Description: after 20-30 minutes (or miles) of driving I will begin to get hard bucks (misfires beyond one cylinder) and eventually stall. The car will typically turn right back over - but stall after only a minute or so. If I leave the car off for around 15 minutes it will run fine for a while and then stall out again.
It sounds as if the car is running out of fuel which it is not. The pump remains primed and the pressure is normal.
What I’ve done so far:
- Fuel pump has been swapped
- Fuel filter has been replaced
- Fuel lines have been verified (even cleaned to rail - injector heads and intake manifold… It’s been a fun weekend)
- Fuel pump relay has been replaced
I have also recently replaced the ignition coil due to an unrelated issue for which I will provide detail so that you too can rule this out. I had random multiple misfires in bank 3 - replaced the coil and the misfires were gone. When the problem came back I was suspect of the new coil and originally believed that this had failed at temp. This coil has been tested hot and cold and passed each way. I also swapped out for the coil with the issue on bank 3 just to verify.
I have read in a few forums which point towards either the ASD relay (which I was also suspect of early in the process of elimination) itself failing when heated or the camshaft position sensor and or the crankshaft position sensor causing the relay to trip when they are heated.
If anybody out there has any input or a logical path of trial and error forward - all advice would be appreciated.
If you’re looking for the path of trial and error, experience tells me that the next thing to replace would be the camshaft sensor.
If you’re looking for a diagnostic procedure, you’ll need access to a complete wiring diagram, a scan tool that can give you live data stream, and a labscope or graphing multi-meter.
Thanks for the input. Camshaft position sensor will be replaced today after work.
New camshaft position sensor - still having the same problem.
The engine should run without the cam sensor. I would like to monitor the crankshaft position sensor output with a scan tool but without a scan tool you’ll have to replace it and hope for the best. While your under there inspect the wiring harness to the crank sensor, oil leaks can damage the insulation on the wiring.
My first guess on reading the symptoms above was a faulty crank sensor. During their failure mode, they tend to act up when they get hot. If you want to continue on with swap-tronics method, that would be what I’d replace next. If that didn’t work, I’d next replace the coolant temp sensor (the one used by the computer). If that didn’t work, I’d hook u a fuel pressure gauge on the fuel rail and see if the pressure holds steady as before after driving a while until the symptoms start. I’m no sure what the ASD relay does.
If this were my car, at this point, probably even before now, I’d be inclined to call in the experts. You need someone with Mitsubishi drivability problem diagnostic experience and the Mitsubishi scan tool. With that they can check the fuel trim and other engine real time parameters and narrow down the cause more quickly than replacing gadgets based on common sense guesses. Best of luck.
Much appreciated again for the input. Ironically I’m currently waiting for the crank sensor to arrive. I’m leaning that way myself. The fuel pressure remains consistent until the bad idle and fail - but that has part to do with the quick rise and fall of the rpm. I also checked the voltage to the pump. I have a pretty good feeling about the crank sensor at this point - and haven’t put more than a diagnostic check will cost me into parts. If this doesn’t work - to the dealer she goes (ASD = automatic shut down - kills the power to the ignition, injectors and fuel pump. Simple relay - but this checked out clean for me hot and cold as well as its harness.)
hmmm … the fuel pressure changes at the same time as the bad idle and stall? The rpm is not involved with the fuel pressure. Rail fuel pressure is usually only determined by the fuel pump pressure and intake manifold vacuum. When the intake manifold vacuum increases, the rail fuel pressure will decrease. That’s the way it works on my Corolla anyway. The fuel pressure should remain steady unless the intake manifold vacuum changes. As your car engine stalls during idleing, I’d guess the manifold pressure would get less negative, so the rail pressure should increase at the point the engine stalls. Does it?
Solved - George, you are correct but with the issue which turned out to be the crankshaft position sensor - whenever there is no signal received on this car it triggers the ASD to shut down ignition and fuel - so with intermittent signal coming from the crank sensor - the pump was kicking on and off along with the ignition coil. Again - Thanks to all who took the time to read - and comment for assisting with this solve for what is one of the most difficult troubleshoots.
Thanks for taking time to post the solution @Ohat … glad you got her running like a top again!