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2000 3.0 p0304 loss of power under hard acceleration
Hello, I'm new to the org and I've been doing a lot of searching and haven't really found anything related to the problem I'm having.
First off a little about the car in question. Auto trans, 3.0, mileage unknown, modified injen cai, manzo headers and y-pipe, cat-less, no b1 s2 o2, no b2 s2 o2, maf a year ago recently cleaned, upper IM gasket a year ago, ngk iridium 9 plugs, cleaned TB,also tested resistance on all injectors (read 18-20 respectfully).
Now for the issue at hand. I've had the car for 2 years now and I've had the p0304 cylinder 4 misfire since I've owned it, but for about 10 months I've been experiencing a huge power loss when gas pedal is pressed 1/3 to full throttle, between 3k-5k rpms especially at OT. At this point I'm scratching my head. Pulled codes today still have the same p0304, as for the reason I tested my injectors. I also ordered a vias block off plate because I've read in a thread that this could be a problem with acceleration. I haven't installed it yet, been too busy with work and me being a little lazy, lol. Any insight would be greatly appreciated. Thanks in advance.
A little idea of what we are discussing
2" megan racing lowerng springs, fcs performance struts, all new front suspension parts, 19mm hub adapters, 235/40/18 uhp velozza, black and red TRD rims, and custom painted grille.
Easy problem to diagnose and fix. Since your code is 0304, that's the fourth cylinder, which is dead middle right in front of the manifold (not underneath). Hopefully when you do the diagnostic, this cylinder does indeed fail.
Do the unplug a coilpack one at a time trick and listen for a change in RPM. If no change, then you've narrowed down the cylinder and coilpack/injector.
Swap coilpack with another cylinder. Repeat test and see if the no change in RPM moves with the coilpack. If so, that's your coilpack to replace. If not, then it could be the injector failing on the original cylinder.
Easy problem to diagnose and fix. Since your code is 0304, that's the fourth cylinder, which is dead middle right in front of the manifold (not underneath). Hopefully when you do the diagnostic, this cylinder does indeed fail.
Do the unplug a coilpack one at a time trick and listen for a change in RPM. If no change, then you've narrowed down the cylinder and coilpack/injector.
Swap coilpack with another cylinder. Repeat test and see if the no change in RPM moves with the coilpack. If so, that's your coilpack to replace. If not, then it could be the injector failing on the original cylinder.
Start there. Free and easy diagnostics.
Thanks for the quick response. unfortunately I've already done this with the coil and the plug and still the same problem exists. I forgot to mention that the reason I bought the new coil was when I bought the car, cylinder 4 had a mitsubishi coil (wtf?!), and I replaced it with a coil from the dealer. Then the problem still exists. When I pull the intake to install the vias block off plate and valve cover gasket I will pull the injectors and check for cleanliness. That won't be until next week though.
Last edited by vqmaximus30; 04-21-2016 at 01:09 PM.
Thanks for the quick response. unfortunately I've already done this with the coil and the plug and still the same problem exists. I forgot to mention that the reason I bought the new coil was when I bought the car, cylinder 4 had a mitsubishi coil (wtf?!), and I replaced it with a coil from the dealer. Then the problem still exists. When I pull the intake to install the vias block off plate and valve cover gasket I will pull the injectors and check for cleanliness. That won't be until next week though.
(Update)
I done a compression test Tuesday, all cylinders checked out between 100-120 psi. Checked continuity on cam position sensor and ohm'd it, again sensor checked out 2.73 kilo ohms, didn't check the sensor condition though. I've been working 6 days a week, and it's been really hard to find time to work on this. The problem is gradually getting worse. I'm planning on just replacing all the coils, next week. Hopefully this will solve it, really unsure about this though because I've already replaced the supposed "bad one". Any other suggestions would be greatly appreciated.
(Update)
I done a compression test Tuesday, all cylinders checked out between 100-120 psi. Checked continuity on cam position sensor and ohm'd it, again sensor checked out 2.73 kilo ohms, didn't check the sensor condition though. I've been working 6 days a week, and it's been really hard to find time to work on this. The problem is gradually getting worse. I'm planning on just replacing all the coils, next week. Hopefully this will solve it, really unsure about this though because I've already replaced the supposed "bad one". Any other suggestions would be greatly appreciated.
