2004-2007 Cadillac CTS-V General Discussion Discussion, CTS V P0305 Engine Misfire Code in Cadillac CTS-V Series Forum - 2004 - 2007; I really need advice on a problem with my CTS V. I have been getting a p0305 code for a ...
I really need advice on a problem with my CTS V. I have been getting a p0305 code for a couple months, it runs rough at idle, and it smells rich at startup. However, it feels fine under throttle.
So far, I've:
Swapped injectors between cylinders 3 and 5.
Swapped coils between cylinders 3 and 5.
Swapped plugs between cylinders 3 and 5.
Replaced the wires.
Swapped the coil assemblies from the right bank to the left bank.
Put a noid light on the Fuel Injectors to check for signal.
Checked for Spark on cylinder 5.
Taken off the valve covers to look for broken springs and make sure the valves open/close correctly
did a compression test on 5.
Tried to check for a vacuum leak on the intake with propane as well as starter fluid
Looked at the O2 sensors with a Scan Tool... both banks look the same and seem to fluctuate like they should
Looked at the long and short term fuel trim valves. They seem high at startup, but they look good in closed loop
Did my best to look for bad spots in the wiring harness
Everything seems to function as it should. I did find a spot in the harness on the front left side of the harness that looked like it was abraided on a bolt slightly, but the wire looked intact. It is a Brown wire with a white stripe, but it didn't look damaged.
I may have tried more diagnostic measures, but I can't think of them right now. I am at a total loss of what to try next.
Any ideas? Or anyone now a good LS guy in the Houston area?
I finally got a chance to look more closely at pulling the intake. I thought it was like the old small blocks and the seals were a nuisance. I guess I'll try to get to that this weekend. Anything to look for there other than a bad seal going to cylinder 5?
I did do a couple more things, though. Checked the fuel pressure and it was a solid 60 psi. Also pulled the computer and ohmed out all of the wires that were unique to cylinder 5 and the cam position sensor, and they came out OK.
Mine indicated "random miss fire" rather then the specific cylinder.
I decided to make P0300 my bitch. I get the code if I let the cold engine idle within 2 minutes of start. If I keep it at 1k rpm for 30 seconds after start I don't get it. It must be something with my tune that it thinks with the cam loping that its a misfire. Oh well.
Good luck with your issues. You are in good hands here.
OK, finally gave in and sent it to the shop. Supposedly it is now fixed. What was the problem? Bad o-ring on an injector. I really don't understand how an o-ring can fail at such low pressures just sitting there, but apparently it happened.
Anyone seen this before? When I swapped the injectors between 3 and 5, both o-rings looked fine. It must have been one on either side of 5 on the firing order.
According to the literature - "If a fuel injector concern exists, it is possible to misfuel an entire bank of the engine, causing multiple cylinders on the same bank to misfire even though the root cause is a single fuel injector."
OK, it worked fine for a few days after he replaced the o-rings, but then started misfiring again.
Then, out of desperation I put a can of seafoam in with about 1/2 tank of gas. When I started it after work that day (after driving about 25 miles), it ran fine. After I got home that night, the Check Engine light turned itself off. I couldn't believe that the seafoam actually fixed it.
Two days later, started missing again. I am guessing it must be fuel related, but Don't know what to try. Any more suggestions at this point?
I know you said you monitored the O2's and they were swinging just fine but perhaps try swapping banks and see if the misfire follows? I know you think it is fuel at this point but that isn't that hard to do to rule it out.
From darkman's DTC .pdf.
"Swap the Position 1 O2 sensors side to side to see if the misfires move to the other bank of the engine. If
so, replace the O2 sensor."
Oh and also I looked at a stock file and it takes 2 fails to set the DTC just FYI.