Multiple cylinder misfire failure in my 99 V6 Camry. Coilpacks, injectors, fuel pump, filter, compression, all electrical tests look good. Failure is always 2, 4 and 6 cylinder misfire. Cylinder 1, 3, or 5 never misfire. Coilpacks already replaced. One additional info (not sure if it is related to the problem on hand): Fuel pump does not turn on with Ignition switch in ON position, but in START position car runs fine except for the misfire issue. Fuel pump is fine, relays are fine. Short of replacing the ECU, what could I do to fix this problem? David

Diagnostic Trouble Code (DTC) P0303 is a cylinder-specific misfire code indicative of a cylinder-specific problem. In other words, all potential component failures that are not specific to cylinder #3 can be ruled out. For the fuel system this would include the fuel pump, fuel filter, fuel pressure regulator and fuel itself. For the ignition system (which is a distributor-type on this vehicle), this would include the ignition coil, coil wire and rotor. Finally for the mechanical system this would include the crankshaft, camshaft and timing belt. With these things in mind, consider which components are cylinder-specific. For the fuel system the only item is the fuel injector which could be inoperative electrically (no command from the powertrain control module (PCM) or open control circuit) or mechanically (internally stuck closed despite being commanded to open). For the ignition system there's the pole in the distributor cap, ignition wire and spark plug. Mechanically, there could be low compression caused by piston rings, intake valve or exhaust valve or the cylinder could be contaminated with coolant from a failed head gasket. You can read more here: https://www.yourmechanic.com/article/p0303-obd-ii-trouble-code-cylinder-3-misfire-detected-by-spencer-clayton_2

Common for injector sub harness to fail. If you have an injector code p0201-p0206 this may be the cause.

code p0300 refers to random/multiple misfires--misfire detected===causes--spark plug/sHT leads--injectors--ignition coil/s---low compression---wiring
code p0171 refers to system too lean, bvank 1===causes--intake/exhaust leak--AIR system--fuel pressure/pump---MAF/VAF sensors---injectors---HO2S sensor
The common thread is fuel so have a pressure test done on the fuel system to check for pump and / or faulty pressure regulator, then progress to injectors.

code p0101 refers to MAF sensor and VAF sensor--range /performance problems===causes --intake leakage/blockage ---MAF/VAF sensor failure.

code p0300 refers to random misfires multiple cylinders ---causes --spark plugs /HT leads --injector /s-- ignition coil/ s--low compression ---wiring

check fuel pressure in manifold and HT leads

code p0171 refers to system too lean bank 1 ===causes --intake /exhaust air leak---AIR system---MAF/VAF sensors ---fuel pressure /pump---injectors ---HO2S sensor

Basically there are two codes referring to the MAF/VAF sensors so check them out and two codes referring to fuel pressure and pump so have a pressure test done on the fuel manifold to determine if pump or pressure regulator.

You are misfiring. If you have Autozone (or similar) research your check engine light, they will come up with one or more of the following codes P0300, P0301, P0302, P0303, P0304 etc. etc.P0308. The P0300 code refers to "Random/Multiple misfires" whereas the other codes refer to that particular cylinder (last digit) misfire. The P0300 code sets when 2 or more cylinders misfire (can be the same 2 over and over, but it takes at least 2 cylinders to misifre to set that code. The others only take one misfire to set the code. Now that you know what is happening, here is how to fix....
Takes all to fire a cylinder (Fuel, Spark, Air & Timing) properly. If you have random or multiple misfires, it is likely something that is COMMON to all cylinders - like the air intake/throttle body area - throttle body can get carbon buildup and not open/close properly. Check the fuel pressure to the fuel rail(s), fuel filter clogged? When you turn your key to the "ON" position, do you hear the fuel pump turn on (whine) and then shut off? No whine, means no fuel pump. Check all fuses and fuse relays related to the fuel delivery system. Check the distributor cap/rotor for any signs of carbon tracking/arcing. Do you have good spark from coil? Check wiring for the Camshaft Position Sensor/Crankshaft position Sensor for timing issues. Finally, check compression on all cylinders. Need good compression for combustion to take place.

