Aygo mystery

[scott87]

Hi all, I have a 2007 aygo, the engine only starts with an obd reader plugged in but will also misfire on no 1 cylinder I've switched coil packs and injectors to different cylinders but the fault doesn't follow and all compression is good, any suggestions?

[Bper]

Hi William,IMO based on the symptoms described, including difficulty starting the engine without an OBD reader and misfires on cylinder 1 despite swapping coil packs and injectors, the likely cause of the issue is a malfunctioning sensor, such as the camshaft position sensor or crankshaft position sensor. These sensors are crucial for proper ignition timing and fuel injection. The starting problem may be related to a communication issue between the sensor and the engine control unit (ECU). Inspecting and potentially replacing these sensors should be the next step in diagnosing and resolving the problem.Hope this helps.

[flash22]

sounds like a ground issue

from experience with immobilizer issues

the obd2 (DLC3) ground is shared with the coil grounds

pics from the other thread

Ground point is located at the front right of the cylinder head (as you look at the engine)

 

[tsikis007]

Plug-in obd scanner.

[scott87]

On 4/7/2024 at 7:10 PM, flash22 said:

sounds like a ground issue

from experience with immobilizer issues

the obd2 (DLC3) ground is shared with the coil grounds

pics from the other thread

Ground point is located at the front right of the cylinder head (as you look at the engine)

 

Awesome thanks for the advice, I just tested continuity between this earth point and the negative terminal on the Battery and is was open circuit, I made up a new earth and now it runs without the scanner plugged in I was really hoping this would sort cylinder one but no joy, I checked continuity between the black and white on the coil pack plug to earth and it was 0.1 ohms, it may be a sensor as mentioned by bper in a previous comment

[flash22]

look at the spark plug that will tell what is happening, be it a bad plug or injector

is it a constant misfire, does it do it at idle or underload/throttle ?

 

[scott87]

5 minutes ago, flash22 said:

look at the spark plug that will tell what is happening, be it a bad plug or injector

is it a constant misfire, does it do it at idle or underload/throttle ?

 

It's a constant misfire