need help diagnosing my terrible misfire!

Smokinhot

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Jul 4, 2007
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It started last week, I put SHITGO premium gas from the hood bc the price was cheap. I ran a whole new tank of 93 from Shell along w/HEET and seafoam and it still misfired.

Today I changed the plugs w/NGK Iridium and the o2's back to new stock Delphi ones bc I was having o2 DTC codes like crazy . It ran GREAT and then started misfiring 15 minutes later on my way to work. They bank 1 plugs (TR5's) looked good but bank 2 was caked in soot, same for the o2's. What could it be?

Fat Tony said he had similar problems when his fuel pump was on the out, but wouldn't it cause misfires on all cylinders not just 1 bank?

Thanks
 

Dasfinc

Ready for the EVlution
Sep 28, 2007
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:ford: :nutz:

But seriously, hurry up and get it fixed, I'm pushing to get mine fixed by Sunday

Sounds like it could be a coil(s) issue, or even an ECU issue.

Have you driven it since? Does it drive fine for 15 min and start up again, or as soon as you start it up at this point its misfiring again?
 

SuperDaveGSE

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May 14, 2009
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I'd check the coil packs and plug wires, maybe switch them around to see if the misfire travels with them. Also at night with the motor running you can use a spray bottle with water in it, mist it over the coils and wires to see if any of them are arching anywhere. I would also clean the MAF and check the screen for damage which could throw off the readings.
 

Smokinhot

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well, I have been getting low voltages DTC's for Bank 2 sensor 1

B1S1 reads around 700ish mV, and dips down some
B2s1 reads around 300ish mV, and drops into the 100's

B1S1 reads 1.6-7.2% LTFT's, bouncing around but that's norm
B1S1 reads dead @ 25.0% and NEVER moves
 

Stink Star

Don’t Drive Angry!
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Jan 20, 2008
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So for some reason or another the computer is going full rich....

One thing to check is there are 2 grounds on the back of the motor. One on the drivers side kind of near the oil pressure sensor and one on the passenger side kind of where the trans meets the block. If they are broken/loose, or even just slightly rusted you will get a bunch of weird concerns and codes (the grounds are for ECM/sensor reference voltages).
 

Smokinhot

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I checked, I have the strap on the driverside that goes from the firewall to bellhousing. And I have the ground connection in the loom behind the intake connected to the block.

I logged on HPT, I reset the fuel trims and went for a drive from a cold start and the o2 runs good up until it heats up than flatlines. Its gotta be in the wiring or something. I'm gonna try to trace the heater wire and see if it was pinched somewhere. Don't know what else to do
 

Smokinhot

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Jul 4, 2007
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I logged on HPT, I reset the fuel trims and went for a drive from a cold start and the o2 runs good up until it heats up than flatlines. Its gotta be in the wiring or something. I'm gonna try to trace the heater wire and see if it was pinched somewhere. Don't know what else to do

Any other suggestions on this ^ before I bring it into the dealer to get diagnosed

It seems like it loses voltage, and as stated it is a brand new o2
 

02BlueGT

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Feb 21, 2008
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Did you check your fuses? Also check all your grounds, not just the close ones, Back-feed voltage can fuck with many a sensor.... The O2's should have at least a fuse for the heater circuit, the 5v feed is probably all PCM based. Also visually inspect the 02sensor harnesses for physical damage and burns.

Are any other sensors going crazy? Did you try running the car in open loop? (can be forced in the HPT scanner, or just unplug the 02 sensonrs)
 

bikrboy128

Some say.....
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Jul 15, 2007
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bank 2 is pegged lean, causing the computer to just dump fuel. i would verify power and ground at bank 2 sensor 1 o2, then measure the signal wire between the PCM and sensor harness connector. it sounds like the truck runs like shit as soon as it goes into closed loop. try unplugging bank 2 sensor 1 O2 (forcing it to stay in open loop fuel control) and see if the truck runs any better.
 
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