What should I do with this??

[Breeze1]

In my seemingly never ending search for the reasons behind my car's stuttering, I took off and thoroughly inspected my intake manifold yesterday, fixed a few very small leaks and discovered that the guy who installed my M52TUB28 had not put a vacuum cap in the M54B30's IM (driver's side, near the brake booster).

I also discovered that a hose labelled " bmw 16 13 1 184 528" was just hanging in there and not attached to anything. After googling the part, it happens to normally go into a "Fuel Vapor Detection Pump" linked to the E39 528i model, which makes sense since that's the donor car for my engine.

Now what I'm trying to understand is quite simply, what do I do with it? It doesn't seem to equip 3 series, and I have flashed my DME with a 328's software anyway. Can I just put a cap in it and "let it be" or will I risk hurting the engine/fuel pump, whatever? Could it be related to my stuttering issues (I'm guessing it is)?

Thanks!

[bmwdirtracer]

The evaporative emissions system is nothing more or less than a way for the car to test whether there are any vapors leaking from the fuel tank...like from a loose gas cap. The computers will become angry if that happens, because the car will fail emissions inspection. Of course, none of this effects you....except that there's a big hole in the intake manifold where this system is supposed to input any vapors it has collected. If you plug this, and any other holes in your intake system, you'll be fine, in this regard.

Now, a couple of caveats: E46's DO have a vapor recovery system, and you SHOULD see some description of a plastic pipe, about 8mm diameter, running under the car, next to the other fuel hoses. Out of general principle, you should connect this to your engine's purge valve, via that hose you describe.

Intake leaks usually cause trouble mostly at lower rpms. Higher rpm misfires are more often caused by inadequate fuel delivery, or bad coils, exhaust restrictions, improper fuel maps, etc. Have you tested fuel pressure, under load, when the car is misfiring?

[Breeze1]

Thanks for your reply Chris. If I understand you correctly having this hose open to the air causes a vacuum leak. So that should be the last one then, since I put a cap on the IM, where it was missing. I tried putting the hose instead at first (which fits perfectly and sits "naturally" close to that hole) but I figured it was a bad idea just from the increased stuttering it caused.

I will see about connecting that to the 8mm pipe you mentioned later, once I have gotten rid of the stuttering, because honestly as of now all I care about is being able to enjoy driving my car.

I have basically 2 different "misfires": the ones at low revs, and more like a "choking" around 4000rpm.
What makes this very difficult to track is that it doesn't happen everytime. Both come and go randomly, to the point where I thought my car was fixed on several occasions.

They don't seem to follow any temp pattern, whether ambient or engine temp...

I haven't tested fuel pressure yet since I still have to get a FPG, but my way of testing the FP, I guess, will be to try another one next saturday at a scrapyard. Basically I test the part see if it fixes the issue before paying for it. That's one of the perks of buying used parts...

P.S.: my exhaust manifold seem to be leaking - slightly- again, after having had the bolts tightened recently. Probably an indication that the gasket is either missing or shot. Will have to look into that as well...

[bmwdirtracer]

The plastic pipe from the gas tank should attach to the plastic pipe you're talking about, somewhere near the bottom of the curved plastic panel which encloses the front of the brake booster compartment. Your front plastic pipe would then go to the Purge valve, which mounts to the front end of the intake manifold, via a rubber collar. The purge valve then has a rubber hose which leads under the intake manifold where you can't see it....and then....somewhere under there, it connects to the intake manifold. I do not recall it going to the rear of the manifold, though....perhaps someone else will remind me.

Swapping a used fuel pump for yours is not a good way to test fuel pressure. What if the fuel filter is clogged? What if the pressure regulator is bad? (I forget whether this is part of the fuel filter, or part of the "running loss" equipment under the car, for an early E46.)

ESPECIALLY when you have intermittent issues, you have to establish baseline testing, to prove or disprove each possible culprit.

[Breeze1]

I'll have to check again but as far as I remember it's coming from somewhere under the IM. Judging by the part number, it's not something that came with the M54B30 IM, but from a "528i", ie with the engine. I'll try to find where I could connect it near the plastic panel you're mentioning, although I don't recall seing any plastic pipe there. My (Mann or Mahle) fuel filter is new and comes with a pressure regulator.

About that hose, if I just want to solve vacuum issues for now, can I just put a cap on it? Would that be a good indicator, or could the fact that the pipe coming from under the car is not "sealed" itself cause misfiring?

[bmwdirtracer]

An intake leak the size of the purge valve hose would likely cause the engine to idle a bit roughly. I doubt it would cause an actual misfire, even at idle. It won't cause anything at 4000 rpm.

Really, we need diagnostics. I understand that's very difficult, but without knowing what the computer is seeing, without knowing the trouble codes, without being able to measure fuel pressure or run a smoke test, I am at a loss to tell you how to proceed.

[Breeze1]

I did ran a dianostic on it with INPA, before fixing the leaks (minus that purge valve one, which will be sealed as well) and here are the only codes I found:

* n°56: "signal ignition current measuring resistor"
* n°246: "throughput rate secundary air system to low bank 2"
* n°45: same as 246 with low bank 1

The last 2 ones are SAP related (I deleted it), the 1st one made me check all ground connections in the car, which are all good, and visually inspect the coils for oxydation or arcing (is that what it, and they seem to be good.

Spark plugs are new (bosch platinum 4).

I guess that now that vacuum leak is out of the way it's down to either MAF, fuel pump, or coils...

[bmwdirtracer]

Bosch Platinum 4 spark plugs SUCK. They are absolutely NOT correct for your car. They are generic crap, almost as bad as an Autolite.

Now, there ARE Bosch plugs which are just fine for your engine -- the BMW recommended ones. I'm sorry, I can't find my factory spark plug chart, and I do not remember the Bosch number for M52 TUs and M54s....because I'd never use that plug....I'll ALWAYS use the OTHER factory plug for these engines: The NGK BKR6EQUP.

Please note that I am NOT saying your +4s are responsible for your misfires....but I can promise you that I'd swap them for the above NGKs immediately, if I were hunting misfires and poor performance.

That said, if you have actual misfires, you should be showing codes for misfires.


Sometimes INPA gives code descriptions which I don't fully understand, likely because the program was written in German, and translated by a Brit, into 'Murican English. "Signal, ignition current measuring resistor" is one that I do not understand. Maybe Abel will happen along, and explain what set off this code, but since it did not specify a particular cylinder, I'm going to have to GUESS that the coil grounds are loose, or the DME has a faulty resistor. This is nothing but a guess, don't do anything more than checking the coil grounds.

[Breeze1]

The "bad news" is, the coill grounds have been checked and are good. So unless it is one particular coil gone bad that shows up as a general thing, it could be the DME. That being said, it doesn't necessarily mean that's what is causing the misfires.

There does seem to be an electrical issue with the car since lately I have had the cluster's digital screen flicker and that little alarm that sets off when you open the door has made a "flickering" sound as well on two occasions.

The coils are bmw ones and look like new...