318IS M44 with idle problems and 4 fault codes.
 

Hi there, I just joined this forum searching for knowledge and help before taking the car to a dealer where they are gonna blow my wallet. The car seem to has a misfire once started in the morning, after 1min. it gets normal but with rough idle, and the rpm seems to drop after a while or when stopping at lights, and the car start rattleing really bad, all plastics inside rattle like im driving over the railroad. Anyways, I also retreive the fault codes and got the following: P1140 (manufacturer specific - mass flor sensor) P0505 (Idle control valve) P0420 (Catalyst efficiency below threshold) P0302 (cylinder #2 misfire) Now, reading thru a bunch of forums and posts, seems that there is a unbalance in reading between MAF and TPS causing this faults. Have no idea where are the misfire coming from. I have in stock new ignition wire set (BMW PERFORMANCE), and camshaft position sensor. My injectors are freshly rebuilt, new intake gasket, new starter, spark plugs, oil, oil filter, fuel pressure regulator hose new, and injectors air hoses are brand new ass well. I replaced all this since i had to remove all the intake to replace starter, so it was time to replace all hard to reach hoses and clean injectors. Now, somebody can help me start pin pointing the problems on this car, or get an idea of where to start. Thanks and will appreciate your comments/suggestions.

Get a can of brake cleaner, start the engine, spray brake cleaner all around the intake manifold, intake boots and vacuum hoses. When you hear the RPM's go up, you found your leak. Only AFTER you've done that should you look into replacing parts. Don't come back here and tell us "well I changed this" or "I swapped this" or "I messed with this", do the brake cleaner thing FIRST. Don't be shy with the brake cleaner either. Hose everything down. Try getting it up under the intake manifold and on the ribbed rubber boot just downstream of the MAF.

If you don't find any leaks with the brake cleaner(the engine doesn't rev up), then you could try cleaning your MAF and idle control valve. Your local autoparts store sells MAF/electronics cleaner, or you can simply use isobutyl alcohol on a Qtip. Make sure you also clean the pins on both electrical connectors as well as the strip of film inside of the MAF. Be very gentle when cleaning the film. The ICV can sometimes get gunked up. You can clean the ICV with brake cleaner. Look closely at the black plastic piece on the front of the ICV, does it have any cracks? If cleaning those two components doesn't fix the problem, then you should replace them.

Look in your spark plug holes. Are they full of oil? If so, then you need to replace the valve cover gasket and spark plug seals.

You may have a bad cat. I'm assuming your car is '96 or newer as the codes you've listed are OBDII specific codes. If that's the case, then you'll need a Genuine BMW cat. Aftermarket cats simply do not work on OBDII BMW's. Unfortunately OEM cats are really expensive(about 1800 bucks) and it's illegal for junkyards to sell used cats. You might be able to find a used one in one of the part-out threads on the forum. Just make sure you find one from an OBDII 1.9L BMW(4cyl Z3, '96+ 318i, 318is, 318ic, 318ti) with the lowest mileage possible. Used cats typically sell for 150-300 bucks depending on the mileage and condition. However, keep in mind, you'll likely be installing a part with 100k+ miles on it, so don't expect it to last forever. It might be better to just bite the bullet and buy a new cat from BMW. Yes there's ways to cheat the system by using spark plug non foulers but that's ghetto and will only cause problems later down the road. If you get a new cat, you might as well replace the O2 sensors. Doing so will likely give you a nice boost in performance and fuel economy.

Thanks cooljess, here is the thing I miss to post, the post-cat o2 sensor was replaced 2 weeks ago, and ICV was cleaned when installing all the intake back. Im gonna try the brake cleaner test later on today, and will keep you posted about this. Thanks again

Ok Cooljess, made the brake cleaner test, and there was no changes in idle speed at all, so I assume there is no vaccum leat so far. Now what you recommend to do after this. BTW, i did install the new ignition wire set I already have on my, just as a tune up routine, was changed 5yrs ago the last time.

One thing I forgot to mention was to check your oil cap(the fill cap on the valve cover). I accidentally twisted it on crooked before and the car wouldn't idle, it felt like it was running on three cylinders. The next thing I'd check would be the CCV. This is a round plastic disc located just behind the intake manifold on the driver's side. When those get clogged, they tend to hiss. Have you noticed a hissing sound? Those two things are just random guesses, but not likely the culprit.

The fault codes generally point you in the right direction, but I just wanted you to check those things before you invested money in new parts. When you replaced the plug wires, did you install them one at a time or did you remove all of them and replace them at the the same time? Is it possible that two of the plug wires got swapped onto the wrong cylinders? They should be different lengths(longest goes furthest short goes closest etc).

If those three things are good(oil cap, no hissing from CCV, plug wires in correct order), then I think it would be safe to assume the ICV is bad since you cleaned it and it didn't seem to help.

Don't quote me on this, but I seem to recall reading somewhere that you can check the MAF by unplugging it. If the idle levels out while it's unplugged, I think that indicates a bad MAF. I could be wrong though, so you might want to investigate that further.

And finally, the cat. Cats usually fail in one of two ways. Either they get clogged up or the honeycomb monolith inside rattles loose and blocks the air passage. Some people report that their exhaust smells like rotten eggs when the cat fails. BMW had a recall on the cats, but it expired a few years ago. So that's a bummer. I'd clear the code and see if it comes back. Like I said, cats are very expensive and most aftermarket cats don't work on OBDII BMW's. There was one member that that claimed to have good luck with an aftermarket cat, but I can't remember who it was or what brand they used. But IIRC it wasn't a cheap one, it was still pricey.

Hope that helps, and I wish you the best of luck getting things sorted out.

I've had good results with a Magnaflow Cat, but that is on a 95 M42 and would not apply for your 96. The 95 only has a pre cat sensor.

UPDATE:
I have the P1140 code still on. Found a cracked head, so rebuilt head, changed every hose on the vaccum system (only missing the one to the brake booster and the one from throttle to carbon canister.), rebuilt injectors, new air filter, checked leaks with carb cleaner and nothing. Just replaced ICV since had P0505 too, and got rid of it already. Now im just stuck with the P1140 code. I decided to look for some more help here before spending the $300 on a new MAF sensor. If someone have some knowledge on this, help will be really appreciated. Thanks u all!!

PS. saw a thread from a guy that disconnected his battery, and after reinstalling it, hasnt got the code again. I still get it even after reseting with scanner. stay on the pending status, them comes up with the CEL.