99 camaro 3.8l engine code p0300
recently i bought a 1999 camaro 3.8L. it started but rough idle and found out milky motor oil. so, i removed the engien and disassembled it. i found out two problems, one was lower intake manifold gaskets were bad that's why water went into the crankcase. another one was water went into number 6 and 3 cylinders which might be caursed by bad head gaskets. besides these, all other engine conponnents were still in good condition. so, i put everything back with new bearings, gaskets, and seals, and make sure i was doing right, torque every bolts in specs. now, i start the engine, and the engine runs quiet but still has little rough idle. the engine light came on steady with p0300 random misfire. i had it test drive and feel ok when accelerated. just little rough idle and idle speed stay in 650 RPM. there are new plugs and wires. the coils and ignition module has been tested in good. all injector resistance are in 12 ohms which is good. the fuel pressure is 40 psi(should be ok), i checked no vaccum leaks for sure, EGR valve ok.
i have driven the car over 50 miles, there is no additional engine code, just P0300. That's all i know about this car. what else could causes the problem, Bad MAF sensor or Camshaft sensor...? i have no idea and don't want to spend too much money to test. anyone knows what's going on my car, i need your helps thank you |
did you have the heads machined?
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Random misfire means just that. Either an ignition problem or a lean condition. A bad MAF could cause a lean condition. You can run with the MAF disconnected. It will set a MAF code, wich you can temporarily disregard, and force the PCM to run open loop. If engine now runs better, it indicates that one of the sensors is bad, and not necessarily the MAF. Sensors age and the output drifts. The PCM has no way to know that, so check the sesnor outputs with a scanner and see if they make sense,
This is from Alldata: DIAGNOSTIC AIDS The scan tool provides information that can be useful in identifying the misfiring cylinder. If the DTC P0300 is currently stored as DTC status Failed Since Code Clear, the misfire history counters (Misfire Hist # 1-# 6) will still contain a value that represents the level of misfire detected on each cylinder. A misfire DTC may set if components that affect the crankshaft position (CKP) sensor have recently been replaced, and the CKP system variation learn procedure has not been performed. If the diagnostic table does not identify a condition, perform the CKP System Variation Learn Procedure. The crankshaft position system variation learn procedure should be performed if any of the following conditions are true:
IMPORTANT: If the level of misfire was sufficient to cause possible catalyst damage, and if the MIL was flashing, ensure that the DTC P0420 test is completed and passed after verifying the misfire repair. If the misfire is random, check for the following conditions:
CKP System Variation Learn Procedure The crankshaft position (CKP) system variation compensating values are stored in the PCM non-volatile memory after a learn procedure has been performed. If the actual crankshaft position system variation is not within the crankshaft position system variation compensating values stored in the PCM, DTC P0300 may set, refer to Diagnostic Aids for DTC P0300. The crankshaft position (CKP) system variation learn procedure should be performed if any of the following conditions are true:
The crankshaft position system variation learn function will be inhibited if the PCM detects a malfunction involving the camshaft position signal circuit, the 3X reference circuit, or the 18X reference circuit.
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99 camaro 3.8l code p0300
i found out why my car has P0300 random misfire bacause the four cylinder compression are kind of low. #1- 98psi, #2-200psi, #3- 125psi, .#4-100psi, #5-175psi, #6- 120psi. and also did the wet test and got almost same compression as dry test, which means the piston rings are good. maybe the problem is about the valve train parts. but i not sure which are bad. i am for sure the valves, rocker arms, push rods, and springs were good condition. only things i am not sure are the lifters. the bad lifters will cause the low compression with no ticking noise. i know the bad lifters will make kind of noise when engines run. how can i check the lifters are good or not?
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Just a pssibility, the valves could be mal-adjusted and not closing fully, or a head gasket could be blown. Adjacent cylinders 1&3, and 4&6 have low compression, which indicates the possibility that the gaskets between those cylinders may be blown.
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Originally Posted by automotive_solutions
(Post 441267)
did you have the heads machined?
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heads are the problem
i sent the heads to the machine shop to check, and they found out the four intake valve seats were bad that cuased losing pressure. i think that's the problem.
thank you all |
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