Over the last week, I've noticed that I'd get a quick stumble when accelerating whether is be at speed or from a stop.The car is now much harder to start when hot as well. It was hard to start but now it's at the point where it needs some help.

I've been a bad man when taking care of the Max over the last 5 years but I left my300zx fuel filter on for like 5 years. DOH!!!! The car had continued to run fine but the last time i had this issue, I changed my spark plugs and everything went back to normal. I do have a faulty EGR system as well but the hose is disconnected. The car still drove fine in this state.

Yesterday, I changed my spark plugs (the ones I took out still looked good but did have a lot of miles on them) and fuel filter, dumped some fuel system cleaner into the gas tank to see if the issues smooth out over the next week.

Some of the older threads on the org state there could be issues with the coils (which I don't think is the case because the stumbling would exist at any rpm range not just between 2000 and 3000. I've seen references to the IAC and PCV but no clear facts as to why? Haynes is pushing me over to thinking I have some bad stuff going on in my fuel system so I'm going to keep dumping cleaner in the tank for now.

Any other views will be appreciated.

 

Just go to a shop and have them throw an O scope on her. Thats the best thing I can say you could do. I am betting bad coils as well. Knock sensor could cause issues. Check ur maf?

 

MAF is fine and it's just been cleaned with MAF cleaner. I could spray it down again just for kicks.

We'll save the "go to a shop" as the last resort.

Thanks,

 

Does it stumble at steady throttle or when you get off and on the throttle. Mine has a jerky miss sometimes when get off and on the throttle.Is yours a 5 speed?

 

The miss happens when I let off and jump back on but it also feels like when I'm at speed, when I give it more gas, it lopes a bit until it gets over 3000 rpm.

 

You've seen my previous post on all of the other threads, I'm in the same boat as you... As of now I've replaced/cleaned...

Spark Plugs
Fuel Filter
TB (Cleaned)
IACV (Cleaned)
EGR (Cleaned)
MAF (Cleaned)
Injectors (Cleaned)
Seafoaming

Still have the stumble (But it's nowhere near as bad as it used to be, I have to really try to get it to happen now, the hesitation to go to WOT is pretty much non-existent now).

On my to do list... Coil cleaning and wrapping, and fuel pump replacement (I think it may be bad, I still have really long starts @ random times).

 

I actually didn't see your thread but it's good we're posting this now so we can try to get this figured out.

Well, I figured I may try to fix this by starting with the Engine Coolant Temp Sensor even though I'm still getting good readings from Digimoto. I'm going to drive around with Digimoto in the car to see if I can notice any changes in voltages regarding my other monitored sensors at some point tomorrow. The only thing I can correlate this with is the weather right now because when it was cold out, I didn't have the issue at all.

mmgio, I have an auto.

 

how bout a crank/cam sensor? when i chipped a tooth off of my timing ring, it would basically stop accelerating at a certain rpm, and pick back up. or is it a different type of hesitation?

 

I didn't start a thread... Or maybe I did... I don't remember, but I did remember coming to the conclusion in another thread that it was mainly a 5 speed problem... Obviously it isn't a 5 speed only problem anymore.

We played around w/ the idea of it being TPS, but someone had replaced theirs w/ a new one and still has the hesitation/stumbling (IIRC someone got a new ECTS too, not sure on that one, but definitely let us know on the results).

What OTHER symptoms do you have w/ your car? Do you also have trouble w/ hot, warm or cold starts taking too long?

It really feels like multiple mini misfires, it literally sputters, it's too hard to record because a camera won't show it that well, cause the tach doesn't move enough to show the boggy feeling you're getting.

BUT! While dealing with this issue like I said earlier, I have to try to get my car to do it. Since I've did the previously mentioned maintenance from above I have only got it to stumble in this situation:

Sitting in any gear (except 1st, it's too short lol) @ 2k-3k rpm, sitting on the throttle, let off the throttle and quickly jab it to a nice cruising position, the car stumbles/bogs/hesitates/misfires.

Again, this rarely happens now during regular driving, probably the only situation where it would happen is me trying to make a yellow light.

But in the past, this car had a really hard time with rapid throttle changes, it's getting better and better with more and more maintenance though, the problems (Acceleration/Fuel related) are only down to... Long starts and the stumbling (I'm so glad the maintenance list is getting so short now, felt like I've done something during the last 10 months).

I have a video idea, I'll make a video tomorrow before I do the coils.

