Weird TPS problem - W40 software

[Davo]

Hello all,

I am at my wits end with this weird TPS problem i've got on a VS V6 running W40 software. Is a manual vehicle although the RT ECU is an old auto board without VSS hardware added to it. Don't know if this is the attributing factor. Basically what happens is the TPS reads 0% in gauge screen then afterstart it'll read 3%-5% TPS this causes the damn thing to idle up to 2500rpm. With a bit of bliping the throttle I get it either back to 0% or a TPS stuck fault. The measured TPS signal is 1.1v or there abouts. I know it is high but vehicle is cammed and needs heaps of air. I've played with all 6 or 8 TPS variables (around 30-40 in the list) but I can't find anything that works for me.

Does anyone have ideas ?

I'm about to read through chokos SP3 manual, hopefully it has something in there.

Davo

[Hooter]

First thing, which Im sure you would have done, is check that it is actually closing properly and not held open by not enough slack in throttle cable, or dirty etc.
If ecu doesnt see 0% it wont go into closed loop idle and then rev as you describe.
It is quite common on eco's to have dicky TPS, so try another or 3.
BTW, no trouble codes??? eg 21 or 22???
Cheers
Al

[Davo]

Hello Allan,

Thanks for the reply. I have checked the throttle plate,accel cable and TPS - throttle shaft for the plastic sleeve thing. The throttle body bore is clean and not sticky. I was tuning Acceleration enrichment parameters and got a M19 TPS stuck code. Main problem is the damn thing will log 0% throttle and then just after start(like the finish of starter crank) it'll shoot up to over 1.2% throttle and i'm stuck in IAC openloop and get damn throttle follower keeping the revs up. A quick blip or 2 on the throttle will have it back to 0%.

Could it be an earth fault ? I haven't physically checked though.

Out of interest with the SP3 manual it states as a last resort that there is a TPSthreshold parameter. I looked through the W40 software but nothing is making sense to me. Is there a parameter to carry out the same function ?

Will try a new TPS tomorrow.

Davo

[Davo]

Hello all,

Edit: TPS voltage reading at idle with key on engine off is .57v then it shoots up to .7v when engine running. Haven't touched the accel pedal, just leaned in and hit key.

This problem still plagues me. I've done almost everything. The Car is now going back to the owner running like balls. The list is as follows:-

*replaced Earth leads from both Engine and Body to battery.
* Solder terminal lugs to make positive connection on earth wire in loom that share the same bolt as battery-to-body earth.
*Replace and solder new lugs onto earth wires in loom that ground on engine in the r/h/f position onto heater hose outlet and l/h/r position on back of cylinder head.
*fitted short circuit wire from both oxygen sensor reference earths and ECU earths now also go to bare metal point on body next to ECU plastic bracket. All soldered.
*Replaced TPS with new item
*Fitted 3 new wires from TPS back to ECU for diagnostic purposes. All the original wires were snipped off at the TPS for this test. Only outcome was a lower TPS reading in general.
*Swapped coil packs and DFI module with known good setup from another VS commodore.
*Fitted factory standard ECU (automatic ECU, this car is a factory manual car though) and MEMcal which has never been erased and flashed before- to my knowledge. No change
*Fitted Factory ECU with finished tune on EEPROM into another factory VS V6 manual car. Problem did not follow the ECU so i'm assuming at this point the fault is with the car.
*Disconnected both the +VE from back of alternator and removed accessory drive belt. No change in problem.
*Disconnected the IAC motor and started car. Problem seemed to be less pronounced, like only half the normal increase in voltage was seen (from usually 4% TPS to only 2% TPS)
*Swapped IAC motor with another 2nd hand IAC. Problem still there as before when wiring harness is plugged into it.
*Connected electraspec to vehicle and found nothing conclusive. Everything is within specifications as per Electra and my basic/common knowledge.
*Connect multimeter to both earth and +5v wires from TPS (neg onto earth wire and pos onto +5v wire), started vehicle and observed absolutely no fluctuation in voltage.
*Disconnected TPS and started vehicle and no induced voltage was seen or present as far as I could work out on the TPS signal wire. (nothing on the Kalmaker laptop screen and similtaneously nothing on the Bosch KTS screen.)
*Pulled my hair out and dropped my coffee mug on the ground.(Not a good couple of day's at all!!)
*checked voltage drop on alternator charge wire 100mv drop, replace terminal lug for alternator output bolt, almost no voltage drop. No change
*Checked all fuses under the bonnett.
*This thing has a gizzmo tach/shift light fitted. Disconnected it to see if would help but... nothing
*This thing also has NOS on it. disconnected EVERY wire to and from the NOS distributor box (dry shot) and still.. nothing.

Only other weird thing i can see is the charge rate on the Kalmaker screen is lower by about .7v compared to the actual at the battery. Perhaps try to replace the positive battery cables ? I can't see how this would bother it as charge rate is over 12v's so every output voltage is regulated internally through ECU.

I'm now trying to think outside the square with this car.
Has subwoofers and amp fitted. Couldn't see any engine harness wires that were spliced into.
The injector rail isn't bolted to the upper plenum, i think the customer lost all the bolts when he fitted the new injectors.

What about disconnecting the dash cluster ? could it be a blown/short circuit in one or more diodes ?

I'm lost guys please help.

Davo

[stormtrooper]

Davo, are you sure the car has the correct TPS fitted? The V6 and V8 TPS are different and go in opposite directions.

