Misfire with no CEL
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Misfire with no CEL
I have a 1998 F150 4.6 that has a misfire with no CEL. I have already tried the following: checked fuel pressure, change cam shaft sensors, changed coil, checked MAf seems ok, spark plugs and wires. On my scan tool it wont show any misfires when obviously its misfiring. When driving it will run good for about 10 seconds and then misses for about 10 seconds and it just keep going in this loop. Any suggestions?
Hotshot
Joined: Jan 2004
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From: St Louis
Pretty common mild misfire issue.
You have to go into Mode $06, TID $51 or $53, and look at the individual cylinder misfire counts whenever the fault is not severe enough to set a DTC and light the MIL.
You have to go into Mode $06, TID $51 or $53, and look at the individual cylinder misfire counts whenever the fault is not severe enough to set a DTC and light the MIL.
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misfires
I did go into the individual cylinders and look for misfire and it don't show any. On cylinder 7 I got it to show 16 misfires and then it went to zero instantly then it went to cylinder 8 and done the same thing. every now and then it will count to 16 but never past that number. it is definitely misfiring but I can not get scan tool to log anything. any other suggestions would be greatly appreciated.
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misfire and trans code now
Also since I have got a code for Trans temp hot and solenoid. This code come as soon as I started the truck cold so trans temperature would not be hot at this point. Has anyone experienced this before. I was wondering if it could be a wiring or splice problem that power them or corroded bulkhead connector in the battery harness?
Lead Driver
Joined: Sep 2006
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Iceman I don't know how to say is any gentler but your not using the Scan tool to max advantage, not understanding what you see and doing to much guessing and parts replacement to no avail.
Not giving codes you see for the transmission then asking for help.
Your statement of obvious misfire is just a guess again with no code and verification with the scanner.
The cylinder monitors don't just reset that fast unless power is being lost or a clear is done.
They are monitors on an ongoing basis not a hit and clear or they cannot act as monitors to store the counts to have any diagnostic value.
This is a HINT. No power no codes either under certain conditions.
Check out the ECM relay, seating and fuse seating.
Be sure the crank sensor plug is seated.
If your Scanner has a trap feature try it after you check these other possibilities.
Good luck.
Not giving codes you see for the transmission then asking for help.
Your statement of obvious misfire is just a guess again with no code and verification with the scanner.
The cylinder monitors don't just reset that fast unless power is being lost or a clear is done.
They are monitors on an ongoing basis not a hit and clear or they cannot act as monitors to store the counts to have any diagnostic value.
This is a HINT. No power no codes either under certain conditions.
Check out the ECM relay, seating and fuse seating.
Be sure the crank sensor plug is seated.
If your Scanner has a trap feature try it after you check these other possibilities.
Good luck.
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misfire and code
Sorry for the lack of information. The codes are P1746, P1747 and these codes are hard faults. They return immediately after erased. P0713 returned after erased but took a little bit. P0712 has not returned. Just noted P0742 new to the mix. Observed abnormal readings related to the P0713 code. Voltage is toggling between open and shorted.
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Hotshot
Joined: Jan 2004
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From: St Louis
Did you notice those are all transmission-related codes?
Did the 98's programming put the PCM into a limited operating strategy that might mimic a misfire in the event of certain faults in the transmission? You'd likely need to check with Mark K on that one and see if he knows.
In any event, suggest you perform a careful visual examination of the wiring harnesses anywhere in the vicinity of the exhaust system, the front drivetrain (if 4X4), and then disconnect and inspect the connector on the transmission itself looking for transmission fluid or other problems in the connector.
The presence of contradictory fault codes for the TFT and TCC solenoid suggests the engine isn't the problem.
Did the 98's programming put the PCM into a limited operating strategy that might mimic a misfire in the event of certain faults in the transmission? You'd likely need to check with Mark K on that one and see if he knows.
In any event, suggest you perform a careful visual examination of the wiring harnesses anywhere in the vicinity of the exhaust system, the front drivetrain (if 4X4), and then disconnect and inspect the connector on the transmission itself looking for transmission fluid or other problems in the connector.
The presence of contradictory fault codes for the TFT and TCC solenoid suggests the engine isn't the problem.
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Lead Driver
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Absolutely agree with project.
If you list the codes then look at the description's you can plainly see it is a harness issue.
Burns, cuts etc that is causing shorts and grounds.
The EPC, Torque converter solenoid and temp sensor are all involved and appear in the same harness bundle.
Get under the truck and check it the full length from the right rear of the motor to the transmission plugup.
Leave the motor alone.
Se how much accurate info is worth?
Good luck.
If you list the codes then look at the description's you can plainly see it is a harness issue.
Burns, cuts etc that is causing shorts and grounds.
The EPC, Torque converter solenoid and temp sensor are all involved and appear in the same harness bundle.
Get under the truck and check it the full length from the right rear of the motor to the transmission plugup.
Leave the motor alone.
Se how much accurate info is worth?
Good luck.
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