All cylinders misfiring

xtreme_exploder

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Got a really weird misfire issue with my car. It runs like complete crap at all rpms and loads, and it won't idle on it's own. I pulled the plugs and they're all wet with gas. I changed them all just to see what would happen, and nothing changed. I checked the frps and it don't have any gas sucking through the vacuum line or anything like that. The only code that showed up after it ran for a while was a P1114 (IAT 2 low output). Is it possible for an IAT 2 sensor to make the car run like this? I feel like it would fall back on the other IAT sensor or something if the IAT 2 failed. Doesn't makes sense to me but who knows. To make things more interesting, the problem came up about 2 minutes after I made a little 2-3-4 wot pull. Anyone seen something like this before?
 

01yellercobra

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Pull the FRPS and try to blow through it. When mine went I didn't have any gas in the vacuum line. The fact that it happened after a WOT blast makes it the likely suspect to me.

I would think the IAT1 would cause it more than the IAT2. If the computer doesn't think the engine is warmed up it could cause the ECU to keep it rich.
 

xtreme_exploder

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So things keep getting weirder. I checked everything I could, including pulling off the frps, and it's all checking out. The coils are getting battery voltage and they're firing. What's weird is when I pull the some of the coils on the driver's side it actually starts running better. That makes me think timing is way off, at least for those cylinders. The only code that keeps popping up on my code reader is U1262, which mean SCP communications failure, and it says it's for the ABS, but I have no ABS light on. Is it possible that this code is related to my issues? Also the engine revs can be heard pretty clearly through the radio static when it's on, is this normal?
 

Wings65288

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The engine revs heard through the stereo is most likely due to both noise interference sensors missing/unplugged off the back of your block I believe. I have mine off and don't hear anything through the radio. I could be wrong on this, it was a long time ago.
 

03' White Snake

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Hold the pedal to the floor and crank it over for 10-15 seconds or til it starts. This will shut off your injectors. Sounds flooded due to a bad FRPS. Replace it and go from there.

Turn the key on to prime the pumps, press on the shredder valve on fuel rail, do you have gas come out? Another way to check a bad FRPS.
 

oldstv

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I'm guessing no, but I will ask anyway. Do you by chance have a 2step? If so take it out.
 

xtreme_exploder

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Yeah checked the rail sensor, it don't leak. Also has plenty of fuel pressure in the rails. No two-step, but I do have an msd tach adapter and I bypassed that to make sure that wasn't the issue.
 

xtreme_exploder

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Been running through the factory service manual on this thing, haven't found anything wrong yet. It keeps looking like a failed computer, but I need a good scan tool to get better diagnostic data. The only abnormal looking reading when I use my sct data logging stuff is low fuel trim on both banks. The U1262 code has me concerned, as that's the only sure thing I have to work with right now.
 

hotcobra03

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I read thru manual.

Abs/traction

Being you can read at dlc

A ground wire is what I’m thinking

I did have a strange issue once.

The eye hook on radiator support was cracked but not off.

A wiggle did break it.

This little break caused car not to run
Acted like yours.

I had gauges sweeping lights on and off on dash theft freaking.

I also had the short ground from battery to radiator support burn up inside casing

I would do a compression test first on at least 1 hole on each side.

I have been burned on this before and found 1 dead hole will cause weird stuff also.
 

01blckcobra

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Check the wiring harness going to the coil pack. Sounds like you have a short somewhere. Disconnect the battery and let it sit for 10mins or so with the headlights on while battery is disconnected. Try a kam reset and while the battery is disconnect start looking at the wiring harness, 02 sensors
 

01blckcobra

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I've ran into a bad idle control valve that made it run rich... Other than hooking up a good scan tool knida a crap shoot. MAF clean? not oil present in the intake tube... Hunt a search. Air filter clean? . Disconnect the abs module also. seen some have shorted and do weird effects to other components. Have a video of how it runs?
 

xtreme_exploder

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Don't have a scan tool at the moment, but I can see a lot of stuff with my data logging on the laptop, and everything seems like it is reading like it should. You can see injector pulsewidth jumping around a bit, and the map readings bounce with RPM changes and injector pulsewidth, but can't see why it's doing that. MAF readings look smooth and normal. I've tried running the car with almost every sensor, the IAC, and ABS disconnected, and it don't make much difference. I can get a video up after work.
 

03' White Snake

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How are you checking the FRPS? Are you putting a vacuum gauge on it and applying vacuum and seeing if it is holding? The smallest tear or hole will cause all kinds of issues. This is not a visual check.

Also depending on the intake, if it's a JLT, you need to check your maf wires as they rub on valve cover or are bent to tightly and crack inside the insulation and you cannot detect.

So try jiggling the maf wires while its running and see what happens.
 
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hotcobra03

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Po1114. See DU20

DU: Intake Air Temperature 2 (IAT2)

2003 PCED On Board Diagnostics


SECTION 5: Pinpoint Tests



Procedure revision date: 08/19/2002


DU: Intake Air Temperature 2 (IAT2)

← DU: Introduction
DU10 DTC P1115: SIMULATE OPPOSITE SIGNAL TO PCM
  • With IAT2 temperature sensor disconnected, connect a jumper wirebetween the sensor signal and SIG RTN circuits at the temperature sensor harnessconnector.

  • Key on.

  • Access IAT2 temperature sensor voltage PID.
Is the IAT2 temperature sensor voltage PID less than 0.2 volts?


