I have a largely stock 03 8 at about 220k miles. I have been chasing an issue where after everything is very heat soaked suddenly it won't idle at all (this loves to happen when I'm in traffic). I throw in the clutch, take my foot off of the gas, and within a second or so I'm coasting. The tach needle pretty much goes straight to zero. Otherwise in gear it seems to run normally.

I figured it had been cooking the driver side coil. After roasting a number of aftermarket coils I got a mitsu coil gently used and placed that. So far so good, but I had some aftermarket coils last three weeks before they nuked. My Mitsu service suggested that I may be loosing my (exhaust) cam sensor. He had a used spare he used for testing and gave it to me. That failed on the drive home with a bad misfire. I bought a new mitsu cam sensor and that ran well for almost a week before I'm back to no idle. I put the factory cam sensor back in to get it home.

At home I read the codes, aP0340 cam sensor code I was expecting, and a P0335 crank sensor code that I wasn't. I cleared the codes but haven't taken the car out of the driveway since I don't trust it. Running the motor for about 5 min with no codes after clearing. I have another cam sensor coming tomorrow, and I have a gut feeling that this one is going to crap out quickly too.

One of the possibilities I was considering is that my ECU is somehow over volting these things (like the cooked coils), and I don't know if its possible for it to cook something like a cam sensor. One thing the dealer did do is clean all of my grounds, but the no idle keeps repeating with this bad sensor. I'm running out of ideas, and my dealer had it two times totaling more than a week without tracking it down for $400.

Please if anyone has any good ideas I'd love to hear it.

 

Why did the dealer charge you if they didn't fix anything?

From your initial description of the behavior I would suspect the IAC. It's pretty common that the egr starts to leak on our engines and cooks the IAC.

All that other stuff going on though...was it throwing codes for those sensors before you started messing with them?

 

You're throwing a lot of parts at this thing that aren't fixing the issue.

I highly doubt a brand new cam sensor failed in 3 weeks.

Seeing a crank sensor code makes me think crank sensor. And it can cause these intermittent symptoms your are describing.

 

When it was eating coils I’d replace the coil and the problem went away immediately. Both times I had the exhaust side cam sensor go I switched back to the factory sensor and the problem went away immediately.

I had to pay the dealer for the diagnosis and the stuff they did to treat the problem. The second go round they charged me a lot less since the first effort did nothing. The coil they gave me is holding up so far.

but you are right, I’m treating symptoms with no cause. I may have a bad sensor (crank, cam) that’s causing my ecu to do destructive things?

 

The ECU can't destroy sensors/coils like you're describing.

Unfortunately with the cam/crank sensor codes the Mitsu ECU isn't very good at self diagnosing these sensors, so it can be a bit of guess work.

 

The electronics guy at the dealer said that ECU can be over volting things like coils, that this possibility turning probability is just about the only thing left that can do what I'm seeing. I wish it was true that it can't believe me. By a unknown used ECU and give up my flash. Then possible pay for more sensors and whatever else gets nuked. If it's something else I want to hear it. Cam sensor #3 is here, if it kills that I'll know I guess.

 

Easy enough to test, unplug a sensor and put a meter on the harness.

The ECU doesn't send volts to the coils, it sends ground (active low)