 

guys i have the same problem with my 99 . i replaced the filters ,knock sensor . spark plugs and the belts . Im looking into solving this as well . i just ordered a set of used coils from a orger here , will see what happens

 

I too also have this problem but codes are only Knuck sensor which I visually looked at and tested. It was fine but replaced it anyways and the codes still will not clear. I have misfires at idle which is not enough to trigger the CEL light. I tried ohming out the coils and they all passed with the procedure in the FSM. Somewhere on here, an orger stated that the Haynes manual give you a different testing for the coils. Do any of you know what it is

 

After cleaning my throttlebody and spraying the hell out of my EGR system with cleaner, it seemed to start idling a little rough but I didn't sweat it because I knew I needed to change my fuel filter. For the last 6 years it became hard to start when I'd let th car sit for about 30 minutes to an hour. Now it's taking more time to start. I ordered a new coolant temp sensor based on the recommendations of the Haynes manual to see if I can clear up that issue.

I took a ride this morning and noticed that when starting from a stand still, I get a slight bog at 1900 rpms. Tomorrow, I'll throw on the Digimoto's Data Logger to see whatelse I can find.

The car also feels like it doesn't want to downshift which may mean powerloss. I littlerally have to floor it to get it to downshift. The auto tranny has been know to have a sucky shift program anyway but it definitely is doing something different based on whatever this bog/hesistation issue is.

 

It feels like a slight bog or a quick hesistation. My auto has 291K on it and it's always been butter smooth until it started to get warm here in NC.

The best way to explain it is when I owned an 86 Toyota pickup with a bad EGR system. When it was hooked up, it would hesitate when I'd slow down to take a turn and hit the gas again to accelerate, almost to the point of the truck shutting off. The Maxima's issue happens much quicker so it doesn't make the car feel as it's shutting off.

 

Check your coils with a multimeter. It's really not difficult at all, and since you have a haynes I'm not going to go into the how-to. Have you looked into your fuel pressure regulator? its on the end of the fuel rail on the right bank. It is on the return line with a vacuum line coming out of the bottom. It could be some other things that people have already said, but I don't see the sense in repeating them. haha

 

I just sprayed the hell out of my MAF again because I may have contaminated it with the spray oil for my Road Hog filter (aka K&N drop in). It seems to be running a little smoother now but the real test will come this week during my hikes back and forth to work.

 

Are you still running the original MAF ? You wont get a code for it and
your car will only buck/stumble occasionally ...

 

Yes, it's the original. It may be the MAF and it may not be. I'm not really focused in the MAF but just trying to go over a few thing before I start shelling out more cash.

 

Tried to get it on video, with no luck, it's just too hard to record what you "feel".

 

check the coils, make sure they're fully plugged in because sometimes the prongs get bent because that sounds like you have a misfire

 

my 96 does this **** and ive tried to figure it out and it just doesnt wanna stop i had all my cois tested and they were all fine i even swaped out coils between mine and my ex girlfriends and it still did the same but my coils didnt effect her max. im good with cars but this one has got me stumped

 

check your fuel pressure. u said that u didnt change a fuel filter for six years!!!1 wow that a long time. your pump could be bad from the resistance in the filter. someone stated earlier check it with a o scope. its the best diognostic tool out there. if you cant get your hands on one and fuel pressure is low check for ohms on the pump with a dvom. good luck

 

I changed the filter this weekend but I bet there were some impurities messing with the flow of fuel. After driving to work this morning, it seemed to smooth at about 30 miles of driving. I just took another drive and it's not hesitating now. I did throw some fuel system cleaner in the tank this weekend as well so I'm going to run through another tank and see what I get.


Guys, I think you're wasting your time with the coil theory. I did a lot of research on this issue and like I said before, the coils could fail at any RPM if they go bad.

 

I noticed the same thing too when I did my fuel filter, even when I tried to make my car do it, it still won't do it every time, I'm with you too on it not being a coil issue cause the prev. owner replaced em w/ 97s, I just un screwed and re-screwed them back in to make sure they were seated in correctly.

::edit::
I think my starting problem may be my FPR, not fuel pump.

 

Only a certain brand of coils had the failure issue anyway. My coils have been rock solid for the last 13 years. Not saying that can't go bad but they are still in good shape.

I would go will the FPR (even tho I haven't checked mine yet), the coolant temp and air temp sensors.