1999 BMW 318


Dr. Hagerty

July, 22, 2010 AT 7:50 AM


Inspect the crankcase vent valve, replacement of the valve is typically the solution to your dilemma. It is #1


Dr Loot

July, 23, 2010 AT 12:29 PM

Sorry I have been a little busy and unable to get back to you. I will now step you through the diagnostic procedure: ROUGH OR UNSTABLE IDLE

1. Fouled spark plugs: remove all of the spark plugs and check them for contamination, gas or oil residue, make sure the spark plugs are cleaned and properly gap before reinstalling.

2. Burned or sticking valves: this procedure is a little bit more difficult so we will bypass it for now.

3. Intake manifold air leak: get yourself a little propane torch like the plumbers use, with the engine running take the torch do not light it! Just turn on the gas and check all are found the intake, injectors, all vacuum lines and the intake duck, if the engines smooth out you found your vacuum leak, if there is a vacuum leak.

4. Incorrect valve timing: this may be an issue due to the fact that you stated "The problem comes 7-8 months ago and increase gradually" when was the timing belt last changed? As the timing belt gets old it stretches and changes the valve timing, remove the timing belt cover and inspect the belt.

5. Ignition system malfunction: the engine on TDC remove the distributor cap makes sure of the rotor and the cap are in good condition, also make sure the rotor is pointing to cylinder number one, inspect the spark plug wires make sure they are in good condition, and when you put them back on the spark plugs make sure they click on every spark plug.

6. Fuel injector not operating: take a small piece of hoses, long enough to reach the injectors and your ear, so you can listen to see the injectors are operating, the injectors will make a distinct clicking sound make sure they sound all the same, if you have one injector that is making a different clicking sound that is your problem, you can try some injector cleaner to resolve the problem or replace the injector.

7. DME/Motronic control unit malfunction: the only way to determine if the computer is not functioning properly it is usually intermittent, it will work until it gets hot and then it will shut down a certain function, ignition, timing advance, injectors, ect.

8. Blown head gasket: if the vehicle has the blown head gasket you will have a dead cylinder, you can determine this by a compression check, also examine the spark plugs if it has the blown head gasket sparkplug will usually be very clean, or it will have white particles of coolant stuck to the spark plug.

If you need any more help or have further questions do not hesitate to respond.



July, 25, 2010 AT 1:55 AM

Hi Doc,

Thanks for your prompt reply. Well let me me start troubleshoot as per you guide lines and will come back to you with my observation.



Dr Loot

July, 26, 2010 AT 11:52 PM

And dont forget to do what Dr. Hagerty said "Inspect the crankcase vent valve, replacement of the valve is typically the solution to your dilemma. It is #1"


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