You must be aware of it, but: At 100-120 psi, your compression is very low! It should be at least 142 psi, and preferably up to 185 psi.
Even if the low compression doesn't explain all your problems, it must be a major contributor. Try to determine whether it's your valves or the rings, and go from there.
You must be aware of it, but: At 100-120 psi, your compression is very low! It should be at least 142 psi, and preferably up to 185 psi.
Even if the low compression doesn't explain all your problems, it must be a major contributor. Try to determine whether it's your valves or the rings, and go from there.
I think his tester must be way off or leaking. A 3.0 would need serious miles/abuse for those to be correct (unless it was boosted previously). If correct, the motor needs replaced.
Have you checked the TPS voltage or simmed the knock sensor? Idk what the misfire is about, but those are two whacky ****ers that will destroy performance.
Last edited by Child_uv_KoRn; 04-28-2016 at 11:29 PM.
Swap injectors, erase codes, see if code moves to the new cylinder. You haven't tried all the free and basic stuff yet, yet you're willing to throw money at the car and replace all coilpacks.
I wouldn't replace all the coils. That's a pretty pricey guess. It sounds like you've already ruled out the coil.
Do the coils have a white dot of circle on them? If so, they're the updated coils. A lot of these cars came with weak coils. The new coils are updated and much better.
Get a mechanics stethoscope ($5 at Harbor Freight) and listen to the injectors. They'll be pretty noisy if they're working and they should all sound similar. If the bad one is quiet or sounds a lot different you'll have your answer.
I wouldn't replace all the coils. That's a pretty pricey guess. It sounds like you've already ruled out the coil.
Do the coils have a white dot of circle on them? If so, they're the updated coils. A lot of these cars came with weak coils. The new coils are updated and much better.
Get a mechanics stethoscope ($5 at Harbor Freight) and listen to the injectors. They'll be pretty noisy if they're working and they should all sound similar. If the bad one is quiet or sounds a lot different you'll have your answer.
Okay, so I asked my friend that helped me with the compression test if he remembered the reading he got from the test itself. He replied, "I don't remember the exact numbers but it was over 100." That being said I'm not going to take his word for it even though he's been a tech for 15 years. He helped me for free so I don't expect him to actually do a good diagnostic. It just runs way to good for the engine to be bad. I'm not loosing a serious amount of oil, a little from the VC but I'm gonna replace those soon, and the tube seals are NOT leaking. That being said I will test it myself later.
I did have a little time to tinker today so I unplugged #4 injector to see if there was a change... yes, there was. So now the injector is probably not the issue. Unless it's just failing intermittently. This misfire only happens about every 8-13 seconds and it is very annoying. The misfire is not really the most annoying thing though, it is the loss of power in mid rpm range with the gas pedal pressed anywhere from 1/3 to full throttle. The loss is so immense that I would probably have trouble keeping up with a Honda running a stock d16. Both of these problems start when engine is warming up and happen more often at OT.
I did notice something today though, a pretty loud hissing noise coming from the back side of the intake plentum. Sprayed TBC all around and listened, no drop in rpms... I will check tps tomorrow. Also my front engine mount is bbbaaaaaaaddddd. I've read that some of them are monitored electronically, would this cause a loss of power?
Last edited by vqmaximus30; 05-01-2016 at 04:41 PM.
Could still be an injector. It could be ok at idle but acting up under load. It could also be working but not working properly. If that's the case then unplugging it would still have some effect.
Where is the o2 sensor on those headers? Is it mounted on one of the runners so it's only reading one cylinder? If so, your #4 could be running rich or lean and you'd never get a code for that bank running rich or lean.
Next step is to pull all three plugs and compare them. Run it hard till it starts messing up first.
If your car is auto you have electric mounts. I'd unplug them now to protect your ECU. It wouldn't cause this problem though.
