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Matt
Matt, Mechanical Engineer
Category: UK Car
Satisfied Customers: 20614
Experience:  BEng hons Mech engineering, in auto industry 22 years
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I have a 1998 BMW Z3 M44. It recently died and we cannot

Customer Question

Hi, i have a 1998 BMW Z3 M44.
It recently died and we cannot figure out the problem.
Plugs are fine, Fuel is fine, Sensors are changed, Compression tested..
Submitted: 10 months ago.
Category: UK Car
Customer: replied 10 months ago.
The funny thing is that i am able to have the car started and running with rough idle when i removed 1 of the spark plug from the engine block.
Customer: replied 10 months ago.
crankshaft position sensor, camshaft position sensor have been replaced.
wideband O2 sensor has been fitted.
Expert:  Matt replied 10 months ago.

Hello

I'd 1st check the resistance of the spark plug leads ( 13-15Kohm / metre) and replace if any doubt or high resistance - Also replace the spark plugs if any of them fail this checklist:

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqread.asp

You can also try spraying some water on the coil pack with the engine running. It is possible the coil is faulty and causing the misfire. If you see sparks arcing with the water, then replace the coil.

I'd check the condition of the injector plugs / connections as this could be a lean misfire if an injector isn't firing properly - the best way to check this is with a 'noid' light

http://www.noidlight.com/

Then check all the connections to the engine sensors one at a time, remove each one and examine for signs of corrosion or damage and a squirt of contact cleaner ( not WD40) will also help.

This could be an airleak after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

It’s also worth getting the fuel pressure checked as if this is low due to a blocked filter or faulty regulator or even a poorly pump will all result in insufficient fuel being delivered to the engine

Customer: replied 10 months ago.
I check it all.. But why does it start when 1 spark plug is out
Customer: replied 10 months ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Matt replied 10 months ago.

Hello

to be honest thats an odd one

It might be worth double checking that you have the right coil and injector wiring going the right cylinder

Customer: replied 10 months ago.
Hi, in that case, you didn't really answered my question, and I know the things you mentioned before asking. I found the problem, the mid pipe was blocked, thus no exhaust air is able to escape. When 1 plus is out, the open allows the air to escape thus enabling the engine to run. Thanks anyway..

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