01 Burb 5.3 ~290K P0303 Bad Engine?

Messages
2,653
Location
San Rafael, CA
Recently purchased this vehicle which seemed to run and drive great. I let it sit for a couple months and now I'm driving it again and I seem to have a problem. Everything was fine but the other day I had to merge into traffic using a lot of power and it started flashing the check engine light and felt down on power. Had a P0161 code... hmm, whatever, o2 sensor... Ignoring that one. It now does this (misfire and flashing CEL) every time I am on the highway and give it a lot of gas. Around town it's fine. Finally it did set a P0303 code. I changed the coil and it did not fix the problem. I changed the plug wire and it did not fix the problem. Finally I removed the spark plug and found this plug. it's covered in oil, wasn't even tight, and I don't even think it's the right spark plug... the part number shows it's for 2011+ GMs not 2001. odd. So I put in a cheap copper ACDelco R44LTSM and still, same issue. The engine sounds fine except when cold with medium application of gas pedal there is a sort of squeaking ticking sound, and when it's warm under high load (but not at medium load) it does the same noise. Engine oil looks fine and I haven't had to add any oil. My friend who works at a GM dealer looked at the picture of the plug and told me I need a new engine, probably my valve springs/lifters are toast which might have resulted in piston damage. I'm not ready to spend like $5K on replacing the engine so I would like to do some further diagnosis. I'm thinking compression test and pulling valve cover? Any input appreciated. Thanks in advance! [Linked Image from i.imgur.com] [Linked Image from i.imgur.com]
 
Messages
4,876
Location
Fort Worth, Texas
I see oil on the exterior of the plug.....Valve cover gaskets. If it's making ticking noises......Pull the valve cover & check for a broken valve spring & the Rocker Arms for dumping their Trunnion needles. Also, Wipe the plug off & check for cracks in the porcelain! I've seen too many engine's be deemed bad over over broken valve springs & compression testing is inconclusive at times!
 
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dogememe

Thread starter
Messages
2,653
Location
San Rafael, CA
Originally Posted by clinebarger
I see oil on the exterior of the plug.....Valve cover gaskets. If it's making ticking noises......Pull the valve cover & check for a broken valve spring & a the Rocker Arms for dumping their Trunnion needles. Also, Wipe the plug off & check for cracks in the porcelain! I've seen too many engine's be deemed bad over over broken valve springs & compression testing is inconclusive at times!
Ok thanks I will pull VC when it stops raining. Safe to drive for now?
 
Messages
4,876
Location
Fort Worth, Texas
Originally Posted by dogememe
Originally Posted by clinebarger
I see oil on the exterior of the plug.....Valve cover gaskets. If it's making ticking noises......Pull the valve cover & check for a broken valve spring & a the Rocker Arms for dumping their Trunnion needles. Also, Wipe the plug off & check for cracks in the porcelain! I've seen too many engine's be deemed bad over over broken valve springs & compression testing is inconclusive at times!
Ok thanks I will pull VC when it stops raining. Safe to drive for now?
If it does have a broken spring......The keepers can come loose & the valve will fall down in the cylinder & ruin the engine for sure!
 

dogememe

Thread starter
Messages
2,653
Location
San Rafael, CA
Originally Posted by clinebarger
Originally Posted by dogememe
Originally Posted by clinebarger
I see oil on the exterior of the plug.....Valve cover gaskets. If it's making ticking noises......Pull the valve cover & check for a broken valve spring & a the Rocker Arms for dumping their Trunnion needles. Also, Wipe the plug off & check for cracks in the porcelain! I've seen too many engine's be deemed bad over over broken valve springs & compression testing is inconclusive at times!
Ok thanks I will pull VC when it stops raining. Safe to drive for now?
If it does have a broken spring......The keepers can come loose & the valve will fall down in the cylinder & ruin the engine for sure!
OK thanks I'll check it ASAP!
 
Messages
442
Location
Nevada
Tough to tell from your photo, but it doesn't appear that the spark plug is damaged, just oily. So I wouldn't condemn the whole engine. I would start with a compression test.
 
Messages
4,876
Location
Fort Worth, Texas
Compression tests are inconclusive with broken valve springs.....I recently had a 2008 Ford F-250 5.4L that returned great (150psi) readings on cylinder #4 three out of five times.....One time was 90psi & the other was Zero psi. Now the Relative Compression test via a Scan Tool caught it!......It had a broken exhaust valve spring on #4 cylinder. You can hear a dead/low compression cylinder by cranking the engine with spark & fuel disabled, But again inconclusive with broken springs. In fact I sometimes have a hard time with this on gasoline engines where diesels are really noticeable with their high compression.
 

dogememe

Thread starter
Messages
2,653
Location
San Rafael, CA
Originally Posted by clinebarger
Compression tests are inconclusive with broken valve springs.....I recently had a 2008 Ford F-250 5.4L that returned great (150psi) readings on cylinder #4 three out of five times.....One time was 90psi & the other was Zero psi. Now the Relative Compression test via a Scan Tool caught it!......It had a broken exhaust valve spring on #4 cylinder. You can hear a dead/low compression cylinder by cranking the engine with spark & fuel disabled, But again inconclusive with broken springs. In fact I sometimes have a hard time with this on gasoline engines where diesels are really noticeable with their high compression.
if the valve spring is broken cleanly with no bits and bobs floating around can it be changed w/out removing head?
 
