Nissan Altima Forum banner

1 - 9 of 9 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
Please bare with me as the newest vehicle I own is an '87 and I've never owned anything with OBD2. I picked up an '06 Altima 2.5 cheap because it has high mileage and a starting issue. I needed something 4-door and easy to keep a car seat in. Most times it starts right up, other times it might run the battery dead turning over and I have to get jumped off but it always eventually starts. It had two codes when I got it and now it has four codes. This seems like a car I could spend hundreds of dollars throwing parts at it and it's just not worth the investment. I don't care about the high miles and if it lasted a year or two I'd be happy but since it's so new it has to pass emissions to get it registered. Could any of these codes cause it to be so hard to start intermittently? P0420, P2A00, P0300, P0303. The last two just started a couple days ago. The first two are O2 codes and I don't think they do anything on startup. The car runs perfect after it starts and everything on it still works. I'd hate to scrap it and cut my losses but it might be inevitable.
 

·
Registered
Joined
·
399 Posts
You definitely have a bad catalytic converter with the P0420 and a bad A/F (front O2) sensor with the P2A00, and with a bad cat the misfire codes could turn into very bad news. If the cat disintegrates the engine will inhale the debris and that will be the end of the engine. The P0303 indicates a consistent misfire on #3 cylinder and the P0300 indicates other cylinders misfiring intermittently, and the unburned fuel from those misfires will be heating the cat. The misfires may be something as simple as a bad battery ground or old spark plugs, but a cat plus an A/F won't be cheap and you'll need both if you're going to save the vehicle. Intermittent no-starting is probably the least of your worries.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #3 ·
You definitely have a bad catalytic converter with the P0420 and a bad A/F (front O2) sensor with the P2A00, and with a bad cat the misfire codes could turn into very bad news. If the cat disintegrates the engine will inhale the debris and that will be the end of the engine. The P0303 indicates a consistent misfire on #3 cylinder and the P0300 indicates other cylinders misfiring intermittently, and the unburned fuel from those misfires will be heating the cat. The misfires may be something as simple as a bad battery ground or old spark plugs, but a cat plus an A/F won't be cheap and you'll need both if you're going to save the vehicle. Intermittent no-starting is probably the least of your worries.
Could the cat and the sensors cause the no start issues? There doesn't seem to be any pattern as far as hot or cold engine or air temp. I know of one of these cars being parted out with a bad trans that I could get it's whole manifold with cat and sensors fairly cheap but the not start is what's really getting on my nerves at the moment. I don't want to put $1000 into a $400 car with 230K miles on it.
 

·
Registered
Joined
·
399 Posts
The most common causes of intermittent no-starts on Alties are a dying fuel pump that has trouble getting started or a crank or cam sensor (usually crank) that's dying but not dead yet. You can rule the fuel pump in or out by spraying Brakleen or something else combustible down the intake next time it misbehaves. If it starts and then dies you have a fuel issue.

Just keep in mind that fixing the annoyances won't do you any good if the engine is trashed. QR25's are all Miller-cycle engines and they will inhale the cat if it disintegrates. That's fatal about 99.999999% of the time. We're talking dead-dead, not rebuildable.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #5 ·
It finally wouldn't start at home where I could investigate it. The fuel pump seems fine. I checked for power at the pump and the pump always cuts on to prime. I pulled the air box out, held the throttle blade open and sprayed starting fluid straight into the intake with no change. I pulled the cam sensor and cleaned it but no change. Granted it still could be the problem. I swapped relays for the ecu with no change. If it was an old car I'd swear it's out of time. With it spinning over sometimes I can hear it thump back through the air box. Before I had a chance to pull a coil and check for spark the car started so I'll have to wait a few days til it happens again. Upon inspection the manifold with pre cat appear to have been changed. Couldn't say new or used but they don't match the rest of the motors grease and rust on the heat shield. The downstream o2 sensor has been changed and the coolant temp sensor. The previous owner told me this just started but it seems he's already been throwing some parts at it. Some parts have junkyard markings on them. The radiator, two coils and even the battery is from a junkyard. On a side note, I know the car has a lot of miles but it only gets about 16 mpg. I have a carbureted V8 pickup that gets better mileage.
 

