed up.

[moroza]

You sound like you'd've already thought of it, but have you looked at the spark plugs and their gaps?

[cobb 535]

The recent PO said he replaced the plugs but discovering his lack of mechanical ability with other repairs he has done, I should and will check them when I get back in town next week. Guess I'll have to drive the Nissan to the airport.
The check engine light operation is what has me looking in circles. I assume it is a weak/loose connection or electrical component that interfaces with the computer.

[E30NEIN]

Check engine light is really a "Check emissions system" light, this is true for all vehichles. (Should be)
You most likely are reading rich whenever the miss occurs, and lambda=O2 sensor. (If that hasn't been covered here already.)

Spark sounds about right, plug wires and plugs ok?

[moroza]

lambda=O2 sensor.

Eh? Why would there be two separate codes for them? And why on earth is it called "Lambda"?

My understanding of engines (I'm not exactly a mechanic/engineer) is that lack of spark - from a disconnected, over-gapped, under-gapped, fouled, or otherwise malfunctioning spark plug - means that the air/fuel mixture for that cylinder goes unburned, continues down the exhaust path, and gets picked up by the O2 sensors. Since they're not designed to factor in a missing cylinder, AFAIK, they assume everything's fine except your A/F mixture, so tell you you're running rich.

[E30NEIN]

Don't ask me why there are two, the 1222 is the only code I've ever seen for O2 on an M30B35.
So from his description and the code he said is present, you could figure that it is O2, which it is.

There should also be a knock sensor on the engine.

[moroza]

Don't ask me why there are two, the 1222 is the only code I've ever seen for O2 on an M30B35.
So from his description and the code he said is present, you could figure that it is O2, which it is.

There should also be a knock sensor on the engine.

I thought M30's didn't have knock sensors?

[E30NEIN]

I thought M30's didn't have knock sensors?
Same here, but I saw recently someone posted that it had one.. and showed the part number and diagram of the part... I could be mistaken, and I did think they did not have knock sensors as well.

[xatlas0]

Only time I had a flickering CEL was when I had a hole in one of my valve cover gaskets, causing a vac leak. Only really affecting things when I was coasting down a hill, very strange.

Couldn't hurt to check for vac leaks too.

As for the knock sensors, I have only seen knock sensors on a M30-era BMW from Dinan, and that was the S38 turbo.

[E30NEIN]

As for the knock sensors, I have only seen knock sensors on a M30-era BMW from Dinan, and that was the S38 turbo.

Maybe that was it... :dunno :sleep

[Gunslinger]

Start by checking for vacuum leaks.

Lambda control error basically means that some value - air, fuel etc. is too far our of range for the DME to compensate.

[cobb 535]

The car was on jackstands for a week awaiting new tranny mounts and drive shaft center bearing so I went after some potential causes of my problem. I replaced the spark plugs - they were dark but not fouled. Replaced the fuel filter and any suspect vac lines. The intermittent check engine light and miss are still there but a little less. I did not disconnect the battery when she was resting on the jacks. The stomp test gives code 1444 - no codes stored. I suspect I have issues that are not storing "hard" codes that may be unrelated to the code 1222 -lambda issue I have previously been experiencing. I have a mostly complete parts car to "test by swapping" if necessary. I am going after electrical connections and grounds with electrical conductive antioxidant gel this week. Any other suggestins would be appreciated.

I WILL get to the bottom of this!!

[Goat128]

Start by checking for vacuum leaks.

Lambda control error basically means that some value - air, fuel etc. is too far our of range for the DME to compensate.

+1

1222=vac leak

on the m60 its almost always intake gaskets.

[cobb 535]

Went over connections and tested TPS and airflow sensor - again!! with no success. Out of desperation I swapped the motronic unit (ECU) with a spare I had from a 735 of the same year. Problems vanished! I reinstalled the old computer just to make sure. The problem returned. Today I am hapilly driving my 89 535 with an 89 735 computer installed.
Both computers have the same BOSCH part numbers. The smaller white tag has the same larger numbers. The very small numbers under the bar codes on the white sticker have a few differences. Do I need to swap chips with my old "flakey" unit or just be happy it is running so well ?

[DannyH4]

Good Job!