I bought a an LS1 swapped 1993 RX7 about a month ago. Supposedly it's a 99 LS1 with PCM being an 00 out of a T/A. Attempted to make a 20 hour drive home because of how confident the seller was that the car runs absolutely perfect. Nothing wrong, 100% mechanically sound. This is why you don't trust people... Ended up leaving it at a shop, scheduling a transport trailer, and buying a 1 way ticket home.

This hopefully will be a condensed version, but I feel like I've got a lot of work ahead of me!

After leaving his house, a check engine light came on. He said it should just be for O2 sensor and clearing it will make things better.. I was noticing lack of power, sputtering, and hard starts. Especially when cold. At idle, feathering the gas pedal was needed to get RPM's to rise. Otherwise just pressing the throttle down would cause the car to sputter and sometimes die. The only other unexplained symptom is when I was driving at constant speed on the highway, every once in a while the car would have some random knock/thump/click noise that seemed to come from the driver's side engine bay. The RPM's would surge minimally every time that would happen. Really difficult to explain. With minimal tools with me, stopped at a shop to pull codes.

P0342 CMP sensor low
P0327 Knock sensor malfunction bank 1
P0131 O2 sensor low
P0332 Knock sensor malfunction bank 2
P0506 Idle speed too low

The shop replaced knock sensors and CMP (didn't have any physical damage to the bottom, no metal bits stuck to it). Also noticed the wiring going to CMP looked a little raggedy so they crimped in new wires to the harness. It was also blowing the 40 amp B1 fuse, but I found a rubbed through wire in driver side wheel well that seemed to fix that.

Fast forward to today: Only code I was getting is P0342. Car is a little rough to start, but idles fine for a few minutes. Then when the code comes back it'll run rough. Removed the intake to get at the CMP sensor. Battery is a little low (11.66 V) and I was reading 10.41 V on the red wire. Expected 1V on the brown signal wire, but was only getting 250-ish mV. Unknown if that's just due to the battery not currently being at a full 12.4-6 V or not.. To make sure the connector or splices weren't the problem I cut off the connector to test the wires and got the same, then cut the splices off and also got the same. Waiting for new sensor connector/pigtail to come in the mail right now.

In reading about this sensor wiring, it should go straight from the connector into the PCM. But when I started removing wire looms and electrical tape, it seems that these 3 wires are going towards the driver's side of the car, NOT towards the passenger side where the bundle goes through the bulkhead to PCM that's mounted in the passenger foot well. Anybody have any clue on this?

I looked up that the "official" GM PCM test connector kit is like $300. Which is equal to 3 hours of troubleshooting at my local shop.. Trying to find next steps here to ID if it is in fact that these wires are bad, the PCM is faulty, or hopefully not cam bolts that have walked out. It'd be great to ID root cause before I replace the intake gaskets and put it back on. There is absolutely 0 room behind the FAST intake where the firewall is above the CMP sensor for any movement.

 

Battery is really low, are you sure the alternator is working properly