Messages
25,006
Location
Upstate NY
Originally Posted by heynow
Tough to tell from your photo, but it doesn't appear that the spark plug is damaged, just oily. So I wouldn't condemn the whole engine. I would start with a compression test.
Compression test. Do you have an endoscope to look at pistons through the spark plug hole? Pulling the valve cover and examine each valve stem to be tight and where it should be.
 
Messages
4,876
Location
Fort Worth, Texas
Originally Posted by dogememe
Originally Posted by clinebarger
Compression tests are inconclusive with broken valve springs.....I recently had a 2008 Ford F-250 5.4L that returned great (150psi) readings on cylinder #4 three out of five times.....One time was 90psi & the other was Zero psi. Now the Relative Compression test via a Scan Tool caught it!......It had a broken exhaust valve spring on #4 cylinder. You can hear a dead/low compression cylinder by cranking the engine with spark & fuel disabled, But again inconclusive with broken springs. In fact I sometimes have a hard time with this on gasoline engines where diesels are really noticeable with their high compression.
if the valve spring is broken cleanly with no bits and bobs floating around can it be changed w/out removing head?
Yes sir...Requires a GOOD/Reliable source of compressed air of at least 125psi, A 14mm compression tester Whip, A good pencil magnet & a Spring compressor. The always break clean & wind around themselves.
 
Messages
9,886
Location
Birmingham, AL
Sounds like what my 02 Ranger did when it plugged up it's y-pipe pre cats. Low power, flashing CEL, weird whistling noise, never set a catalyst code. Not saying that's it, but something to consider.
 
Messages
445
Location
Kevil,Ky
If you don't have a good compressor and the spark plug adapter for it, I have used some 1/4 inch cotton rope thru the spark plug hole and then bring the piston up with a wrench to compress the rope against the valves. Guess that may be a red neck way to do it.
 
Messages
4,742
Location
Suburban Washington DC
Originally Posted by dogememe
So I put in a cheap copper ACDelco R44LTSM and still, same issue.
If I was chasing a misfire code, I would put in the proper spark plug from the get go.
 
Messages
2,556
Location
wv
I have an 03 Suburban and one cat failed causing misfires, loading of fuel, ruined two 02 sensors, and threw a code for cam sensor. The loading of fuel and misfiring led to the other cat failing shortly after.. Both cats replaced..now all is well. Take it to an exhaust shop and have a heat gun test on both cats. Just to rule that out
 
Messages
12,117
Location
OH
Originally Posted by clinebarger
Compression tests are inconclusive with broken valve springs.....I recently had a 2008 Ford F-250 5.4L that returned great (150psi) readings on cylinder #4 three out of five times.....One time was 90psi & the other was Zero psi. Now the Relative Compression test via a Scan Tool caught it!......It had a broken exhaust valve spring on #4 cylinder. You can hear a dead/low compression cylinder by cranking the engine with spark & fuel disabled, But again inconclusive with broken springs. In fact I sometimes have a hard time with this on gasoline engines where diesels are really noticeable with their high compression.
Great posts, thank you for them! thumbsup
 
Messages
1,991
Location
North Carolina
Any reason not to try installing new plugs and wires and see what happens? Also since it sat, any chance the fuel has moisture in it or could be from bad fuel when filled up? Trying to think of simple things first before jumping to conclusions.
 
Messages
10,003
Location
Waco, TX
Originally Posted by vwmaniaman
If you don't have a good compressor and the spark plug adapter for it, I have used some 1/4 inch cotton rope thru the spark plug hole and then bring the piston up with a wrench to compress the rope against the valves. Guess that may be a red neck way to do it.
That's how I have always done it... except used nylon rope (like what a recoil starter uses)
 
Messages
741
Location
New Hampshire
I'd pull the valve cover off and take a look. Weak valve springs are rare, and you won't be able to tell unless you do your compression test at over 2,000 rpm's. Idle is useless for checking weak springs. However if you pull the covers, you'll be able to see a broken one. You could also do a leak down test on the cylinder...piston at TDC of the compression stroke. If it leaks out your exhaust or intake or crankcase?? Don't bother going any further...engine is junk. Not worth replacing the heads on an engine with 290k on it, or replacing pistons.
 
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