For a single cylinder (example Cylinder #2) - Easiest to check is spark. Pull the plug and look at it. Is it wet and smell like fuel? If so, then swap it with cylinder next to it. If the problem moved, then its the plug. If the misfire is still on Cylinder #2, then swap the plug wire (both ends). If the misfire is still on Cylinder #2, then swap the coil. (see where this is going?) If the plug is dry, then check the fuel injector for operation. Noid light tester or you can get a long screwdriver and stick one end on your ear and the other on the injector - it should make a steady, rhythmic clicking sound if it is functional when car is running. No sound? Replace. Is the plug oily? Check cylinder #2 for compression. No compression or little compression means either head gasket blown or bad/sticking valve (intake or exhaust) = big money to get fixed. Timing on one cylinder is hard to test without correct test tools. Timing is likely not a problem on a single cylinder misfire. Good luck.

code p0300 refers to random/multiple cylinder/s--misfire detected===causes--spark plug/s--HT lead/s---injector/s--ignition coil/s---low compression---wiring. Most of your mates will tell you to replace the plugs and leads and that may fix it but injectors are a major fault in misfires. So have a pressure test done on the fuel manifold first and check the fuel pump/pressure regulator/filter. If the pump is not producing fuel or the regulator is set too low then the injectors will not deliver the fuel at the correct amount at the right time (misfire- random cylinder). Plugs and leads will cause a constant misfire not every wherever cylinder.

I would take it back and demand a refund. Could be the crank or cam sensors, an intake leak, faulty coil, or a list of other components.