Yes No
REPLACE suspect sensor. KEY OFF. REMOVE jumper wire. GO to DU11.
DU11 CHECK TEMPERATURE SENSOR SIGNAL AND SIG RTN CIRCUITSFOR OPEN IN HARNESS
  • Disconnect PCM.

  • Measure resistance of sensor signal circuit between PCM harnessconnector pin and IAT2 sensor harness connector.

  • Measure resistance of SIG RTN circuit between PCM harness connectorpin and IAT2 temperature sensor harness connector.
Is each resistance less than 5.0 ohms?


Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)). REPAIR open circuits.
DU12 CHECK TEMPERATURE SIGNAL FOR SHORT TO VREF IN HARNESS
  • Key off.

  • Disconnect PCM.

  • Measure resistance between IAT2 temperature signal circuit atthe sensor harness connector and VREF circuits at the PCM harness connector.
Is the resistance greater than 10,000 ohms?


Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)). REPAIR short to VREF.
DU20 P1114: SIMULATE OPPOSITE SIGNAL TO PCM
  • Disconnect harness from IAT2 temperature sensor.

  • Connect scan tool.

  • Key on.

  • Access IAT2 temperature sensor voltage PID.

  • Key off.
Is the IAT2 temperature sensor voltage PID greater than 4.2volts?


Yes No
REPLACE sensor. GO to DU21.
DU21 CHECK VREF VOLTAGE TO TP SENSOR
  • Refer to schematic at the beginning of the pinpoint test.

  • Disconnect TP sensor.

  • Key on, engine off.

  • Measure the voltage between VREF and SIG RTN circuits at theTP sensor harness connector.
Is voltage between 4.0 and 6.0 volts?


Yes No
There is sufficient VREF voltage. RECONNECT TP sensor. GO to DU22. KEY OFF. GO to C1.
DU22 CHECK TEMPERATURE SIGNAL CIRCUIT FOR SHORT TO GROUNDIN HARNESS
  • Disconnect PCM.

  • Measure resistance between sensor signal and SIG RTN circuitsand then between sensor signal and PWR GND circuits at the PCM harness connector.
Is each resistance greater than 10,000 ohms?


Yes No
REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)). REPAIR short circuit.
DU30 P0127 IAT2 TOO HIGH. CHECK SUPERCHARGER INTERCOOLERPUMP OPERATION
  • Connect scan tool.

  • Access Output Test Mode.

  • Select Mode: ALL ON.

  • Command pump to run.
Does supercharger intercooler pump run?


Yes No
GO to DU31. KEY OFF. GO to KP8(Charge Air CoolerPump).
DU31 CHECK INTERCOOLER SYSTEM
  • Check intercooler system for:

  • low fluid level.

  • cracked coolant lines.

  • blocked heat exchanger or coolant lines.

  • crossed coolant lines.
Is intercooler system OK?


Yes No
KEY OFF. GO to DU32. REPAIR as necessary.
DU32 SIMULATE HIGH IAT2 VOLTAGE SIGNAL
  • Connect scan tool.

  • Key on.

  • Access IAT2 VPID.

  • Observe PID while disconnecting IAT2 sensor.
Is PID greater than 4.0V?


Yes No
GO to DU33. REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)).
DU33 SIMULATE LOW IAT2 VOLTAGE SIGNAL
  • Access IAT2 VPID.

  • Observe PID while connecting a jumper wire between the sensorsignal and SIG RTN circuit at the temperature sensor harness connector.
Is PID less than 1.0V?


Yes No
RECONNECT sensor and GO to Reference Values, Reference Values.COMPARE IAT2 PID to reference values under the given road test conditions.If sensor is not in range, REPLACE IAT2 sensor. REPLACE PCM (refer to Section 2, Flash Electrically Erasable Programmable Read Only Memory (EEPROM)).
  • Intro

This may be issues. You had posted it but said now only U1262
 

decipha

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yes IAT2 sensor is a critical sensor and is used a global fuel modifier Ive seen bad temp sensors destroy engines.

Fix the iat2 before doing anything.

Sounds like you probably have other issues as well.
 

xtreme_exploder

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Yeah running through that IAT2 diagnostic procedure leads to the conclusion of replacing the PCM. However, I can't get any codes to show up anymore, besides the ABS code.
 

xtreme_exploder

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Update: forgot to get a video of how it runs, but I have yet to figure it out. Tried a million things, including swapping out the iat2/map sensor and the computer. I noticed that it has 2 cylinders on each bank that don't really hit (those header pipes are much cooler than the others). I moved injectors to see if the problem would move with them, but it stayed with the cylinders. I pull those plugs and they're usually wet with gas. I forced the computer into open loop because before, all the plugs were wet. I think the computer was getting a false lean from the dead cylinders and was adding more fuel to compensate. It almost runs like when it cuts cylinders with traction control. My only thought right now is that the U1262 has to do with a communication error making the computer go into traction control mode all the time?
 

hotcobra03

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Update: forgot to get a video of how it runs, but I have yet to figure it out. Tried a million things, including swapping out the iat2/map sensor and the computer. I noticed that it has 2 cylinders on each bank that don't really hit (those header pipes are much cooler than the others). I moved injectors to see if the problem would move with them, but it stayed with the cylinders. I pull those plugs and they're usually wet with gas. I forced the computer into open loop because before, all the plugs were wet. I think the computer was getting a false lean from the dead cylinders and was adding more fuel to compensate. It almost runs like when it cuts cylinders with traction control. My only thought right now is that the U1262 has to do with a communication error making the computer go into traction control mode all the time?

What was you results on pintest for voltage?
 

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