Live Data analysis

[AbnMike]

The leaking manifold gaskets would align with the LTFT values being high positive, and short term being negative. (you had a long standing issue with leaking exhaust leading to diluted O2 values - after it's resolved, the engine recognizes that it doesn't need to dump as much fuel to compensate)

LTFT values can take a long time to change. I'd monitor over a couple of weeks and see if things are moving in the right direction.
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Well I'm clearly using a ton of gas now, at least over what other people are showing, so if this is the culprit would simply changing to new 02 sensors now resolve the problem sooner?


I mean hell, two upstream sensors are cheaper now than continuing to pour fuel out the tailpipe.


Or can they be removed and cleaned and put back?


or is it something that's going to have to fix itself (if it's the problem) regardless?

 

[Tugela]

I found NGK/NTK D1 O2 sensors on Amazon for $50 or $60 each. They have worked just fine. If you haven't replaced your sensors in a while or their history is unknown it's an inexpensive and relatively simple fix (provided the threads on the sensors aren't seized, which could result in needing them cut out and new ones welded in). Also, reaching the upstream connectors is a little tricky. Being tall helps. Also note that D1 O2 sensors take an unusual size wrench. I ended up buying a special O2 socket specifically for the job.

 

[CalebP]

If you look at the first image, the ecm states no active codes, and the ecm is in closed loop.So most likely the engine is cold, and the ecm is ignoring the o2's, to assist in getting the engine up to temp quickly. On the second and third image you can see short term fuel being pulled, meaning the engine is getting close to being warmed up. If the engine has an active dtc, fuel mileage is not a concern for the ecm,so it will use a default fuel and ignition curve.

 

[AbnMike]

Your short term fuel trims are OK, but long term seem high. Anything under 3% is ideal, 5% is reasonable, but you're at around 13% (max is typically 20% before it can no longer adapt). I'd be concerned about a vacuum leak.

Also, is the truck idling, or are you holding the throttle partially open? The engine rpm is 842, which is too high for an idle, and the throttle indicates ~15% open. The two numbers roughly correlate, as long as you're holding the throttle when the measurements were taken.

Ran it again after driving home and temp needle solidly half way.

TP is 14.1%
Idle 793

If Fuel Sys CL means closed, then both those values were still CL at the time I did live data.

 

[Dave03S]

As a side note to this thread, I recently increased tire size to 265/75R16 from stock. I read a lot on the forums about how my mileage and power would suffer. Did a lot of analyzing and testing and what I found was that neither thing changed at all.

What I did learn that most of us have been measuring MPG incorrectly. Myself included. Not that the math is wrong but the data is wrong.

Stock tires my speedometer read low compared to the ultragauge. 5mph low. If the speedo say 60 the UG said 55. I chose to go by the UG fwiw.

New tires seemed like i was passing everyone on the freeway. Hence testing.

What I found was that BOTH the UG and the speedometer are wrong. Therefore your odometer is wrong... and... your MPG data is wrong. You don't really know how many miles you went unless you use a google maps type app. I found on a 320 mile trip, stock tires the odometer said it was 337 miles... New tires said 297 miles. Googlemaps says 320 from exact address to exact address.

337 miles / 24 gallons = 14 MPG... 297 miles / 24 gallons = 12.375.

I ended up using a MPH app along with mile markers and stop watch (operated by navigator) while driving the various versions of "60 MPH" on a lonely stretch of highway. The app matched up exactly 60 miles per hour in 60 seconds at exactly the mile marker.

My results indicated that old tire my MPH were 5 MPH low at 60. New tire size I am actually going 63 when it reads 60. My MPG math was obviously wrong the whole time too.

Finally given a known distance and using the fill up method, over a 130 mile non stop freeway drive I calculated 16.4 mpg averaging 70 -75 mph using cruise control as much as possible. I've since repeated that test twice with the same result. So I can't say bigger tires reduced my mpg or power.

Better methodology though led to me finding two more gauges to not believe in the instrument cluster. And don't believe the speed/miles on your OBD reader either. It may be a different sensor from your speedometer but that doesn't make it accurate either. My speedo and UG MPH reading are still 5mph apart with the UG being low... UG=55 Speedo=60 real=63

03 4.6, 2"lift, running chevron supreme. no heavy objects attached.

 

[salvvia]

What kind of plugs are you running d1 like those RN11YCC. I have had good luck with the E3 high priced as hell but they dont carbon as bad
Try cleaning intake
Test your oil and see if your dumping fuel in cylinders are you gaining oil?
Like he said use google and get a true mpg if you believe Bobby Google because if its on the interweb it is always TRUE

 

[AbnMike]

Changed the plugs and wires today. All the plugs look like the first one. The black one is no 7 and the other side of it is white.

Gapped to .48 or so.

 

[discostew]

I agree with squirt. The long term fuel trim is adding fuel and the throttle is at like 20%. I would make sure the throttle isnt being held open by the throttle cable. Those two 8 mm head bolts holding the cables to the upper intake get torqued with that bracket holding the throttle open. Then after that a vacuum leak.

But your rough road signal fault has to do with a coms line between SLABS and the ECM. The truck uses the rough road signal to decide if its monitoring misfires right now. I don't remember for sure but I think there was a software patch for some problem like this. It has something to do with not monitoring misfires on decel or some kind of shittery.

 

[AbnMike]

I've sprayed carb cleaner checking for leaks, doesn't seem to be any unless you guys know of an overlooked culprit?

Cleaned the butterfly plate and MAF. Throttle cables have slight slack and plate snaps fully closed. Live data shows TP 14.1 at idle still fully warm.

 

[AbnMike]

There was a small vacuum hose under/near the throttle linkage that goes to the throttle body that was split. Idle down to 730 now. Will compare live data after a couple cycles.

