# Please Help!



## Spbynack (Dec 23, 2016)

2005 Nissan Altima 2.5s stalled out on thanksgiving night. After it stalled I tried to start it a few time and it would start but idle rough for about 5 seconds then stall again. I have replaced the fuel pump, replaced the coil packs, spark plugs ran a compression test and it all boils down to my 3rd cylinder not firing! Power is running to the 3rd cylinder coil pack and injector there is a new injector that was just installed. Compression test on the 3rd cylinder reads at about 125! Any suggestions?


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## rogoman (Dec 16, 2004)

One of the first things to do is perform an ECU code readout with a portable scan tool to see if any fault codes are set. The tool can be purchased at most auto parts stores. Post the actual codes here on the forum so that we may be able to help you further. If there is one or more fault codes set, they can help point to the malfunction. If you have a copy of the FSM for your vehicle, the code readout procedure is described there along with a listing of codes. You can download a copy of the FSM sections from the Nico Club web site; here's the URL: http://www.********.com/FSM/ (replace the asterisks with "nico club" spelled as one word). The section EC.PDF is the one you need to read.

At this point you'll have to determine if there's an ignition or fuel delivery problem:

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

Pull the coil pack 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 when starting the engine.


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## Spbynack (Dec 23, 2016)

Yes sorry we did run the codes and it came up p0300 for random misfire we found out that the 3rd cylinder was not firing at all.we ran tests on the power running to the coil packs and the fuel injector and found they are both getting power we then replaced the fuel injector in the 3rd cylinder and that didn't change anything we looked at the spark plugs and pulled out each one and found that when we pulled out the 3rd plug and coil the engine didn't change we ran a single cylinder compression test and found that the 3rd cylinder is running at about 125


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## rogoman (Dec 16, 2004)

Just because you're getting a constant 12 volts to the coil pac and the fuel injector doesn't mean that they are operating correctly. You haven't gone far enough with your diagnosis. Like my post suggests, the fuel injector may not be firing (not getting pulsed by the CPU). This can be tested with a "noid" light probe for the injector harness connector. To see if there's an ignition failure, pull the coil pack 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 when starting the engine.

The compression in #3 cylinder is low. Standard - 185 psi, Minimum - 142 psi


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## Spbynack (Dec 23, 2016)

The coil pack is firing! The coil pack was removed and tested and there was a spark coming from it


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## rogoman (Dec 16, 2004)

Well, the ignition appears to be OK. Now on to the injector. You'll need to obtain a NOID light to see if the injector is firing; using a volt meter is not going to cut it.


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## Spbynack (Dec 23, 2016)

We hooked a noid light probe up to the fuel injector and it is working we also checked the spark plug and it's wet


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## rogoman (Dec 16, 2004)

Well it's got to be one of two things; either the ignition is not firing or the fuel injector has a massive fuel leak. Try swapping the #3 coil pac with another coil pac and see if the problem moves to the other cylinder. Did you buy a rebuilt fuel injector or a brand new one; Most auto parts stores sell both types. Rebuilt injectors generally are much cheaper but many of them are CRAP. I've seen many rebuilt injectors DOA upon installation so I never use rebuilt ones.


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## smj999smj (Jan 1, 2006)

If the engine got flooded and washed down the cylinder walls, low compression would cause the plugs to foul and prevent starting, as well. A fuel pressure leakdown test would confirm leaking fuel injector(s). I would also disable the fuel system, add a little oil to #3 cylinder and see if the compression builds up to specs. A lot of these early QR25DE engines had issues with the front catalytic converter breaking down and bits of substrate getting sucked into the combustion chamber due to the EGR system which uses the variable camshaft timing rather than a conventional EGR valve. When the substrate scores up the cylinder walls, it creates a low compression engine which can only be fixed by rebuilding or replacing the engine.


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## Spbynack (Dec 23, 2016)

We have swapped out pack to see if that changed anything and it didn't switch cylinders. So far I've been told the valve could be stuck I've been told the camshaft is bad, and that the seals are bad.... and I've been told to get a new motor for it


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## smj999smj (Jan 1, 2006)

There are ways to find out. A cylinder leakdown test will tell you where the compression is going. If a valve is stuck open, the air will go out the intake if it's and intake valve and out the exhaust if it's and exhaust valve. It will go out through the coolant system as air bubbles if the head gasket is blown or if there is a crack in the block between the coolant jacket and combustion chamber. If it is pushing past the rings, the air will come out of the crankcase through the hole for the oil cap in the valve cover. I would still start by doing a wet compression test to #3 cylinder to see if the compression builds up to spec.


