HELP! M42 hesitation.

[911 Rod]

Need some help please.
95 318/M42 is hesitating under acceleration sometimes.
Feel like it is surging, but must be hesitation.
After sitting for a couple of days it has a rough idle for the first couple of seconds.
At regular idle it is a little rough, but I'm the only one who notices.
Coil?
Oxygen sensor?
New plugs and fuel filter last year.
Thanks
Rod

[blkongry]

Have you washed the car recently? Sprayed any water down in the engine compartment? Pooling of water around the spark plug location and causing arcing (showing up as hesitation, sputtering, rough idle, and more) is common with these. First time I had it happen on my G-friend's 318 I had a shop explain it to me... a nice $50 lesson.

[911 Rod]

Originally posted by blkongry
Have you washed the car recently? Sprayed any water down in the engine compartment? Pooling of water around the spark plug location and causing arcing (showing up as hesitation, sputtering, rough idle, and more) is common with these. First time I had it happen on my G-friend's 318 I had a shop explain it to me... a nice $50 lesson.

No water.
This problem has been steadily getting worst over the last 6 months.
Does not make any difference what the weather is.
I would like to take care of now as my summer car will be taking up my garage space soon.
I am afraid it will die at -40 in a snow storm.

[Jeron]

Air filter?
Oil weight too heavy?
Vacuume leaks?

Check the coil and plug connections. I use a very thin layer of electric contact grease.

Like blkongry said check the plug wells. Besides water, you could also have oil leaking from the valve cover into the well causing plug grounding. While you're at it pull and check the plugs.

[911 Rod]

New K & N filter.
Mobile 1 oil.
Could be a vacuum leak, but why is it intermittent.
Electric grease for the plugs seems like a good idea.
I'll check the plugs, but they are new and I didn't see any oil when I installed them.
I've heard these cars have coil problems.

[Jeron]

Most BMW's spec 30W oil a few are 40W, just don't use the 50W some P-cars use.

If you put electric grease or spark-plug anti-seize on the plug threads don't put any on the first 3 threads. You don't want the grease exposed inside of the cylinder. I put a drop or two the 4th thread and then wrap my thumb in a paper-towel, put my thumb nail in the threads and spin the plugs so that my nail works the grease up the plug away from the electrode.

I also put a little electric grease on the connector tip of the plug.

They do have coil problems. I think yours is a single coil. Check the wires too.

Vacuum leaks suck

Run a bottle of Techron. Be very careful that you buy actual Techron, they have 3 similar bottles and only 1 has Techron.

[911 Rod]

Mobile 1, I believe it is 5W30. The for "Newer Car Formula" one.
I have never used anti-seize on plugs. Many other places.
I don't think it is necessary if you change them as recommended.
Do you think a little electric grease would help with a bad connection on the plugs?
Spray WD 40 on the wires?
I believe it is a single coil. I think the Bentley has a method to check them.
Vacuum leaks suck? No pun intended?
Cleaning the injectors and/or throttle body might be the first step.
I have a feeling there might be a little R & D on this one.

[Jeron]

The spark-plug interval of 100k on the E46, for instance, is too long to not either use anti-seize or at least re-torque the plugs at 50k. I like to use a little anti-seize to ensure proper torque and prevent possible seizing.

I think electric grease helps the connections and reduces corrosion.

[911 Rod]

I think electric grease helps the connections and reduces corrosion. [/B][/QUOTE]
I have every grease but.
Can I use white grease or petroleum jelly?

[Jeron]

I wouldn't use a subsitute.

[911 Rod]

I didn't think "There is no substitute" applied to bimmers.

[blkongry]

I saw you recently changed out your plugs... did the problem start soon after that? Sounds like you may have an intermittened (SP?) grounding problem on your ignition... grouding out somewhere, and once it's started, it will eat that pathway and the problem will get worse. This grounding problem is the same symptoms of the water in the plug wells (because it does the same thing) and same with oil, as Jeron said.

My guess is your plug wires... any frayed, melted, cracked spots on them? Try moving them around, supporting them with something insulating and see how it runs.

