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  #1  
Old 12-06-2019, 11:02 PM
Tab_fsu Tab_fsu is offline
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Rough idle and shaking

Hello so a month back I had a coolant hose blow on the upper radiator that also connected to the oil coolant housing gasket, I had replaced the hose and also replace the over flow hose as well. While I was in there I decided to replace the oil housing gasket due to oil build up around it. Since I had everything a part I also decided to replace the intake filter and the cabin air filter as well. So I got everything back together filled up the fluids and the proceeded to take it for a test run it ran great came back home turn off the vehicle the next time I went to start the car the check engine light came on, so I went back through and looked over everything found out the MAF sensor wasn't connected. I contacted the sensor and then engine starts to idle and shake bad! I decided to order a new one which I installed today same problem occurs. I disconnect it and it runs smoothly any suggestions I also have my o2 codes all on but don't think that would be messing with the MAF. Any suggestions or help would be appreciated!
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  #2  
Old 12-07-2019, 08:04 AM
dharmabmw dharmabmw is offline
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Could you clarify " all my o2 codes are on" for us?

If you disconnect the maf sensor the computer has no way of knowing wtf is happening in terms of air flowing into the engine so it can't possibly control the fuel correctly. This would lead to the car running rich, with poor fuel economy and eventually failed catalytic converters and a whole lot of other problems........
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  #3  
Old 12-07-2019, 08:20 AM
Tab_fsu Tab_fsu is offline
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Mein Auto:
2c40- controle unit, internal fault 02 sensor 2 evaluation module

2c9c- sensor heating before catalyst, actuation

2c9d- sensor heating before catalyst 2, actuation

2c9e- sensor heating before catalyst, actuation

2c9f- sensor heating before catalyst 2, actuation
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  #4  
Old 12-07-2019, 08:28 AM
Tab_fsu Tab_fsu is offline
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The other day I had also changed out the MAF fuse due to it being blown and after starting up the car it again blew! I feel like my next steps should be to check the o2 heater fuse in the glove box, clean the throttle valve and do a smoke test.
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  #5  
Old 12-07-2019, 09:25 AM
relative4 relative4 is online now
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Mein Auto: '08 335xi E90 manual
Short in engine wiring harness, bad DME... lots of fun options here. Follow the blowing fuse to the pot of gold.
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Old 12-07-2019, 09:47 AM
gbalthrop gbalthrop is offline
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Mein Auto: 2007 328xi E91
Quote:
Originally Posted by Tab_fsu View Post
[07 328xi E90 I presume from your post history? Please complete your "mein auto" OR add that vehicle info each time you post] ...I had a coolant hose blow on the upper radiator that also connected to the oil coolant housing gasket, I had replaced the hose and also replace the over flow hose as well. While I was in there I decided to replace the oil housing gasket due to oil build up around it. Since I had everything a part I also decided to replace the intake filter and the cabin air filter as well. So I got everything back together filled up the fluids and the proceeded to take it for a test run it ran great came back home turn off the vehicle the next time I went to start the car the check engine light came on, so I went back through and looked over everything found out the MAF sensor wasn't connected. I contacted the sensor and then engine starts to idle and shake bad! I decided to order a new one which I installed today same problem occurs. I disconnect it and it runs smoothly any suggestions I also have my o2 codes all on but don't think that would be messing with the MAF...
Hi Travis, Welcome to the Forum!

You probably have a "vacuum leak", or air which is NOT "metered" by the MAF entering the intake manifold, causing a LEAN running condition. ALWAYS check for Fault Codes any time the SES or "check engine" light comes on. There are literally DOZENS of P-codes that relate to faults of some type related to signals from one of the FOUR O2 Sensors, or their Heaters. We can't do anything but GUESS without knowing what the codes are. So here's my SWAG:

Based upon your statement that you changed the "intake filter", and later found that you had NOT re-connected the MAF Sensor Connector after replacing the Air Filter Housing, the most likely scenario is that the air duct that runs from the Air Filter Housing (where the MAF is) to the Intake Manifold is NOT properly connected in some way, or has cracked and is leaking. This allows air to enter the engine which has NOT passed the MAF Sensor and is NOT measured by the Sensor & reported to the DME. This if particularly likely IF you have one or both Fault Codes P0171 or P0174, TOO LEAN, Bank 1 (cylinders 1,2,3) and/or Bank 2 (cylinders 4,5,6).

You have just provided a classic example of how one can test for a "vacuum leak," by disconnecting the MAF Sensor Connector.

The reason that the engine runs smoothly when the MAF Sensor Connector is DIS-connected, is that WHEN there is NO signal from the MAF to the DME (Engine Control Module), the DME computes the injector pulse duration (which determines how much fuel is injected) and therefore the "Enrichment", based upon "Mapping" or algorithms saved in the DME. The primary inputs that are used are PROBABLY Accelerator Pedal Position (and/or ESS signal of Eccentric Shaft Position/ Valve Lift) and Engine Temp, along with Load & RPM.

