# 05 2.5 Altima, misfire issues



## Lester86 (Jun 6, 2015)

Hello all,

New to Nissan forums but I recently was given a call it project car after my lady's Altima started having a minor miss on a Sunday morning (minor meaning that we were driving around and noticed a loss of power) happened a low rpm 2-3k then when away. Then later on in the day the miss continued to get worse (happening more frequently). Then late afternoon a " service engine soon light came one" but not readable codes (stopped at autozone while it was happening). Drove home and the light stayed on then went off. Happened again about a mile from home it stayed on took it to another autozone (Service engine light was on) left it running and plugged up the code reader only to have the code PO303 pop up, while I was there I noticed white smoke and bad smell come from the exhaust. Barely got it home parked it and told myself that I would take a look first thing Monday and unless something obvious is there when I check it I'm not spending a penny on the car (good amount of money spent on the car in short time, frustration I suppose). 

When I checked the following day I check spark plug on cyl 3 and it looked normalish. Checked the rest looked normal except cyl 1. Cyl 1 the entire coil pack and plug was soaked in oil. I was shocked but thought perhaps its just come bad boot seals. Just my luck no seals available for the 2.5 Nissan had to buy the valve cover. Swapped it out and then started the car. I would say it ran for a second normal then got a light knocking or tapping I would call it and misfire was back. Said screw it and drove it to a local shop they noticed unburned fuel in cyl 3 (no surprise) they swapped a ignition coil with another cylinder to see if that would get cyl 3 running no luck, checked fuel injector no issues. Ran compression test and told me its a compression issue and I would need a new engine. Now my lady hearing this lost it and ended up buying a new car. I kept this one to see if I can get it running perhaps. Worst case swap the motor on it maybe. Or junk it. 

I've been working on it on and off and first thing I didn't I ran a quick compression test the engine cold (not the best idea for accurate readings) for semi even compression. One thing I did notice right off the bat is that I have excessive blow by (first thought bad rings?) Then I popped the oil cap and got alot of pulsing air. Also the pcv system is got a lot of pressure coming out of it and oil particulars. When I unplug the pcv or leave the oil cap off or open the intake in-let (bypass's filter) all cause the car to die. Yesterday I ran more compression test results below. Any ideas would be greatly appreciated. I'm leaning towards rings but I really hope in wrong.

Dry test 
1- 135
2- 139
3- 129
4- 136

Wet test
1- 141
2- 144
3- 140
4- 156

2nd wet test
1- 155
2- 150
3- 149
4- 154

Dry test after car ran for a few min
1- 135
2- 139
3- 131
4- 151

White smoke sputtering from tail pipe.


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## rogoman (Dec 16, 2004)

The common problem with these engines is the catalytic converter breaks down and bits of catalyst substrate get sucked back into the combustion chamber and score the cylinder walls. The QR25DE uses the variable valve timing for EGR rather than a conventional EGR valve. It opens the exhaust valve slightly during the intake stroke to accomplish this. The catalytic converter, which is part of the exhaust manifold, is so close to the head that the bits of debris get sucked in past the exhaust valve with the exhaust gases. Nissan claimed the reason for this was the ECM programming. A recall for 02-04 QR25DE equipped Sentras and Altimas was initiated years ago to correct this problem. An updated ECM was provided, updated manifold heat shields and several other things and in some cases, replacement of the exhaust manifold assy. and engine short block. At this point, Nissan probably won't do much for you if this is the issue, especially if the vehicle has already had the campaign performed (we still hear about oil burning QR25DE's on vehicle's that have had the campaign performed). You can test to see if this is the issue by performing a compression test to the engine and comparing it to the service manual specs. If it is under spec, likely you will find burnt oil on the inlet side of the catalyst media when you remove the manifold (you might need a telescoping probe to view it) unless it has been recently replaced. Head gasket failures are also not uncommon. A cylinder leakdown test would be helpful. Excessive blow-by is a sure indicator of worn rings. The compression specs are: standard - 181 psi, min - 154 psi.


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## Lester86 (Jun 6, 2015)

Rogoman,

Really appreciate the info by the looks of things I might be Sol when it comes to this engine. Is there anyway I can verify of the ecm recall was done on this vehicle would hate to get another motor only to find this will happen again sooner or later. As it did with this one.


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## rogoman (Dec 16, 2004)

You would have to go to a Nissan dealer with your VIN# and have them verify if a recall was done on your vehicle.


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