I just replaced and adjusted the tps. Only when Im in gear, the car will hesitate around 2 grand and then all of the sudden the rpms will rise. This is only on light throttle and only in low rpms. Any suggestions?

 

you may have adjusted the TPS, but did you check it's movement on a meter? It's getting more and more common that they're developing "Flat spots", where it doesn't send that you're accellerating, yet the car is still taking in more air due to the throttle plates being opened..

The easiest way to test this is with a cheap, mechical voltage meter... then you can watch what happens as you hit the throttle at different speeds. A lot of digital voltage gauges don't have the resolution to display the voltage change fast enough to see it.

 

The tps has no flat spots. It goes up smoothly.

 

i had the same prob/ i was watching mine on my safcII. i messed with it for a while, made it worse, asked for help, got ignored( as usual on this subject) and just accepted the slight bucking.

 

i have horrendous bucking with mine. I tried to adjust it today but I made it worse. when i started the tps was only reading 80 ohms at idle and 6k at wot. I tried to adjust it but couldnt get it any better than 80 ohms it would stay between 60-80. I am going to try and adjust it again tomorrow hoping that it fixes it but in all honesty i have a feeling that i might need to purchase a new tps.

 

yeah mine is all the way through the rpm slightly. i hate it! but i kust cant adjust it right. wonder if mine is shot?

 

yours might be i dont think i can adjust mine to be perfect so like I said I have been thinking about getting a new one... the only thing is they cost like 150 if you buy them new and thats outrageous

 

Could it be non tps related. It bucks real bad. If im in first, starting from a stop I have to slip the clutch like crazy, otherwise it will stall.

 

You prolly flung some apex seals from runing that 12psi on stock fuel system. :-)

Do any of you with this have a moded TB? That mod will cause intermitent bucks as the throttle plates open and close. A bad water thermo sensor can acount for a wierd ride at times. Bad grounds, ground the PS if you have a 86 model ONLY. Mainly it is a flat spoted TPS.

 

Ive got the same problem in my na. it doesnt happen when I accelerate hard, just when I try to take off smoothly

 

If you unplug the TPS and the problem goes away, then you have either a mis-adjusted TPS or you have a bad TPS.

Pretty cut and dry test.

90% of the time it is a mis-adjusted TPS... dead ones are pretty rare.

 

i dont mean to be an *** but has anyone considered engine mounts/tranny.... my car does the buck on decel i know its because i have new delrin bushings and mazdacomp mounts in the back and old shiznit in the front..... deeead mounts

 

I don't see how you're being an *** there, man Seems like a good enough idea, but the only thing I see is that if your engine/tranny mounts are shot, then you'll get a lot of vibration, not nessicairly bucking. I know I need new tranny and rear end mounds, and that gives me a decent amount of vibration.

 

Another possibility besides the TPS--did you do anything to the BAC? Mine once caused bucking identical to what you described. If I was cruising at, say, 20MPH in 2nd gear, it had an on/off feel to it.

I had taken the BAC apart and cleaned it, destroying the calibration on all the set screws (I didn't know better). I eliminated the bucking by adjusting the socket head screw facing the front of the car.

 

Mine is starting to buck some under medium slow acceleration.
The TPS checks good (idle & sweep).
I'm checking the AFM sweep (electrical & mechanical) next.

 

Thanks guys.

 

sure shoot did you find out what you bucking was???
mine started doing this slightly and has gotten a little worse over the past week or so. I checked the grounds they look good I think im gonna unplug the TPS as was said befor in this thread, but when I search most people have beed saying grounds for the bucking problem Im gonna add some grounds using rotaryresurections write up. then im not quite sure what to check next.

 

No it hasnt stopped bucking. ENgines basically blown now.

 

I've had this problem since I got my 89N/A. Replaced the TPS, it got alittle better but still there. For me, the only thing adjusting the TPS does is move the flat spot up or down the throttle range. I've got mine adjusted to the dead center of the FSM specs.

 

I have the same problem with my GXL right now. It's driving me up a wall. It is definitely the TPS, combined with other issues, because I unplug the TPS, and it still bucks, just not as predictably at a given throttle position (namely, the position required to maintain cruising speed at 2500RPM)

I'm tempted to just megasquirt the stupid thing and be done with all these problems.

 

I dont know what the deal is it seemed to do it more lastnight when it was colded and boost was a little higher, I think my boost gauge is broken cause ite only showing like 9 on the vac side at idel and I put a Greddy FMIC and boost didnt change should have droped a little I think.idels fine starts fine. Im gonna try this.......
1:set timing
2:get a fuel pressure gauge to make sure im getting the right fuel even though my AFR shows its running rich.
3:add grounds
if all that dont work im gonna try
changing and zip tieing all vac lines under UIM and get T clamps for all my IC pipes and change TPS and then Im not sure what else.

 

Just did a comp. test. The front rotor is completely gone.