p1111 System Pass (No DTCs Available)
P0107 BARO Circuit Low Input
P0l08 BARO Circuit High Input
P0112 IAT Sensor Circuit Low Input
P0113 IAT Sensor Circuit High Input
P0122 Accelerator Pedal Sensor Circuit Low Input
P0123 Accelerator Pedal Sensor Circuit High Input
P0197 EOT Sensor Circuit Low Input
P0198 EOT Sensor Circuit High Input
P0220 Throttle Switch B Circuit Malfunction
P0221 Throttle Switch B Circuit Performance
P0230 Fuel Pump Relay Driver Fail
P0231 Fuel Pump Relay Driver Circuit Failure
P0232 Fuel Pump Relay Driver Failed Off
P0236 Turbo Boost Sensor A Circuit Performance
P0237 Turbo Boost Sensor A Circuit Low Input
P0238 Turbo Boost Sensor A Circuit High Input
P0261 Injector Circuit Low - Cylinder 1
P0262 Injector Circuit High - Cylinder 1
P0263 Cylinder 1 Contribution/Balance Fault
P0264 Injector Circuit Low - Cylinder 2
P0265 Injector Circuit High - Cylinder 2
P0266 Cylinder 2 Contribution/Balance Fault
P0267 Injector Circuit Low - Cylinder 3
P0268 Injector Circuit High - Cylinder 3
P0269 Cylinder 3 Contribution/Balance Fault
P0270 Injector Circuit Low - Cylinder 4
P0271 Injector Circuit High - Cylinder 4
P0272 Cylinder 4 Contribution/Balance Fault
P0273 Injector Circuit Low - Cylinder 5
P0274 Injector Circuit High - Cylinder 5
P0275 Cylinder 5 Contribution/Balance Fault
P0276 Injector Circuit Low - Cylinder 6
P0277 Injector Circuit High - Cylinder 6
P0278 Cylinder 6 Contribution/Balance Fault
PO279 Injector Circuit Low - Cylinder 7
P0280 Injector Circuit High - Cylinder 7
P0281 Cylinder 7 Contribution/Balance Fault
P0282 Injector Circuit Low - Cylinder 8
P0283 Injector Circuit High - Cylinder 8
P0284 Cylinder 8 Contribution/Balance Fault
P0301 Fault Cylinder A-Misfire Detected (CYL 1)
P0302 Fault Cylinder B-Misfire Detected (CYL2)
P0303 Fault Cylinder D-Nlisfire Detected (CYL 3)
P0304 Fault Cylinder E-Misfire Detected (CYL 4)
P0305 Fault Cylinder F-Misfire Detected (CYL5)
P0306 Fault Cylinder G-Nlisfire Detected (CYL 6)
P0307 Fault Cylinder C-Misfire Detected (CYL 7)
P0308 Fault Cylinder H-Misfire Detected (CYL 8)
P0340 CMP Sensor Circuit Malfunction
P0341 CMP Sensor Circuit Performance
P0344 CMP Sensor Circuit Intermittent
P0360 Glow Plug Circuit Malfunction
P0381 Glow Plug Indicator Circuit Malfunction
P0460 Fuel Tank Level Indicator Circuit Malfunction
P0470 Exhaust Back Pressure Sensor Circuit Malfunction
P0471 Exhaust Back Pressure Sensor Circuit Performance
P0472 Exhaust Back Pressure Sensor Circuit Low Input
P0473 Exhaust Back Pressure Sensor Circuit High Input
P0476 Exhaust Pressure Control Valve Maffunction
P0476 Exhaust Pressure Control Valve Performance
P0478 Exhaust Pressure Control Valve High Input
P0500 Vehicle Speed Sensor (VSS) Malfunction
P0503 Vehicle Speed Sensor Noisy
PO541 Manifold Intake Air Heater
P0542 Manifold Intake Air Heater
P0560 System Voltage Malfunction
P0662 System Voltage Low
P0563 System Voltage High
P0666 Cruise 'On" Signal Malfunction
P0566 Cruise "Off' Signal Malfunction
P0667 Cruise 'Resume' Signal Malfunction
P0668 Cruise "Set' Signal Malfunction
P0669 Cruise "Coast' Signal Malfunction
P0571 Brake Svdtch A Circuit Malfunction
P0603 Internal Control Module KAM Error
P0605 Internal Control Module ROM Error
PO606 PCM Processor Fault
P0640 Manifold Intake Air Heater
P0670 Glow plug control circuit malfunction
P0671 Glow plug #1 circuit failure
P0672 Glow plug #2 circuit failure
P0673 Glow plug #3 circuit failure
P0674 Glow plug #4 circuit failure
P0675 Glow plug #5 circuit failure
P0676 Glow plug #6 circuit failure
P0677 Glow plug #7 circuit failure
P0678 Glow plug #8 circuit failure
P0683 Glow plug diagnostic signal communication fault
P0703 Brake Switch B Circuit Malfunction
P0704 Clutch Pedal Position Switch Input Circuit Malfunction
P0705 TR Sensor Circuit Malfunction
P0707 TR Sensor Circuit Low Input
P0708 TR Sensor Circuit High Input
P0712 Transmission Fluid Temp. Sensor CKT Low Input
P0713 Transmission Fluid Temp. Sensor CKT High Input
P0715 TSS Sensor Circuit Malfunction Fault
P0717 TSS Intermittent Failure
P0718 Noisy TSS
P0720 OSS Sensor Circuit Malfunction
P0721 Noisy OSS
