Description of a "problem"

[bmn]

Hey friends,

I'm new to this forum.

I have no idea at all concerning the "mechanical terms" in a car .

I'm studying electrical engineering(high current).

I drive an E-36 320IA 1995.

I'm satisfied with my car ,but there is "something" happening.

I'll describe it for you...maybe you'll get the picture.



When i start my car,after 10 or 15 secs,and sitting in the driver's seat,i feel 1 or two "hits" of the motor .

When i open the hood of the car,nothing appears .The motor is like a clock.


This issue is repetitve but not continuous.

When i put my palm hand in front of the exhaust,i can feel what is happening.

i Can feel the individual bursts of exhaust with my hand when the car is idling.

it's like that : periodic periodic boom periodic boom periodic periodic boom :P

Note:this phenomenon occures only when the car is in Park or Neutral mode.

lol got the idea???

The car works great.
So...what could it be ???

Is it an air filter problem??my mechanic told me it could be the air pump !!

if it is,Is it Serious??

Any help is usefull.

Note: This "problem" is 3 months old.

I did a car scan twice(i had a dead oxygen sensor for over 3 yars :P which has been replaced shrtly,1 mth ago ),but nothing showed up after.

No PCV,No Spark plugs problems.


For clarification,ask me "simple" understood questions (since m not a mechanic)

Thank you.

Najib

Hopefully you got an idea .

Plus,it it's an air pump problem..is it hard and does it cost to replace??

Looking forward to hearing from you.

[Jeron]

It only happens right after you start the car? What if the engine is warm vs cold?

[bmn]

Yes,

It only happens right after i start the car.

If you open the hood,the motor seems fine,no vibration or trembling.
He's working like a clock.

but when you are sitting in the driver's seat,you can feel it.

What could it be???

Please anything would be usefull.

[Jeron]

The secondary air pump only runs during "cold" starts. So that is why I asked if it happens warm vs cold.

You description sounds like the engine is "missing", meaning not firing a cylinder every once in a while. If you have checked the spark plugs and there was no oil in the plug wells then the next item I would guess is a bad coil pack but they usually throw a code.

Is this effecting drivability or just a nuisance?

[Manolito]

And this periodic boom goes away as the car warms up?

In spite of your detailed description, I am having a hard time visualizing exactly what the car is doing. If it clears up as the car warms, it is probably not a serious problem.

I rather suspect, that the car is running just a bit lean while cold. This could be caused by an inaccurate reading from a temperature sensor, or low fuel pressure, or a leak in one of the air tubes between the mass airflow sensor and the throttle valve. The last of these three is a common problem, but it would not be expected to improve as the car warms up.

[bmn]

Yes ,that's what my mechanic exactly told me.""meaning not firing a cylinder every once in a while"""

He told me the spark plugs are brand new.

This problem is 3 mths old...I did a scan check twice to my car,and nothing appeared concerning throwing a code for a bad coil.

This is only effecting a nuisance.

Concerning the drive of the car,she's tough ,active ....No problems there.

Plus,i warm my car before i drove by.

[Jeron]

If it only does it a couple of times right after startup then goes away I'd probably ignore the problem because you've already checked the basics. It's going to be very hard to diagnose since it seems to be a rather rare occurrence.

The only item I can think of so far is bad solder on the ECU board. Since you are studying electrical engineering you may enjoy pulling the ECU and checking the solder on the board where the spark plug signals are sent.

[bmn]

i did a scan check yesterday,.

Vanos Mechanical Error.

My mechanic told me there was an inequivalent timing between the vanos and the motor!

What do you say???

[Jeron]

It's not a problem I am experienced with. There is a solenoid that controls oil pressure to the VANOS and therefore the advancement of the CAM.

I dont know hte symptoms of a failed VANOS system.

You might check out DrVANOS.com he's a good guy.