question about fuel pump and tps

[jonahs_supra]

87 7mgte 5spd
Mods...
46 trim ct26 with 12 degree clip
New AFM with 5k miles
3in down pipe
3in exhaust
2.5 intercooler piping and fmic
HKS ssqv
New plugs and wires
Stock boost to break in turbo...turned up to 12 Psi 2 weeks ago

Question 1...
What switches the fuel pump from 9v to 12v?
Im looking at a wiring schematic and see IDL wire from TPS connects to yellow wire running to fuel pump control relay
Does that wires switch pump over from high to low?
When does the pump know to switch voltages?

Reason for asking is after turning my boost up to 12psi I noticed while in a higher gear like 3rd
I'll start out at 3000 rpm and floor it
Turbo spools quick and supra takes off
About a second later the car feels like it hits nitrous...which I don't have
And really hauls ass
To me it seems the pump is switching to 12v

Question 2...
Decided tonight I would diagnose code 51...
I have had the code ever since owning the car ...8 months now
Never had a problem...CEL has never turned on due to code
I did a resistance check and all pins checked good except for E2 and IDL
I get no resistance
What does the IDL wire tell the ecu?
Well I plugged TPS back in and drove home
Decided to tromp on the throttle
Right when boost hit 10psi I hit fuel cut
Checked for boost leaks when I got home...with a tester
No leaks...checked codes 21, 34 and 51
Exhaust smells rich now lol

Any help and walk through on how the fuel switching system and IDL wire would be greatly appreciated

Thanks

 

[Dan_Gyoba]

Question 1: The ECU switches it, from what I've seen, it's based on an RPM/Load table. You can see that point on people's dyno graphs, where air/fuel is mapped on the graph. Doesn't seem to have so much to do with power, that's just your engine hitting its torque curve.

Question 2: IDL at the TPS tells the ECU that the throttle is at the idle position. If this is closed to E2, your engine will hit FCO at 1600 RPM, and not return until below 1200 RPM. (Detailed in the TSRM here: http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&P=125 ) This SHOULD have non-infinite resistance to E2 when the throttle is closed, and infinite resistance as soon as the throttle is opened.

 

[jonahs_supra]

Thanks for the info
So if I'm thinking correctly
If there is no resistance at E2 then my car shouldn't rev past 1800rpm...correct?


Sent from my PC36100 using Tapatalk

 

[Dan_Gyoba]

E2 to IDL. E2 should be a ground point, and it can be any non-infinite amount of resistance (IE, the inside of your TPS gets wet for whatever reason and there's a high-resistance contact between E2 and IDL, you'll still have no revving, which is what happened to me.)

 

[jonahs_supra]

My car revs fine and have never had a problem with revving
I suspect tps is bad so ill order a new 1 after I do a little more diagnosis

 

[suprajztwenty]

wow, i have the same exact problem!

i have noted it down to these things as possibles (efi troubleshooting in the manual)

process of checks

valve clearance
cold start injector (unplugged mine since im in tx...havnt blocked off the line though)
fuel pump voltage/pressure reg/injectors-
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=59

tps-
http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=FI&P=55

injector wiring

i havnt gotten time to go through it all. heres the thing about my problem, it does it in almost every gear, mostly higher gears. feels like a slight miss and then boost starts to hit and its like flicking a switch and POWER. this problem is really hard to describe...and its not just because im hitting boost, i can get up to 4psi before the power hits, and it hits hard.

at first i figured crap plugs/wires, so i upgraded to accell 8mm wires and ngk iridium...seemed to solve an idle stumble but the main prob didnt go away. so i changed the fuel filter and did the fuel pump resistor mod (though i havnt checked for power back there, the mod says i should have 12v all the time now) no change. i did find a somewhat loose battery connection and thought that would be it for sure, but that didnt do it either...i think all things combined its helped to an extent but the main problem is still there.

i started having idle issues, it would happen randomly and when it did, sounds like its camming. i pulled each injector clip untill i got to #3 which was the least difference in engine tone...still made a change in pitch though.
also when i try to hold the rpm to anything above 1k (sitting still) and i can hear a small pop/puff in the exhaust note every 3-5 seconds.


i put lucas fuel cleaner and ran 3/4 tank, no fix...this last tank i used a higher dollar lucas fuel cleaner (white bottle, blue label) and this time it seems to be making a difference now that i have almost 200 miles on this tank, seems like mpg went up a bit but ill have to see when i fill up.

the idle problem hasnt returned, going up hill/grade i still feel like lower power, but it doesnt feel like it missing a cyl now...but still, untill it starts to hit boost and its like flicking the switch and power, but its not quite as big of a power change as before.

im 90% certain its a tps or injector clog problem. im going to run this tank the rest of the week and see how it does...i found a guy selling me stock injectors for 25bucks so its worth a shot, and this way i can send out mine to see how clogged they really are.

ive been through every connector in the engine and pressed all terminals to make a new/tight connection, no good either.

the main thing that leads me to injectors is first startup after sitting over night....it takes about 2 extra seconds for it to fire. it seems like fuel pressure has bled off and needs to be primed back up. ive read theres a check valve in the fuel pump that could cause this, but im also wondering if i have an injector thats stuck open.