Also. inspect the harness plug for the #4 coil. They might have messed it up or even hacked on it to get the other coil to plug in. If the pins on the other coil were thicker or offset at all the female pins in the plug may have been stretched out enough to make a shaky connection.
Last edited by Derrick2k2SE; 05-01-2016 at 11:22 PM.
Could still be an injector. It could be ok at idle but acting up under load. It could also be working but not working properly. If that's the case then unplugging it would still have some effect.
Where is the o2 sensor on those headers? Is it mounted on one of the runners so it's only reading one cylinder? If so, your #4 could be running rich or lean and you'd never get a code for that bank running rich or lean.
Next step is to pull all three plugs and compare them. Run it hard till it starts messing up first.
If your car is auto you have electric mounts. I'd unplug them now to protect your ECU. It wouldn't cause this problem though.
Also. inspect the harness plug for the #4 coil. They might have messed it up or even hacked on it to get the other coil to plug in. If the pins on the other coil were thicker or offset at all the female pins in the plug may have been stretched out enough to make a shaky connection.
Today I re-done my compression test and the results are, #1 190, #2 210, #3 158, #4 196, #5 202, #6 198. Also I checked all the coils, all oem nissan except the one on #3. Not sure if it is bad but I swapped it to #5 and for now I haven't had a misfire and the loss of power is barley noticeable. I asked one of my co-workers and he said that it is likely that that coil is bad or going bad and with it being on a cylinder with weak compression made the car manipulate a misfire on #4 because the coil didn't produce enough spark to push the piston back down fast enough. Makes sense, we also done a leak down test and confirmed the rings are wearing on #3...guess that coil was weak for a very long time and wore the cylinder.
Probably going to invest in another coil to replace the weak one and and a front engine mount. Hopefully I can get at least another year out of her if I can, in the meantime I will buy another engine for it, rebuild it top to bottom with some juicy internals, maybe turbo if the car holds up for longer than a year. I want to see if I can get 500 horses, I don't know if it will be possible if things go the way I plan then there is hope, lol.
Also thanks for all of the help and advice. I will let you guys know in a few days if this issue reoccurs. Thanks again!!
I don't think you're understanding us. At the risk of sounding like a broken record, just because you notice a change in RPM when you unplug a coilpack, it doesn't mean the injector is good. It only means that probably the coilpack is good. The injector should still be on the suspect list.
I don't think you're understanding us. At the risk of sounding like a broken record, just because you notice a change in RPM when you unplug a coilpack, it doesn't mean the injector is good. It only means that probably the coilpack is good. The injector should still be on the suspect list.
I will definitely keep it in mind, but for now I want to see if the problem comes back, it usually takes about 30 minutes of driving around. Don't really have any place to go at the moment and with it being almost pay day the wallet and the gas tank is looking a little slim lol. I did drive around for a bit today, picked up my daughter from school, back from work and to the grocery store and back. I didn't notice any miss and like I said before the miss was more noticeable at idle when at OT, sat with the car in drive at idle for a good 15 minutes in car line at my daughter's school. Also as I said before the loss of power is very hard to notice now even at OT, and that's when both of these problems occurred most often.
Last edited by vqmaximus30; 05-02-2016 at 05:15 PM.
I will definitely keep it in mind, but for now I want to see if the problem comes back, it usually takes about 30 minutes of driving around. Don't really have any place to go at the moment and with it being almost pay day the wallet and the gas tank is looking a little slim lol. I did drive around for a bit today, picked up my daughter from school, back from work and to the grocery store and back. I didn't notice any miss and like I said before the miss was more noticeable at idle when at OT, sat with the car in drive at idle for a good 15 minutes in car line at my daughter's school. Also as I said before the loss of power is very hard to notice now even at OT, and that's when both of these problems occurred most often.
Just a quick update. I love my car again, nuff said lol. Also I would like to thank everyone for their suggestions and insight to give me a place to start because I was honestly to the end of my wits.
Just a quick update. I love my car again, nuff said lol. Also I would like to thank everyone for their suggestions and insight to give me a place to start because I was honestly to the end of my wits.
04-20-2016, 07:01 PM
