2004 Suburban 5.3L Engine performance.

[Eric D Plante]

I have a 2004 Suburban Z71 4x4 with a 5.3L. I decided to fix the exhaust leaks from both exhaust manifolds, which turned into a disaster. I had to replace the drivers side head with a rebuilt one. It seems that I do not have the same performance as I did prior to all this work. I tow a 32 foot travel trailer and noticed this year that their wasn't the same power as before the engine work was done. I am also noticing that the temp rises above 190 now when towing up steep hills, where as before it was always rock steady. On occasion I get a rough idle when in gear and stopped, this only seems to happens after I have gone WOT. I do know that with regards to the running hot issue, I may have to flush the coolant system as I had mixed the coolant types. Will that be the cause of the running hot-ish issue, not sure really. So to date here is what I have replaced During the exhaust manifold work and afterwards.

-Both exhaust manifolds

-New intake gaskets

-Head and gasket

-Spark plugs

-Spark plug wires

 

I notice the tire won't break loose at all when I floor it from a stop, I know the Burb is heavy but I would think it still should have some wheel spin. Also when I got back from my last camping trip it seemed like the truck had no power. Backing my trailer up on a slight him into my yard from the street it couldn't do it. I had it floored and it wouldn't move. I had to put it in 4WD low to get it up into it's parking spot. Again this is something I had not needed to do before the exhaust work and head replacement. I did a comp test to make sure all the valves were set right, and that passed, same numbers on both sides of the engine, and well within specs. My thought was possibly a problem with the TPS but it's just a guess. I have had random misfire codes come and clear themselves a few times, though not since replacing the plug wires. I believe the code never cleared the memory and re triggered the MIL as the chime didn't go off when it came back on, it just turned on. I am frustrated as to what is the issue. I don't want to throw parts at it without knowing if that's the fix. It's a waste of money and time to do that. I am about to head out on a 3500k mile round trip with the trailer next month and I'd like to have this issue resolved. 1 note, when the truck is running warmer then usual I notice the power drops off noticeably, and I have to slow down to 50 and try to get the engine to cool down before i notice any power increase. It never overheats, I make sure to not let it get out of control like that. The worst it got to was about 230 degrees, with a significant loss of power. Seems the temp and power are inversely related.

 

On another note:

I had a "small leak in the evap system" code come up before and again after I did the work to the engine. It cleared after I connected the battery post engine work, but came back again not long afterwards. I replaced the purge valve but the code never cleared. I finally went and disconnected the negative terminal and let it sat for a few hours to try and clear the MIL, which it did, and has not come back since. It's been a month.

 

I just would like to solve these issue.

[intheburbs]

My '01 with the 5.3 and 4.10 axles has NEVER been able to break the wheels loose. Even with a tune. Just too much weight on the rear tires. Maybe one tire, when going around a corner, but never when it was pointed straight.

 

Maybe you have a plugged cat, and now that you fixed the exhaust leaks it's sapping your power? That's just a guess.

 

The only time I've ever gotten mine up to 230° was towing my TT in Florida. In the summer. With the A/C blasting. In traffic. You definitely have a problem, and I wouldn't head out on a towing road trip until you get it fixed.

[Eric D Plante]

I have a feeling the running warm issue is because I had mixed the original coolant with the green stuff. I will be getting it flushed and have the correct coolant put back into the system. Last night I was driving the beast and I guess the power is more then I had thought, no it didn't break the wheels loose but I was rolling a little too. Maybe I just need to clean the TB and MAF sensors. Tomorrow I get the joy of replacing the ABS pump/valve assembly. I got bad motor in it. Gonna see if I can remove just the motor from the unit 1st, if succesfull I will avoid having to bleed the brakes, which is a PITA with ABS, from what I have read.

[wrenchbender]

Sounds like a lean mixture issue. Take a look at your plugs for evidence of running too lean, white with "coke" build up on the electrodes. I would think you would have a code related but who knows what else is happening. Lean mixtures will cause high temps and low power. Vacuum line? Faulty o2 sensor(s)? Just my guess. Good luck!

[Eric D Plante]

Yes that does make sense. I did notice that the driver's side new exhaust manifold had bluing, which to me means it's getting real hot. Where as the other side, also new did not show this.

[wrenchbender]

Bingo! For steel to show blue it had to be red recently. I believe your on the right track.

[artr8]

Just had the P0101 code for the Mass Air Flow sensor on my truck. Low power and code for intermittant cylinder miss on the right side.

Changed the Mass Air Flow sensor, little help but not much. Continued to have both codes.

Changed spark plugs. Again, little help but not much. Ran vacuum check under load. Had vacuum reading of 15-17 at idle, dropped to 10 under load but recovered slowly after load removed. Thought it could be exhaust restriction.

Pulled EGR off to allow tube to breath and blocked off vacuum source. Instant change to vacuum signal. Never dropped below 12 and recovered quickly.

Put EGR back together and punched hole in right cat. Stayed good on vacuum signal with load.

Replaced cat and codes disappeared and power is back.

Hope this helps all.

[Eric D Plante]

I just noticed last night after the WOT rough idle issue that I can smell the rotten egg smell from the cats, so I am thinking it's running to rich when it's running rough after WOT situation. I am hesitant to replace the TPS as I am not getting "reduced power" issues.

 

As for running hot it hasn't done that in a while, maybe an air bubble that finally worked it's self free? Hmmm.

[Eric D Plante]

Update:

I cleaned the MAF sensor with CRC MAP/MAF sensor cleaner. I cleaned the Throttle body with CRC throttle body cleaner. No noticeable change, though driving immediately after cleaning the idle was acting a little weird, was high a little, but has since calmed down.

I bought a wireless scan tool. It is showing the bank 2 O2 sensor 1 is not working as it should. Stable read back where as Bank 1 sensor 1 is reacting to exhaust gas readings. LT fuel trims are as follows, Bank 1 is 1.6% and bank 2 is 0.0%. I am replacing the bank 2 O2 sensor tomorrow. I am also replacing the Bosch plugs I just installed over the summer with Denso Iridium plugs. I am thinking the ZTJ16 R10 plugs. Thoughts? Attached 2 screen shots of data below.

 

 

[Eric D Plante]

I just replaced both upstream O2 sensors. Truck seems to be running a little smoother. LT fuel trims are in the 7% ranges now and Bank 2's sensor is not sitting at high mV readback now. Will know more if the truck is fixed after some time. I am contemplating replacing the Bosh plugs with a set of ACDelco's I picked up yesterday. Hmmmmmm