$500 in parts- now have stumbling issue

[Hallen]

Wait. Does the car have the original engine in it? If the engine is from an e or es that reading would be right. Hmm. Well i'll talk to my mechanic buddies and see what they think.

And if it isn't an e or es, then you have the wrong part? It's still a long shot, but possible. Resistance goes up as things get hot. It might start missing more teeth as it gets hot.

[Philo]

Wait. Does the car have the original engine in it? If the engine is from an e or es that reading would be right. Hmm. Well i'll talk to my mechanic buddies and see what they think.

[bimmerboy12]

OK- so I just ran the checks on the TPS; I got full resistance until about .020 then full continuity just like the Bentley manual said if it is good. However, I never got full continuity on the other lead when it was cracked wide open. I don't think that would do anything to the idle though.
For the reference sensor, the bentley said I should have 500-600 ohms of resistance. I read 900 ohms on the brand new sensor. I don't know what that means, and I hope my ohm meter is reading correctly (its only about a year old). I know my reference sensor gap is .060 which is correct. Any other ideas? Is this reference sensor bad? I will try to get my dad's ohm meter and double check it this weekend.

[Hallen]

There is also a specific gap for the reference sensor to the vibration damper (if I remember correctly). Make sure that gap is correct. Just for giggles, and because it's easy, make sure there is no crud stuck to the teeth on the vibration damper and that no teeth are missing.

Sorry, it's a long shot, but should be easy to check and rule out.

PS, I do get that rhythmic idle after I have had the battery disconnected. I don't know why, but it always goes away and does not come back until I disconnect the battery again.

Good luck. I hope you find it.

[Philo]

Also test the reference sensor please. I've heard stories of people buying bad new parts. The test is simple and takes 30 seconds. G/L

[bimmerboy12]

Sorry for not responding, I was in Vegas for the last week for work. Back now and ready to dive into this again.
Concerning reference sensors, I believe only the E cars had them that referenced off the flywheel? I just have a crank position sensor on the front, which is brand new and one of the parts I replaced with the other 500 bucks worth of parts. I may be erroneous to assume that the problem is with the parts I have replaced- it could be that the parts replaced brought out the problem, like the new ignition components somehow revealed a weak link somewhere else.
Anyways, I am planning on doing the TPS check tonight as suggested by BritishBMW. I will let you know what happens... and the saga continues on.

[houstonh]

I have a brand new Crank Position Sensor and every last symtom this guy has. I dont think that's it.

I put on an old cap on my car. It still has the same symptoms.

One day someone will get to the bottom of this and I am sure all of us who are subscribed to this thread will rejoice.

My history. My car has had issues with idle since I got it in 2007.

When I first got the car I swapped in known good AFM. The car then became driveable, but stumbled just as this whole thread describes the stumbling.

I have done the following.
New Plugs
New Wires
Swapped to known good IACV, new intake boot
New hose from valvecover to TB
Seafoam'd at least 3 times.
New Cap
New Rotor
New Temp sensor
New Timing belt/Water Pump
swapped MSD for a known good bosch coil
New Heater core
bled bled bled bled bled bled

New CPS (mine was rigged and finally gave up.. I was hoping this might help the idle issue.. nope)

Swapped AFM for MAF swap (Split Second) .. same f'n idle issues

swapped to a whole different ECU. With BAVAUTO Chip for MAF swap... same idle issues

Swapped all the MAF/ECU crap back to AFM/Stock for my yearly inspection... Which I passed with flying colors on a cat with 200K on it. Still crappy idle!!



Went back to old cap... as suggested in this thread somewhere. still have crappy idle.

I have noticed one other thing that I am not sure anyone has mentioned.

If I am under no load and revving in Nuetral. I rev to say 3000 and hold steady. It seems to drop down to say 2900 after the initial rev. I am thinking this might be fairly normal.


I have mentioned this before, but.. I have the crappy narrow band 02 sensor and I can always see that it is leaning out when the idle hiccups.

[Philo]

Reference sensors can cause no starts, misses at constant speeds, and a lowered rev limiter. These sensors are known to go bad at any point in time. Mine went out after I drove to school. So YES this could be the problem. The OP has been M.I.A for awhile so i have no clue if he's figure this thing out or not. A chipped tooth in the flywheel could cause the sensor to read wrong.

P.S. Reference sensor, Crankshaft Positioning sensor, Pulse sensor, Speed sensor are all the same thing. (at least on this car)

To test it you need to find the connector plug for the sensor, which sits next to the oil dipstick. Looking from the drivers side of the car it is the sensor on the left in the two bay area. Pull the rubber shield around the end to reveal the color of the wires, then use an Ohmmeter to test the resistance between the yellow and black wires. It should be 540 +- 54.

[xLibelle]

reference sender? like crank position sensor? these either do or dont work. if they dont, then the car wouldnt even run.
...still trying to think of other reference senders

[klayvon]

Hey, so I've read all 8 pages of this thread and the one thing that I haven't seen any mention about is your reference senders. If these get dirty or old, they can cause a lot of issues. Try cleaning them, if that doesn't help, replace them. I could be totally off on this one, but hey, it's food for thought, right?

[Philo]

Any luck? Can we get an update?

[Philo]

In your bentley manual look at the bottom right hand corner of page 29, section 6, fuel system. That is where information on testing the TPS is located. There is a possibility that this is the problem, therefore, you should check it just to be sure. Post your findings. If it is not the problem I will give a couple of my BMW mechanic friends a call and see if they have any advice.

Keep on keepin' on
-tim

[bimmerboy12]

Is the problem still there when on the throttle (acceleration and parked)? Also describe what you mean by stumbling.

Best of luck
-tim

no as soon as gas is applied it smooths out perfectly, when in drive and in park.

By stumbling I mean it sounds like a random miss, very intermittent.

[Philo]

Is the problem still there when on the throttle (acceleration and parked)? Also describe what you mean by stumbling.

Best of luck
-tim

[bimmerboy12]

So just for clarification, the car stumbles but the tach shows no decrease or increase in rpm? I assume your TPS is good. I've seen this thread floating around for ages so I thought i'd try and lend a hand.

Correct, when the car is warmed up, the car will ALWAYS stumble, it is an intermittent stumble with no pattern. The tach does not register the stumble because it doesn't vary enough. However, sometimes when starting cold, it will sometimes idle decently, or it will sometimes waver rhythmically. When idling like this you can see the needle bob +/- 200 rpms.
I have not performed a check on the TPS, I never touched it so assumed this was not the issue. I couldn't find a test for it in the Bentley. Any thoughts?
Yes this thread has been around for ages, and the problem has been too. I am so frustrated at this point Im willing to try anything. This car idled perfect before performing all the maintenance!