2003 5.3 P0300 Assistance

[jwh463]

I have had a P0300 since about August of 2011 94k miles, rough idle, somewhat worse MPG but beyond that it doesn't run bad. It uses no oil between changes and I have never used anything but Mobil One. I occasionally get a P0305. Last August I took it to the local dealer and they wanted to tear down the motor. Their report:" customer states CEL is on, low compression on #5. Misfire on #5, swapped ignition coil, spark plug and plug wire. misfire remained on #5. performed inj. bance test and all inj drop the same. found low compression on #5 125psi cust declined tear-down and inspect"

 

Now with 102K miles, code still there and I can't pass state inspection. The catalyst monitor and Evap Sytem Monitor will not will show ready, I can pass if one of those 2 will show ready. I have a code reader and can reset the P0300 code it it will not reappear unless it idles longer than 3 or 4 minutes.

Now since August I have replaced the follwing:

• replaced spark plugs & wires (AC OEM all the way)
  
• replaced fuel & air filters
  
• replaced all coil packs
  
• replaced Mass Air Sensor
  
• replaced thermostat
  
• all four O2 sensors (just this week)
  

 

I even replaced the ECM (spare ecm store on ebAy ) and nothing changes

 

Running out of ideals with out going ahead and allowing a tear down starting with possible valve spring replacement. Is the code associated with the 2 failed inspection items? I have to get a state inspection to be able to park my truck at work.

 

Ideals?

[jwh463]

Picked up the truck today, parted with $2459. Nice quite smooth idle with no tic tic sounds. Donor motor came from a rolled 2004 with 41k miles. Mechanic is going to try and do an autopsy on the old motor before they send it back to the vendor, I asked for some pics

[00Silverado4x4]

Good to hear so far. Please make sure to post of the pics, hopefully they find "the" problem. The more I thought about the more I'm thinking it sounds like a loss of lubrication led to the cam lobe wear. Just a thought though.

[Jsdirt]

Probably vacuum leaks, just going by the condition of GM's underhood rubber products I've seen manufactured the past 15 years or so ... If you don't have a big, aftermarket cam. Ignition timing could be another cause ... but less likely with these newer vehicles.

 

If compression & leakdown are good, then the engine is mechanically sound (timing chain, crank bearings, etc. notwithstanding).

[jwh463]

Probably vacuum leaks, just going by the condition of GM's underhood rubber products I've seen manufactured the past 15 years or so ... If you don't have a big, aftermarket cam. Ignition timing could be another cause ... but less likely with these newer vehicles.

 

If compression & leakdown are good, then the engine is mechanically sound (timing chain, crank bearings, etc. notwithstanding).

 

 

cam lobes/lopes? are worn, the valves in #4 and %5 arent working properly. Due to labor costs of just those repairs they are ordering a used 5.3 from a local vendor. I have asked for a breakdown on 5.3 vs 6.0. My wallet is sad

[Jsdirt]

Yep - that'll do it too. Sorry to hear that.

 

I've said it before & I'll say it again - I'll never buy another GM built after '72.

 

And if we lived in a normal world again, you could just keep driving what you have until it's dead. Thank the EPA for your empty wallet ...

[00Silverado4x4]

...and why did the lobes wear??? There are sooo many members here that have easily hundreds of thousands of miles on their trucks without seeing that problem. Also new valves and a camshaft replacment cost MORE than a USED engine replacement? I must be out of touch with the cost factor of these trucks/engines....

[Jsdirt]

Can thank GM for that - miles of wiring, multiple intake manifolds, no room to work - takes you couple hours just to get in there. Replacing it is the easy part.

 

If you bought that used maybe the previous owner never changed the oil. If it's been taken care of, then chalk another faulty part out to GM trying to save a buck. Same reason we have Youtube videos of trucks with 500 miles smoking out their garages.

[00Silverado4x4]

Can thank GM for that - miles of wiring, multiple intake manifolds, no room to work - takes you couple hours just to get in there. Replacing it is the easy part.

 

If you bought that used maybe the previous owner never changed the oil. If it's been taken care of, then chalk another faulty part out to GM trying to save a buck. Same reason we have Youtube videos of trucks with 500 miles smoking out their garages.

 

 

Tell us how you really feel...

 

Actually I did watch some videos last night of people using carbon cleaners on their vehicles. They weren't all GM products and not all the people using the stuff were Einsteins either. Find the one where he thinks he is pouring the cleaner into his brake booster line.

[jwh463]

...and why did the lobes wear??? There are sooo many members here that have easily hundreds of thousands of miles on their trucks without seeing that problem. Also new valves and a camshaft replacment cost MORE than a USED engine replacement? I must be out of touch with the cost factor of these trucks/engines....

 

I asked the same question about the cam considering I only had 103K miles. This is our FIFTH GM vehicle with the 5.3 and our first one requiring this much engine work. I guess I just got a bad one...babied it and nothing but Mobil One every used in it. Our 2005 Envoy XL also has the 5.3l and we recently gave it to our son with 125K and he has had no problems.

 

Repair vs replace; It was explained to me these motor are a dime a dozen. For instance they found a 5.3 with 56K miles locally for $900. The shop replacing it will warranty it for a year.

[00Silverado4x4]

I'd hope you'd get some kind of warranty. I guess that's why I'd rather be the small engine (relatively speaking) mechanic that I am. Repairs of this nature tend to be easier since the engine are lot easier to remove and work on. The biggest we have is a V6 Detroit diesel that you can remove in 2 hours or less, if you need to.

[jwh463]

I'd hope you'd get some kind of warranty. I guess that's why I'd rather be the small engine (relatively speaking) mechanic that I am. Repairs of this nature tend to be easier since the engine are lot easier to remove and work on. The biggest we have is a V6 Detroit diesel that you can remove in 2 hours or less, if you need to.

 

shop just called, $2400 out the door (including labor incurred this week) the 5.3l was in a 2004 with only 42k miles. The money kills me but I am relieved this will take care of all the problems I was having

[00Silverado4x4]

So $900 for the engine and $1500 in labor/misc parts. Dang, that does hurt. Did you get an estimate on just repairing the current engine? Just a curiousity question since either way you should be getting a warrantied repair IMHO.

[jwh463]

So $900 for the engine and $1500 in labor/misc parts. Dang, that does hurt. Did you get an estimate on just repairing the current engine? Just a curiousity question since either way you should be getting a warrantied repair IMHO.

 

$1600-1800 for the repair...most of that was in labor. I view the newer motor as piece of mind.....I was so close to filling it with 20W50 and trading it in for a Mini Cooper..decided I like only making motorcycle payments. My wife has 2011 Sierra Crew so I don't really need another truck but I dont want another payment either

[Jsdirt]

If there's low compression on #5, then there is no other way to correct that other than, at the VERY least, to remove that bank's head.

 

I would do a compression test on my own to verify what the shop has already told you.

[jwh463]

If there's low compression on #5, then there is no other way to correct that other than, at the VERY least, to remove that bank's head.

 

I would do a compression test on my own to verify what the shop has already told you.

 

is 125 really low if all others were 145-150?