How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask TIM Your Own Question
TIM
TIM, SERVICE MANAGER
Category: Dodge
Satisfied Customers: 6177
Experience:  DODGE SERVICE MANAGER- 20 + YEARS
6531745
Type Your Dodge Question Here...
TIM is online now
A new question is answered every 9 seconds

2002 Dodge Ram 1500: 2wd..misfires..the coil packs on cyl 8 and cyl 4

This answer was rated:

I have a 2002 Dodge Ram 1500 2wd 4.7L, Major misfires on cyl 4 a few on cyl 5 and cyl 8. Plug on cyl 4 severely carboned. I replace the coil packs on cyl 8 and cyl 4. Ran good for 20 miles then went back into the same problem. Pulled plug 2 days later on cyl 4 very carboned again. Code is P304b, also a code for Evaporative emissions manufature controlled. At idle the vehicle will run intermittently rough. Go down he road and the motor feels like it is under constant load.Have OTC genisys scan tool. Vehicle originally

hello, are you using or losing any engine coolant?tim

has any other sensors been replaced such as the cam and or crank sensor?

fuel pressure checked?

did this happen all at once?tim

 

Customer: replied 8 years ago.
No coolant loss.This did happen all at once. Vehicle was started one morning cold to warm up
when customer came out vehicle was running rough as described earlier. cam and crank sensors have not been replaced, nor has fuel pressure been checked . Thanks Rob

i will give you this diagnopstic flow chart-- hopefully you will be able to use your scan tool to follow through with the diagnosis,tim

possible causes

INTERMITTENT MISFIRE

SECONDARY IGNITION

ENGINE MECHANICAL PROBLEM

FUEL SYSTEM PROBLEM

ERRATIC CAM/CRANK SENSOR SIGNALS

OTHER POSSIBLE CAUSES FOR MIS-FIRE

PCM

With the scantool, select DTCs and RELATED FUNCTIONS. Read and record the

FREEZE FRAME DATA. Select OBD II MONITORS. Read and record the MIS-FIRE

SIMILAR CONDITIONS WINDOW DATA.

With these screens, attempt to duplicate the condition(s) that has set this DTC.

When the vehicle is operating in the SIMILAR CONDITIONS WINDOW, refer to the

WHICH CYLINDER IS MISFIRING screen.

Observe the WHICH CYLINDER IS MISFIRING screen for at least one minute.

Is the scantool counting mis-fires at this time?

All

Yes ! Go To 2

No ! Go To 8

2 With the scantool, read the FREEZE FRAME DATA.

Use the FREEZE FRAME DATA and attempt to determine the cause of the Misfire

DTC.

In the FREEZE FRAME DATA, is the LOAD VALUE over 50% and the operating

temp normal?

All

Yes ! Check secondary ignition components and perform a cylinder

leakage test.

Perform FUEL SYSTEM/MISFIRE MONITOR VERIFICATION

TEST.

No ! Go To 3

3 Check for any of the following conditions/mechanical problems.

ENGINE VACUUM - must be at least 13 inches in neutral

ENGINE VALVE TIMING - must be within specifications

ENGINE COMPRESSION - must be within specifications

CYLINDER LEAKAGE TEST - must be within specifications

CAM LOBES - must not be worn excessively

WEAK or BROKEN VALVE SPRINGS

ENGINE PCV SYSTEM - must flow freely

TORQUE CONVERTER STALL SPEED - must be within specifications

POWER BRAKE BOOSTER - no internal vacuum leaks

FUEL INJECTOR - plugged or restricted injector; control wire not connected to

correct injector

Are there any engine mechanical problems?

All

Yes ! Repair as necessary.

TEST.

No ! Go To 4

4 With the scantool, read the FREEZE FRAME DATA.

Use the FREEZE FRAME DATA and attempt to determine the cause of the Misfire

DTC.

In the FREEZE FRAME, are the adaptive fuel percentages greater than +/- 15%?

All

Yes ! perform the Checking Fuel

Delivery symptom.

TEST.

No ! Go To 5

With the scantool, read the FREEZE FRAME DATA.

Use the FREEZE FRAME DATA and attempt to determine the cause of the Misfire

DTC.

In the FREEZE FRAME DATA, is the engine RPM over 3000 and the operating temp

normal?

All

Yes ! Test CMP and CKP signals with Lab Scope, check valve timing,

and perform running vacuum test.

TEST.

No ! Go To 6

6 Note: Anything that affects the speed of the crankshaft can cause a misfire

DTC.

The following are other possible causes for mis-fire:

Injector harness connectors, PCM power grounds, restricted exhaust, intake restriction,

damaged trigger wheel, contaminated fuel, carbon build up on valves, or the

accessory drive belt (serpentine belt).

Do any of the above causes exist?

All

Yes ! Repair as necessary.

TEST.

No ! Go To 7

7 If there are no possible causes remaining, view repair. All

Repair

Replace and program the Powertrain Control Module in accordance

with the Service Information.

TEST.

8 NOTE: The conditions that set the DTC are not present at this time.

An intermittent problem may have been caused by moisture in the secondary

ignition.

WARNING: WHEN THE ENGINE IS OPERATING, DO NOT STAND IN A

DIRECT LINE WITH THE FAN. DO NOT PUT YOUR HANDS NEAR THE

PULLEYS, BELTS, OR FAN. DO NOT WEAR LOOSE CLOTHING.

With the scantool, select DTC's AND RELATED FUNCTIONS. Read and record the

FREEZE FRAME DATA. Select OBD II MONITORS. Read and record MIS-FIRE

SIMILAR CONDITIONS WINDOW DATA.

With these screens, attempt to duplicate the condition that has set the Misfire DTC.

While using FREEZE FRAME DATA, pay particular attention to the DTC setting

conditions, such as speed, temp, load, and map vacuum.

Does the mis-fire reoccur?

All

Yes ! Restart diagnostics beginning with Test 2.

TEST.

No ! Test Complete

please let me know if this helps,tim

TIM and other Dodge Specialists are ready to help you
Customer: replied 8 years ago.
Tim should I perform these tests at idle ?

well, as stated -- some are with just the key on -- the engine mechanical side -- vac etc -- are at idle---electrical connections are engine off key on,tim

if i had to guess- based on what i have seen -- i would pay close attention to the pcm wiring -- and also do a compression test to see if we have internal mechanical issues first,tim

Customer: replied 8 years ago.
Thanks Tim I appreciate the information.
I wont be able to perform these tests until tomorrow when I am at the shop. But hopefully
this will provide a solution. Thanks again.
                                        Rob

goodluck and let me know how you make out,tim