When the MAF is then plugged in, the MAF sends a signal to the DME of the Mass-rate of air that is entering the engine (presuming NO "vacuum leaks"), and the DME then provides the necessary amount of fuel to be "burned" by that air in the combustion process, which is actually a chemical reaction which combines Oxygen and Hydrocarbon (gasoline) to produce Carbon Dioxide (CO2) and Water (H2O), plus Energy = GO.

The Pre-cat O2 Sensors measure the amount of Oxygen (O2) in the exhaust gas. If the sensor on either Bank detects O2 which has NOT combined with the gasoline in the combustion process, that means the fuel mixture (enrichment) is TOO LEAN, and based upon that O2 Sensor Signal of "Excess O2" received by the DME, the DME adds more fuel (Trim) to that Bank by slightly increasing the injector duration. The system is SEPARATE for each bank of 3 cylinders, but if you have a vacuum leak, usually BOTH banks will be affected. When the "Trim" enrichment is NOT sufficient to eliminate Excess O2 at the Pre-cat sensor(s) the SES lights and a Fault Code is set.

For more details on the "Stoichiometric Ratio" (~ 14.7:1) of air to fuel, by mass, and the physics & chemistry involved in what is actually going on in those cylinders that we take for granted, Wikipedia (LOOOVE Wikipedia ) has some excellent information:
https://en.wikipedia.org/wiki/Air%E2%80%93fuel_ratio

George
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Old 12-07-2019, 10:38 AM
gbalthrop gbalthrop is offline
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Quote:
Originally Posted by Tab_fsu View Post
The other day I had also changed out the MAF fuse due to it being blown and after starting up the car it again blew! I feel like my next steps should be to check the o2 heater fuse in the glove box, clean the throttle valve and do a smoke test.
We need to know your engine & build Month/Year. If you have 2007 model, the wiring and fuse designations depend upon whether built BEFORE or AFTER 3/1/2007.

Please ALSO indicate specifically WHICH FUSE is blowing. I doubt it is the fuse that powers the MAF, as on most models, that also powers the Crankshaft Sensor, and if that blows, the engine shuts down due to lack of signal from Crank Sensor.

Please also indicate what Scan Tool you are using to read codes, and WHERE you got the Fault Code Definitions you posted in Post #3. If you had simple P-codes, they would provide better indication of WHAT EXACTLY the code indicates. Bentley suggests those 4 Hex-codes indicate EACH of your 4 O2 Sensor Heaters is NOT getting power. The MOST LIKELY explanation for that would be that either fuse F79 (on 2007 model built AFTER 3/1/2007) or F04 (in E-box) on models built BEFORE 3/1/2007 is the fuse that is ACTUALLY blowing.

Have you had the Breather Heater Recall performed? The FIVE components on either of those two fuses are the same: the FOUR O2 Sensor Heaters, AND the Breather Heater. The classic failure mode of the breather heater is to short out and blow F04 on early 2007 model or F79 on Late 2007 model. Here are Fuse circuit diagrams for F04 Early 2007, and F79 Late 2007 models in THAT order:
https://www.newtis.info/tisv2/a/en/e...4-fuse/uM1qAq9
https://www.newtis.info/tisv2/a/en/e...9-fuse/vEO0UYq

Note that TIS incorrectly describes the 5th component as "Crankshaft" breather instead of CRANKCASE breather heater.

Here are the "Lambda Control" or O2 Sensor circuits for Early & Late 2007 models:
https://www.newtis.info/tisv2/a/en/e...ontrol/otwHfc8
https://www.newtis.info/tisv2/a/en/e...ontrol/x5UZsdI

I would suggest taking the time to understand what is available in TIS circuit diagrams, and how to use & navigate them for YOUR specific vehicle. Here is the Home Page for US-English -- just enter the last 7 characters of your VIN, and save/Bookmark that page to get specific info on YOUR car (works same as RealOEM.com).

Please let us know what you find,
George
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  #8  
Old 12-07-2019, 04:01 PM
Tab_fsu Tab_fsu is offline
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Just an up date I got the car on the lift and checked the o2 sensors on the exhaust there were no shorts and were reading properly so I dropped down the car to examine the o2 sensors on the top of the engine and realized I pinched bank 1 when I removed the manifold to fix the oil housing gasket and tighten it back down. I was able to reconnect the wires And heat wraped them back together. Replace the bad fuse that blew and cleaned the codes started her up and ran perfectly fine.
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  #9  
Old 12-09-2019, 06:33 PM
Horse Whisperer Horse Whisperer is offline
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Sweet

Great job Tab!!!!
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  #10  
Old 12-09-2019, 06:38 PM
Tab_fsu Tab_fsu is offline
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A rookie mistake but was thankful to discover the issues
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