When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have been chasing this issue for the past day or so. I took my truck (5.3 swapped Colorado) out for its first drive the other day, and was met with a few codes on the dash.
first code was a P0300. Which is the random misfire code. I also got a P0171, which is the drive side bank is too lean. So I check fuel pressure. Sure as hell, its was right at 59 psi. So I went from that to the spark plugs, I had originally gap them at .055", and I went smaller to .040". I also noticed the complete bank on the driver side seemed fouled. Seems like they are running very rich. The passenger side looks brand new. When the truck is driving, it sometimes runs great, but it mostly has trouble at 2500-3k.It breaks up bad, and sounds like absolute ****. Is their anything else that could be causing this issue?
I figure the next bet is to check the driver side 02 sensor with the parts store scanner. (if their scanner allows it.) I wanna see the data to insure that it is bad.
The engine is otherwise stock minus a mild cam and stall. (212/218 113 lsa) and 2800 rpm, and ls6 valve springs.
I have not swapped them. But I will see what will happen if I do. My harness is suppose to be plug and play so I did not change anything on the harness.
EDIT:
Picture of o2 sensor:
The spark plugs look much the same.
EDIT EDIT:
I cooled the engine down, started it back up and hit with carb cleaner. No change in rpm. So I suppose it is not a vaccum leak.I hit all the runners on the side, the brake booster, pcv valve. I then hooked up my dads old timing light, and I sure have spark on one of the coils. so next ill check compression. hope this isn't the issue.
Could this be a tuning problem? I am thinking about contacting the local tuner, because idk what is on the computer in terms of a tune.
Last edited by flyer123; Feb 24, 2017 at 03:30 PM.
You have at least one (probably just one) cylinder misfiring. The unburned oxygen makes the o2 sensors tell the computer to add fuel. You then get every cylinder on that bank running rich as hell, in addition to a misfire. I don't know why you have a cylinder down, but I do know it will take the rest of them with it if you don't find the problem. Try to find an infrared thermometer or something equivalent to see which exhaust port is cold. This will narrow your search.
edit-- The most common cause I have seen for this is a faulty plug wire.
You have at least one (probably just one) cylinder misfiring. The unburned oxygen makes the o2 sensors tell the computer to add fuel. You then get every cylinder on that bank running rich as hell, in addition to a misfire. I don't know why you have a cylinder down, but I do know it will take the rest of them with it if you don't find the problem. Try to find an infrared thermometer or something equivalent to see which exhaust port is cold. This will narrow your search.
edit-- The most common cause I have seen for this is a faulty plug wire.
I checked all the wires and they seem to be fine. on the 2000 ohm setting they all read the same (850-904 ohms). even the apparent good ones. So imma go through its coil tomorrow and put it on a light to see if it is getting spark. Other than that, I don't think there is much I can do with out some sort of computer/scan tool to read what is going on with the fuel trim.
Yeah I am gonna test the compression tomorrow. I don't have a leak down tester. I suspect that because I changed the valve springs to accommodate the cam , maybe did something that is not allowing the valves to close all of the way. who knows.
My little project might have become an ad on craigslist. I am not ripping into to this bad boy again lol
all the fuses are good? Gotta start with the simple stuff.
-verify each cylinder is getting spark - pull a wire, install a loose plug against the head and turn the engine over (fuel injectors disconnected)
-verify power is getting to each injector/coil
-verify grounds at the back of the left head
-all other sensors are plugged in?
-etc etc
all the fuses are good? Gotta start with the simple stuff.
-verify each cylinder is getting spark - pull a wire, install a loose plug against the head and turn the engine over (fuel injectors disconnected)
-verify power is getting to each injector/coil
-verify grounds at the back of the left head
-all other sensors are plugged in?
-etc etc
yeah I am going to re go through the simple **** tomorrow. I am interested to know the compression because I was gonna throw a 100 shot at it.
But here is something: Being my first LS build, I have a ground on the coil bracket that sits on the valve cover. Could that be an issue? I thought about it, but my reasoning is that they are bolted metal to metal, and should send ground to the head. There is not much room in the rear of the head (head to fire wall) so ill see what I can do tomorrow. Maybe ground it to the block somewhere?
yeah I am going to re go through the simple **** tomorrow. I am interested to know the compression because I was gonna throw a 100 shot at it.
But here is something: Being my first LS build, I have a ground on the coil bracket that sits on the valve cover. Could that be an issue? I thought about it, but my reasoning is that they are bolted metal to metal, and should send ground to the head. There is not much room in the rear of the head (head to fire wall) so ill see what I can do tomorrow. Maybe ground it to the block somewhere?
