Rough Idle

Just changed my fuel pump and nope...didn't help. I haven't changed my coil pack yet but I think it might help, hopfully.

Originally Posted by Dunzo

Okay, so I have completed my overhaul of the intake system. Here's my check list:

-Broken air box replaced with CAI.
-MAF cleaned.
-Throttle Body Housing cleaned.
-Upper and Lower Intake Manifolds cleaned.
-ICV cleaned.
-All associated gaskets replaced.
-All vacuum hoses checked for leaks.
-All associated sensors & connectors cleaned and greased.
-Spark plugs replaced. (NGK)
-Camshaft cover gaskets replaced. (Old plugs were covered in oil)
-O2 sensor replaced. (NTK)

I have spent months and a great deal of time and effort to do this work, everything was reconnected and put back together with precision and patience. I am confident it was all connected properly. So after two months of sitting cold, it finally came time to start it.

And... *drumroll*

The problem is not fixed. The engine still starts and nearly dies unless I give it gas, after holding the RPM at around 1100, the car eventually warmed up after 15 mins and could stay running, but not without the throttle fluctuating. I imagine after a short drive it might stabilize, which is how the car ran when I bought it. The snake was doing this with the car before I would come see it, so I wouldn't notice the issue. He always made up some reason about why the car was running.

Anyway, back to the drawing board. I imagine once I fix this problem all the work I did with the intake will pay off, but for now I am still stuck with my E36 in the garage. I am also still getting code 1222 which is O2 sensor reporting lean/rich. Any more ideas?

NiiCKSTURR and Dunzo,

This is getting confusing, since we're diagnosing two cars with apparently the same or very similar problems. I may or may not be addressing both of you, since I can't keep straight who's car is doing what. It doesn't help that you quote each other's postings.

So far you two have changed just about everything except the color of the car(s) , but no where in this discussion have I seen any mention of testing the fuel pressure and fuel pressure regulator. Regardless of whether the fuel pump(s) are working correctly, if the fuel pressure regulator(s) aren't working right, the engine(s) won't work right, either. A FPR that's going bad will drop the pressure enough that the engine will run lean. Think about it. You're getting high idle speed. To do that you introduce more air (open the throttle). That's why we always say check for vacuum leaks when presented with a high/rough idle situation. Well, the same thing can happen if the fuel pressure is weak. The mix gets lean, and idle speed goes up as the engine struggles to run.

Anyway, check the fuel pressure at the fuel rail. The Bentley manual has a test procedure for the FPR. Look it up, run the test and report back

Okay, replacing the MAF did not fix the issue in the slightest. Officially moving away from the air intake. Going to investigate the FPR as Horn suggested.

holy hell..


Check, clean, replace as necessary the MAF and 02 sensors.

Stop trying to fix things that arent broken.

Re-Stomp test.
record codes.
reset codes.



Buy parts from a reputable source.
Look in vendor section on THIS forum if you are unsure of WHERE to buy.


DO NOT BUY CHEAP PARTS..
CHINESE CRAP DOES NOT WORK ON GERMAN CARS.

MAF was cleaned, O2 replaced as I previously mentioned. No change.

Replaced the MAF with another one. No change.

Same code, same problem.

All parts are OEM and/or BMW factory parts.

FPR was tested, and I even swapped it out just to see, no change. Might be a bad fuel filter or pump, I don't have the means to check though, car will be in the shop next week for miscellaneous work. I'll have them check the fuel pressure and check the pump.

Happy to say this problem is now solved. It was a bad IAC valve, which was apparently getting stuck preventing a proper idle. It was not fixable, so it was replaced. Car now runs perfectly, especially with a nice clean intake. Though I would honestly not wish this problem on my worst enemy. Rough idles are extremely difficult to diagnose and half the time you just end up cleaning things and replacing things until you find the problem. Anyway, case closed.

Thanks for posting back with the outcome. Glad you got it sorted.