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Discussion Starter #1
Hello all.

Long time browser first time poster so I'll just jump right in. Could be a longish post so be warned but I'd really appreciate some input and help.

My mate bought a 2003 Vauxhall Astra MK4 1.6L 8V off a sweet old man a couple days ago. It only had 58,000 miles on the clock.

We both looked at it. Test drove it. Inspected it. All seemed fine and dandy until he drove home.

Driving home, slowed for a roundabout engine warning flashed on and engine cut out. Started again and drove home fine but the speedo drops off intermittently until you hit 30mph and it's fine. I then drove it no issues. I did pedal test got P0400 - EGR valve.

The next day he's driving to work, engine warning light and lack of power. Brings it home I put proper code reader on it - P0303 - cylinder 3 misfire, nothing about EGR valve. So I removed the EGR valve and cleaned it, removed the throttle body and cleaned it and removed the spark plugs. Spark plug 3 looks **** so I cleaned them and switched 3 and 4 to see if fault moved. Cleared code and test drove, no problems but I ordered new Bosch plugs.

Today he's driving it, drive to work fine and drove home fine until last 5 minutes the engine warning light and misfire back. Check code - P0304 - Cylinder 4 misfire (where the bad spark plug has been moved). Fit the new spark plugs, cleared codes by disconnecting battery for an hour. Switched it on, no light, no misfire. Drove it about 10 miles. No issues except speed still dropping out between 10mph and 25mph.

Got home - pedal test - P0303 - cylinder 3 misfire apparently but it's not misfiring? I guess coil pack or EGR valve is next step regarding misfire.

As for the speedo dropping out and the random cut out - vehicle doesn't have ABS so just a speed sensor in N/S/F bearing. Had ignition on and tested voltage to sensor (0.06V but does it need to be in motion to create a voltage?). Ignition off and tested resistance/Ohms in wiring to speed sensor.. it was getting 20K (20,000 ohms?!?) In the wiring? At first I figured it needs a bearing w/ speed sensor but now I'm wondering if it's a wiring fault?

Final issue I just noticed. This car has an electric power steering pump - when the car is sat and idling, wheels dead straight, you can hear a high pitched but not loud whine which is drowned out around 2000rpm. Turn it full lock and the whine gets louder as the motor works harder. I'm wondering though - is normal to be able to hear the motor just whining a little bit even when stationary?

Sorry for such a long post. Mates pulling his hair out as he started a new job and needs a car and I'm doing everything I can but I'm just an apprentice so still learning myself.

In summary:
- P0303 misfire - new plugs - not misfiring now but code there?

- Speedo dropping out at low speeds - not sure if bearing w/ sensor or wiring as resistance was super high and voltage super low?

- Engine cut out randomly slowing down - I need to replace a split breather pipe but think this is related to speedo/speed sensor/wiring fault.

- Can hear electric power steering pump all the time. It's not loud but you can always hear it when stationary unless over 2000rpm. Can't hear when driving at any RPM.

Please advise. Really appreciate some input in this! Thanks in advance! :)
 

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The wheel needs to be spinning to see the voltage changes
Plenty of fliud in the power steering bottle ?
What scanner are you using to retrieve fault codes?
 

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Discussion Starter #2
The wheel needs to be spinning to see the voltage changes
Plenty of fliud in the power steering bottle ?
What scanner are you using to retrieve fault codes?
OK then that's no worries, I'll RE-test with the wheel lifted and spinning. What about the resistance though? That seems excessively high doesn't it?

As for fluid level looked OK to me. There is no distinctive MIN or MAX marking, just some lines and it looked OK to me. Maybe some air trapped in the system?

Used pedal test first and now ove borrowed my mates Autel scanner. He uses it for a few odd jobs here and there and seems very happy with it.

Any reason why I might still get P0303 - Cylinder 3 misfire despite new plugs and the car isn't actually misfiring now?
 

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OK then that's no worries, I'll RE-test with the wheel lifted and spinning. What about the resistance though? That seems excessively high doesn't it?

As for fluid level looked OK to me. There is no distinctive MIN or MAX marking, just some lines and it looked OK to me. Maybe some air trapped in the system?

Used pedal test first and now ove borrowed my mates Autel scanner. He uses it for a few odd jobs here and there and seems very happy with it.

Any reason why I might still get P0303 - Cylinder 3 misfire despite new plugs and the car isn't actually misfiring now?
A code P0303 may mean that one or more of the following has happened:
  • Faulty spark plug or wire Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Running out of fuel
  • Poor compression Defective computer

Read more at: https://www.obd-codes.com/p0303
Copyright OBD-Codes.com
 

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Discussion Starter #4
A code P0303 may mean that one or more of the following has happened:
  • Faulty spark plug or wire Faulty coil (pack)
  • Faulty oxygen sensor(s)
  • Faulty fuel injector
  • Burned exhaust valve
  • Faulty catalytic converter(s)
  • Running out of fuel
  • Poor compression Defective computer

Read more at: https://www.obd-codes.com/p0303
Copyright OBD-Codes.com

Hey, thanks for reply.

Weird thing though is the car isn't misfiring yet the pedal test still said P0303..?
 

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Discussion Starter #10
Was the code present when the code reader had cleared off the code ?
When I did pedal test it was P0400. When I checked with a code reader it was P0303. Cleaned spark plugs, switched bad plug (3) with good plug (4) and deleted codes and returned code reader to work friend.

Next day misfire and light back on. I had no code reader so did pedal test. Got P0304 which is where I moved the bad plug. Replaced all plugs and disconnected battery for an hour. Get in car and light gone. Test drove for 45 minutes and all good. Did pedal test when I got home and P0303 was back no light and no misfire?
 

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When I did pedal test it was P0400. When I checked with a code reader it was P0303. Cleaned spark plugs, switched bad plug (3) with good plug (4) and deleted codes and returned code reader to work friend.

Next day misfire and light back on. I had no code reader so did pedal test. Got P0304 which is where I moved the bad plug. Replaced all plugs and disconnected battery for an hour. Get in car and light gone. Test drove for 45 minutes and all good. Did pedal test when I got home and P0303 was back no light and no misfire?
Disconnecting the battery won’t clear diagnostic trouble codes off.
 
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