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V6 3.4L THERE ITS NO MISSFIRE BUT KEEPS SETING PO301 FUEL…

Customer Question
V6 3.4L THERE ITS...

V6 3.4L THERE ITS NO MISSFIRE BUT KEEPS SETING PO301 FUEL TRIM ITS PERFECT IT HAS NEW PLUGS AND NEW COILS

Mechanic's Assistant: Has the vehicle turned into a gas hog? And how does it start -- same as usual?

YES

Mechanic's Assistant: What is the model/year of your Toyota?

2004 TUNDRA

Mechanic's Assistant: Are you fixing your Tundra yourself? What have you tried so far?

Compression its good and we put new toyota plugs and new coil on #3cil

Submitted: 1 month ago.Category: Toyota
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Answered in 3 minutes by:
3/16/2018
Toyota Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 1 month ago
Chad Farhat
Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: Toyota
Satisfied Customers: 5,208
Experience: Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic vehicles
Verified

Hi, I'm Chad. Welcome to JustAnswer. I'm reviewing your question and I will be posting your reply ASAP.

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Toyota Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 1 month ago

Hey how are you ,I will Try to Help you with This Issue
In some cases, I may need more info to assist better.I apologize for any delay.
I am here Sunday through Friday from around 5 am to 9 pm Eastern time.Zone If you respond and I do not respond back right away I will do so as soon as I can.
If you see a call request on your screen ,That is an automated feature the web site offers all customers.

1- new plugs , new coils good compression all that is good, that leaves injector , or vacuum leak under # 3 or the power and grounds for coils and injector ,pcv , ecm etc we need to check that

CLICK ON LINK TO VIEW THE PDF FILE AND THE TROUBLESHOOT NEEDS DONE TO BE ACCURATE

Troubleshooting

DTC P0301 Cylinder 1 Misfire Detected

CIRCUIT DESCRIPTION

DTC Detection Condition

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Misfire: The ECM uses the crankshaft position sensor and camshaft position sensor to monitor changes in the crankshaft rotation for each cylinder.

The ECM counts the number of times the engine speed change rate indicates that misfire has occurred. And when the misfire rate equals to or exceeds the count of indicating that the engine condition has deteriorated, the MIL lights up.

If the misfire rate is high enough and the driving conditions will cause the catalyst to overheat, the MIL blinks when misfiring occurs.

HINT:
- For any particular 200 revolutions of engine, misfiring is detected, which can cause catalyst to overheat (This cause MIL to blink. 1trip detection logic).
- For any particular 1,000 revolutions of engine, misfiring is detected, which causes deterioration in emissions (This cause MIL to light up. 2trip detection logic).
- When codes for a misfiring cylinder are recorded repeatedly but no random misfire code is recorded, it indicates that the misfires have been detected and recorded at different times.

MONITOR DESCRIPTION

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Monitor Strategy

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Typical Enabling Conditions

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Typical Malfunction Thresholds

The ECM illuminates the MIL (2 trip detection logic) if:
- The misfiring rate exceeds a threshold value and could cause emissions deterioration.
- During the first 1,000 engine revolutions after the engine starts, an excessive misfire rate (approximately 20 to 50 misfire per 1,000 engine revolutions) occurs 1 time.
- After the first 1,000 engine revolutions after the engine starts, an excessive misfire rate (approximately 20 to 50 misfire per 1,000 engine revolutions) occurs 4 times.

The ECM blinks the MIL (MIL blinks immediately) if:
- Within 200 engine revolutions at a high rpm, the threshold for "percent of misfire causing catalyst damage" is reached 1 time.
- Within 200 engine revolutions at a normal rpm, the threshold for "percent of misfire causing catalyst damage" is reached 3 time.

Wiring Diagram

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CONFIRMATION DRIVING PATTERN

a. Connect the hand-held tester or the OBD II scan tool to the DLC3.
b. Record DTC and the freeze frame data.
c. Use the hand-held tester to set to the Check Mode.
d. Read the value on the misfire counter for each cylinder when idling. If the value is displayed on the misfire counter, skip the following procedure of confirmation driving.
e. Drive the vehicle several times with the engine speed, load and its surrounding range shown with ENGINE SPD, CALC LOAD in the freeze frame data or MISFIRE RPM, MISFIRE LOAD in the data list.