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## Spbynack (Dec 23, 2016)

Ok so we ran all the tests we could even replaced the whole motor the car starts and runs but not well! Compression tests were ran with a cold motor and a hot motor and compression stayed the same so now we know nothing is wrong with the motor! Fuel injector for #3 cylinder has been replaced spark plugs and coil packs for all 4 cylinders have been replaced still scratching heads on what can be the problem could it be the whole wiring harness?


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## Spbynack (Dec 23, 2016)

Ok so we ran all the tests we could even replaced the whole motor the car starts and runs but not well! Compression tests were ran with a cold motor and a hot motor and compression stayed the same so now we know nothing is wrong with the motor! Fuel injector for #3 cylinder has been replaced spark plugs and coil packs for all 4 cylinders have been replaced still scratching heads on what can be the problem could it be the whole wiring harness? If so what would I find that under?


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## smj999smj (Jan 1, 2006)

Do you have 12v power to the #3 fuel injector harness with the key on? If you do, did you try installing a noid light to see if the ECM is firing the fuel injector? If it isn't, you have to test the ground circuit between the #3 fuel injector harness connector and the appropriate pin in the ECM harness connector for an open or shorted circuit. If the circuit is bad, you'll need to repair it. If the circuit is good, you likely have a bad driver inside the ECM and the ECM will need to be replaced. But, before doing that, make sure you check all of the grounds for the ECM.


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## rogoman (Dec 16, 2004)

Spbynack said:


> Ok so we ran all the tests we could even replaced the whole motor the car starts and runs but not well! Compression tests were ran with a cold motor and a hot motor and compression stayed the same so now we know nothing is wrong with the motor! Fuel injector for [URL=http://www.NissanForums.com//usertag.php?do=list&action=hash&hash=3]#3 [/URL] cylinder has been replaced spark plugs and coil packs for all 4 cylinders have been replaced still scratching heads on what can be the problem could it be the whole wiring harness? If so what would I find that under?


Let me get this straight. You're saying that you actually *REPLACED* the entire engine and you're still having the same identical problems as with the old engine; still getting a P0300 and #3 cyl not firing? If so, that's a hell of a diagnostic procedure to go through just to prove the old engine was OK. Follow SMJ's last posting. Also check the fuel pressure which should be around 51 psi; low pressures can cause strange things to happen.


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## smj999smj (Jan 1, 2006)

Well, at least he's got a spare!


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## Spbynack (Dec 23, 2016)

That's what i was thinking spend some money on the spare and rebuild it for later


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## Spbynack (Dec 23, 2016)

No light came on with the noid test how would I go about testing the ground connection and finding the right pin for the #3 cylinder?


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## smj999smj (Jan 1, 2006)

Well, the noid light not flashing means the injector is not firing. First thing to do is take a 12v test light and make sure you have power at one of the wires in the injector harness connector. If you don't, you first need to trace the power circuit to the injector. If you have power, then the issue is the ground circuit, which includes the ECM. You need to get a factory service manual for your vehicle and locate the appropriate wiring diagram in the EC "Engine Control" chapter. It should give you all the info you need under the diagnostic procedure for DTC P0303. It will have a pinout diagram of the ECM harness connector, connector numbers, wiring colors, etc. You will need to unplug the ECM and the #3 injector. They will usually show the back side of the connector in their references. You may need to remove a cover at the back side of the ECM harness connector to locate the wire. There are a lot of wires and many of them similar or same colors, so take your time and made sure you have the right one! You'll need an ohmmeter or multimeter with an ohmmeter function. You'll first check for continuity between the circuit and ground, which there should be none (continuity to ground would indicate a shorted circuit). Next, you backprobe the harness connectors and measure resistance on the circuit between the two connectors; there should be minimal resistance---almost 0 ohms. If you have a continuity function, it should show good continuity. If testing shows the circuit is "open" or if there is too much resistance, the circuit will need to be traced to the problem spot and repaired. If the circuit tests ok, I would check the pinout for the ECM harness connector and find the terminals for the ECM grounds; they will usually be all next to each other on one side of the connector. Make sure there is good continuity to ground at each one of the terminals. If those are good, plug the ECM and injector back in and start the engine. If #3 is firing, you likely had a dirty or poor connection at one of the harnesses. If #3 is still not firing, you likely have a bad driver inside the ECM and need to have the ECM repaired or replaced. Companies like Circuit Board Medics can repair ECM's.


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