2004 5.3 4WD Suburban runs rough after heavy acceleration


migs_auto
06-17-2010, 01:35 PM
My 2004 Z71 with 4WD/5.3 with 81 k miles has an intermittent problem. After heavy acceleration (gas pedal floored) the engine runs very rough, exhaust smells really bad, and check engine light comes on. After turning the car off and back on again, the problem is gone, engine runs fine no check engine light, exhaust back to normal. This has happened twice now. The car is normally driven rather gently but I have a new driver so . . . it gets tested a bit. I am thinking maybe a borderline O2 sensor or maybe a partially blocked cat (ouch). I have not yet changed spark plugs on this engine. Oil is always Syntec 5w30. I may try to recreate problem tonight and get the codes with my scanner.

I should add this engine had its heads replaced back in December. It was, apparently, leaking small amounts of coolant into the crank case for at least a couple of months. Not enough to make milky oil but enough to have to add coolant once per month. Dealer says " There was a batch of bad heads in 2004". Would have been nice to know that. Also, my gas mileage is not as good as it was at, say, 60 K miles. It is now 17 mpg hwy vs 18 - 19 hwy.

Any thoughts or advice will be appreciated.

thanks in advance.

migs_auto
06-18-2010, 08:26 AM
Took it for a test run last night. Never saw the check engine light but did induce a "Lean Condition detected" code (I forget the code number) by flooring it and accelerating up to 75 mph. Engine speed got up to 4800 - 5000 rpm. Never saw any rough idle or bad smelling exhaust. Just another data point.

MT-2500
06-18-2010, 08:37 AM
Took it for a test run last night. Never saw the check engine light but did induce a "Lean Condition detected" code (I forget the code number) by flooring it and accelerating up to 75 mph. Engine speed got up to 4800 - 5000 rpm. Never saw any rough idle or bad smelling exhaust. Just another data point.

We need that code no?
With that many miles replace plugs with good AC delco plugs.
Check fuel filter and fuel pressure and camshaft retard setting.
Scan VCM for past and present and history codes and any missfires.
And then clear codes and recheck after driving.
Post back any and all codes.

migs_auto
06-18-2010, 09:40 AM
Thanks MT will do, but what is "camshaft retard setting" and how is it checked ?

Spark Plugs - easy cheap will do this weekend.

Fuel Filter - not sure where it is but I will get a book.

Fuel Pressure - I do have a gauge for this and will give it a check.

VCM for past and present codes - I just have an ODB II reader. Do I need to bring it in to get past codes ?

MT-2500
06-18-2010, 11:55 AM
Thanks MT will do, but what is "camshaft retard setting" and how is it checked ?

Spark Plugs - easy cheap will do this weekend.

Fuel Filter - not sure where it is but I will get a book.

Fuel Pressure - I do have a gauge for this and will give it a check.

VCM for past and present codes - I just have an ODB II reader. Do I need to bring it in to get past codes ?

The good plat Ac plugs are not real cheap but are good.
Camshaft retard setting is the position of rdist rotor to spark plug terminal.
Will need to be checked or set with a engine capable scanner.
Post back fuel pressure readings and any codes no you get.
Check the book on fuel filter.
Some fuel filters are in the fuel tank.

migs_auto
06-24-2010, 01:52 PM
Small update:

Spark plug replacement in 2004 5.3 L w 4wd. Not real easy and not so cheap. AC Delco Iridium plugs $7/plug. That's $56 + tax. But they last 100k miles so maybe not so bad.

Passenger side back plug is a pain in a$$ to get at.

Not like my Dad's '78 suburban with a 350. I could (and did) climb inside that engine compartment to work on stuff.

MT-2500
06-24-2010, 02:42 PM
Did that fix it?

migs_auto
07-13-2010, 09:56 AM
UPDATE - replaced Plugs car ran well, still just 17 mpg highway, during a two week vacation that put about 2000 miles on. On the way home, just a few miles from home, check engine light came on after acceleration. It went off a bit later. Light came on again yesterday, again after acceleration and I caught the following codes:

P0151 Low volts Bank 2 Sensor 1
P0174 System to lean Bank 2
P0300 Random/Multiple cylinder misfire

thanks in advance.

MT-2500
07-13-2010, 10:15 AM
UPDATE - replaced Plugs car ran well, still just 17 mpg highway, during a two week vacation that put about 2000 miles on. On the way home, just a few miles from home, check engine light came on after acceleration. It went off a bit later. Light came on again yesterday, again after acceleration and I caught the following codes:

P0151 Low volts Bank 2 Sensor 1
P0174 System to lean Bank 2
P0300 Random/Multiple cylinder misfire

thanks in advance.

3 things that should be done.
Did you put in the good Ac delco plugs?
Was fuel pressure checked?
Was the camshaft retard setting ever checked?

migs_auto
07-13-2010, 10:47 AM
1. AC Delco Iridium
2. Did not check fuel pressure, yet.
3. Still do not understand "camshaft retard setting" in the context of my 5.3 (no distributor, 8 coils) or how to check it.

Last time I had car with P0151 I had to replace an o2 sensor.

migs_auto
07-13-2010, 10:48 AM
btw - the plugs I took out looked terrific, very little wear.

MT-2500
07-13-2010, 11:22 AM
1. AC Delco Iridium
2. Did not check fuel pressure, yet.
3. Still do not understand "camshaft retard setting" in the context of my 5.3 (no distributor, 8 coils) or how to check it.

Last time I had car with P0151 I had to replace an o2 sensor.

No dist on a 5.3 rules out camshaft retard setting.
Codes do not say replace sensors.

How is the fuel pressure?

What cylinders are missing and how many missfires on each cylinder?

migs_auto
07-16-2010, 09:49 AM
UPDATE - Replaced Passenger side upstream (bank 2 sensor 1, between engine and Catalytic Converter) O2 sensor ($50 for Bosch at Advanced Auto). R & R wasn't too bad. The one that came out was covered in black stuff. My first one I've done so I don't know if this is normal or not. Gave it a test run (heavy acceleration) and no codes. This would always throw at least one code before. Looks good. I will test again later. If it passes then I will deem this as fixed. Unfortunately there is a chance running probably rich on one side may have done some damage to the cat. I hope not. Hopefully gas mileage will return to normal.

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