Still having TPS issues

[Sleeper-6]

Last week I posted that I was having high TPS issues at cruise. Over the weekend I did some troubleshooting and only managed to confuse myself further. Some claim to cruise at 80 mph with under a 1V reading on the TPS sensor. I have tried two different sensors and at 1V TPS my engine will only be turning about 1900-2000 RPM in park. This is with no load at all, I can't see any way that I could maintain a decent cruise speed at under 1V. The arm on the Throttle body is only sitting about 1/8th of an inch away from the IAC stop screw when the TPS shown 1V. Why would my ECM show such a high TPS reading with such little actual throttle being applied. My current settings are .42-.44 at idle and about 4.3 at WOT. Could it be an ECM Prob?

 

[S10xGN]

Personally, I don't see what your concern is with the "volts at cruise" thing. Do you have a stock throttle-body and TPS? Are you having driveability issues? The only thing that stands out is the WOT volts - should be > 4.65 according to most here.

 

[scottyb]

3 things you need to check for TPS:

1. Idle setting between .38 and .46

2. WOT reaches a min 4.0 (actually more like 3.75 for PE mode, but 4.0 to shut off AC compressor)

3. Smooth increase in TPS voltage as you slowly open the throttle.

Do all these by hand with engine off of course.

As was pointed out to me today, details are at Vortex Buick

 

[Sleeper-6]

The problem I'm having with cruise TPS is that because it is too high my converter will not stay locked of on the high way at anyhting over 55 Mph. The ECM thinks I'm trying to accelerate while all I'm trying to do is maintain speed. Bob has offered to tweak my chip for me, but I would like to find the problem instead of covering it up.

What I have noticed is that the TPS increases smoothly it is not linier to the throttle opening. I have tried 2 different sensors, Maybe they are both the wrong ones? And yes, the throttle body is the stock piece.

 

[salvageV6]

You may want to check the ground and power (5V) wiring for intermittant open connections.

As well as the return voltage line to the ECM.

It should be rather linear in operation by hand.

 

[scottyb]

Are you sure the TPS is causing the converter to unlock? Are you watching the TPS voltage on a scantool while driving?

I have to mash the go-pedal pretty damn hard to get it to come out of lockup. It more likely may be a loose brake switch or tired lockup solenoid. An easy check of the brake switch would be to gently pull up on the brake pedal while cruising (with your foot, of course)

 

[Sleeper-6]

I'm pretty sure it'd the TPS causing it. I can watch it on the Direct Scan. Like clockwork, as soon as I go past 1.75V the TCC indicator light goes out and I can feel it unlock. Very consistant and repeatable.

I have at one time verified that I was getting the 5V to the sensor, but I am interesed in trouble shooting the rest of the wires that go to the TPS. What readings would I be looking for on which wires that would indicate a problem or not?

As a side note I get a different reading in the TPS voltage between when the car is running and when it's off and just the ignition is on. Usually around 0.10V. Is his normal or could it be part of my problem?

 

[zam70]

That's normal. Your reference voltage is higher with the engine running

 

[scottyb]

I believe the .1 difference you see after startup may be high. I think a .02v rise is normal, from .42 to .44 for instance.

Are you seeing 1.75 during cruise? Since it's consistant for you, I'll assume that 1.75 is the threshold that the chip commands unlock, but I don't think that is seen during normal conditions. I watched my tps on the way home last night and never exceeded 1.50, even in *average* acceleration from a stop light. I had the cruise set at 55, 4th gear and lockup and it did get to 1.46 while going up an overpass.

Long story short, you've gone beyond my understanding and may need to check the wiring as already suggested. Please post back your solution.

 

[zam70]

Your right scottyb. I was thinking he meant .01. If you are going up .1, you've got problems. I typicallt see +.02 upon startup.

 

[Sleeper-6]

OK, I guess I'll have to dig into some wiring this weekend.

