Engine Issue

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KieranZ

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Sep 2, 2020
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Hello people i am looking for a little advice. It i will start with a little background info. I recently bought a 2000 Z3 (2.0 6 Cylinder) Prelockdown as a project for me to complete while the country was on hold. The car was off the road for 4 years prior to purchase, i thought it a good opportunity to learn some new skills and make it into a car someone can enjoy. I am not trying to make a profit i bought it as a learning opportunity however i would prefer not to make a loss. The Z3 has been full stripped inside and deep cleaned then put back together and the exterior has all been rust proofed and undercoated.

Now onto my problem, When i bought it the engine was not running. The first thing i set about was a full service changing the Oil, Filters (Oil and Fuel) Spark Plugs along with a brand new battery. The engine still would not start which i eventually diagnosed to a broken fuel pump, after changing this the engine started for the first time in 4 years (Very proud moment). Upon revving the car however it seems to have a slight issue, the revs will build to 3000Rpm at which point the EML light comes on, the engine splutters and the revs fall. The engine does not die completely, if the throttle is held down the engine will surge up to 3000 (ish) and fall repeatedly. I have plugged in a cheap diagnostics i got off Amazon and it says Idle Air Control Sytem (Code: p0505), i have tried replacing the ICV with one i know to be working and this did not fix it, i have also replaced the intake hose and boot along with the MAF sensor.

Any ideas are appreciated i have done a lot of research and cant seem to find the answer, i am hoping it is something i can fix myself, however if this post isnt successful in finding an answer i will take it into a garage,
Thanks everyone,
Kieran
 
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OK i am no expert but maybe investigate the Oxygen sensor(s).
Alternatively it could be a component that is failing due to the heat or vibration coinciding with 300rpm.
But if the Fuel Pump was broken.........is something still causing fuel starvation at 3000 rpm....
Sorry but i seem to be giving you more worries and no answer.........I shall be intrigued when you find the cause. Good Luck
 
Did you get my PM?
 
Here is some more information on P0505

Try unplugging the ICV as per the above links testing.

The usual cause is a faulty ICV. But you have already changed it.

Get the wiring diagrams for your car's build date. They are in the "Resources" section of this forum. There are 3 wires going to the ICV, power, earth and control. Test all three and ensure that the control signal is changing with the rev's.
 
Kieran Monaghan said:
OK i am no expert but maybe investigate the Oxygen sensor(s).
Alternatively it could be a component that is failing due to the heat or vibration coinciding with 300rpm.
But if the Fuel Pump was broken.........is something still causing fuel starvation at 3000 rpm....
Sorry but i seem to be giving you more worries and no answer.........I shall be intrigued when you find the cause. Good Luck
Click to expand...
Oxygen Sensor is something i can look into had not even crossed my mind thank you!
 
Murray Wall said:
Here is some more information on P0505

Try unplugging the ICV as per the above links testing.

The usual cause is a faulty ICV. But you have already changed it.

Get the wiring diagrams for your car's build date. They are in the "Resources" section of this forum. There are 3 wires going to the ICV, power, earth and control. Test all three and ensure that the control signal is changing with the rev's.
Click to expand...
I have tested to ICV by unplugging it and the codes still appear, i shall check the control signals as you say and see what that gives me. Thank you
 
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