·
Registered
Joined
·
399 Posts
The 16 mpg is a clue, it's running very rich so your no-starts may be from flooding. Get a scanner that can stream the MAF and see if what's coming out of it makes sense. You should see a bit more than 1 gps for every liter of displacement at idle, so a 2.5 should probably read around 3 gps. If you see a lot more than that, then the ECM is adding too much fuel because the MAF is lying. It could be a bad MAF, but try having an IAVL (Idle Air Volume Learn) done to re-match the MAF to the ECM. Someone may have changed the MAF, or the readings may just have changed with old age. Check the IAT (intake air temp) readings too, if the IAT is dead and the car thinks it's in Alaska, it will run crazy rich.
 

·
Registered
Joined
·
84 Posts
It finally wouldn't start at home where I could investigate it. The fuel pump seems fine. I checked for power at the pump and the pump always cuts on to prime. I pulled the air box out, held the throttle blade open and sprayed starting fluid straight into the intake with no change. I pulled the cam sensor and cleaned it but no change. Granted it still could be the problem. I swapped relays for the ecu with no change. If it was an old car I'd swear it's out of time. With it spinning over sometimes I can hear it thump back through the air box. Before I had a chance to pull a coil and check for spark the car started so I'll have to wait a few days til it happens again. Upon inspection the manifold with pre cat appear to have been changed. Couldn't say new or used but they don't match the rest of the motors grease and rust on the heat shield. The downstream o2 sensor has been changed and the coolant temp sensor. The previous owner told me this just started but it seems he's already been throwing some parts at it. Some parts have junkyard markings on them. The radiator, two coils and even the battery is from a junkyard. On a side note, I know the car has a lot of miles but it only gets about 16 mpg. I have a carbureted V8 pickup that gets better mileage.
Since you ruled out a fuel delivery problem, the loss of ignition is where you're at. You can test all four coil packs; use a spare spark plug in each 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. If there's no spark at all of the coil packs, then there may be a missing 12V supply at the harnesses, bad camshaft/crankshaft position sensors or a bad ECU. You can also use a "noid test light" probe kit to test each coil pack; makes it a lot easier because you don't have to pull any coil packs, mess with jumper wires or using a spare plug.
If you plan to replace the camshaft/crankshaft position sensors, always use Nissan OEM parts from a Nissan dealer; aftermarket electronic items generally are not reliable, don't last long, and many times are DOA. The sensors are not very expensive; around $75.
 

·
Registered
Joined
·
4 Posts
Discussion Starter · #8 ·
Well, the car has started every time for months without me doing anything. Gas mileage is still low. The check engine light goes on and off at random but at least it's been starting. Then Monday right back to the same thing. Wouldn't start first thing in the morning and won't start back every four to eight tries. I tossed it up to the cold weather causing the issue but now I'm convinced there's some electrical problem or issue with the ecm. I don't understand how it can be perfect for no reason then go right back again.
 

·
Registered
Joined
·
84 Posts
Well, the car has started every time for months without me doing anything. Gas mileage is still low. The check engine light goes on and off at random but at least it's been starting. Then Monday right back to the same thing. Wouldn't start first thing in the morning and won't start back every four to eight tries. I tossed it up to the cold weather causing the issue but now I'm convinced there's some electrical problem or issue with the ecm. I don't understand how it can be perfect for no reason then go right back again.
A common problem with random engine shutdowns or unable to start the engine is a marginal camshaft position sensor or a marginal crankshaft position sensor. Most of the time when this happens, the "check engine light" never comes on; subsequently when performing an ECU code readout, there was no fault code set. There's been many members here on the forum that have had problems similar to yours and the fix was replacing those two sensors.

The best and cheapest fix for this situation is to replace both sensors at the same time; the reason for doing this is there is no way to determine which sensor is at fault with this type of condition. You can take your vehicle to a dealer/repair shop and they'll tell you there is nothing wrong after they go through with diagnostic tests because at that time the vehicle was running OK. You could end up spending $200 or much more depending on how much time/parts are used.

When replacing sensors, always use Nissan OEM parts from a Nissan dealer; aftermarket electronic items generally are not reliable, don't last long, and many times are DOA. The sensors are not very expensive; around $75.
 
1 - 9 of 9 Posts
Top