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Idk what kind of plugs you should use in the 5.3, but I use ngk iridium in all my cars. Never heard of fuel leaking through an injector, so I'm glad that other guy knows about it. Learn something new every day! To confirm whether or not it's leaking, shut it off then pull some plugs and run a little tube down into the cylinders and take a whiff thru the tube. If it smells rich of gasoline you have your answer. Or take the intake tubing off the throttle body, open it manually, and take a wiff.
Idk what kind of plugs you should use in the 5.3, but I use ngk iridium in all my cars. Never heard of fuel leaking through an injector, so I'm glad that other guy knows about it. Learn something new every day! To confirm whether or not it's leaking, shut it off then pull some plugs and run a little tube down into the cylinders and take a whiff thru the tube. If it smells rich of gasoline you have your answer. Or take the intake tubing off the throttle body, open it manually, and take a wiff.
Actually, I've seen it with my own eyes...
Pulled the fuel rail and turned the key to Key On Engine Off and saw fuel leaking out of (at least) one injector. That was a whole 'nother long story!
She's off to the shop that put in the Fuel Pump this morning for another pump. If she'll make it under her own power...
Yesterdays logs show that my STFT's were now closer to 40's than 30's like they'd been, so there's been an increase. I'm going to try and get a Fuel Pressure Regulator on my way to have that too. Another Filter as well, I guess, since I've got my throwin' arm cocked back...
So, it turns out that I did not need to buy a $60 FPR...too bad the lame shop I had the pump installed at couldn't figure that out 'til I already did and they put it in...after he lied to my face (OK...my ear...we were on the phone...) about how my stock fuel pressure was only supposed to be ~13#'s...he looked it up on AllData! Liar! I was standing at O'Reilly's at that moment and the counter guy was able to look it up and print out the specs for me. I'm sorry I now have to break in a new shop.
It also turns out that whatever Fuel Pump they obtained from CarQuest is a POS...Replacing it (again) brought my Fuel Pressure up to 50#'s.
Fuel Pressure is holding for quite a long time after shut-off.
All of this has gotten me to ~95% of where I need to be. It's running 1000x better than it was, but it's still not very strong 'off the line'.
I guess I still need to replace the Spark Plugs. And I picked up a Harbor Freight Compression Tester when I got the Fuel Pressure Gauge, that I suppose I'll try to utilize while I'm doing that.
I suppose that the high STFT should have been a more obvious clue that it wasn't getting enough gas.
Also, for some reason, after adding LTFT Bank 1 & Bank 2 to the app, I'm only getting data for Bank 1. Not too sure what that's about. Any ideas?
Almost there!
Thanks for the help!
-Kyle
Last edited by kpeters59; 03-04-2016 at 01:53 PM.
Reason: Forgot Attachments
Hell yeah, I'd just continue going over the list of crap you and I have thought of and I'm sure a tune up would help. Truck not wanting to go off the line could defintely be spark, check all ignition components. As for your missing LTFT, you got me, no clue.
Friday a week ago it was determined that my brand new fuel pump was not brand new enough. I'd guess that it's because the filter was disgusting? It seems to me the shop that put it in should have insisted it get a new fuel filter. Good thing I took one with me!
Anyway, Sunday Night, the nearly brand new Transmission (don't get me started; see page 1...) crapped out and the Tahoe spent the week in the tranny shop getting re-rebuilt.
Today, after receiving my NGK TR5 Spark Plugs, I undertook the task of removing the plugs, using my shiny brand new Compression Tester and Remote Starter Switch and installing the new freshly gapped to .050 Spark Plugs. After all that, I've still got some performance issues.
Is this what my AC Delco Sparks plugs were supposed to look like after I removed them?:
(No, it's not an 11cylinder motor...I just took several pictures of 1 plug because I thought it might not have photographed properly)
Those tips sure do look tiny! The NGK's were much larger.
After replacing them, it really wasn't running much better. I sure do wish I'd gone ahead and ordered wires...just for thoroughness.
Any ideas on where to look next?
Do I just need to get it back to a tuner?
-Kyle
Last edited by kpeters59; 03-13-2016 at 05:49 PM.
Reason: Clarity
Looking for help diagnosing Poor Running 5.3 - Log files attached
I'm running behind (dealing with family hospital stuff), I did not get a chance to look at the HPT logs , what LTFT do they show...?
Recap:
- are any DTC's present...?
- is rail pressure now correct...?
- were any injectors leaking...?
- were there any airleaks (at intake and/or at exhaust)...?
I'm running behind (dealing with family hospital stuff), I did not get a chance to look at the HPT logs , what LTFT do they show...?
Recap:
- are any DTC's present...?
- is rail pressure now correct...?
- were any injectors leaking...?
- were there any airleaks (at intake and/or at exhaust)...?
What fuel? Is that a trick question? Of course it's the cheapest I can find...87. (It was tuned on 87)
There are no DTC's.
