$500 in parts- now have stumbling issue

[scabzzzz]

I keep watching this thread and without seeing the car, I really dont know.

My bet is the timing is off a tooth and you're just not seeing it. Like maybe you marked it wrong and its lined up perfect with the wrong tooth. If it was a tooth off, I think the effects would be similiar to what you're experiencing. Amirite?

[bimmerboy12]

I keep watching this thread and without seeing the car, I really dont know.

My bet is the timing is off a tooth and you're just not seeing it. Like maybe you marked it wrong and its lined up perfect with the wrong tooth. If it was a tooth off, I think the effects would be similiar to what you're experiencing. Amirite?

I just can't see it. The pulleys can only go on one way rotationally. I put on the belt and rotated the engine by hand two full rotations and verified both marks were hitting at the same time... dead nuts on. Although its been awhile, I have timed many motors in the past with no issue. Also, sometimes the stumbling is worse than other times. The car drives awesome and has tons of power when you get past idle... more than ever in fact and I've been driving it since 2000.

[scabzzzz]

The car drives awesome and has tons of power when you get past idle... more than ever in fact and I've been driving it since 2000.

Advanced timing!

[bimmerboy12]

haha yeah don't think so, notice it from 1K-6K. I KNEW somebody was gonna say that!
I would attribute it to all the new ignition components.

[bimmerboy12]

OK-Im getting full resistance across the CTS prongs when the car is off. 799 ohms when the car is running, then 1650 after turning the car back off. Tonight it started and idled really nice, then got shitty when warmed up. Sometimes its shitty right when i start it cold. It is completely temperamental. Another thing I noticed is a really shitty throttle response when the car is cold. If you punch it right after starting there is a half second of nothing then it takes. After its warmed up this problem goes away (although I must admit the throttle response is not perfect). I double checked for any arcing in the dark and saw absolutely nothing. I know some of you said the cap and rotor look rough for how new they are. What would have caused this? These are both Bosch items.
Any other ideas?

[Philo]

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.

[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!

[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]

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]

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

[Philo]

Any luck? Can we get an update?

[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?

[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

[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.

[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.