JCBroman
New Member
The ECU throws a code of P0303 and P0353. To better observe the situation with the coil and the injector, I rigged up LED’s to flash with the firing of the coil and the activation of the injector. I taped these to the outside of the windshield with black duct tape and voila…instant in-car monitors.
When the car is running well, the LEDs for cylinders 1 and 3 and flashing perfectly. But then sometimes the check engine light will come on and an injector LED stops flashing on. Pulling over and restarting the engine clears the problem until it decides to misfire again. The ECU supposedly shuts off any injector of a cylinder that is misfiring to save the cat from damaged due to unburned fuel.
So what is causing the intermittent misfire? Here is what I have done already:
1) Swapped coils between 3 and 5…problem stays with 3
2) Swapped spark plug between 3 and 5…problem stays with 3
3) Installed new injector for cylinder 3. Still misfires.
4) Swapped injector between 3 and 5…problem stays with 3
5) Check engine compression. Excellent and within 10% of each other.
6) Changed the crank sensor, since that is supposedly how the ECU detects a misfire.
Other hints:
1) The problem sometimes happens to cylinder 1, too.
2) I sometimes get a whiff of fuel when this behavior is happening
3) Both times I pulled the fuel rail to replace/swap injectors, the problem disappeared for 100+ miles before it returned. (No I don’t want to make a fuel rail pull a 75 mile maintenance routine!)
I hesitate to take it to the local mechanic or dealer because most just go the route of simply replacing stuff (at my expense) without having a real clue of the root cause.
Ideas of what to look at next?
When the car is running well, the LEDs for cylinders 1 and 3 and flashing perfectly. But then sometimes the check engine light will come on and an injector LED stops flashing on. Pulling over and restarting the engine clears the problem until it decides to misfire again. The ECU supposedly shuts off any injector of a cylinder that is misfiring to save the cat from damaged due to unburned fuel.
So what is causing the intermittent misfire? Here is what I have done already:
1) Swapped coils between 3 and 5…problem stays with 3
2) Swapped spark plug between 3 and 5…problem stays with 3
3) Installed new injector for cylinder 3. Still misfires.
4) Swapped injector between 3 and 5…problem stays with 3
5) Check engine compression. Excellent and within 10% of each other.
6) Changed the crank sensor, since that is supposedly how the ECU detects a misfire.
Other hints:
1) The problem sometimes happens to cylinder 1, too.
2) I sometimes get a whiff of fuel when this behavior is happening
3) Both times I pulled the fuel rail to replace/swap injectors, the problem disappeared for 100+ miles before it returned. (No I don’t want to make a fuel rail pull a 75 mile maintenance routine!)
I hesitate to take it to the local mechanic or dealer because most just go the route of simply replacing stuff (at my expense) without having a real clue of the root cause.
Ideas of what to look at next?