Misfire when hot and under load

Hello All,
About two weeks ago, my 03 LS V8 went into failsafe mode with a couple of codes about throttle body actuator. Reading about other people having the same problem and it being most likely caused by bad valve cover gaskets. After checking it, the right side gasket was leaking oil into plug wells 2 and 3. I replaced the gasket, plugs and the 2 coils. No fail safe mode again.

Now, car runs rough when warmed up and under load. Codes I receive are p0300, p0303 and p0355. The part I don't get is that 1 out of ten times I erase the code and the code is set again, it's a p0300 or p0303 and 9 out of ten times it's the p0355 on the bank I did not touch.

I have switched the plug and coil on number 3 and 5 with other cylinders but the problem does not follow.

I did have a fuel injector service done but no change.

Drive cycle test shows EGR, O2, ... are all okay.

The following are last two freeze data.



Global OBDII

Non OBD Freeze Frame

Frame 1 Mod $00
MIL STATUS OFF
TROUB CODE P0355
ABSLT TPS % 32.5
ENG SPEED RPM 2495
CALC LOAD % 90.1
MAF FLOW GR/SE 68.07
MAP KPA 92
COOLANT �F 215
IAT �F 91
IGN ADVANCE DE 15.5
ST FTRM1 % 28.1
LT FTRM1 % 9.3
ST FTRM2 % 28.1
LT FTRM2 % 1.5
ST FTRM3 % -100.6
LT FTRM3 % -100.6
LT FTRM4 % -100.6
ST FTRM4 % -100.6
VEH SPEED MPH 46
REL FRP KPA 4.05
FUEL SYS 1 OPEN2
FUEL SYS 2 N/A
O2S11 V 0.105
ST FTRM11 % -4.6
O2S12 V 0.740
ST FTRM12 % 99.2
O2S21 V 0.370
ST FTRM21 % 2.3
O2S22 V 0.225
ST FTRM22 % 99.2




Global OBDII

Non OBD Freeze Frame

Frame 1 Mod $00
MIL STATUS OFF
TROUB CODE P0355
ABSLT TPS % 29.4
ENG SPEED RPM 2757
CALC LOAD % 86.6
MAF FLOW GR/SE 70.23
MAP KPA 90
COOLANT �F 203
IAT �F 75
IGN ADVANCE DE 18.0
ST FTRM1 % 25.0
LT FTRM1 % 5.4
ST FTRM2 % 25.0
LT FTRM2 % 0.7
ST FTRM3 % -100.6
LT FTRM3 % -100.6
LT FTRM4 % -100.6
ST FTRM4 % -100.6
VEH SPEED MPH 52
REL FRP KPA 4.00
FUEL SYS 1 OPEN2
FUEL SYS 2 N/A
O2S11 V 0.680
ST FTRM11 % 2.3
O2S12 V 0.785
ST FTRM12 % 99.2
O2S21 V 0.835
ST FTRM21 % 4.6
O2S22 V 0.350
ST FTRM22 % 99.2

Hope someone has a suggestion on where to start or the direction I need to look at.
Thanks, Drew

1) When you removed the plugs was there oil on them?
If they do,your Spark-plug seals are bad on cylinders 3 + 5.
''Oil can cause a short and the car will misfire.''
Note: CHK NOTES,AND BOOK,make sure we a working on 3 + 5.
2) Lift hood and Poor a bucket of water on windsheld and than look were to see the water is going!
3) If water don't stay in the COWEL,it poors right on your Intake and Electrical buss Lines.
4) If vavle cover caps are off,water gets into the coils, causes Misfiring and Shorted coils.

I'am sure glad FORD doesn't make condoms!

Note: Oil and water will cause a shorted sparkplug coils + Misfiring.

When you short a Sparkplug terminal to ground,current is going to take the path of less resistance.
She's going to miss,or run like shit.

MCGIVER

I didn't notice any oil on them but wouldn't oil cause it to misfire all the time? There is no misfire at idle or before engine reaches the normal running temperature.

There was no misfire till I replaced the bank 1 valve cover gasket.
Drew

When you say you switched the coils on cylinders 3 and 5 with others, but the symptoms don't follow, do you mean the misfire codes remain on cylinders 3 and 5, or do you no longer see the misfire codes?

Also, you mention you replaced the valve cover gasket on bank 1, the plugs, and the two coils. Did you replace the coils for cylinders 3 and 5, or 2 and 3?

Code P0300 could be due to an issue with the EGR system. Even though you say the drive cycle shows the EGR system okay, depending on the response the scan tool you're using gives, "okay" doesn't necessarily mean "passes." You may want to remove the EGR valve and inspect the valve and passages. Also, do you recall what the fuel level was when the P0300 code was set? According to the service manual, a fuel level below 1/8 tank could trip a P0300. That makes me wonder if you might want to replace the fuel filter as well if that hasn't been done recently.

-Rod

I switched the plug and coils with cylinders that had no misfire but misfire stayed on 3 and 5. I get misfire counts on 1,2 and 3 when run diagnostic scan but only set a p0303 (the highest count). Never got a p0305 but a p0355 everytime I feel a misfire.

I replaced the coil on 3 at first when I changed the gasket. (#2 had very little oil in the well)
Then Changed #5 because of p0355.

It has been almost full since it started having problems. (Not driving the car) I have seen a p0300 TSB (17382) but can't find any info on this tsb at Alldata or Mitchell.

The way it acts, it point to EGR but could I have caused this problem while it was going to safemode before changing the gasket? It has an electronic EGR, when I take it off, what would I be looking for? Changing fuel filter next.

Thank you for your time and help.
Drew

HEAT - When HEAT go's up resistance go's up in copper.
VERY HOT - Went HEAT gos up resistance go down in a COIL.
Were's there No Voltage,theres is no Drop!

Is the electrical bus line going to coils 3 + 5 Good?

Note: Theres two signal wires per coil,so 3 + 5 (4 wires),They need tobe checked.

Is the connectors going to 3 + 5 good?

Take a peace of copper wire the same gauge and bend it a couple of Times,and see
WHAT HAPPENS: Break

ALSO-The faster you go the more oil pressure pushed through those spark-plug seals.
Take a bad coil and Spark-plug and push them together.
''It fits Loose'' oil can sneak from the grd of that plug and short the Terminal.
What Happens? Misfiring ,and a shorted coil.

PS. Please keep us Informed,we are trying our Best to help you.



MCGIVER