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I have an 07 Altima. About a month and a half ago it overheated and I pulled off of the road to allow it time to cool down to add fluid to it (hole in the radiator, so I was told). So used to this occurance now and then. Allowed it to cool, went to start it, zip. Had a friend come and jump me right fast and made it home just fine, not another issue out of it. Same scenario came up a second time, bout a week ago. Overheated, pulled off the road, waited for it to cool. Fun fun fun. Car didn't want to start. Again. Attempted to get the battery charged up but this time it didn't cut it. Finally got a TEENSY bit of charge to it a few days after having it towed home and it acted as if it wanted to start up, but it just wouldn't turn over. Next morning battery drained. Tried again this morning to see if even the initial lights and gadgets on the inside would come on still so I could have a diagnostics test ran on it to see what codes it may throw only to be answered with a rapid clicking noise. I get that it could be the alternator, or the battery, or the connection and so on. I know the battery itself is weak because it was tested a bit ago, but what would cause it to drain only after overheating? Never an issue out of it any other time other than these two instances. My question is what in the hell could have been the cause of it not starting both times that it overheated? I have brains enough to replace parts but damn sure not the knowledge to figure out what the issue is or what to look for or well, anything.

Let's add in that about two weeks ago I threw codes P2A00 and P0128. After some digging around today I read that overtime an issue with the A/FR sensor can cause cylinders to possibly crack, damage to the pistons, so forth. I don't know. I'm lost but can't exactly afford a mechanic right this moment.
 

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First of all what engine do you have; QR25DE or VQ35DE; and also what transmission.
When your engine overheated the first time, you should have replaced the radiator at that time. Continual overheating will screw up the engine block/head. From the second overheating, there may be a major blown head gasket situation that is preventing engine start up. You need to perform a compression test on all the cylinders to determine the condition of the engine.

If you're unable to start the engine, then at this point you'll have to determine if there's an ignition or fuel delivery problem:

* Testing fuel delivery:
An easy way to test the fuel pump and filter is to disconnect the fuel feed hose from the fuel rail and connect it to a long length of spare hose with the other end draped over the fender going into a catch can placed on the ground. Now turn the ignition key to the run position but DO NOT START THE ENGINE. You should see fuel going into the can at a good rate for several seconds.

Tee-in a temporary fuel pressure gauge between the fuel feed hose and the fuel rail. If the engine is unable to start, turn the ignition key to the run position but DO NOT TRY TO START THE ENGINE. The fuel pressure reading should be around 51 psi which would be a static reading.

The fuel injectors may not be firing. This can be tested with a "noid" light probe for each injector harness connector.

* Testing ignition:
Pull several coil packs to test; use a spare spark plug in the coil pack to test; ground the plug base with a jumper wire to the engine block; see if you're getting a spark while trying to start the engine.

* The cam timing may be incorrect:
Check for a broken chain guide. See if it's broken or it may be cracked and has skipped some teeth.
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The P0128 fault code is a result of a thermostat malfunction. The engine coolant temperature has not risen enough to open the thermostat even though the engine has run long enough. This is due to a leak in the seal or the thermostat stuck open. It's possible the overheating may have caused the thermostat to fail.

The P2A00 fault code is a result of a problem with the Air Fuel Ratio (A/F) sensor 1. Possible causes:

• Bad A/F sensor 1
• Bad A/F sensor 1 heater
• Incorrect fuel pressure
• Bad fuel injector(s)
• Intake system vacuum leaks
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If the battery has a problem keeping a charge:
A properly working charging system puts out about 13.2 to 15.0 volts, but this is a general spec, and the factory service manual should be referenced for the correct charging system voltage specifications for a particular vehicle. A battery should have a static charge of 12.2-12.6 volts. If a battery is not good, the charging system may not be able to charge properly. If a vehicle is not charging properly and the battery is good, the first thing to do is to turn the ignition switch to the "ON" position without starting the engine and make sure the charging system warning light is operating. If the bulb is burnt out, the charging system will not charge. If the bulb is OK but still does not illuminate, the circuit must be tested. If the warning lamp does illuminate, then the next thing to check is to make sure the circuit between the battery positive post, or fusible link, to the connection in back of the alternator is good. On Nissans, this will be a thick (approx. 10 gauge) white wire to the "BAT" post on the back of the alternator. It's not uncommon for this wire to get corroded and burn up, creating resistance in the circuit. So, before assuming an alternator is bad, make sure this circuit is good and battery voltage is getting to the alternator. It's also important to make sure the alternator belt is tight and not slipping and the battery connections are clean and tight.

Assuming the charging system voltage is ok and the battery is good, the next thing to do would be to have a parasitic draw test performed; there should not be more than a 50 milliamp draw on the system with the ignition switch in the "OFF" position. If there is a higher draw, you need to do some testing to find out where the draw is coming from. Remove fuses one at a time until the draw goes away or falls into acceptable range.

The later-model cars have adopted what Nissan calls “power generation voltage variable controls.” This system monitors battery current and varies voltage to the regulator, reducing the load on the engine and resulting in better gas mileage. By varying the voltage to the alternator, engine load due to power generation of the alternator is reduced and fuel consumption is decreased. The battery current sensor is installed on the battery cable at the negative terminal. The battery current sensor detects the charging/discharging current of the battery and sends a voltage signal to the ECM according to the current value detected.

Also, it is NOT a good idea to disconnect a battery cable on a computer controlled vehicle while running to test the alternator. This is a good way to damage an ECM. When a charging system is not charging, or overcharging, a lot of "strange" things can occur. It's not uncommon to see a multiple of stored trouble codes in the ECM memory. So, whenever a car is setting a multiple of trouble codes, idling funny or stalling, or anything out of the "norm," test the charging system before you start pulling hairs!

When replacing electrical components such as alternators, starters and distributors, fuel injectors and sensors, always replace with new or reman'd Nissan OEM components; aftermarket components generally don't last long, don't work right and many times are DOA.
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I think I've given you enough diagnostic info to get you started on the road to permanent fix. Good luck. Let us know how you make out.
 
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