I'm pretty sure that there was at least 1 leaking Injector, but am not 100% because I had my 'spare' set cleaned and swapped them out. It definitely ran better afterwards and the 'flooded' condition upon restart went away. Fuel Pressure is now stable after the 3rd fuel pump in 90 days. Maybe the nasty fuel filter (that I thought was changed with 1st pump) caused the pumps to fail? And cause injectors to get dirty faster? (duh!) Fuel Pressure holds for quite a while at engine shutdown.
I recently added LTFT monitoring to my ECM App (Not HP Tuners) and can observe LTFT's on Bank 1 (they seem to hang around +5), but there is no data ever displayed for Bank 2. Haven't figured that out yet. For some reason, there is also no logged data for either Bank 1 or 2 LTFT's. An inquiry to ScanTool has not been replied to yet as to why that might be. STFT's are now above and below zero.
No Cats, only Bank 1&2 Sensor 1. Other things like EGR and AIR are currently 'disabled' until such time as the hardware were to become installed.
There still exists the possibility of an exhaust leak, but I can't hear one. It's pretty loud though. It passed a 'smoke test' a while back, but that was done by the shop that didn't replace the Fuel filter, so...
The CAI seems to be tight.
How can I verify if the MAF or MAP data is appropriate? They seem to change with engine speed and the like.
I hope (and pray) everything's OK there. Thanks for helping!
-Kyle
Last edited by kpeters59; 03-13-2016 at 09:52 PM.
Reason: Clarity
Oh yeah, now starting the motor wants to take several attempts. Even with verified fuel pressure. It's mostly started right up until the last few parts were replaced, so that's new.
ya the tuning one is mine, i had another one as needing help with horrible fuel mileage and only a couple responses. Id be interested to see if one you these guys could help when yours is solved
I would get a multimeter out and start testing everything. You'll have to search for the appropriate perameters. So let's recap here. What are the current symptoms now? And your compression is kinda low, isn't it? Possible to do a leakdown test? But honestly I'd be looking into ignition. I mean if the fuel system is right but you are still lacking performnce, it would have to be ignition if not some sensor issue. Again I'm not too familiar with the 5.3 system, but check the coils or distributor, icm, coil, ect. And have we entertained the idea of a clogged cat or something? Not sure if you run one or not. I made mention to your erratic timing earlier, but you didn't say anything. That seems to point to ignition, as it appears the timing is being moved around quite a bit as if to compensate for knock or something.
I would get a multimeter out and start testing everything. You'll have to search for the appropriate perameters. So let's recap here. What are the current symptoms now? And your compression is kinda low, isn't it? Possible to do a leakdown test? But honestly I'd be looking into ignition. I mean if the fuel system is right but you are still lacking performnce, it would have to be ignition if not some sensor issue. Again I'm not too familiar with the 5.3 system, but check the coils or distributor, icm, coil, ect. And have we entertained the idea of a clogged cat or something? Not sure if you run one or not. I made mention to your erratic timing earlier, but you didn't say anything. That seems to point to ignition, as it appears the timing is being moved around quite a bit as if to compensate for knock or something.
Looking at the Timing in relation to RPM, it looks to me like it's trying to change timing with engine speed, but I don't know much (anything?) about it.
Maybe the Knock Sensors are misbehaving? I don't see any Knock Sensor readings in the Log, so I don't know how to tell. I've read some threads about it, but again, how to tell? Hopefully they're not tuned out in my Tune!
When I did the Compression Test, I used my Remote Starter Switch to turn the motor over. I believe that the instructions were to let it 'Flutter' the gauge 4 times? So, that's what I did. Maybe that's not enough? Afterwards, I remembered that I forgot to block the Throttle Body open, so there's that too. I was under the impression that the readings were all just supposed to be within ~10% of each other. Do they really seem low? I was being pretty happy they seemed OK. There shouldn't be 100k miles on this motor.
I'm pretty much out of ideas (if I had any to begin with...) and was probably going to try to get it to a shop not too far away that was recommended as LSx Swap Friendly pretty quick. Unless there's more I should try first...
I've attached a recent Log File.
Thanks,
-Kyle
( oh yeah...apparently my LTFT's are OK. When I double-checked the 'Gauge' for LTFT Bank 1, I'd inadvertently selected the adjacent STFT selection for that display...doh! ) Both Bank 1 and Bank 2 LTFT's pretty much read 0 all the time...is that expected?
Anything over 120 is pretty good, how many miles are on the engine? All cylinders are pretty well balanced roughly 135 from a glance and I believe GM specs 100 which IMO is low.
Anything over 120 is pretty good, how many miles are on the engine? All cylinders are pretty well balanced roughly 135 from a glance and I believe GM specs 100 which IMO is low.
The junkyard 'said' it was an '06 with 86,000 miles, but who really knows?