P0722 OSS Intermittent Failure
P0732 Gear Two Ratio Error
P0733 Gear Three Ratio Error
P0741 TCC Circuit Performance
P0743 Torque Converter Clutch System Electrical Failure
P0750 Shift Solenoid 1 Malfunction
P0755 Shift Solenoid B Malfunction
P0781 1-2 Shift Malfunction
P0782 2-3 Shift Malfunction
P0783 3-4 Shift Malfunction
P0800 Logon to http://web.archive.org/web/200701120...utoadvice.com/ A.S.A.P
P1000 OBD 11 Monitor Checks Not Complete. More Driving Required
P1105 Dual Alternator Upper Fault (Monitor)
P1106 Dual Afternator Lower Fault (Control)
P1107 Dual Alternator Lower Circuit Malfunction (Control)
P1108 Dual Alternator BATT Lamp Circuit Malfunction
P1118 Manifold Air Temperature Sensor Low Input
P1119 Manifold Air Temperature Sensor High Input
P1139 Water in Fuel Indicator Circuit Malfunction
P1140 Water in Fuel Condition
P1184 Engine Oil Tamp Sensor Circuit Performance
P1209 Injection Control System Pressure Peak Fault
P1210 Injection Control Pressure Above Expected Level
P1211 ICP Not Controllable - Pressure Abow/Below Desired
P1212 ICP Voltage Not at Expected Level
P1218 CID Stuck High
P1219 CID Stuck Low
P1247 Turbo Boost Pressure Low
P1248 Turbo Boost Pressure Not Detected
P1249 Wastagate Fail Steady State Test
P1250 Electronic Passive Anti-Theft System
P1261 High to Low Side Short - Cylinder 1
P1262 High to Low Side Short - Cylinder 2
P1263 High to Low Side Short - Cylinder 3
P1264 High to Low Side Short - Cylinder 4
P1265 High to Low Side Short - Cylinder 5
P1266 High to Low Side Short - Cylinder 6
P1267 High to Low Side Short - Cylinder 7
P1268 High to Low Side Short - Cylinder 8
P1271 High to Low Side Open - Cylinder 1
P1272 High to Low Side Open - Cylinder 2
P1273 High to Low Side Open - Cylinder 3
P1274 High to Low Side Open - Cylinder 4
P1275 High to Low Side Open - Cylinder 5
P1276 High to Low Side Open - Cylinder 6
P1277 High to Low Side Open - Cylinder 7
P1278 High to Low Side Open - Cylinder 8
P1280 ICP Circuit Out of Range Low
P1281 ICP Circuit Out of Range High
P1282 Excessive ICP
P1263 IPR Circuit Failure
P1284 ICP Failure - Aborts KOER or CCT Test
P1291 High Side No. 1 (Right) Short to GND or B
P1292 High Side No. 2 (Left) Short to GND or B
P1293 High Side Open Bank No. 1 (Right)
P1294 High Side Open Bank No. 2 (Left)
P1295 Multiple Faults on Bank No. 1 (Right)
P1296 Multiple Faults on Bank No. 2 (Left)
P1297 High Sides Shorted Together
P1298 IDM Failure
P1316 Injector Circuit/IDM Codes Detected
P1391 Glow Plug Circuit Low Input Bank No. 1(Right)
P1393 Glow Plug Circuit Low Input Bank No. 2 (Left)
P1395 Glow Plug Monitor Fault Bank No. 1
P1396 Glow Plug Monitor Fault Bank No. 2
P1397 SYstem Voltage Out of Self Test Range
P1464 A/C On During KOER or CCT Test
P1501 VSS Out Of Self Test Range
P1502 Invalid Self Test - APCM Functioning
P1531 Invalid Test -Accelerator Pedal Movement
P1536 Parking Brake Applied Failure
P1662 IDM EN Circuit Failure
P1663 FDCS Circuit Failure
P1667 CID Circuit Failure
P1668 PCM -IDM Diagnostic Communication Error
P1670 EF Feedback Signal Not Detected
P1690 Wastegate Control Valve Malfunction
P1702 TRS Sensor Intermittent Circuit Malfunction
P1704 Digital TRS Failed to Transition State
P1705 TR Sensor out of Self Test Range
P1711 TFT Sensor Out of Self Test Range
P1713 TFT Stuck in Range Low-Below 50'F
P1714 Shilt Solenoid A Inductive Signature Malfunction
P1715 Shift Solenoid B Inductive Signature Malfunction
P1718 TFT Stuck in Range High-Above 25OF
P1728 Transmission Slip Error
P1729 4x4L Switch Error
P1744 Torque Converter Clutch System Performance
P1746 EPC Solenoid Open Circuit
P1747 EPC Solenoid Short Circuit
P1754 CCS (Solenoid) Circuit Malfunction
P1760 EPC Solenoid Short Intermittent
P1780 TCS Circuit Out of self Test Range
P1781 4x4L Circuit Out of Self Test Range
P1783 Transmission Overtemperature Condition
No Code No Communication
No Code Auxiliary Powertrain Control System
No Code Tachometer

check fuel injectors, fuel pressure regulator, air filter. cat converter, O2 sensor. failure of any of these wastes fuel. air/fuel ratio should be normal.

look for weak valve springs.