Should I Change TPS Myself?

[johna_99_99]

hey guys.......i recently ordered another TPS for the car. I called Nissan and they said they can change it for 70 bucks labour. Can I save 70 bucks and do it myself? i have minimal mechanical knowledge and im not sure if this is a hard job........when i look at the tps i can see 2 bolts holding it onto the throttle body. Is it just a matter of taking these 2 bolts out...take it off and put new one on? can anyone explain to me what to do or is it best to bring it to the dealer which i do not like doing. thanks

[Neil]

you can do it, it only takes a couple minutes but nissan has to pro-rate the labor cuz they cant charge less than one hour.

Just get the TPS and check around for FAQ's on how to set it up. You'll need a multimeter, a 7mm (i think) wrench, and a paperclip.

[johna_99_99]

thanks dude i replaced it today and it was easy as hell....didnt realize how easy it was.....the only is after i changed it my idle sits at 1800 now....but shes running 100% better

[Neil]

To set the idle you have to unplug the TPS and turn in the IACV screw (down in between the 1st and 2nd intake runners) till the tach reads 700/800rpm at idle after the motor is up to operating temperature. Unplugging the TPS and setting the idle are the first 2 steps in setting ignition timing, so you might as well get out your timing gun and make sure it's right.

Did you use a multimeter to get a reading off the middle wire on the TPS plug to make sure it was between .35 and .5v with the throttle plate closed?

[johna_99_99]

yes i adjusted the voltage to be 0.45V...........the car is running better but now as it idles(1800) it hiccups or backfires every 30 seconds or so........and when im driving......if i step on it then release the pedal....as the rpms drop i can hear many small backfires.....but it doesnt backfire after i shift like it used to.......does this have to do with ignition timing???? so when i set the idle properly this will fix the problem????? i do not have a timing gun

[johna_99_99]

ok neil i adjusted the idle to be about 850rpm..........now im stumped as to what to do....is there another step i have to take to complete the job?

i thought all you had to do was change the tps and thats it......i guess i was wrong..........

[Neil]

Well, your problem may not be 100% tps.

If its running a lot better then that's awesome, but it sounds like there's somethin else minor going on. Ignition timing effects idle speed as well.

The thing is, with motorsets, at whatever warehouse they sit in, you can almost guarantee that each motor has had parts picked off of it for one reason or another. They may very well have stolen your motors original cam angle sensor for another motor and replaced it with another one when the time came to sell you your motorset, and it's not possible to clock the thing properly without the motor running. Even if they inserted it and snugged it down in the exact same spot, manufacturing discrepencies from the factory between each CAS may result in needing slightly different clock angles. The Original Equipment Manufacturer makes all these things adjustable for that reason.

You can rent a timing gun from Autozone for probly $30, or you can just buy your own for as much... preferably one without a dial cuz they may make it more confusing. Timing guns have +/- clamps for the battery and another clamp that is meant to hold onto Cyl No.1's plug wire. It reads whenever there's current in the wire and fires the light at that time. However, Since an SR is coil-on-plug, there's no plug wire to read off of. If you have a KA wire kicking around, cut the distributor cap end off and stuff it up into the coilpack, and put the other end down on the plug. This will give you a good temporary place to get a reading off of. At 700rpm idle with the TPS unplugged, 15°Before Top Dead Center (2nd mark from the right on the crank pulley) should line up with the pin stickin off the lower timing cover every time the No.1 plug fires. If you rotate the CAS back and forth you'll see the mark move as well as hear the idle rise and lower. Get the timing mark lined up and re-adjust the IACV. Then you should be golden.

If you still have a problem after that you at least know what it isn't. I would move on to diagnosing the Oxygen Sensor next, verifying any wiring you did if you lengthened the plug and checking it's wire at the ECU for proper voltage. I know if you have a Blacktop SR you can buy a '96 300ZX-T pre-catalyst sensor and its plug and play. If you have a Redtop, there's another sensor you CAN use but you have to swap around plug wires.


