Misfires, fuel/air issues. Where to start?

[Zimmerly]

Just a thought- my vent line is cut as well, if you remember.
Perhaps a scrapyard tank that was thrown in, wired and grounded pump so they could just sell it right away? Just a thought.

 

[funnyfarm]

Hey guys.
98 K1500 ext cab, 5.7 Vortec.
Background of myself, I own a truck identical to it that I rebuilt a lot of. No schooling, self-educated mechanic with fairly good knowledge of the GMT400.

Now on to the truck... I just bought it a week ago. It runs a rough idle, smells rich, and has noticeable misfires. Looking around, I notice a new nylon main fuel line from the tank to the engine bay. The tubes going into the injectors look newer as well. I can tell the evap tubes have been messed with, because the upper one isn't routed the way it should be around the upper rad hose. The lower tube looks to have been replaced. Looking back on the driver side frame rail, I notice the fuel vent tube has been cut out, from the drivers door to about 1ft before it becomes rubber near the tank, so there is no vapor going into the evap canister. I have a feeling this isn't my main issue, but then again I'm not a pro. The previous owner said he just installed a new cap and rotor, and I know he did (or at least someone did), because it's black, while the rest of the distributor is still the stock gray color. He said he [thinks] it needs a new ignition coil. I've already replaced the PCV valve because it was rattling while running, and I thought there was a long shot that might've been what I needed, but of course not.
I used my Bluetooth scanner with Dashcommand, and found lots of misfires. A little on bank one, but a LOT on all of my even numbered cylinders, which I found interesting.
Since my other truck and engine are identical in model and year, I plan on swapping coil units to see if that's the case, but I'm having my doubts. I don't want to just throw parts at it based on personal "hunches", so I came here for help. I've turned to this forum so many times, and to be honest, I would not have been able to complete a LOT of projects on my build, if it wasn't for this great community. Anyway, enough of the sappy crap.
I just don't know where to start. I do know it's getting too much air and not enough fuel. I checked all air connections and tubes. Everything seems put together. It's leaking oil, and looking in back of the intake I see some oil next to the distributor, so I suspect it needs a gasket.

Here we go with the codes-

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These are the codes I'm getting:

PO300 -Engine Misfire Detected
P0452 -Fuel Tank Pressure (FTP) Sensor Circuit Low Voltage
PO463 -Fuel Level Sensor 1 Circuit High Voltage
P0174 -Fuel Trim System Lean Bank 2
PO401 -Exhaust Gas Recirculation (EGR) Flow Insufficient
P1153 -HO2S Insufficient Switching Bank 2 Sensor 1
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If someone could lead me in the right direction, it would be great. I'm ordering some tubing to patch up my vent to canister line and I'll go from there. Thanks in advance!

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I own the same vehicle I have worked on many different Vortec Motors for the last 20 years they all have major problems with the fuel spider when you say you check the hoses going to the fuel injectors did you actually take the time to pull off the top plenum air intake because that's where the central port fuel injection system sits it's known as the Chevy Vortec spider it is a huge POS normally those will crack and break because they are plastic hoses you will get misfires and a whole bunch of other codes due to the air intake starts to fill up with gas do a little research on Chevy Spyder for that year and you'll see what I mean I just put a post up yesterday I had my fuel pressure regulator go bad it's part of the spider I replaced it with a multiport system brand new installed it it worked for 2 miles and then to injectors stuck wide open hydrolocked my engine and I ended up having to rebuild the motor I ended up going old school going carburetor the thing runs like ***** ape and is amazing now long story short you definitely need to look at the fuel system and start with the fuel spider

 

[Zimmerly]

long story short you definitely need to look at the fuel system and start with the fuel spider

What is leading you to think it's a problem with the injection, and not vaccuum/o2 issues? Wouldn't o2 sensors be the logical first thing to address before just assuming they're reading correctly and jumping into messing around with my fuel injection on just a hunch? Just wondering what you're seeing that others are not.

 

[Zimmerly]

Alright, after tracing the wire loom up to the engine bay, it seems the orange/black was tied into a thicker orange wire somewhere along the frame rail, and ran up to the Aux A positive terminal at the engine bay fuse box, with a terminal loop connection on the end.

WHERE DOES THE ORANGE WIRE ACTUALLY TIE INTO THE CIRCUIT?

The gray pump feed wire is running by itself as well, all the way up to the fuse box. Not too surprised to find there was a hole cut in the bottom of the actual fuse box underneath the fuel pump relay so they could wire the pump feed wire into it. I ran a jerry-rigged ground wire from the one that was cut, to the erroneous terminal connection that was screwed into the crossmember, beside what I think is the fuel pump ground, so I could see if the wiring solved the guage issue.

