About the car: 98 M6 Camaro with iron block 408ci and ported L92 heads. Ran fine and needed a retune until the below...





Recently performed a heads cam swap from stock L92 heads and custom cam for some ported L92s and a larger Cam Motion cam.

Start up was good and I ran it on the old tune around town for a few days as I was chasing down an overheating issue. I swapped the clogged radiator and put in a new thermostat. Took it for a long drive to monitor temps. Everything checked out as it eeked past 180 degrees at the most after driving four over an hour.

My fuel gauge is off so I didn't notice she was out of gas. It was stumbling and losing power. I limped it to the nearest shell station and refueled it with more 93 octane.

Once refueled the car still hasn't run right. It shakes violently, far more than a big cam should. It sputters badly and backfires on accel and decel. NO SES light.

I've swapped plug wires with AC Delcos, plugs are good, and changed fuel filters about 1k miles ago. The fuel pressure gauge reads about 58 psi during idle. In summary, I don't think fuel or spark is the issue. I did read that running low on fuel could cause the car to suck up gunk and build up from the bottom of the tank. Eh...

I recently resolved an O2 sensor problem and have a new one in there as well. I don't think my car would run this bad all of a sudden due to a failing O2.

I've run it a little more to see if a SES comes on but no dice. I've checked the grounds (passenger and driver side block, and driver side head). I pulled the PCM and didn't see any noticable discoloration on the pins. Any thoughts?

Cliff notes: Car started running incredibly bad after nearly running out of gas. Refueled and still runs horrid. Checked the usual culprits (plugs, plug wires, grounds) to no avail. The car isn't​ throwing a SES.

 

My .02 I would change fuel filter to rule out crud at bottom of
Tank clogging filter by running to low.
I would add a bottle of AMSOIL PI, or Chevron Techron as well
After.
Good Luck

 

What do you have to tune it with or log with?

 

Changed the fuel filter with no luck.
I just have your typical diagnostic scanner, and Bluetooth ob2 scanner for the torque app.

I can look at live data though...anything I should focus on?

 

Actual cyl misfires. check fuel pressure while running also not just at idle.

 

Okay I think I set up the Torque app to count cylinder misfires and send a log...updates to come.

 

Update: I tried the Torque app and it wasn't picking up any data for misfire counts.

Ive changed plugs,plug wires, coil packs, cam position sensor, and an O2 sensor. Still running like crap with no codes.

I even tried seafoam to no avail.

Car is running real rich by the looks of the plugs.

Any other ideas?! Getting pretty frustrated.

Could this be a PCM/ tune issue?

 

It could very well be a tune issue.

 

Yeah, just strange that it would happen all of a sudden like that. It was driving good for awhile as I was working through overheating issues.

 

A log would at least tell you how its operating and give you feedback instead of pissing in the dark and throwing parts at it.

 

Popped the valve covers off and had a loose rocker arm!!! I think our mystery is solved...

 

Wow thats interesting. Seems like it is. Check the other side also imo. It may not be a popular idea but i always use thread locker or thread sealant on them.

 

Ditto...any collateral damage from running so long like this? Pushrod is straight.

 

Not really but the lack of ses light for p0300 usually means it was turned off in the tune which should not be done.