That could easily be it. The valve cover is insulated from the motor by the gasket. Best ground is to the cylinder head. That's where the factory harness grounds.
That could easily be it. The valve cover is insulated from the motor by the gasket. Best ground is to the cylinder head. That's where the factory harness grounds.
Ok so I put the ground to the rear, managed to squeeze it back there, but throws a code still. So I am going to continue on with the little list above. maybe ill figure it out.
Could just be a bad O2 sensor. I've seen many that just get stuck at a low voltage and drive the fuel trims high on the bank they are on. Easiest test you can do is just swap L&R O2s and see if the problem moves to the opposite bank. You need a scan tool that will show O2 sensor voltages and fuel trims while running.
Could just be a bad O2 sensor. I've seen many that just get stuck at a low voltage and drive the fuel trims high on the bank they are on. Easiest test you can do is just swap L&R O2s and see if the problem moves to the opposite bank. You need a scan tool that will show O2 sensor voltages and fuel trims while running.
I will do this next after I clean it off. It will be hard telling which side is causing the issue with out the scan tool. Suck because I can not get these 02 sensors anywhere. I have to wait like 3 days to get them :O anyway, I tested each coil with a sparkplug jammed against the head and well, they all have spark.
In the absence of a scan tool just let it idle for 10-15 minutes and pull a plug from bank 2. It doesn't take long to soot up plugs with a bad O2 stuck low and pegged fuel trims. Disconnect the battery for a few minutes after you swap O2s to reset the fuel trims.
In the absence of a scan tool just let it idle for 10-15 minutes and pull a plug from bank 2. It doesn't take long to soot up plugs with a bad O2 stuck low and pegged fuel trims. Disconnect the battery for a few minutes after you swap O2s to reset the fuel trims.
Ok cool i was wondering how swapping the 02 sensor would help see if they are still miss firing. I figured i would get the same code. But now that i know, ill take the truck out for a little drive around the block to see if i cant get them things nice and dirty.
EDIT: Ok i swapped them out, and it through a code, it ran and heated up a bit and went away. I drove it for about 15 mins, and it seemed ok. I never exceed 4500, but the trans stopped shifting mid drive. so, idk what is up with that haha. always something
EDIT EDIT: Went back out to the truck and got the P0300. Gonna wait for it to cool down again and see what is going on with the plugs. I also got a P0131 again. So something is up. I then picked up two more codes: U0001 and U2100 which might point to the trans issue. IDK, this thing is one problem after another.
Last edited by flyer123; Feb 26, 2017 at 05:22 PM.
The engine is a 03 flex fuel, and the PCM is from a 06 trailblazer SS. I think that code might come from the miss fires. I am gonna check the compression on the cylinders. I tried the other day, but the parts store gave me some junk that was made for 4 cylinders and stuff. Made it almost impossible to get the line on because I had to twist the entire line, I could not get a good seal and blew air out of the cylinder. I am gonna rule out (or in) that something could be majorly wrong. I am also going to replace the plugs on that side. They look bad haha, so I don't think they will help the cause
Last edited by flyer123; Feb 26, 2017 at 08:20 PM.
The engine is a 03 flex fuel, and the PCM is from a 06 trailblazer SS.
That is an odd combination running a LS2 E40 PCM with a 03 5.3L FF. Guessing it was tuned for the 5.3L? There are definately some things that are going to be mismatched.
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Slideshow: The controversial Ferrari F6 swaps its original flat-12 for a Corvette Z06-derived LT4 V8 and sends power to four rear wheels through a custom-built drivetrain.
7 Most Reliable High-Performance Engines GM Has Ever Built
Slideshow:These GM engines didn't just make huge power, they survived abuse, boost, track days, and six-digit mileage with a reputation for refusing to quit.
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Slideshow: From wobbling harmonic balancers to failed EBCMs, these are the issues that define long-term C5 ownership and what repairs typically involve.
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Slideshow: A modern Camaro transformed into a retro icon, this limited-run "Bandit" build blends nostalgia with brute force in a way few revivals manage.
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Slideshow: Cadillac didn't just crash the high-performance luxury vehicle party, it showed up loud, supercharged, and occasionally a little unhinged...
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Slideshow: A one-off sports car that looks like a vintage Italian exotic-but hides a C6 Corvette underneath-just sold for the price of a new mid-engine Corvette.
Bank 1 running completely rich 
