i think my tps is shot. but how can i be sure?
 

well i have heard many similar threads but i cant be sure that my case is the same. well it started after i installed my 720 primaries into my 88 turbovert. there has been an idle surge apparent ever since i installed my 1000cc secs. well i start it up one day and i let it warm up and i pull off as per usual and i notice that as i increase in speed in 1st it starts to hesitate (2.8-3k). so i shift and cruze at the same speed with less rpm. after a bit i come to a stop, do the same thing but this time it disapears. like it only happened while warming up. so next day, same thing, but this time its more drastic. problem prevails even after warm up and and so i decide to give it some gas in 2nd and it goes right threw like nothing was there. i come back to cruize at that rpm and the same damn bucking and hesitation comes back. so after a longer period of time it goes away all together. .....i come home from a 100 mile trip today and on the last leg the bucking and hesitation comes back out of nowhere...and yet, i can go WOT and fly threw the rpm range. i should mention that now while warm up, right after its ready to drive ill rev it and the fuel just gets cut or something and it sputters and sometimes doesnt reach past 3k before dieing back to idle.

the idle surge might be related. i noticed after i installed the 720s that now matter what i did the idle wouldnt go below 1.5k with 11afr. natural, considering the injectors. so i adjusted the best i could with the 2 adjustments up front. and i would take it for a drive and come to a stop. it would either go up and down, or become steady at 1.5k. magically however, i would blip the throttle, and it goes down to a perfect 900.

between gears, this problem also presents it self. ill disengage the clutch between gears, and it would rev continuously at that one spot for like a half second or so and THEN drop. it seems like the injectors are staying on and shooting fuel with out the throttle or something. on occasion, when i am cruising and the bucking persists, it will buck and jump on deceleration.


to sum it up- idle ok, only when i blip it, slight rev in N and in gear NOT OK. heavy throttle okay, but only after warmed up....


SO! where to start first? is the real question.:scratch:

First of all, how are you controlling your larger than stock injectors?
Secondly, how have you checked for vacuum leaks?

doh! forgot to list my modifications.


okay stock ports (engine with 7k) 1000/720 combo, rewired walbro 255, new FPR, banjo bolt. newISH fuel lines, all silicone vac lines, SAFC/innovative lc1 tuned to 12 across the board, rtek1.7 (with hes. fix), turbonetics t04 bybrid(1/2bar)/ full exhaust/intake, stock top mount intercooler.

my vac reading on my boost gauge is normal, and it is not fluctuating with this hesitation happens....at all (while not boosting of course)

Well, testing the TPS is really easy, so start there.

http://howto.globalvicinity.com/gv_w...i=58&co=1&vi=1

I've got a TPS that has proper resistance across the A to B terminals, but not A to C, and it give me a bouncy idle during warmup. It goes away completely once the idle gets down to ~900, but still has a bit of roughness going through the 1k to 1.3k range. Not exactly what you're getting, but definitely worth checking out in your case.

okay went for a drive today and i let it warm up for like 10 min. and i started off and it only did it a little bit once, then it went away for the duration of the drive...

and the afr while at a slow cruise of like 10mph are at a steady 11afr while the hesitation occurs

That's really rich for partial throttle cruising. The computer is likely not getting the correct info, and then messing up the mixture.

hrm, well it doesnt seem to help when i make the mixture any more lean during cruise

i want to check the tps, but the link was dead in the beginning of the thread. also, in section 4b i think of my fsm it mentioned something about it but it says i need some kind of tool. but i do know there is a simple way for checking it. ill get my search on.

okay here is a video. sound is terrible, but every time you see the needle leave idle im holding it at about 1/3 throttle. and its like hesitating and cutting out and whatnot.

http://media.putfile.com/weird-rev

okay i just checked my tps!!!!
 

well i measured the ohms of the TPS plug and if you are facing it with the 2 pins on the right and the one pin on the left, the top 2 measure 2.35! after warm up and shut down. and the two bottom ones measure 5.88!!! i read on the fc3s site that the top 2 pins should measure 1.... damn. ill try messing with that screw and ill let everyone know.


ok, one more update, i went back out to fiddle and it seems that when i depress on the tps nob manually i can get it to hang around 1ohm. the only problem is that in order to do this, the throttle needs to rotate (if your facing the engine) 1/8 inch counterclockwise to swing the arm INTO the TPS nob.

has anyone had problems with the throttle cable it self either being to short or hooking it up wrong? i think my tps is still good, its just way out of wack

thanks everyone.

hate to post so much but i feel i should just put it out there. after driving the car with the adjustment screw all the way in, it wont drop below 2. which is better then it was, and i DID notice a difference while driving, it was smoother. so i think the verdict it that i need a TPS. anyone selling a new one for under 200? lol


but i bet i could cheat by extending the arm of the tps. no idea how i would do that though.

They sell new ones for $135, but you can get a used one from the junkyard for less than 10 dollars. Just take your meter out there and test it first.

malloy has em new for 191. lol where can you get one for 135?? ill buy one right now, if you can find it 135 new. i would rather put a new one in and be done with it for another 150k miles.

but the more that i think about it, the more it makes sence. i noted that when ever the car would be at normal op temp, the problem would go away, and as i measured the sensor, the would be closest to 1 when it was hottest, and as it cooled, it gradually rose in resistance (correct?). so that would mean that when i first start the car, its all out of wack, and when it warms, it gets closer to normal....even though its still not there.

ebay? ebay is everyones friend

I checked my source again after you asked and it went up to 191 as well. Junkyard ftw.

yeah but im on my second one already. i think in the long run it might be a better idea if i just buy a new one. i mean, who knows. i could buy one from a junk yard and it might take a dump on my 1000 miles from the time i install it.


has anyone cracked a tps open to see if they can repair it?

The TPS should always be set when the car is fully warmed up, and you should see the resistance across the A & B terminals drop as the car warms. A & C resistance would increase as the car warms up, since the plunger is being pressed in more.

You mentioned that you thought the arm that presses the TPS in needed to be extended 1/8"; have you adjusted the screw as far as it will go, or do you not know that is can be changed? The screw is probably upside down on a turbo's TB, but you can probably get in there with a short screwdriver.

This pic shows the adjust screw on a S4 NA, but it should just be flipped for a turbo TB.

alright, so i bought a NEW tps from malloy 191.87 and all the problems have been fixed. i swear i better not have to touch my tps for another 100,000. miles lol

I bought a new TPS from Malloy too and I couldn't be happier. Good price, and no more TPS bullshit.