DTC codes 2004 Chevy Avalanche - P0300 P0449 P0330

lots to chew on here will add more after cking DTC trouble tree for the listedp0449, p0330- FYI P0449 is NOT EGR what are ALL the current codes....a gas cap advisor and no code? the vehicle is STOCK - no miracle magnets - filters, plugs, let us know remote start or aftermarket alarm. With the piston slap comment- check fuel pressure and leak down rate...as the miss stops under load How does 2&7 plug look - rich? a little more effort but a suggestion run a compression test on 2-7 - PS - try the carb spray to isolate a vac leak - easier than smoke - spray on a "leak' will cause a change in rpm

I have a 2003 Express, 6 cyl. I experienced the Knock Sensor code and misfire on cyl 5. It was always cyl 5. No matter what I tried, new cap, rotor, wires, plugs, it was always #5. I was at wits end too. This went on for over a year, the van would reach 150 degrees then any random event would cause unacceptable drivability problems, especially on left turns and bumps, it even died on the highway a couple of times while at 55-60 mph. The MIL stayed on and returned after clearing the codes. When the weather was cooler, I.E. winter, I had no problems at all, only once it was warmed up in warmer weather. Weird huh? Last month I stumbled upon a reference to the crankshaft position sensor causing the symptoms very similar to what I was experiencing. I spent $79 for a new CPS and upon replacing it the van did not start at all. I had no spark from the distributor. Thinking the thing was toast, I actually began seeking a replacement vehicle until I stumbled on another reference regarding the wiring harness having known issues with the ABS, Crank Position Sensor and Cam position sensor connectors. Checking the parts store, the CPS connector with pigtails cost $25 so I thought "What the H..., let's give it a try". So I pessimistically cut off my old connector and just twisted the new wires from the new connector to the proper wires on the harness, not really expecting it to work. Imagine my awe when I turned the key and it instantly started right up! Well, now...I soldered the wires together and used heat shrink tube to protect them before tucking them permanently back into the wire loom. The test drive was successful, the Knock sensor code went away, the MIL stayed off after the reset and the van has run perfectly ever since. So, in summary, check the Crankshaft Position Sensor connector, even replace it if the $25 isn't too much of a burden, and maybe the CPS itself. Of course, you may also check the Cam Pos Sensor and connector too, but my experience didn't involve it. Discover more Chevy pump DODGE RAM 2500 If this works, let me know. You can take the money you might save buying a new vehicle and buy your family that steak dinner. I don't need one myself, though I appreciate your kind offer. Write to me at michaelat56 at yahoo dot com and let me know what you come up with

OK, so here's an update. To review - Stone cold stock 04 Chevy Avalanche 4WD with the 5.3L V8 base package, no aftermarket anything on the engine. 200K miles. The steak dinner bounty is still in effect for a 100% dead-on diagnosis. Current codes are P0449 Evap and P0300 misfire. I did have a knock sensor code earlier; have since replaced BOTH knock sensors with OEM including the harness, but did NOT do the intake gasket that day. I now have one and will be putting it on this weekend. I've also got a new solenoid and valve coming for the EVAP and will replace at the same time. And check the canister for blockage or water; I saw a TSB about water in the canister for 5.3's. Random misfires happen consistently on Cyls # 2 and 7 at idle. But on the road, under load, they go away. Also, while watching the data stream at idle in the garage you can see that periodically the misfires just drop off almost to 0, then come back up again. Here's a list of what I already tried. I swapped "simple components with the near cyl; IE #4 for 2, #5 for 7. So I swapped the plugs, misfire stays 2 and 7; wires, stays 2 and 7; coil; stays 2 and 7; injectors; stays 2 and 7. In other words the misfire stays; it doesn't follow the components. Should rule those components out. (plugs, wires, coils, injectors) It had trouble starting in the AM; thought there was bleed-off in the fuel pressure. Replaced the fuel regulator. On this model that is in the gas tank as part of an entire assembly; regulator, sensor, pump, and sender. So those are new; and didn't fix the problem. I earlier had random knock sensor codes coming up. So we replaced both knock sensors with OEM (not junk aftermarket). As long as I was there, I replaced the wiring harness for the sensors too. We didn't have a set of gaskets that day, but the gaskets looked perfect so we used the old ones (hence the new ones going on this weekend). Still no change. We put a set of "noid" lights on the injector bank to see if they were firing differently. All appeared to be even and consistent. We thought there may be an issue with blocked cat-converters so I pulled the 02 sensors figuring that may relieve the back pressure and validate bad cats. Nope; Ran very loud, but still have the problem. Then we tried to locate any vacuum leaks using a can of carb cleaner sprayed all around in the engine bay. No dice; no matter what we sprayed where, it didn't change the engine RPM's at all, and we even watched the data stream on the scan tool. There was no change in the rate of misfires either, so no apparent leak. This weekend's agenda is to replace the EVAP solenoid, the EVAP valve, clean out and make sure the evap canister is not plugged, and not full of water. Then replace the intake gaskets. I also want to pull and inspect/clean the EGR valve and give it the "seafoam treatment". If that doesn't fix the probem I'm thinking of a 12Ga through the radiator and a road flare for the front seat. Somebody, ANYBODY, PLEASE! Help me find out what the @$#$%@# is causing this!!