Modified by Neil at 11:14 PM 3/8/2006

[johna_99_99]

hey neil thanks for your help

ok well i picked up my own timing gun......50 bucks..........is there anything you can use other than a spark plug wire, because i dont have any old ones lying around and i dont wanna buy a set of brand new ones just to rip apart........

also is this the CAS? and if it is it doesnt seem like it can rotate???????

[Neil]

yep That's the CAS allright... It wont move cuz there's 2 bolts that hold it to the head. One on the top right and one underneath. loosen them a little till it can rotate and just snug them back up when youre done. They dont have to be very tight and you don't want to strip the head.

as for getting a reading without an extra plug wire, there was someone who said they tried a way to get a reading off of the middle wire in the coilpack plug, however he went on to say that he couldn't get it to work. I don't even know what he used to attempt it.

I would ask around for a wire... A Junkyard or auto-wrecking joint is a very good option, or you could go to a garage and see if they have any with straight plug boots they just tossed out... or ask one of yr gearhead friends if they have any spares? i've got a ton in my garage and I couldn't tell you where most of them came from. If worse comes to worst, i could ship you one of mine for $5 to cover shipping.

p.s. nice lookin install

[9240sx]

You can use the first coilpack harness..Iv used the spark plug wire and you will get the exact same reading if you just hook the timing gun up to the coil pack harness.

[Neil]

You mean just clamp the sensor around the whole jacket?

[johna_99_99]

ok update...........im trying to get the idle to 800 before checking timing.......but when i start the car with TPS NOT plugged in i cant gett he idle to drop below 1200 rpm..........but when i unplug TPS while the car is running and idling at 800......the idle will remain there.........ok well idling at 800 rpms......i clamped around the center large wire from the 1st coil pack...........and i got a reading..........the timing was way off it seemed.......it was maybe 4-5 ticks to the right of the very right tick.....so it wasnt 15.....it wasnt 20....it was maybe 35? ok well now ill try rotating that CAS.....im just having trouble getting the screws loose because my hot pipe is the way.........ill just take it off the hotpipe.... loosen then put back on.......ill be back with an update.............heres another pic of my SR lol....i took these a few days ago......

[johna_99_99]

ok i loosened those 2 screws......but it doesnt rotate.......i took that black plastic piece off....and theres a round thing underneath.....is that what im supposed to rotate???????

[johna_99_99]

sorry guys this probably all sounds really dumb and simple to you guys but its my first time checking my timing and appreciate the help your giving me

[Neil]

yeah put the dust cover back on. The 2 bolts youre supposed to loosen are either 10 or 13mm i think. They should also be recessed for a philips screwdriver. They are NOT the litlle gold colored guys that hold the black cap on.

The whole thing SHOULD turn with the 2 bolts loose... If it doesnt, give it a LITTLE BIT of 'help' with a hammer on the upper slotted ear that one of the aformentioned bolts goes through.

But yea let the car warm up and get down to around 800rpm and then pull the tps plug.

Then adjust the timing via rotating the CAS.

The marks go:-5° 0° 5° 10° 15° 20°

you want the 2nd from the farthest right. If no amount of playing will get you that mark, the CAS may be off a tooth (which would confirm my suspicion about it getting borrowed at the warehouse... )

once youre certain the timing is set to 15° BTDC, re-check the idle and if you have to make any adjustments to it, double check the timing afterward.

