Okay, I have tried to figure out what it was and fix it but I have had no luck and I am hoping that someone can help me out.

Here is my problem...

I have replaced my intake and pulleys, and put on ground wires, everthing is mechanically sound and correctly installed. Now when I rev the engine in neutral it works perfectly and there are no idle problems, but when I am driving in any gear other than first, my engine seems to be sluggish and doesn't want to accelerate on the road when the gas pedal is depressed(pushed in) more than 1/4 of the way, less than that it works fine. But sometimes when I depress it in all the way and hold it(floor it) the car then accelerates like it should (this case is only for gears 1-4, 5th and 6th always have the problem). To better describe the problem, the car accelerates as normal but when it gets to about 3K-3.5K it then almost stops accelerating and the engine very very slowly increases the RPMS and it feels like the throttle body just about closed up.

At first I thought that it was the mass air sensor but if that was the case, why does it work like it should sometimes when the car is in gear and being floored? The car always revs fine when it is in neutral. Does it make a difference if the engine has a load by being in gear? I have taken it out and cleaned it with an electronic parts cleaner. Still no difference.

I thought it might be limp mode but I have reset the ecu a few times and went through the procecdures for resetting the throttle positioning sensor. Still I get the problem.

Has anyone had an acceleration problem where the car almost starts to jerk back and forth around 3K+ RPMS at speeds greater than 40MPH?

I am going to check the throttle body to make sure it is opening up all the way to rule that out. If it does then I am guessing that I have a faulty MAF??

Thoughts anyone?

 

I know you said it's all mechanically solid, but make sure you don't have any intake leaks and the belts are properly tight.
Good luck.

 

Try to reset your throttle position sensor. Don't remember how to do it, but I'm sure someone here knows the procedure.

Doubt it's an intake problem. If it's doing it at WOT it's ignoring your MAF etc, so it wouldn't be taking that info into account anyways.

 

Jesseenglish,

Are you saying that at WOT, the car ignores the signal from the MAF? I was saying that at WOT sometimes I do NOT have the problem, but that is only in gears 1-4. I am at the point where I would like to replace my MAF because I think that is what is causing my problem. If you can think of anything else that would have this effect. Please let me know. Thanks.

350ed,
The intake is connected together well and there are no leaks. The belts are tight but I don't think that they would have anything to do with this problem.

 

Okay, I have just talked with a parts rep from Nissan and they told me that the problems that I am experience is from the MAF and that it is sending mixed signals to my ecu causing the car to buck when accelerating. Hence I have to get a new MAF.

So to anyone reading this, if you have a MAF for sale, I am interested in buying it.

If you have one for sale, please make sure that it matches this part number:

#22680CA000.

If you look at the MAF (if you have one for sale), the part number might be a little different in that the letters "CA" might not be listed on the part and instead might say "S7". Thanks.

 

you can reset the throttle position sensor by turning your car to the on (then off) position 3 times within 5 seconds.

 

Cool, thanks.

ZxRage, I'd try this first before I went and bought a new MAF. Just because a parts guy says that's the problem doesn't mean it really is. They want to sell parts so it's to their advantage to tell you certain things.

Never heard of "mixed signals" If the MAF was bad the car should just be in limp mode at all times and you should get a "Check Engine Light". Not just when at higher RPMS and in closed loop.

 

its not your MAF! my car started this crap yesterday at VIR. i switched MAF with another Z and it did the same thing. I have reset the computer & TPS and its still messed up. my car does great at 25% throtle but anything more and it feels like a honda civic. I think my cats are clogged up or comming apart. I will find out tommorow if i can get it to the dealership!

 

I had a problem similar to yours. My car "bucked" at high engine loads and it felt like it was either stopping and then going repeatedly. Mine mainly did it in 2nd gear. I came to find out that I had a bolt underneath the strut bar slamming into it, which caused the engine to sense knock and shut off and on.

This is a longshot, but it would be relatively easy to check for and fix. I would just check all the nuts and screws that you took out and replaced to see if they're a little too close to anything that might touch when engine vibrates.

BTW, my check engine light never came on or anything making me aware of the knock issue.

---- Best of luck

 

well my problems were the random tech. cats. they broke up and clogged up the exhaust. all is fine now ( after gutting them ).

 

I will be eliminating the MAF entirely and going to a MAP setup, if I still get this problem then I am back to square one, I will keep everyone posted. I will also check to see if anything is touching the engine to give it a possible sense of knock.

 

Why do you want to go with a MAP? You don't have FI. That's the only time I could see it being useful to add a MAP.

 

Ahh,

Jesseenglish,

You are seeing into my future....

Here is a hint as to what is going on,

AEBS 4.3L Titanium sleeves, a full balanced crower set of internals, and possible APS Turbo kit. The goal: 25lbs. of boost.

I just hope that when I go to the MAP setup that the problem will go away. If not then I will have to maybe take it to a dealer to have the car diagnosed, but then I will let them know that I have voided my warranty by modifying my car. I don't want them to know that yet.