After starting the truck, I think the guage is still acting funny. It turned upside down, then read about 1/4 tank, which I think is atound how much fuel I have in the tank After shutting it off, it's no longer maxxed out. I had to run an errand with the wife and wasn't able to get any further before it got dark outside. Anxiously waiting to jump back into it tomorrow.
Any thoughts? Let me know. Thanks!
-Jacob

[The end of the orange wire, engine bay]

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[Hole cut in fuse box for pump feed wire]

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[Road Trip]

I actually couldn't find an upstream Denso sensor on Rockauto, and the downstream one states "exc. Canada built", and mine was built in Canada.
What about universal sensors? Are there any you would recommend, preferably comparable price? Or should I get vehicle specific? Sorry so many questions, I've been reading a lot of contradicting things on pages lately.

Universal sensors can work, but to me that's more in the realm of you are going to trust but verify
all is working correctly by also having a wideband O2 sensor in place for confirmation. (No doubt
others have successfully used universal sensors just by plugging them in, but trying to assist
remotely I have to err on the side of caution.) YMMV.

For what it's worth here's the Denso website where you can cross-check that the right part is
being recommended to you: (Denso)

As for using house brands, here's one of many threads in here on that subject that is typical: (which brand O2 sensor)

VCMs can be finicky. O2 sensors are relatively simple conceptually, but it's the real-world
implementation that will help determine true compatibility and long service life.

 

[Road Trip]

1-Do these 3 fuses share a connection, along with the fuel pump relay? Gonna take a look at the wiring schematic.

Here's the big picture of the power circuit you are interested in. The fuel pump relay's pump power source is being fed by
the 20A ECM B fuse as shown below:

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8/22 EDIT:

For troubleshooting purposes, note that the input to this fuse is from a "Hot At All Times" feed. And that
these 'always at Battery potential' wires in the Underhood Fuse/Relay box are color coded Red (Pre Maxi-Fuse)
and Orange. (Mini-fuse & relay)

If you are missing the +12v on the input side of this fuse then the connection must have fatigued/broken.
This has been known to have happened to others previously.

More in a bit.

 

[Zimmerly]

Well, more issues. No power going to the fuel pump relay... ugh.
All other fuses and relays check out. Just fuel pump relay.
Not having much luck finding out where the relay gets power from, because it seems to be re-wired. Have a feeling I might've done something while messing with the fuel tank wiring. Any advice is appreciated. Until then I'm gonna try to double check what I messed with yesterday.
-Jacob

 

[Road Trip]

Z71_Zimmerly said:

1-Do these 3 fuses share a connection, along with the fuel pump relay? Gonna take a look at the wiring schematic.


According to the wiring diagrams, fuses ECM B (#12), HORN (#13), and A/C COMP (#14) all share a common 'Hot At All Times'
input feed:

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Depending upon your exact symptoms, this should narrow down exactly
where the loss of continuity has occurred:

* Horn & A/C hot, but no ECM B power?
* All 3 of the above fuses dead, but rest of Underhood Fuse Block hot?

Between this diagram and the one in a preceeding reply, you now have a pretty complete layout
from battery all the way to the ECM B fuse, and onward to the fuel pump relay.

Best of luck undoing the PO's shenanigans --

 

[Road Trip]

Well, more issues. No power going to the fuel pump relay... ugh.
All other fuses and relays check out. Just fuel pump relay.
Not having much luck finding out where the relay gets power from, because it seems to be re-wired. Have a feeling I might've done something while messing with the fuel tank wiring. Any advice is appreciated. Until then I'm gonna try to double check what I messed with yesterday.
-Jacob

To further clarify, is the missing power on the Control Side of the Relay? (Relay pin '85' to Connector B3)
(Does the pump prime for ~2 seconds when the key is switched to ON? Ultimately this control signal comes from the computer.)

Or, is the missing power for the load (fuel pump motor) the 'Hot At All Times' input on Relay pin '87' to Connector B1?

Obviously, the Control vs Load side of the relay is 2 different circuits, so we need clarification here in order to follow
the story.

 

[Zimmerly]

To further clarify, is the missing power on the Control Side of the Relay? (Relay pin '85' to Connector B3)
(Does the pump prime for ~2 seconds when the key is switched to ON?)

Or, is the missing power for the load (fuel pump motor) the 'Hot At All Times' input on Relay pin '87' to Connector B1?

Obviously, the Control vs Load side of the relay is 2 different circuits, so we need clarification here in order to follow
the story.

I have no power to any pins in the fuel pump relay slot in the fuse box. #86 is Blk, white tracer (ground?), 87 is orange (goes into large harness with rest of wires), 87a (which has a female spade at end of wire coming out of fuse box, I don't know if it's supposed to be there) is red, 85 is grn with white stripe (ignition switch?), 30 is the gray wire that was wired-in seperately from fuse box to tank. I assume the orange is the constant hot that goes into the relay? It feeds into the huge harness and i cant find any info regarding where to find it's source. Svc manual states "ecm-b", but don't know where to find it. Getting dark soon and I have work in the morning. Ugh. Lol.