If you have no hand-held tester, turn the ignition switch OFF after the symptom is simulated the first time.

Then repeat the simulation process again.

HINT: In order to memorize the DTC of misfire, it is necessary to drive around MISFIRE RPM, MISFIRE LOAD for the following period of time in the data list. Take care not to turn the ignition switch OFF. Turning the ignition switch OFF switches the diagnosis system from check (test) mode to normal mode. So all DTCs, etc., are erased.

f. Check whether there is misfire or not by monitoring DTC and the freeze frame data. After that, record them.
g. Turn the ignition switch OFF and wait at least 5 seconds.

Step 1 - 3

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Step 4

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Step 5

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Step 6 - 8

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Step 9 - 10

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Step 11 - 15

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Step 16 - 19

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Step 20 - 21

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INSPECTION PROCEDURE

HINT:
- If DTCs besides misfire are memorized simultaneously, first perform the troubleshooting for them.
- Read freeze frame data using the hand-held tester or the OBD II scan tool. Freeze frame data records the engine conditions when a malfunction is detected. When troubleshooting, freeze frame data can help determine if the vehicle was running or stopped, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
- When the vehicle is brought to the workshop and the misfire is not occurred, misfire can be confirmed by reproducing the condition of the freeze frame data. Also, after finishing the repair, confirm that there is no misfire (See the confirmation driving pattern).
- On 6 and 8 cylinder engines, misfiring cylinder identification is disabled at high engine speed and only an general misfire fault code P0300 is stored instead of a cylinder specific misfire fault code (i. e., P0301-P0308). Under the following conditions, only P0300 code may be stored. Misfire starts in the high engine speed area or Misfire occurs only in the high engine speed area. Therefore, when a general misfire fault code (i.e., P0300) is only stored, erase the DTCs after read freeze frame data with the hand-held tester or the OBD II scan tool. Start the engine and drive the confirmation pattern (See the CONFIRMATION DRIVING PATTERN) and read the value of the misfire ratio for each cylinder (or DTC). Perform the repair correspond to the high misfire ratio cylinder (or the misfiring cylinder indicated by DTC). After completing the repair, confirm no misfire is occurring by driving the confirmation pattern.
- When either of SHORT FT #1, LONG FT #1, SHORT FT #2 or LONG FT #2 in the freeze frame data is besides the range of ±20 %, there is a possibility that the air-fuel ratio is inclining either to RICH (-20 % or less) or LEAN (+20 % or more).
- When COOLANT TEMP in the freeze frame data is less than 80°C (176°F), there is a possibility or misfire only during warming up.
- If the misfire cannot be reproduced, the reason may be because of the driving with lack or fuel, the use of improper fuel, a stain on ignition plug, etc.
- Be sure to check the value on the misfire counter after the repair.

CHECK FOR INTERMITTENT PROBLEMS

HINT:
Hand-held tester only:
By putting the vehicle's ECM in check mode, 1 trip detection logic is possible instead of 2 trip detection logic and sensitivity to detect open circuits is increased. This makes it easier to detect intermittent problems.

a. Clear the DTCs.
b. Set the check mode.
c. Perform a simulation test.
d. Check the connector and terminal.
e. Handle the connector.

Are you looking for the most possible causes or you are repairing it yourself .

Please Let Me Know

Thank You

Chad Farhat

ASE Certified Technician

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Toyota Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 1 month ago

Most possible causes for it

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Toyota Mechanic: Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems replied 1 month ago

With that said , my experience, first 2 reasons will be 1- the injector is not pulsing(ecm) issue or injector needs replaced ,2nd most common, intake gasket leak under # 3, so needs intake gasket but testing is needed here

If more help is needed, use the reply tab to continue our conversation.

If no further assistance is needed, kindly rate my service, your 5-star rating is appreciated ( should be a link to click on here or above).

You can rate at any time and we can continue to work on your question as this will not close out your question.

I work on delivering the best answer and help here but in some cases,

It can be difficult to do without seeing the vehicle.

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Chad Farhat
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Chad Farhat, ASE Certified Technician A6 - Electrical / Electronic systems A7 Heating / Air conditioning systems
Category: Toyota
Satisfied Customers: 5,208
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Experience: Owner at Carolina Auto Service & Sales , 20 years Experience in Foreign & Domestic vehicles

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