Can someone interpret a freeze frame?

Here is the deal, I have a 2000 4.8 that keeps getting P0137 and P0157. I changed a rear 02, gutted the cats, replaced the intake gaskets (which did help it run better), and a few other things. When cold it runs very bad and in first gear as well as anything below 4000 it runs bad. Here is some freeze frame data:

Code P0137
100% throttle
3399 RPM
35.6% Engine Load
79.23 GR/Sec MAF
MAP sens 98 KPA
Coolant temp 199*
Short term fuel trim 1 0.8%
Long term trim 1 24.2%
Short term trim 2 0.8%
Long term trim 2 23.4%
Short term trim 3 -96.7%
Long term trim 3 -55.1%
Short term trim 4 -89.7%
Vehicle speed 80 mph
Fuel system 1 OPEN1
Fuel system 2 OPEN1

The CEL only seems to come on at full throttle but the truck runs bad all the time, worse when mentioned above. Any help would be much appreciated. Thanks,
-Evan

if you gutted the cats then changing the rear o2 is a complete waste...the 137 and 157 codes are rear o2 codes...everything else in the scan looks fine...i can help you fix this just let me know when you're ready

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Originally Posted by yournamehere018;285782\

79.23 GR/Sec MAF

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Seems really low for 3300 RPM at 80 MPH. Is the MAF stock?

Quote:

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Originally Posted by yournamehere018;285782\

Long term trim 1 24.2%
Long term trim 2 23.4%

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Both of these are way off, should be close to 0 no more than +/-10% IMO

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Originally Posted by yournamehere018;285782\

Short term trim 3 -96.7%
Long term trim 3 -55.1%
Short term trim 4 -89.7%

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Not sure what kind of scanner this is but GM doesn't use trims 3 and 4...never heard of if and it's not on a TechII. May be just another name for something. At any rate fuel trims on the 50-90 range is weird but like I said, I've never even heard of trims 3 and 4.

I really don't think the codes and the problem are related as mean05 mentioned. If the cats are gutted forget those codes and concentrate on fixing the drive issue.

Rear 02s/cats are JUST emission related, shouldn't affect anything noticeable

if you're not getting into closed loop you probably have bad 02 sensors up front. They may be reading but reading poorly. You really need to put the readings up against a wideband for comparison. You should be into closed loop by about 2 minutes from the time the engine starts, mine gets in there in about a minute. Have you run leaded racing fuel in it or some fuel additives? Is your water temp gauge reading properly?

Yeah but WOT it's always open loop on the scanner.

Well I don't know what the deal is but after I changed the intake gasket it gave me trouble for a couple days and then one night it back fired really bad and the light came on with the same codes. Now the light went out on its own and the truck runs 5 times better. No complaints here though.

Check the fuel pressure. With LTFT's in the 20's and a backfire it might be low.

I checked it before I changed the fuel filter and came up with a steady 50 psi. I need to check it again, and maybe a volume test. Do you know what kind of volume it should push?

There are no specs I know of. Too many variables I assume. 50 is too low.

I am going to go up to work and check again today. I am confused. It will run fine for a while and then sometimes it will run terrible. I noticed light only comes on under full throttle at highway speeds and the truck runs completely awful when cold. I think it may be two unrelated problems. When it first starts up it isn't able to accelerate at all. I can give it a little gas, floor it, or anything in between and it still takes about 15 seconds to get to 40mph. Makes merging with traffic really hard.

They require more fuel cold just like a carb motor with a choke.

Checked the pessure yesterday. Key on, engine off and I got 58 and then it ticked back to 55. That is just about perfect. I noticed the pump was making a lot of noise though.

Have you tried disconnecting the FPR hose and starting the truck to see if fuel is leaking through the FPR and into the intake? Let it run for a few minutes and see if fuel is being pushed out the regulator. A soda bottle or something to catch the fuel in would be advisable.

2000 gmc serria 4.8 L, when cold start below 40 ... - JustAnswer

That seems pretty close to what mine is doing. Maybe the pump is on it's way out? That light only comes on at full throttle and higher rpm/load. Where does everyone get the Walbro pumps?

Nelson Performance, of course. :thumb:

The regulator is brand new. Maybe it is the fuel pump. I don't care about price any more, I just want to find what it is and fix it. The pumps we sell at work are supposedly crap. We get quite a few returns and I don't know if it is the pump or the stupid rednecks working with them. Walbro is pretty good then?

Walbro is all I've ever run and never have had a failure.

racetronix.com sells them, plus they can make you a hotwire kit to run a large gauge wire from the alternator lug or battery cable to a HD relay and then to the pump to make sure you're getting proper voltage, too. It's what I run on my truck.

Cool. I'll see if I can get a price from nelson and go from there. Are these like the obs where it is easier to just pull the bed than lift it and drop the tank?

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Originally Posted by RedHeartbeat

racetronix.com sells them, plus they can make you a hotwire kit to run a large gauge wire from the alternator lug or battery cable to a HD relay and then to the pump to make sure you're getting proper voltage, too. It's what I run on my truck.

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I remember your truck now from dyno day. That is a nice truck man.

Thanks. Its a fun play toy.

IMO....easier to pull bed than to drop the tank, especially if you have a few friends laying around...I use a lift, but cherry picker and friends work just as well

4 guys can lift the bed off

I lifted the bed off last time I changed the pump. I will never ever drop the tank again. I had the bed off completely by myself with no damage to the truck in 30 minutes. I had it back on and bolted down in about 15 minutes. Thats really good for my unmechanical self. Plus with bed off you can test the pump and make sure you dont have any leaks inside the tank that effect pressure. Also a note for the walbro. Make sure you get a real walbro that has a check valve in it. Mine doesnt and I have to cycle the ignition to prime the pump to get it to start.

I use a lift and by myself get one back on the road in 30 minutes from start to finish. Pick ups are tougher than utilities that take about 20 minutes. Do a bunch and you'll see.

Then again...no lift = bed off for me too....no question. 6 bolts, four friends, 24 beers, one ground...:LOL:

Yeah with my old 1991 me and a friend each grabbed a side and carried it back. Now for bad news/good news, not sure which. I checked the fuel pressure again today while the engine was cold. The pump makes a little noise but builds plenty of pressure. I started it up and every time I even touch the gas it goes to 60-65. I am out of ideas.