That's why I thing it's a problem I know that I'm seeing abnormally high readings. And they are not linear to the pedal travel. Now I just have to find out why.

On the voltage at startup, it was not a typo (wish it was) I honectly see a rise from .34 not running to .44 running. I have to set my tps with this in mind so it's at .44 while it's running. otherwise it jumps too much and causes a high idle and sets a code.

Does anyone know what readings I should be seeing on which TPS wires when I check them?

 

[salvageV6]

Black should be a good ground point to the ECM PIN D12, read it with a good OHM meter with some long low resistance leads. Don't read it to battery ground it is a stand alone ECM ground and needs to be read to the BLK wire that goes to D12.

Gray wire is the supply wire and should be a Steady 5 Volts with key on car running and NOT running. Vary perhaps .2-.3 volts car on and car off. Check this first and use the BLK wire to read the ground to.

Dark Blue wire is the output and should read low resistance to C13 point at the ECM wires.

Disconnect the connector from the ECM when reading the OHMS tests.

Dark blue wire should read linearly when moving the tps by hand key on.

 

[TurboBob]

A note, perhaps a sad one.

If your car runs a 103 mph pass with a TE61, perhaps there are more serious engine issues at work here. Have you done compression, leakdown, and camshaft lift checks?

A hurt engine will require more throttle to maintain highway speed.

The offer to mod the chip still stands.


Bob

 

[Sleeper-6]

Salvage, That's exactly what I was looking for. I'll give all that a check this weekend and report back what I find.

Bob, I ran that mph in street trim through the exhaust with my old messed up MAF, no tuning, and my old cam then went flat the next week. So I think it was on it's way out then. And i forgot to lock the converter. So I had lots of stuff stacked against me. I'm getting a reading of about 1V when I only move the throttle arm about 1/8 if an inch off the throttle stop. I'm getting such high readings with Very little actual throttle movement. So I believe it's an ECM or wiring issue of some sort. If I wind up giving up, I'll contact you about tweaking the chip.

 

[TurboBob]

got any volt boosters, TPS-TEC, or other gizmos that tap into the TPS wiring?

B

 

[Sleeper-6]

None that i know of.

 

[Sleeper-6]

Following up

Black wire shows a good connection to pin D12 on the ECM harness showing only 0.1 ohm.

Gray wire shows exactly 5.01V using the black as a ground.

Blue wire showing the same low resistence connection to C13 with only 0.1 ohm also.

As before, voltage at the blue wire while measured with the meter is not linear to the throttle travel. The first 1/4 inch of travel produces over a 1V change while a 1/4 inch near the end only changes the reading by .2 V or so. There are no dropouts along the way, just not a linear reading in relation to actual travel.

I gues this means that I have had 2 bad sensors or that the ECM is at fault??

 

[TurboBob]

seems like you are running out of things to check.

Since you have measured the voltages with an independent tool, there are only 3 things in the circuit: (You did cross check the TPS voltages to the voltmater at several throttle openings, right?)

TPS
ECM
wires in between.

I have never heard of an ECM doing this, but stranger things have happened.

B

As a comparison, block the throttle open with something like 2 quarters and measure it, I will do the same.

 

[Sleeper-6]

Ok, I gave it a try. I used both a digital meter under the hood and the Scanmaster inside, they matched readings each time. Key on engine off reading with no throttle is .36, but this does jump to .44-.46 when the engine is running. The following readings are key on,engine off with the given items between the IAC adjustment screw and the throttle arm.

2 Quarters = 1.70
1/8" drill bit = 1.58
1/4" drill bit = 2.40

Thanks for working with me on this one.

 

[scottyb]

Damn. I went out to measure, but just re-read your post and I'm not going back out.

I placed the same item between the throttle pin and the TPS arm, scanmaster readings only:

.42 base
1.04 - 2 quarters
1.00 - 1/8 drill bit
1.66 - 1/4 drill bit.

What are the chances of 2 bad TPS's?