If you really can't even remotely get the marks to line up, ill find you a link that outlines removing/installing the CAS. this involves removing the valve cover.
Modified by Neil at 2:15 AM 3/9/2006

[johna_99_99]

lol......im an idiot......ok well now im totally confused.......i noticed the timing was off so i backed it up to the second mark from the right via the CAS........went for a drive and the car had absolutely 0 POWER..........i then brought it back home........and readjusted it so the timing was way ahead then i had my power back again....i actually noticed it had a bit more power than before i started playing with the timing......im totally confused here

[johna_99_99]

the only thing thats odd is adjusting the idle.........ill adjust to 800 with TPS unplugged....but then if i turn off the car and back on again.....the idle goes up to 1200.....and i have back off the idle even more..........im totally frustrated here

[PhopsonNY]

Maybe this will help in the mean time

good luck

http://www.frsport.com/sr20det....html

[johna_99_99]

this is where the CAS is right now....car has way more power than it did when it was set to 15 degrees

[Neil]

wait,

you got it set to 15° but it runs better clocked to the right as far as it can go?

or did you mean "car has way more power than when it wasNT set to 15°"

[johna_99_99]

the car has more power now that its set way ahead......

when it was set at 15 degrees......the car had no power at all and i mean no power...i couldve ran quicker

[Neil]

welp, if you're certain the timing is 15° before top dead center, then that's the end of my rope. it should run very well when set properly. I wouldnt stop poking around, you don't want to toast anything with it set up improperly even though it may feel better.

[johna_99_99]

i just went for another ride.....its actually throwing me back in my seat a little bit now.....before i started playing the timing.....the car seemed slow...but now its throwing me back in my seat........i checked the timing aagain when i got home and it was way ahead......lol.....i dont understand but i mean the car is running good.....maybe if i adjusted the timing even further ahead ill get more power? lol....this doesnt make sense to me....

[johna_99_99]

should i bring it to the dealer and let them know whats going on

[Neil]

yeah i wouldnt go adjusting it improperly to make it better. It may be that the timing chain itself has jumped a tooth, which would bring the CAS with it... so when the CAS looks to be set properly the ignition would still be out of phase with the stroke. That would explain the wrong settings making it better but that would suck a lot at the same time.

The dealer would probly hold up a cross and scream "THE POWER OF CHRIST COMPELS YOU!!!" if you brought them an SR. That is, unless canada was an export market for 180's and Silvias with SR20DET's? ... I see your location but i see the pic is of a left hand drive car

just make sure every time you scope and adjust the timing that the TPS is unplugged... it will read differently at idle with it plugged in

[johna_99_99]

ya the last time i brought it to the dealer they had no clue what that engine was..........they would have no clue what a silvia was or anything......i was talking to the technician one time and he had no clue what coilovers were....i guess there new but still...........well im stumped.......could it be possible that by clamping onto that center wire from the first coil pack screw things up?

[Neil]

#1's harness does run down past the other coilpacks so it may be picking up interference and fooling the timing gun... I doubt it but I can't say for sure. if i were there i'd still want to go get a length of plug wire, just to double check.

EDIT: Wait a sec. Does your timing gun have a dial on the back of it?? If so it has to be on 0 for the mark to line up with 15° on the crank pulley.

If you turn the dial on the gun to 15° , 0° on the pulley should line up. If you put the dial at 15 and clock the timing to 15 also it'll be totaly ****ed up.

[johna_99_99]

no there is no dial or anything....its just the cheapest one they had.....it says DIS conventional on it.......no dial......just the light activator.........i went outside to check my timing again.......first i did it with tps unplugged and the timing was ahead.....i then went ahead and plugged it back in.......took a reading and got 20 degrees.........thats the first time i got a reading close to 15 degrees....i dont know whats going on lol

[Neil]

i keep saying youre supposed to set it to 15 degrees with the tps unplugged. Disregard whatever it says with it plugged back in.

unplug tpsloosen casrotate cas till 15 lines upsnug cas downplug in tpstest drive

if you cant obtain 15° with the tps unplugged with any extremity of movement with rotating the cam angle sensor, follow the link someone was kind enough to insert a few posts up on what to look for when removing/installing the cas

[johna_99_99]

yes i did set the timing with the tps unplugged.....the thing is everytime i unplug it the idle jumps.............when it jumped i adjusted the screw so it go to 800rpm.......i then set it to 15 degrees....plugged the tps back in and the car ran horribly............i was reading other posts and some people do the timing with th TPS plugged in.......why is it working for them?