Chevelle_LS

Hello!

I have installed a Ls1 in my Chevelle and am now having issues with the tps sensor. As I have the car in key on but engine not running the tps shows 0% but as soon as I start the engine it hops up to 2,4% or so. I have read that this could be a ground issue so I started measuring the grounds to see that they were okay. As I disconnected the pcm to check that it was ground okay I also measured the TPS wires to ground and it was still connected to ground.

So my question is, should the tps only get ground from the pcm sensor ground, pin 23 blue side? If so the volt meter shouldn't show that it's still connected to ground when the pcm is disconnected.

It's a 1998 camaro engine and harness.

oange ss

iTrader: (50)

all grounds lead to the rear of the driver side cylinder head, you may have a faulty sensor

Compsystems

The TPS ground is separate from regular engine ground and is probably done this way to reduce noise on the signal as you are experiencing.

Sounds like some one may have joined all the ground together.
Im assuming this is a swap engine and harness?

If you look at the diagram for the TPS is shows an isolated ground for the TPS going back to the PCM. So like you said, with the PCM unplugged, testing for continuity from the TPS ground to battery ground should read open.

here is a link to the diagram
http://www.lt1swap.com/1999_vortec_5...%20Sensors.gif

Chevelle_LS

Thanks Compsystems fore verifying my teory.

As I have read on about this i found this.
1998 wiring camaro SS 5.7L 4of4.pdf



I the opend up the wiring harness and found that the "brake out" sensor gnd from pin 23 (where it says s119) was connected to the battery ground.

If it had been in the original car it would have been connected to the antilock brakes but now that it is in a 1970 Chevelle it is not to be used, right?

Haven't hade the time to do this and connect every thing yeat, but I just want to verify my teory furthermore before I try this so I dont do anything stupid.

Compsystems

Correct S119 should be disconnected and removed, not grounded.

the wire should go from the pcm to the tps only.

Chevelle_LS

Thank you!

As soon as I get some spare time I'm out in the garage to see if I cant get the car to idle now that I know it will go into idle mode.

May have some idle tuning questions later on as I'm totaly new to tuning by my self, have hade the car to a tuner and am very satisfide with the tune exept for idel.... as it never went into idle mode... very suprised that the tuner never picked upp on the TPS % being so high.

I may have to upload my tune as soon as I'm done with it so that you can give your opinions on it.

THX fore now!

Chevelle_LS

Got my HP tuners and am now trying to get my car to idle and it is not going so well. So i hope someone can help me to get it right.

First some spec. on the engine.

PCM and engine originates from a 1998 Camaro but is now in my 1970 Chevelle
Ls1 block, stoked to 398
243 heads with bigger valves.
Cam is 222 int./224 exh. and 0.566 int./0.568 exh.
Fast LsxR 102mm intake
Holley Sniper 102mm throttle body
Longtube headers.

It made 414 whp and 580wNm at the dyno. So I have had it to a proffesionall tuner and he tryed to get the idle right but never got it even in the ball park because the TPS was reading over 1% throttle, but that was due to the ground issue that I was talking about earlyer.

Now that is fixed and I am trying to get the idle right.

Problems I am having are that when I put it in gear it stalls or almost stalls and as I take it out of gear it revs up. And when in gear or revers it pulls realy hard, even so that it goes into second gear if i dont stand on the brake.

I se that the LTFT is at 25% for bank 1 but nothing for bank to also.

So, here is my scan and tune as I took the car around the block mostly driving it with the throttle closed as you can see.

Scan 27-06-2017.hpl
Tune 27-06-2017.hpt

Can some one point me in the right direction please or is there a machanicle issue I am not thinking off?

Chevelle_LS

I almost forgot, it is a cable throttle body!