I DO know that at least this one doesn't have oil pressure that would just drop to zero at idle, so that's a good thing!
It has a mildish XFI Cam, so I don't know how much effect that might have on a compression test.
Now if I can just get off idle performance to be decent. Maybe when I get whatever's wrong fixed, my gas mileage will improve, too...
I had a similar fuel pressure problem like yours and the hose on the tank came loose. Nothing like going back into the fuel tank. I used fuel injection clamps the second time and i have been good for 4 years now.
I had a similar fuel pressure problem like yours and the hose on the tank came loose. Nothing like going back into the fuel tank. I used fuel injection clamps the second time and i have been good for 4 years now.
Well, I'd paid someone to replace my fuel pump in November. Early in January, I had no fuel pressure again, so they re-replaced it under warranty (after substantial whining). Then, a few weeks ago, after obtaining another fuel pressure gauge, it was determined that I had low fuel pressure again. Back to that shop it went. After plenty more blaming it on a motor swap, they re-re-replaced it. This time the tech showed me the black sludge from the Fuel Filter. Luckily, I'd brought a replacement Filter with me, because they still hadn't considered replacing it. In fact, they had lowered the truck on the lift without replacing it and I had to ask if they had. They raised the Tahoe back up and swapped it. After that is when he showed me the nasty black fuel that came out of it.
I'm thinking that the nasty filter is why the pump failed twice in 90 days. And why my injectors were leaking.
My fuel pressure now seems to be maintaining the pressure that the 50lb regulator is set to. They installed the regulator before the pump, but it didn't magically make the fuel pump start pumping harder...It was an extra $60, though...
My STFT's are now +/- 5ish. Mostly + it seems to me. Just pretty much lays down 'off the line'. And passing on the freeway requires getting it to downshift before much happens.
I'm wondering if it's the tune now. Cats are tuned out and gone. EGR, AIR, etc are tuned out (for now). Plugs are new TR5's gapped to .050. I'm out of ideas...
Well, I'd paid someone to replace my fuel pump in November. Early in January, I had no fuel pressure again, so they re-replaced it under warranty (after substantial whining). Then, a few weeks ago, after obtaining another fuel pressure gauge, it was determined that I had low fuel pressure again. Back to that shop it went. After plenty more blaming it on a motor swap, they re-re-replaced it. This time the tech showed me the black sludge from the Fuel Filter. Luckily, I'd brought a replacement Filter with me, because they still hadn't considered replacing it. In fact, they had lowered the truck on the lift without replacing it and I had to ask if they had. They raised the Tahoe back up and swapped it. After that is when he showed me the nasty black fuel that came out of it.
I'm thinking that the nasty filter is why the pump failed twice in 90 days. And why my injectors were leaking.
My fuel pressure now seems to be maintaining the pressure that the 50lb regulator is set to. They installed the regulator before the pump, but it didn't magically make the fuel pump start pumping harder...It was an extra $60, though...
My STFT's are now +/- 5ish. Mostly + it seems to me. Just pretty much lays down 'off the line'. And passing on the freeway requires getting it to downshift before much happens.
I'm wondering if it's the tune now. Cats are tuned out and gone. EGR, AIR, etc are tuned out (for now). Plugs are new TR5's gapped to .050. I'm out of ideas...
Thanks,
-Kyle
Kyle, I looked at your second to last log. Like I said earlier, your timing is erratic. So I studied the last log and it seems your timing is great until you go over 24% throttle or so. It averages around 16 degress at 0% throttle, then quickly jumps into the 20's when you accelerate lightly, as it should. BUT, whenever you are at say 30-50% throttle in your log, it pulls timing like a ****! Like down to 11-12 degrees sometimes, and as your rpm climbs the timing sometimes starts to come back up, and I can see it always comes back up when you start to lift off throttle as well. So basically it looks like when you put it under enough load under 2000rpm, it pulls timing until your revs climb or you start to lift up on the throttle some and lessen the load, and then the timing starts comming back up where it should be. I'm telling you, timing is being pulled which is why the truck is slow down low. I don't know why your log doesn't have a knock count, but I'm 99% sure if it did, you would have knock counts. Timing should not drop like that when you step on it! This is your problem! I'm guessing you are getting knock counts and the pcm/ecu is pulling timing. I know loud exhaust/exhaust leaks can cause a false knock, so it may not be the sensor itself. Or, you could actually be getting knock/detonation. Look at the first 26 entries on that log. At 9%, 10%, and 12% throttle you have 28.5 deg of timing. Then you step on it at 32-39% throttle and your timing drops clear to 9 deg! Then as you let up off the throttle dropping to 38%-36%-32%-28%-25%-24%, and 20% throttle, your timing rebounds back into the 20's as you reduce load on the engine. That log is full of examples like that. Retarded timing like that absolutely kills horsepower and mpg. I hope you get this before you take it in!
03-04-2016, 02:47 AM