 

[discostew]

Wires and plugs like Stu said? Anything else to look at? How do I know if it's running too "rich" and how to make it not run as rich?


Could the injectors just be dumping fuel? I would think if so there'd be other symptoms though - it idles smoothly, downshifts smoothly, on flats I could cruise at 70 mph at 2250-2500 rpm, etc.

Your truck isn't running rich. It's running lean. It's adding fuel to make up for a lean condition. At idle with throttle position of 20% or more. Maybe that's why it's adding fuel.

Is the only code your chasing that rough road signal fault?

 

[AbnMike]

Your truck isn't running rich. It's running lean. It's adding fuel to make up for a lean condition. At idle with throttle position of 20% or more. Maybe that's why it's adding fuel.

Is the only code your chasing that rough road signal fault?

Which number is the 20% throttle position? The "TP" has been consistent at 14.1 past few times and it's definitely closed.

The rough line low fault pops up a few times a week. Sometimes it's one, sometimes two faults.

I did throw a random multiple cylinder misfire but not since the new plugs and wires.

I'll read the live data again tomorrow after driving to see if that broken vacuum line was the culprit. It definitely was sucking air.

 

[AbnMike]

So here are the new numbers (after new plugs and wires, fixing a vacuum line near the throttle body, cleaning the MAF and butterfly plate). I[m only putting in the values that had a significant change. A couple of them were within a couple of points of each other.


LOAD PCT% went from 29.4 to 27.8


SHRTFT1% Same at -4.7 (fluctuating)


LONGFT1% 13.3 down to 9.4


SHRTFT2% -3.1 to 2.3


LONGFT2% 13.3 to 9.4


RPM 843 to 739


MAF 0.011 to 0.009


O2B1S1(v) 0.085 to 0.050


SHRTF2B2S1 -2.1 to 3.1

 

[AbnMike]

Anyone? Is this a positive shift in numbers? Negative? Negligible?

 

[seventyfive]

your long term is too high.

bank 1 is trying to take fuel away and bank 2 is trying to add fuel.

When was the last time you took the valve covers off, remove the baffle plates, and thoroughly cleaned all the dried up oil and crud? If your crank case breather is not working properly the intake manifold is going to find another place to pull negative pressure in. Adversely if the the crank case breather system is blocked up its going to find the weakest seal to blow the positive pressure out.

I've said it way too many times here but without a smoke machine you will never pin point vacuum leaks. Spraying starter fluid leads you to a general area. If you have zero vacuum leaks then check the crank case breather system and the valve cover
baffles.

Only numbers you need to be watching is short term and long term. Unless you have a scanner that's also reading fuel trim set point your going to chase your tail. Don't even know if a T1 shows fuel trim set point. Basically the ecu bases long term from short term and that happens once the set point 'balances'. Usually once engine temp is reached the set point starts to settle after 5 or 10 minutes of idle and partial load conditions.

Find a shop with a smoke machine, pay them to smoke the intake. It will save you time trying to find any/all vacuum leaks. If there are no vacuum leaks AND the pcv system is working properly?

As long as you can get long term to 5 or 6 percent additive you'll be fine.

Maybe discostew knows, but if load percentage is actually partial load then that is way too high, should also be about 5-6% additive. Partial load is how much fuel is given while you are under light acceleration. Full load or wide open throttle is always a default fuel additive based on manufacturer.
I'm assuming load percentage is not actually fuel trim partial load. Load percentage is a generic obd block.

Partial load, regarding fuel trim additive, is EXTREMELY important. If the ecu adds too much fuel under partial load that's when you're going to have issues. That usually gets out of whack if there is a vacuum leak causing too much port velocity OR a bad MAF A bad MAF reads too much air and the ecu dumps fuel.

But like I said, load percentage generic obd is just a calculated load value and not actually partial load fuel trim.

 

[seventyfive]

But yes any time you're reducing long term it's a positive step.

 

[AbnMike]

Thanks. I've never had the valve covers off but the top end was rebuilt 20k miles ago with religious 3k oil changes since then.

I haven't had it out other than short trips around town since I put in new plugs and wires and changed the oil and fixed that known vacuum tube near the throttle. I ran seafoam in the oil prior to the oil change to help clean it out.

Tried to pull one of those baffles out of the cover but of course it broke. I'll order another one and get the covers off and see what it looks like in there.

If it's not a vacuum leak could this be bad injectors? Bad 02 sensors?

 

[AbnMike]

What does LONGFT mean anyway? It was at 13 something, but now it's down at 9.4. Every other value changes as I drive except this. I was holding the scanner as I drove and it never changes - at all, regardless of throttle position. Is it a value the ECU reads and only updates every few cycles?

 

[discostew]

What does LONGFT mean anyway? It was at 13 something, but now it's down at 9.4. Every other value changes as I drive except this. I was holding the scanner as I drove and it never changes - at all, regardless of throttle position. Is it a value the ECU reads and only updates every few cycles?

It means that its long term fuel trim adjustment is adding a bunch of fuel. Because your truck is running lean.

 

[AbnMike]

It means that its long term fuel trim adjustment is adding a bunch of fuel. Because your truck is running lean.

I get that. But shouldn't it change at all during driving? That's the part I'm not understanding. I mean it doesn't even fluctuate at 9.3 or 9.5. It's just a very consistent 9.4 regardless of warm, cold, accel, decel, etc.

It also doesn't appear to come out of Closed Loop (CL). Shouldn't it go into Open Loop after opening up past idle?

This link seems to indicate that bad O2 sensors could contribute too. Or a leaky fuel injector (next page)

http://www.autoserviceprofessional....-works-and-how-to-make-it-work-for-you?Page=2