Please Help with this bucking, misfiring
 

Ok here is the deal, 02 6spd 74,000 miles. Bucking, Misfire when engine warms up a little bit. Runs strong when it is cold for the first minute or so. After that, it falls on its face especially at WOT. Seems worse at lower rpms, but it also does it at higher rmps sometimes. No CEL, no codes, not even any pending codes.

MAF is brand new OEM, so that is not the problem. Coil packs seem like the obvious culprit, but I have learned that they usually trigger the CEL or at least throw a code. Plus I don't want to throw down 300 bucks for rear bank coils if they are not the problem.

Any Suggestions?

Since yours is an 01, pulling the coil pack plug on each cyl, and troubleshooting that way is easy. So, maybe try that if it's an obvious misfire. Bucking isn't usually a misfire thing though. It's an obvious and constant stutter. And my CP didn't give me any codes until the 4th or 5th time it happened and that's probably because she pissed me off and I was WOT'ing in order to finally get a CP code, which I did.

Could also test the CP's.

You say you have an 02 6spd so you won't be able to pull the coil pack plug on the rears, unfortunately. Personally, I have found it rather difficult to get misfire codes to actually trigger. What does seem to work best for me is drive slowly around my neighborhood while the misfiring is occurring until I either get a blinking SES or the SES just turns on.

Yes, it is a 02 6 spd (need to update my info) so I cannot check the rear coils. I could go ahead and check the fronts, but it really doesn't idle that bad (About 650 rpms) . I am about to do nwp spacers in a month so I figured I could do rear coils at the same time. But again, don't want to spend the 300 if I don't have to

I was going under what I saw under his profile screen name, which states 01.. my bad. If it doesn't idle bad and it's bucking, it's not a CP.

Well, it bucks sometimes, but it does have a constant misfire feeling too. could this be a vacuum leak?

Not sure about that. I had a few vacuum leaks and it ran @ WOT fine and even just cruising around, albeit a little lean. But it was at idle where I really noticed the vacuum leaks. I had 2 or 3 of tham, silly me I forgot to connect a few lines after the VC change. :bonk:

Check Ignition Coils
 

so this is kinda of a common problem with the 5th gen maxima. you need to check your ignition coils, specially number 3 i think. it will be on the back side of your engine, and the middle coil. in order to access this you will need to take off your intake manifold. you will probably need to replace that ignition coil and it will run fine after that

I guess I will just change the rear 3 coils when I do the nwp spacers, vias block off, and short ram. Another question, should I go ahead and switch to 6th gen valve covers while I have the intake manifold off? I don't really burn any oil right now, but would it be a good idea just as a preventative measure?

when i had to replace mine, i checked all my coils, but only the middle rear one needed to be replaced. the gasket (or whatever it is) that seals around the spark plug was broken, hence it was misfiring. no need to replace all of them if they are sound.

Hate to agree with a random suggestion such as this, but when my car was giving me fits when I first got it, I had all kinds of issues, SES blinking coil, bad crank signal codes, bad cam sensor codes, all kinds of issues. I kept diagnosing, and ended up swapping coils, front to back, to see if things changed. Narrowed it down to #3 pack, even though there was no code. Changed it, and car cleared right up. No more issues ever.

yah i know what you mean. to answer his other question, i have heard replaceing the valve cover with a 6th gen does fix this problem. the 5th gen doesnt seal 100% at the #3 ignition coil, and some oil seeps in, causes the failure of the ignition coil.

Update
 

So I still have the misfire, moved all rear bank coils to front, and checked them one by one and no change. So, either it is the coils on the rear now, that were on the front, or it is something else. I'm thinking it could be a O2 sensor. It runs perfectly fine for the first couple of minutes until it gets warm, and thats when it bogs. still no codes.

Any other ideas?

Oh, and it only does it up to a certain RPM. around 4-5k, it regains power. I'm at a total loss on this

Im having a similar problem with my 2000 Auto.. Seems to be a constant stutter, dont know if its the Crank Position Sensors, Crankshaft Sensors, the only code I have is the PO430. Im replacing the Y Pipe soon. I did clean the throttle plate (Body).. MAF has about 30,000 miles on it.. Rest of car 230,000..

Fuel delivery comes to mind. The symptoms are consistent with the engine getting occasionally starved. Unfortunately, I am not aware of a simple test that you could do to prove/disprove this. I would check the dampener.

Changed all of the ignition coils tonight and it did nothing. Anyone have any input on this? I'm at my breaking point

Have you done a compression test and visually inspected the plugs that are easily-accessible?

