2000 Maxima 5sp 197k

I was having a horrible bucking problem to where I couldn't hardly drive my Maxima. It devolved to where I had to use the accelerator to keep it running.

It threw a coolant temp sensor code (my temp sensor is only 3 months old from AutoZone) and a MAF sensor code. So I replaced the MAF sensor and the car ran perfect again.

(Additional recent replacements: main cat, delphi fuel pump from AutoZone but not a new fuel pump housing, Hitachi ignition coils a year or so ago, and crank position sensors.)

Spark plugs looked good so they're not new, but they would cause misfires not bucking.

I checked the fuel pressure regulators and they're not wet with fuel at the vaccume hoses.

I replaced the MAF with a new AutoZone MAF to fix the problem and the car initially ran great. But the next day, I'm doing 70 mph and the car bucks a couple of times, suddenly. So the problem is still present to a degree. And when I drive for a while and let the car sit for a while before starting it again, it takes a while to start, almost like it loses fuel pressure while sitting.

I pulled codes and it's giving me the coolant temp sensor code still. My coolant overflow tank has coolant in it so I'm assuming the system is full.

Can a bad coolant temp sensor cause the car to buck hard? I've heard it affects cam timing and can cause that.

I don't suspect it's a broken pre-cats, but I guess maybe that's a slight possibility. I could, if need be, shell out the pre-cats just to test to see if they're the problem. But I'd rather get a more difinitive answer and or direction to go than just shelling cats for diagnostics.
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Is it possible something caused the old MAF to go bad and the same problem is causing the new MAF to go bad now? The old MAF was only 1 1/2 yrs old.

Can fuel pressure regulators go bad without leaking fuel into the vaccum lines?
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Any idea what would cause the bucking?

I gotta get this fixed quickly since I can't work without this car (it's a work-outfitted vehicle).
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I've experienced hard bucking at random times in two different cars (Maxima & Corolla) and both times it was a bad MAF sensor. It felt like the engine had an on/off switch and someone would randomly flip it.

Replaced both w/ OEM sensors and never had the issue again.

 

I replaced the MAF with an AutoZone MAF and it was great the first day. But today, it's got the problem again, just not nearly as pronounced.

I get the idea that something may be throwing off the timing (coolant temp sensor) or there's a fuel problem. But I'm gonna be really ticked if something electrical is killing my MAFs.

 

id say follow ukmasterminds advices, get OEM maf, or at least the OEM maf transitor, before you start guessing everything else is wrong.

i had a bad coolant temp senor, and had no drivability issues, only a check engine light.

 

May have to...isn't it the Hitachi MAF?

 

Correct. Hitachi is OEM.

Hopefully that will fix the problem

 

Actually, just found out that AutoZone's Hitachi MAF is more expensive than the dealer's! lol

 

Thanks!

 

nice follow up post, good to hear

 

So you replaced the coolant temp sensor & the bucking has stopped?