When I did my fathers LPG setup I fitted a GasResearch throttle body and it rotates in the same direction as V8 but the V6 TPS wouldn't let the car run at all well. It was only after swapping my V8 TPS over to it that I realised the V6 ones go in the opposite direction.

[Davo]

Hello Storm Trooper,

Thankyou for the reply, yes the TPS does rotate in the correct direction. (anti clockwise when looking at TPS mount on throttlebody). Did fit a second hand V8 TPS initially but found the error in my ways pretty quick. I think M22 fault code came up soon as i touched the throttle.

[DerekBell]

As above.

The only other thing I can think of is it could be is a stuffed TPS, they are basically just a Pot and do stuff up, the change your getting at start could simply be vibration caused

[Davo]

hmm vibration, how would I tighten/Fix the TPS to the shaft ?

It is rotated by the shaft 1 way but the internal spring tension keeps it pushing hard up against the shaft when lift off occurs. I did check the shaft for freeplay. Grabbed the flat that contacts the TPS pivot with stubby nose pliers and tried to turn it, which it did but not like I hoped (I wanted this to be the problem or anything else i've checked for that matter, lol). The next thing I did was get an assistant to start the car while I had my finger on the end of shaft and viola no movement.

I was thinking of grabbing another throttle body with TPS and plugging in the TPS wiring then starting to see if this changes things.

I have noticed that the voltage will go up and down with rpm, But this is only .01-.04v which isn't much be enough to make me think it's inductance of some sort. Any help would be greatly appreciated.

I suppose I could disconnect the oxy sensors and MAF sensor to eliminate them aswell.

Thankyou for the replys guys,

Davo

[stormtrooper]

I was thinking of grabbing another throttle body with TPS and plugging in the TPS wiring then starting to see if this changes things.

Certainly try another throttle body, these cars are 14 years old now so wear and tear is possible anywhere.

Does it have cruise control? If it does is that loose or tight?

[DerekBell]

Try just changing the TPS to start with (If you havent already), as I mentioned, they stuff up and cause some of the issues you are having (Specially around idle as this is where the throttle sits 85% of the time), the vibration I was refering to was the TPS itself vibrating with the engine running, and if it is stuffed will cause TPS voltage irregularities even though your not moving the throttle.

[Davo]

Thanks for the idea Derek. I have put a new TPS on and tried 2 other 2nd hand items. The car has gone home now. I fudged the numbers in the software to make it idle properly straight off start but yeah there are still issues with the car. I hate doing it as everyone does but I can't get to the root of this evil. Customer can take it drag racing this weekend now and it won't rev off into outer space every time he turns it on.

New graph to upload.

[DerekBell]

Another thing I just remembered. the TPS and the MAP shares the same voltage wire, it could be a faulty map that may be loading up the 5V once the engine is started..

[Davo]

MAF sensor you say ? Hmm that is something i've overlooked. Thankyou for that. I will check that out next week. Customer is close and will bring car back if need be.

Thanks again guys I bet it will be something stupid. When in a huff I do tend to overlook the simple things.

Davo

[Hooter]

Davo, the Map and Tps share same 5v on VN 808 (only), but not on VS Eco, and MAF has its own 12v supply, although TPS shares same Earth as CLT sensor.
Something I have seen on VS Eco's is you can get a speed signal flutter that causes an issue, but this is normally on autos with magnetic reluctor vss. Is yours T5 or Getrag??? You can tell it is Getrag easy if it has clutch fluid resevoir (Im sure you know this, but for others reading this) Getrag has magnetic reluctor and can use auto computer fine.
The speed signal flutter seems to be caused by interference noise?????
You will see speedo on Guage View Screen if this is happening.

Next thing is try spare throttle body (v8 or anything, just loose, not bolted on, but plugged in, and see what closed voltage is on that, and then start it and see if you get problem.
If not, you may want to slot the TPS holes, so you can back off and get closed voltage down, or,
Refer to Variable approx 35 to 44 called VAR:TPS:xxxx, and set these thresholds to suit your voltage
Your voltage is getting close to threshold of 1.28 (from memory) and with the high and low deltas added (dithered) it may exceed.
You will be able to virtually proove this with another TB if voltage is lower.
Gen 3's do this as well if you turn idle screw in a bit too much, and only fix is to drill bigger hole......yuk....because variables arent there to remedy it (GM ones are, but not aftermarket (HP EFI etc))
Are you getting any trouble codes???
Remember to clear them by selecting Function, Misc, Clear DTc's ( not avialabe in SP3)
Hope this helps

[Davo]

Hello hooter, thanks for the reply. The vehicle does have a T5 with the Hall effect fitted. From what i've seen now that the iac olp number and iac clp tps number have been fudged is an increase in tps signal almost proportional to engine revs. I'm lost as to why. A switched on autolecy did say perhaps the IAC motor was causing inductance but can't really leave it un plugged cause then the high idle won't happen and you need some throttle to start it which then makes it different testing conditions obviously. Was going to try another Gen 3 maf as I don't know the history of it except it came from ebay for cheap.

Only fault codes I get is VSS cause the RT board is an old auto PCM and purge solenoid cause it aint there. Both are masked though.

Did have a look at the TPS variables in that section (almost top of the list) but could not make sense of it. Dither and delta sometimes confuse me. Did play with them though and didn't get any success. Measured voltage on the gauge screen and with multimeter is .4v engine off key on and up to .68v engine running at idle. Coolant temp is pretty well consistant. Does climb like .02-.04v but I'm putting that down to circulating coolant compared to engine off.

Need to get the car back and try these two tests though.

Thanks again guys.