I have an 03 6spd with ~150K, and I have been dealing with a cyl4 misfire for about the last month. It has been throwing a code for a cyl4 misfire. Turns out the compression is really low in that cylinder, like 65psi. The other easily-accessible cylinders are around 150psi. The cyl4 plug had a lot of oil on it. Replacing it helped for maybe 100 miles. Even right after replacing the plug, the misfire was still noticeable at warm idle. Now it is just as bad as before replacing the plug.

Of course I am up to a qt of oil about every 600 miles, so it all checks out in my case. These old rings have about had it. Hello quest engine! Hopefully its a much easier fix for you.

Did your VIAS code come up?

Have you checked the VIAS hoses?

.

I would check to make sure all of your maintenance is up to date if you haven't been keeping up with it. Check your oil, air filter, maybe run some fuel injector cleaner, and do a coolant system flush. any of these things could cause performance issues, and bad throttle response or laggy acceleration. Check the simple stuff first, and just troubleshoot by process of elimination. That's my suggestion.

The only time I've had bucking/stumbling issues and really poor low end was MAF. O2 sensor seems to be totally irrelevant to performance as it never makes it run too rich/lean to run improperly.

Junkyard MAFs for life. Tuck away a couple MAFs and O2 sensors when ya go. ;)

UPDATE:

Things I have done so far, changed rear 3 ignition coils, tested front three. gutted both precats. Car still does not show any codes or pending codes,

Took it in no Nissan dealer this morning, tech hooked it up to consult i believe, he said no misfires on any cylinder, and both banks are showing 100%, whatever that means. Tech said in his opinion, car needs to be tuned, which makes zero sense, since it did it when it was stock. His hypothesis is that the previous owner put cams in the car.:rolleyes:

Mod list, CGR 3" intake, nwp spacers, vias block off, 75mm throttle body. gutted cats, warpspeed y pipe brm 3" exhaust.

It only falls on its face when it has warmed up, can start car and do a pull or two and it runs like a top. Misfires, stumbles up to about 4K rpms, and then pulls hard all the way to redline.

Anyone have any suggestions, thought?

It did the same thing with the old maf?

yes, it did it with the previous MAF too. Plus, whenever I've had a MAF go out on me, it didn't pick back up at a certain rpm either. I'm really thinking this is fuel delivery. Someone told me that Nissan fuel pumps have some sort of electrical component that works differently at low and high rpms. Has anyone else heard of this?

FINALLY!!!!!

Took it to a local shop (btw, if you're in the East Tennessee area, Addicted Motorsports is a top notch place) they looked at live data while on a drive and figured out that ignition timing was going into the negative degrees.


After a bit of research and q & a with Darren Surratt, I picked up some 470k ohm resistors and bypassed the knock sensor. And, BOOM! Problem solved. A new Knock sensor is on order.

Whoa....nice work!

How did they detect the problem?

Also please explain, "What is a Knock Sensor and where is it located ?"

Thakns

The knock sensor identifies detonation, and tells the ecu it is happenning. The ecu will then pull ignition timing to protect the motor from damage. In my case, the knock sensor is shot, so the ecu does not trust it to detect detonation, so it pulls timin anyway. On our cars, it is located under the intake manifold.

That has to be the oddest KS failure.

Apparently it was a big problem on the 4th gens. Doesn't seem to happen to 5th gens all that much. I'm just glad it's about to be fixed. I'm letting Addicted Motorsports do the work, since unfortunately I don't have the time to. They're doing the KS and fixing the lifter tick I have (replacing whichever valve bucket is out of spec). Since the motor has to be pulled anyway, they are also doing a 2j racing UP, fidanza flywheel, and stage 2 daily South Bend Clutch

Wow...so you are saying that you had to pull the motor to do a KNOCK SENSOR?

No, not for the knock sensor. It can be done without taking the intake manifold off if you have tiny hands. The problem is the lifter tick. The way the valvetrain is designed on the vq35. Instead of having hydraulic lifters or a shim system, it uses valve buckets. The cam lobes actually push the bucket down, which is connected to the valve stem. So if it becomes out of spec, the bucket has to be replaced, and in order to do that, the cams have to come out. In order to do that, the timing chain cover, primary timing chain, and secondary timing chains have to come off, and if you've ever replaced a timing chain on a maxima, it is damn near impossible to do it while the motor is still in the car.

I would swap the motor before wasting time on that LOL. Of course, I would just drive it and not care. No mass produced engine is worth that labor.