jshaw

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?

Thanks for the help.

Nuvey

iTrader: (1)

I'm in the same boat with ya. I'm got a misfire on #4 though. New everthing, and it won't run right, dies alot. If you find anything that might help, let me know. I'll keep looking

jshaw

I'll let you know. Last night unplug the wiring harness and chased the wires for the coil pack on 5, injectors on 5, and cam position sensor. Else cleaned out the throttle body and checked out the MAF. The only thing I can think of to do now is pull off the manifold. I have just been avoiding that b/c i have to buy all new gaskets and everything, and I can't imagine it solving much.

ccrook19

Do you have a aftermarket alarm system in this Vehicle?? has there ever been one in it??

I'm asking this because there is a TSB #02-06-05-004A that could lead to misfire codes because of a improper alarm install...

jshaw

I do not think it has had an alarm in it. I am not the original owner, though. Regardless, I'll try to look up that bulletin.

Nuvey

iTrader: (1)

On another thread people are talking about bad O2 censors causing misfire codes. I would figure that would cause random misfires though. Mine seems to be confined to Cyl #4 only. I'm not sure about an Alarm either. It has the stock radio in it though.

jshaw

Yeah, I think it would be a p0300 instead of a p0305 if it was an O2 sensor. I also wouldn't think that it would make a difference in open loop. Even so, I'll do that if I don't see anything weird when I pull my intake manifold. The only likely culprit I can see now is a vacuum leak into the head at 5. I haven't swapped my o2's yet b/c I have a broken arm that is healing and am not supposed to be crawling under cars.

Nuvey

iTrader: (1)

Get a compression checker, and check the compression in each cylinder. And compair it to #1. I wasn't totally convinced that mine was an O2 censor either. P0300 would convince me of an O2 censor malfunction, but not one specific to a cylinder. But I'm finding out that it's quite common to bend a pushrod on these engines. I don't know about a Caddy but in my T/A it sounds like a pain. But at least it's a cheap fix. 16 pushrods at about $2 - $3 each. Or I found some crome alloy from SLP (I think) for $109 for the set.

Nuvey

iTrader: (1)

Sorry, just noticed you did a compression check. But did you check it on all cylinders? Just to make sure it isn't unusualy low compaired to the rest? I've never heard of a vac leak causing misfires, usualy high idle. But I guess anything is possible. This is my first LS car, and for that matter the first car I had that had Fuel Injection. Even my bike has carbs. Whatever it is, it's specific to that cylinder. I just got my compression checker, and I've gotta check #4 tonight

jshaw

I only checked compression on 3 and 5 because the plugs are a pain to get in/out on this car. 160 psi on 3 and around 150 psi on 5. I haven't done a leak down, but I don't really think that it will tell me much if my compression is OK.

I thought maybe it was bent push rods also. I pulled them out on cylinder 5 a couple days ago and they were fine. I still don't have the intake back on, but after that I am totally out of ideas.

INIT2WIN

iTrader: (9)

I'm having the same problem with my 02 Z. I have a slight pop in my exhaust at idle, but runs great under a load. I've checked almost everything that you have checked, only thing left is a leak down test on #5 for me. Its driving me nutts.

jshaw

I got this intake back on, and it wasn't the problem.

I guess I can do a leak down test now. It just doesn't seem like that would tell me much, though, since the compression looked OK.

I also hear a slight pop in the exhaust, but figured it was maybe just a small exhaust leak.

jshaw

Did a leak down, and it didn't tell me anything. I have no idea what to try next.

joecar

Try doing cooling system pressure test... if there's a small internal coolant leak into #5 then that would be the cause of the misfire.

What misfire counts does your scantool show...?

jshaw

Unfortunately, my scan tool doesn't show misfire counts.

jshaw

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.

jshaw

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?

jshaw

Any fresh thoughts on this? I am still having the same issue.

rooster2d

iTrader: (1)

I'd take the head off and take a look the lifters and make sure it aint grinding down the cam. Make sure you don't have any air leak in your intake near cyl 5 first.

joecar

While the heads are off, look carefully at the top of the piston in #5.

Before you pull the heads off, do a leakdown test on all cylinders.