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Lou P
Lou P, ASE Certified Technician
Category: BMW
Satisfied Customers: 3719
Experience:  15+ years experience in the automotive field on all types of vehicles with access to diagrams and repair info.
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I have a 97 740i, and everyonce in awhile maybe 2 out of 5

Customer Question

Hello, I have a 97 740i, and everyonce in awhile maybe 2 out of 5 times, when I go to start it, it turns over kinda sluggish and has very poor performance when it first starts, along with the car shaking at idle.
JA: How many miles are on the car? What size is the engine?
Customer: 116k 4.4 v8
JA: Are you hoping to fix this yourself? What have you tried so far?
Customer: I havent tried anything yet, the car is blowing out oil smoke on some start ups as well so I need to change the OSV.
JA: Anything else you think the mechanic should know?
Customer: Yes, the car sat for a long time before I started driving it.
Submitted: 3 months ago.
Category: BMW
Customer: replied 3 months ago.
Also, I have changed the plugs already.
Expert:  Lou P replied 3 months ago.

Hello, when you say the car had sat before this happened how long was it?

how often do you drive the car?

Customer: replied 3 months ago.
I drive the car every day,
It only sat for a few months.When I pulled the plugs they seemed ok, back ones were soaked in oil. I'm assuming from the bad osv.I am suspecting a vacuum leak maybe.
Expert:  Lou P replied 3 months ago.

ok , if the car sat then there are a few things that happen. let me explain

Expert:  Lou P replied 3 months ago.
  1. the battery will be weak and cause the slow cranking, there is a constant draw on the battery, these cars do not like to sit more than 2 weeks without an external charger on it
  2. the cylinders will lose oil and cause a slight compression loss so it takes a few seconds before oil is splashed back up on the cylinder walls to help with compression.,
  3. the fuel system bleeds down and gets air in the system so when it does start it takes a second to purge the air at which time the misfires will occur.
Customer: replied 3 months ago.
That's good to know, the vehicle has a fairly new battery, and this is a periodic issue. It can do it after starting after work. Sometimes first thing in the morning.
The shaking at idle happens randomly when driving.Whenever it has a "chuggish" start which is not a slow crank it never cranks slow,
It has poor performance in the lower rpm range. But typically cleans up pretty quickly.I think the shaking at idle isn't related to the poor starting and performance. But I don't know
Expert:  Lou P replied 3 months ago.

gotcha, i know that the intake boot tears and is an issue with airflow, also the plugs are common to fail and need replaced quite often so you are probably right with the vacuum leak., check the intake boot for cracks.

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