Catalytic Converter Estimate QnA

[bcredliner]

K&N filters are re-usable if there are cleaned and oiled. You have to be careful when you re-oil them as too much will cause deposits on the MAF wires.

Since it is so easy to clean MAF I would do so. It is part of the air/fuel control. Just remove the connector and the two wires that hold it in and pull it out. Only use MAF cleaner. Look at the outside and inside wires. Spray them until all wires are clean.

[PROW355]

Thank you for everyones advice! After cleaning the MAF the p1093 (Manifold COntrol Fuel + Air Metering) code has vanished for now, however, funny enough, the p2098 (Post Cat fuel trim bank 2 too lean) code is now present. After looking at some of your posts and other threads online, it seems it could be solved by replacing camshaft sensor, post o2 sensor, or catalytic converter (not happening yet). I have also read about some faulty DME which can cause this code to come up. I have already done the smoke test so I doubt it is a vacuum leak. Based on past success I figured I should begin by once again asking for your advice before moving forward. Thoughts...

[bcredliner]

The pre cat sensors are part of the fuel/air control. The post cats are emissions only.

Assuming you have now driven 25 or so miles---

Since the cleaning of the MAF has adjusted the air/fuel mixture I would clear the code and see if it returns. The DME reads the signals of the pre and post O2 sensors. If the readings change to out of specs a P2098 would result. Initially, the MAF cleaning would change the readings. After some driving the readings could return to specs. I would also check anything I may have disturbed or could be loose or out of place--just because.

[PROW355]

Update...all of the previous codes came back including system too lean (bank 2), post cat fuel trim too lean (bank 2) and manifold control fuel + air metering. Plus now I get the "check coolant level" even though the coolant is topped off AND now the odometer, trip odometer and outside temperature in the cluster are barely visible at times and at others it is out completely. I can only pray I find a solution to these new problems...I plan on taking it to the stealership to diagnose the first three however I want to take care of the new problems first or they will most likely force me to pay for the cluster fix before they can do anything else.

Once I find a soutuion to each and every problem described in this thread, I will provide the solution if not a complete write-up on the fix. As a part time system repair technician, I should be able to solve the dim pixel issue and the coolant sensor issue and once I figure out the first three original codes I should be in good shape....or at least for awhile.

Love the ride...hate the consequences of driving it the way I do.

...to be continued!

[bcredliner]

BMWs are very sensitive to over/under voltage. In that condition there can be various false codes and dash lights. Suggest you have the battery load tested. A local auto parts store will do so free of charge. Also, unlock your cluster and monitor alternator output.

When a cat is going bad it will sometimes rattle. In addition, you should be able to feel a difference in the force of the exhaust from side to side. If there is a bad cat the exhaust will be restricted on the bad side.

[bcredliner]

Do you still have a rough idle? If so, is it all the time or just when engine is cold. Do you notice any loss of power?

Did you replace the pre cat O2 sensors with OE or OEM parts?

How many miles on the plugs?

[PROW355]

Thank you for the helpful suggestions bcredliner!

I got the battery load done and nothing was wrong. The spark plugs were replaced about 50,000 miles ago.

I plan on testing the output from the cluster soon and will let you know what I find. The cluster is acting weird, sometimes the coolant level sensor turns on and the light from it illuminates the odometer which then becomes somewhat readable, no pixels are out on any of the displays, but no light to push the display.

No noticeable loss of power, but it has lost its pep since I got it at 60000 miles (3 years ago). I dont really ever notice a rough idle however im not sure what constitutes a rough idle. I notice it idling higher than the idle mark (a little less than half way above idle line and 1000 RPM, almost all the time). If this is a symptom of rough idle, than yes it may be idling rough. But no vibrations which is what I would call a rough idle.

I have heard a resonating sound coming from behind the engine (with bonet up, looking at the engine, in the back)...but nothing that sounds too harsh. I replaced the pre cat o2 sensors with bosch, which i was told was OEM. The exhaust isnt pushing more or less on either side and no rattling.

[bcredliner]

Often you can feel a rough idle or see the RPMs changing especially if it happens when the engine is cold. You can also put the transmission in manual mode, stay at 20mph in 3rd gear and see if it lurches--doesn't pull steadily. Do that in the morning right after a cold start. Do the same check when engine is up to operating temp. Another way to test for rough idle is to hold a piece of paper over each exhaust and see if the pulsing is even. you may also be able to feel/see a difference in the exiting pressure with the paper.

Please explain the resonating sound you are hearing. Does it sound like an exhaust leak, is it steady or intermittent?

Am I correct that all these issues have reared their ugly head in a very short period of time?

There is a coolant level sensor on the side of the expansion tank that sometimes goes bad. You can disconnect the power connection and see if the dash light comes on. It could be a loose or corroded connection or a frayed wire grounding out.

Is the cluster at full brightness and still dim or does it go from bright to dim or out?

The RPMs change is from what to what? Is it always higher or does it bounce back and forth?

[PROW355]

the original issues (codes) came at once along with the catalytic converter efficiency issues (cat codes solved when plugging a loose vacuum tube and replacing the pre cat o2). The faulty coolant level sensor came a couple weeks after and then the cluster problems are most recent.

So looking at the cluster below (example). The trip and mileage odometer and temp are no longer displayed (completely dark). The check control ("BWTNR:8381810") is completely out initially but every so often the check coolant level triggers it and it illuminates at full brightness...and the brightness from it shines thru the odometer and temp LED and I barely make out their readings however they are working and accurate, just not illuminating.



My X is a manual and the RPM dont ever wave or falter at all. It idles above what it should idle at which is what is strange (see picture below, not identical but close enough). So it idles slightly above the idle line (between 0 and 1) but doesnt really go down all the way to the line even when idling for awhile. There is no unusual sound, like the engine straining when idling.



Ill give the paper test a go...next I guess I could gauge the pressure of the Cat by drilling into the line before and after the cat and use a pressure gauge to find out if there is any unusual pressure. Will report later tonight...

[bcredliner]

The low coolant light cause is the float in the expansion tank, sensor connection, a bad sensor or frayed wire. Most of the time it is a bad connection--start there. If it is the float or the sensor you will lose some coolant to clean the float so it works freely same is true to replace the sensor. If the problem is not the sensor I suggest purchasing a new sensor and cleaning the float so you have it covered other than the wire.

At this point I would not drill any holes to test the cat pressure until upstream causes that will result in a cat error are eliminated.


Make sure the connection to the MAF tube is tight and the intake tube has not been damaged from MAF removal/install as you could have a new vacuum leak. Also, cleaning the MAF doesn't always work. Since the code initially went away after the cleaning and then returned it is logical that the MAF is malfunctioning again. Remove the MAF connection. The idle should change. If it doesn't the MAF is malfunctioning again.

There are conventional bulbs on the back of the cluster for illumination--may only need new bulbs. The cluster is easy to remove just 2 screws at the top and pull it forward slowly so the connections on the back are not damaged. Disconnect the connection and turn it sideways to get it out. Steering wheel needs to be out as far as it will go.

I would do a somewhat accurate test of the A CCV system. You can do so by placing a ballon over the dipstick at idle and see if it inflates or deflates. You can do the same think with a plastic bag over the oil fill hole. If CCV is operating properly there should be vacuum at idle.