wankelhead

like it says.this problem has quickly gotten worse,and i have not found anything clear about it in any searches.when i'm just crusing around with light throttle or light [half throttle or so] aceleration,i start getting some really bad hesitation.feels like fuel or ignition is cuting out for a moment.it has happend at any rpm up to 5k[not gone higher yet-motor break in].the strange thing is,when i floor it,it acclerates silky smooth,no hesitation what so ever.it idles very steady most of the time,but gets real lumpy at completely random times.duno if there is a conection.new fuel filter,plugs,wires 1k miles ago.timing has been set and rechecked several times.tps has been adjusted,but had some problems with it,could it be a potential factor in this?injectors where rebuilt about a year and a half ago,but by a local shop...could this be a injector problem?emmision stuff is gone,no codes from the ecu,i'm a bit lost here.does the car run in open loop at WOT(with all sensor input)?this sucks in a big way...finally got the motor pretty much broken in,and now it wont run for ****!!thanks
david

niner

could be tps, double check to make sure its adjusted right

i'd be looking for intake leaks too. check all hoses/manifold gaskets etc. use propane or starter fluid when its running to help find them. would make sense that you have intake leaks if the engine was just put in recently. after my 1st rebuild i did, the car had problems like you described, turned out to be intake manifold leak

Josepi

How does it act on decel? Smooth? Popping in the exhaust?

gsracer

this is exactly what I was going to search for today. It only happens generally when I am at a constant rpm just cruising. The car surges and it feels almost like it's hitting a mini fuel cut. WOT it is all smooth

wankelhead

josepi-its pretty smooth,a little bit of poping thou.keep in mind,i am running no acv/emissions,and dual exhaust.the mixture seems to be set pretty good,its not runing real rich at idle or anything[no unburned fuel smell].
niner-i will once again recheck for vacum leaks,i have done so several times[i did find some first time around].i have had problems with the tps-it seems to not wanna return to the same point every time.i will set it perfect,rev it a couple of times,and it will be off..and so on.lubricated everything real well,to make sure its not encountering friction that holds it up....how big of a chanche that its the tps?a new one of those puppies is about a 180bucks...
thanks for all the help,guys.
david

Blowtus

I recently had the same problem, which slowly got worse. Hooked a multimeter up to the ecu, measured the throttle sensor voltage input while driving, it was spiking at the same time as my hesitations occured. replaced the tps, it's all fixed.

Charlie

daves86gxl

mine is doing same thing and it's the fuel pump on mine might want to check yours

wankelhead

fuel pump would not make to much sense..if that was the problem,why would i get smooth throttle at WOT,when more fuel is used?
like niner suggested,i have checked again for intake leaks,and i have found one.waiting for parts from mazda,then we will see.strange thing is,even w/o fixing the leak,i have not really had problems with it the last couple of days.i'm hoping the vacum leak will fix it for good,otherwise i'll try Blowtus's idea and monitor the tps for voltage spikes.
d

HAILERS

TPS should be set with a HOT engine and only rechecked when the engine is HOT.

Seems you might want to do as RETED suggests and put a meter on it and run it thru its full range. Looking for opens in the pot. If that checks out ok, try a different technique.

Connect every thing up. Get the engine fully HOT. Locate your tps plug. NO, NOT THAT GREEN SLUG! The tps plug, about four inches from the tps. Look at the harness plug for the tps. See one wire that is GREEN WITH A RED STRIPE? Good. Stick your digital meters positive lead in the rear of the plug where the green/red wire is. Put you negative lead on the battery negative post. Put on dc volts. Start the engine. Wait a minute or so. Now look at the voltage. Should be ONE (1) volt. It not, turn the screw until the meter reads one volt.

Now flip the throttle several times. It should return to one volt. A 0.95 to 1.05 is perfectly acceptable. You should be able to repeat this.

Tomorrow morning it ain't a gonna read one volt. Not until the engine is fully hot. Designed thata way.

If while doing this, you took any plug off or apart, it was done wrong. Start over. Car running will prevent the thermowax from waxing you. I care not what the manual says about initial set couplers or the engine being off. Thats a different method all together.

I'd ohm out the tps first though. Sounds like there is a glitch in the pot, maybe.

wankelhead

thanks for the lenghty relpy,hailers!
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yup,warmed it up to full operating temp every time

i did ohm out the tps,seemed fine.acording to RETED's site,the only confliction i have is,with the digital ohm meter,it goes into OL briefly when it swithes from ohms to kohms.wich,seems normal...

i used the resistance method for this,with the plug apart,engine off,adj. to 1kohm
this is where i had problems,as i would not get consistant readings after fliping the throttle

i had previously been under the impression the the eng. off/resistance check method was the most reliable.i removed all my fast idle/thermowax stuff,so thats a non factor.but i will try the method you recomended.
david

HAILERS

All my replies are lengthy. I rattle on and on and on and on and on and on and on and on and on...............

All those methods work, ohms, led lights, voltmeter. The manual, both 87 and 89 make reference to the tps reading being one volt at idle. Ever check the voltage at the green/red wire after using the light assy or the ohms method? Should be approx one volt.

Wish you had access to a analog meter for checking the pot out for opens. To me its more accurate.