[911 Rod]

I'll start from the beginning.
I bought the car a year ago and changed the plugs, fuel filter and air filter. (And a pile of other stuff not related)
Ran fine before and after.
About 6 months ago it started hesitating/surging.
It is becoming worse.
The car was always stored winters and I doubt he ever put in fuel stabilizer of filled up the tank.
I would think this could gum up the throttle body and injectors but it should have been there when I bought the car.
Must be electrical.
The wires look fine, but I'll check again.
Are the coil and wires one piece?
Or, what about the oxygen sensor?
The car runs great 95% of the time.
I wish it would get really bad so I could find the problem.

[blkongry]

Okay, now you're going to have to be a little more specific on the symptoms. Is it hesitating, stammering, cuttin' out, or surging? Does it feel like you are driving normal, then it gives kind of a bra-a-a-a-a-p under acceleration and feels like it's losing power? That's grounding from the electrical, like when you bump up against an electronic govenor... or it could be something to do with the crank position sensor moving and causing the firing to be out of sync with the motor.

OR, does it drive smooth, drop in RPMs, but then pick up again, like it's cutting out or choking to get fuel/air? Does it then surge? Does it surge and start to pull under constant speed, but then drop back? That could be anything from the MAF to injectors. If your O2 sensor goes out, the car will just be a dog... no power, it'll run rich or lean, and you'll probably see whitish smoke out the back.

If you can clearly describe the symptoms... even try to spell out the sounds it makes, that helps in troubleshooting and diagnosing.

[911 Rod]

Okay (thanks for asking)
The car runs fine unless you accelerate hard. 3500 to 4500 RPM?
At this point it feels like it is surging, but more than likely it is bogging.
Once you get past maybe 4500 RPM it seams fine.
Normal driving with a more subdued driver might not even notice.
I am very picky and feel the car very well.
It does not do this all of the time.
If the car sits for a couple of days it has a rough idle for a couple of seconds before a couple of blips of the throttle.

[blkongry]

That's an air/fuel mix problem... it feels almost like it has more power, but it's not accelerating much? That could be the MAF (mass air flow) sensor, an O2 sensor, some low pressure restriction zone the shows up about at that RPM, or it could be a slight vacuum leak that doesn't show up unless you are right at that specific RPM, and it induces the leak ;-) Those slight irregularities in how the vehicle drives can be hard to diagnose, and they could be something really minor that just doesn't show up until you hit a certain RPM.

[Rick V]

I will argue with the weight of the motor oil. My 92 has 208 on the clock and has had nothing but castrol 20w50 since new. I have never had a problem with pressure, leaking,or starting. Thr BMW shop where I used to work used 15w50 and we never had a problem. BMW didn't make the shift to the lighter weight oil until the obd11 cars came out. The car in question is a 95 which makes it an obd1 vehicle.
What kind of plugs were installed in the car? These cars don't like the platinum type.....well not for long anyway.
The rpm ranges you are describing is where the disa comes into play does it clear out around 5000rpm?

[911 Rod]

Sounds like you guys are headed in the right direction.
Only from 3500 to 4500 RPM (approx.) but not all the time.
Beyond that it goes great, especially in 5th, before that .. well it is a 4 banger.
A disa is?
MAF (mass air flow) sensor, an O2 sensor is sorta where I started.
My feeling is when you try to push too much through a hole and get less than if you pushed less. Push even harder and bam, it comes out big time.
Make sense? I think the MAF would act up at low RPM's, which it does after sitting for a couple of days (which to me would be a fuel draining out while sitting problem but who knows).
It does have a very slight rough idle sometimes.
Hesitation while cold happens sometimes as well.
As I stated previously, I might have to wait for it to get really bad before I can diagnose it.

[Rick V]

Disa is the gimmick that BMW uses to open a butterfly in the intake to give a shorter bigger shot of air to the head. The intake os very long and narrow which is good for torque but sucks for topend. When this butterfly opens it cuts the length of the intake roughly in half. You can feel this under heavy throttle when the rpm's get to roughly 4000.
I say you have the wrong plugs in the car.
Good luck

[parolof]

is there a difference when you accelerate with full trottle or say half trottle and slowly let it build up the revs and speed, if so I had the same problem about a year ago when I bought my car, swapped plugs to the recommended NGK's instead of some French ***** that was installed by the previous owner:-)