I have no clue where to even start with this. My dad thinks it has something to do with the fuel injectors or something. Whats happening is a weird acceleration lag. I'll have it full throttle, pedal to the floor, and for a couple seconds it will bog, and then all of a sudden, I'll get the power. It does it in all the gears at random RPM's but it doesn't seem to do it past 4000rpm. I don't know if i described the sound well enough but basically, it either gets really jerky, as if i were to press and release the throttle very quickly, or it sounds like it's at idle, and then all of a sudden kicks in.

By the way I drive a 1990 rx7 TII. This started happening after i had some exhaust work done but I dont think thats the problem. I have a full racing beat system. Any help would be appreciated, thanks.

 

Does it happen at around 3800 RPMS? Because that's where things like that usually happen, and as far as i know, that's a problem with the grounds.

 

yea i'd say it happened at 3800 rpm. It's kind of random though, sometimes it would make it through the whole gear without doing it. I was praying that it wouldn't do it while I was driving because I looked like an idiot bucking in my car. I tryed accelerating really slowly, and sometimes that worked. I also tryed just putting the pedal to the floor, and that never seemed to work. It was definately happening at or around 3500-3800rpm.

 

Did you put a FCD on it when you put the exhaust on it?

 

This could be completely wrong since it was with another car, but my bronco II did this alot and it turned out the heated oxygen sensor was bad. The car would idle fine but when you gave it a little bit of gas it sounded like it was going to stall, then from about 1500-3500 the whole car was jerking like you were steping on and off of the gas petal really quick.

 

yes i put a FCD on when i bought the exhaust. The exhaust was purchased over a year ago, along with the FCD. When I say there was work done on my exhaust I meant that it was aircare day and I needed to swap in the cat for a day and swap it back out. The o2 sensor sounds like a good candidate actually because I remember doing a really ghetto wiring job on it (was in a rush one day). I'm going to go check that. Thanks

 

i took a look, the wiring seems to be fine. The o2 sensor was replaced about a month ago so I don't think this is the problem...

 

I'm gonna say it's the grounds. I'd just get a ground wire kit and replace it just to be safe. But hey, that's just me.

 

try your fuel filter, i have had similiar probs in the past on other cars and the fuel filter and spark plugs were to blame. clogged fuel filter will cause inconsistant fuel pressures and possibly foul out the spark plugs.

 

Thanks simply, I might just have to do that but I really don't want to since I'm trying to sell this car... Rx7ridah thanks ill try that as well.

 

Could it be the alternator? That might make sense since I just recently installed a FD alternator. How can I check if its the alt?

 

unbolt alt
go to autoparts store and have them test it

 

really dont make it more complicated on yourself
grounds are easy to install just put them on :-)

 

Had exact same issue. How to resolve???.....Re-Wire fuel pump. Pulled harder and no hesitation. Also grounds help.

 

Search "3800 rpm hesitation"

 

This isnt the 3800 rpm hesitation problem that I've read so much about, it's completely different. I don't have time to work on my car anymore like i used to when I first bought it so I'm just going to take it to mazda. I cleaned the air filter, did an oil changed, replaced the fuel filter inside the tank, checked some of the wiring, had my dad look at the alt and none of it seemed to fix the problem. So i'll just take it in, thanks for the suggestions. I really dont have time to redo the grounds :S