I didn't read the entire post but one ??? is did you do a compression comparison check. Believe the 5.3 should be around 140-150 for a 200K mile engine. What is strange is that it changes when you hook up the code reader, if I read that right. A P0300 code is a bear to find sometimes and it looks like you are doing all the right things to chase it down. Had the same code on my 5.3 and it ended up being a new AC Iridium bad plug I installed. It gave a P0308 first and I changed the wire, plug, and coil pac to #6 and then it gave the P0300. After putting all new wires on it, I could tell it was still a single cyl miss, but still checked the fuel pressure, vacuum, fuel pressure regulator,compression test, and all the coil pacs before finally checking the plugs and walah! bad plug. Also are you using Iridium or Platinum plugs. The Iridium come factory gaped at .040 not .060 like the manual says in case you are using them and tried to re gap them. Don't try and change the gap, take them back to the store and get a new one if they are not gaped at .040. The Platinum still gap at .060 however. Some people like to use the Platinum because of the $7.00 price tag on Iridium. Might also make sure the throttle-body is clean. Good luck, doubt this will be much help to you.

i see that Sabre mentions the plugs... they are OEM AC delco? it really matters Is there any other codes- can your scanner read P1xxx series? all you show is p0302 p0307? can you ck fuel trims? can you ck o2 sensor data? Is there any info in freeze frame? BASICS ' fuel pressure, ? - its critical Maybe a vacuum gauge (showing my age) would show a clue. might want to pull valve covers... broke spring? sticking valve... Have you done compression esp 2 and 7-... Any chance this is a flood car, engine been washed? A TSB cought my eye. .

The flood car thing might be part of it; came from Texas and around the Katrina timeline. I've always suspected something. Dealer in Tx to a dealer in Ny, then a dealer in Ma. I'm the first registered owner; even though it was 2 years old and 20,000 miles. What TSB is that?

check for water intrusion int o2 sensor connectors, also engine ground basics as mentioned - can you ck fuel trims? can you ck o2 sensor data? Is there any info in freeze frame? BASICS ' fuel pressure, ? - its critical Maybe a vacuum gauge (showing my age) would show a clue. might want to pull valve covers... broke spring? sticking valve... Have you done compression esp 2 and 7-... pls repost current codes and I will ck TSB's

I have run into this many times on the avalanche 5.3. the camshaft has a problem with flat lobes. you should pull all the plugs, disable the fuel pump, open the throttle plates, and do a compression test. make sure the engine turns over at leaast 5 revs per cyclinder if # 2and #7 are more than 20% less add a little oil and see if compression comes up if it does its rings if not its valves ( cam shaft lobes worn )

I am dealing with the same issue on a 2004 Avalanche. Seems like the 2 back cylinders are not getting fire. I have a 2002 model avalanche that was giving a similar problem and it turned out to be a broken valve spring. Compression on the cylinder would be perfect when I cranked it up but about every 2nd crank it would show 0 compression. It was really strange. The engine had 250,000 miles so rather than pull the head I replaced the engine with a new long block. It acted like a spark issue and I was tempted to replace the computer and I am glad I didn't. I took the truck to the local Chevy dealership and for $100 they told me the problem was no compression on #7. Threw all kinds of codes like multiple mis-fires.