I searched and found many things pertaining to the MAF, injectors, fuel filter, oxygen sensors fuel pump...but couldn't really find a 100% pertinent thread.

My CEL hasn't come on, but I checked regardless, and didn't pull any codes.

Say I'm cruising on the freeway in 5th gear and immediately give the car partial throttle (say 30%), the car will violently hesitate for a second or so (I can literally feel the car shaking) and then the acceleration will smooth out. If I go WOT, it will hesitate for a split second and then smooth out. If I ease into the throttle, there is no hesitation.

Also, the car was seriously bogging the other day, but that problem has mysteriously gone away.

Idle is sorta normal I guess, although I do get the occasional slight "hiccup" in the idle exhaust tone. I have no stalling issues.

Also, my Tomei a/f gauge reads lean during WOT runs where as it used to read rich (normal).

I've already changed the O2 sensors, KS, fuel filter, and MAF (used) already once during the lifetime of the car..albeit a couple years ago. I also installed a brand new Walbro fuel pump a couple years back.

I don't think there's a problem with my coils since I have no problems whatsoever at high RPMs (isn't a sign of bad coils hestiation at high rpms)?

I already ran a full bottle of Techron concentrated fuel system cleaner and also cleaned my MAF and the problem is still there.

 

wow, it sounds like youre talking about my car.

 

I finally Found it !!! http://forums.maxima.org/showthread.php?t=299017
I posted this a while back 4/1/04...I have had this problem for god knows how long...I kinda blame it on the lightened flywheel reacting with the sensor thats on the trans or the lesser rotational Forse of the Flywheel or my MAF..just read through that Post Above and learn...I couldnt find the problem..If I dont think about it, it doesnt happen
Worst is 5th gear, on the highway at like 2200 and I give it alittle throttle the car goes bog bog bog and then goes...very strange

Another Related post = http://forums.maxima.org/showthread.php?t=252443

-matt

 

I thought coils were more likely to show symptoms of failure under load - which is sorta what your problem is... you may want to swap out coils with another Max and see if that resolves the issue. Depending on when you last replaced the fuel/air filters, it might be worthwhile to do those just as maintenance items - cheap and easy to do yourself.

If the problem persists (after replacing the air/fuel filters), as I expect it will, my guess is its either the coils or the MAF.

I think the reason none of the other threads ended conclusively is because its very difficult to exactly diagnose this problem - given that a variety of root causes lead to the same set of driveability symptoms. If people made a habit of posting back what fixed their problems (in the original thread) - that would be invaluable information.

Hope that helps.

 

The bogging that mysteriously disappeared came back tonight. When I left my friend's house, I started the car and immediate drove off (therefore, engine was still cold). Leaving stop sign after stop sign, the car kept bogging. Then 10 min later on the freeway, I was steadily cruising @ 70mph in 5th gear when I felt the car "lose power". It's hard to explain in words, but I'll try. I'm holding the accelerator steady cruising in 5th gear on a flat stretch of freeway, and then all of a sudden, I can feel that the gas pedal becomes "stiffer"...that is, it takes a bit more effort to hold the gas pedal down in the same position. My fuel pressure gauge indicated the same fuel pressure, but my Tomei a/f gauge went from stoich to lean.

I also noticed that I've been getting a bit more exhaust backfire than before.

I dunno if the bogging problem is even related to the hesitation problem. I guess I have to go and borrow some parts from my gf's max (coils, MAF) and do some diagnostic work. Maybe buy new O2 sensors if it comes to that point, although I haven't gotten any O2 sensor codes (either CEL or hidden). I just hope it not a failing fuel injector.

Also, what are the symptoms of a failing TPS??

 

I would have the transmission checked. Your clutch maybe?

 

I don't think its the O2 sensors. Good idea on swapping out the easy stuff from your GFs max.

You can very easily check your TPS - the procedure is in the Haynes... I guess a failing TPS (intermittent) would result in some bucking/jerking (from the ECU being signalled incorrect throttle positions) - but am not sure on that. The TPS is easy to check - do that before replacing it.

 

You could be describing my car, before I finally found the cause anyway. I had a broken wire in the harness leading to one of the injectors. I just about went crazy checking and switching sensors, coil packs, etc!!! There is a Technical Service Bulletin in the Stickys that describes where this problem is commonly found and ways to diagnose it. Good luck!

 

I have the same thing happening with my car right now, it started suddenly.
I was told it might be the MAF, im going to test it with my multimeter tonite. I'll make another post later.

Dave

 

That's funny, my car is acting almost the same, kinda weird too, it bogs down when I shift sometimes, it doesn't do it consistantly though.

 

Try replacing your PCV valve, other people have had this problem and all they need to replace was the PCV valve....and its cheap

 

I have this "bogging" problem in 5th gear too. If I hit the gas a little too quickly in 5th gear the car shakes violently and then slowly comes out of it and accelerates. If I ease into the gas in 5th I have no problems. I have recently done a full service for 90K. I do have failing bearings in the transmission but I doubt that is what the problem stems from. Anyone know what it could be?

 

To the top........

 

Bump...Anyone know what is going on here?

 

So you have already tested your TPS and replaced your PCV valve?

 

I replaced the PCV valve recently when I put plugs in. As far as the TPS, if that was bad then why is this only happening in 5th gear? So no, I haven't tested that. I have the Chilton manual and it apparently isn't as complete as the Haynes.

 

I noticed that my off-the-line bogging problem is at its worse when the motor is still cold (ie right after I drive off in the morning). Does this fact point to anything?...

 

Both my 99 and my 95 have this problem.....going in 4th or 5th, partial throttle and it bogs/hesitatates then smooths out.

 

I have a similar issue, hesitation, if bogging is - me stepping on gas and getting no throttle response until it feels like giving then i'm bogging too, and finlly that gives me weak throttle response sometimes, but not everytime i step on it, it's like a 60% chance.I'm pulling a Vehicle Sensor CEL Code. I'm currently checking that, when i figure out how to take it out. If it fixes it, i'll definitely let you know.

 

i've spent the last 2 months tryin to figure this out, for about an hour last night i had it runnin in the driveway, wiggling wires and probing around with the multimeter...the fu@kin car had to stall at least 17 times, sometimes after a minute or two, sometimes after 5 min. somethings tellin it to shut down???? i have all the same drivability problems and i am still getting no codes... i'm half tempted to buy a new pcm !!!!!

 

I've since fixed the bogging problem with a new MAF, but the shaking during quickly applied partial throttle on the freeway is still there.

 

Check your ignition coils. Disconnect each of them to see if there is a misfire. As you disconnect each one you will see the engine start to shake and vibrate.