 

[jonahs_supra]

^^well are cars must be sickness twins lol
mine does almost the same thing
at idle a pop/miss will be heard once or twice every few seconds
but i think my problem is due to the following...possible bad tps, cracked cps cover and my iscv will act up from time to time lol

it was weird though yesterday
drove to work (40miles highway 1 way)
hit 12psi atleast 5 times...supra ate its 1st honda opponent lol
pulled strong and then really strong once the (what feels like nitrous kicks in)
no fuel cut or nothing
so on my lunch break i unplugged my tps connector to test tps(noticed locking clip fell off)
so after testing i plugged tps back in with locking clip
i didnt mess or touch anything else under the hood
drove home and back to work today...still fuel cutting and rich exhaust when idling
but she still runs like a champ and safely gets me to where i need to go

mine does take about 2-3 seconds to fire up after it set over 10hrs

 

[jonahs_supra]

Ok so I got some good clarification of what my code 51 issue is

Dan what happened with your tps was your IDL pin was shorted and sending a constant voltage to TCCS telling it the throttle body is close
While VTA pin was sending voltage to TCCS telling it the throttle body is open
When VTA sent a signal higher then 1.5v which is the throttle opening
The IDL pin is still telling TCCS the throttle is closed
Now the TCCS is confused and kicks into limp home mode thinking something bad is going on

Where in my case my IDL pin has no resistance
So my TCCS never knows when my throttle is closed
Which in turn never tells the idle control system to turn on
Which explains why my car idles funny from time to time

Thanks JETJOCK
Sent from my PC36100 using Tapatalk

 

[suprajztwenty]

that makes sense, so is it a sensor or harness at this point?

and as for your "nitrous jump"?

my problem seemed to go away with the last 100 miles. today to-from work, 0 issues to note as for power. still has the hiccup every few seconds at idle but that could be a few other issues since its done that since i first got the car.

im getting ready to move onto other things but please keep me posted on whatever you find. i know theres a thread on here for tps calibration, i think ill give that a shot since its never been done...worth a try anyways.

 

[jonahs_supra]

In jetjocks calibration thread...
Says to jumper E2 and IDL on tps plug
Check codes
If 51 is gone then wiring is good for E2 and IDL
did just as he said
Code went away

So since my resistance on IDL pin is reading infinite resistance my tps is bad
Reading should be under 2k ohms

As far as my fuel cut issue
I'm thinking my boost cobtroller is acting up
Adjusted pretty much all the way out...(ball/spring)
Boost still rising to 10 and fuel cut

Going to remove controller and see
Maybe my wastegate is sticking

After I figure out what going on with fuel cut then hopefully tackle the nitrous issue lol

Sent from my PC36100 using Tapatalk

 

[jonahs_supra]

Also test your tps 1st to see if it needs adjusted
If your tps screws are anything like mine then they're a PITA and just want to strip lol
I have another tps ill test tomorrow

Take a video of your car hiccup during idle and ill see if mine is the same

Sent from my PC36100 using Tapatalk

 

[suprajztwenty]

any progress so far? i installed my used injectors and overall theyre better and my idle quality is much much better but the "nitrous" jump is still there.

my problem has gone away from every gear but 4th and 5th gear but its mostly noticeable when i engine brake down a hill and slightly get back on the pedal to start again, then give it a little more pedal and it feels almost like a bog or running low on fuel, give it a little more pedal and you can actually feel the motor straining to maintain speed let alone accelerate...while looking at my boost/vac gauge just before it gets to 0, or sometimes when it gets really bad, 2-4psi+ is when power takes on...it feels like flicking a switch and POWER

 

[jonahs_supra]

no i didnt make any progress
sad to say that my motor said to hell with me and blew my MHG(or cracked head) and began to have some real bad blowby issues lol
she really didnt like a good long hard 4th gear pull
160xxx miles on stock bottom end that i have beat to death since january lol
pulling motor next weekend for a complete rebuild...stock FTW!!! lol

 

[Turbo Habanero]

Blew a metal HG dang. Did you install it yourself and use headstuds and decked both block and head?

I'm sure ya did but i figured the internals would go be for the MHG

 

[jonahs_supra]

Already installed when I got it
Has ARP studs too
I'm kind of thinking surfaces weren't prepped correctly

Sent from my PC36100 using Tapatalk

 

[suprajztwenty]

ha! my previous owner did the same thing and i blew the 1.2 that was in it...installed a composite to try and limp it through the season but leaked 2 weeks later.

well if i figure it out ill try and remember to post for future reference

 

[jonahs_supra]

just by looking at main bolts on my motor mounts and other things
its clear that engine was never taken out...no biggie though

so far i have on order...
hks mhg 1.2mm
gates timing belt
tensioner
full engine gasket kit
toyota front and rear main seals
toyota cam seals
block and head going to machine shop next weekend

more to order once i get specs back from machine shop

 

[suprajztwenty]

oooooooo, you may want to reconsider the headgasket thickness...thats going to jack your compression up (even if no surfacing is req) so when you get both machined youll need an even thicker gasket than stock (1.37 is stock) so, say they take .20 off of the block, .10 on the head then youll need a 1.7mm gasket to compensate for the loss.

for example, my head was surfaced 2 times and the block was taken down some too, so i ended up with a 3.0 gasket and i think thats barely enough...i plan on a new head in the future but for now itll get by, i just dont beat on it.

 

[jonahs_supra]

It'll be fine lol
These motors could use a slight jump in torque and HP when trying to get in boost lol
I run 93 octane all the time
So I see no problem

Sent from my PC36100 using Tapatalk

 

[suprajztwenty]

ok, i wont try and tell you how to build your motor...personally id send it back and wait for some measurements, plug everything into a CR calculator and see where you stand...THEN determine what thickness gasket will gain you a slight increase in compression...but if you want higher cr id rather just buy pistons made for it.

anyways, im 99% certain my tps is faulty, it feels like at one given point in the pedal is the sweet spot (or switch effect) sometimes further, but that can just be normal ecm delay. i just havnt had time to check it out, but it feels as if the idl circ is sticking untill i get about 1/4 throttle or more and then POWAAAA. ill test and confirm in the next day or 2.

goodluck with your build, not trying to preach but please do some research before you throw that gasket on a machined block and head.