Qh: Trans Oil Temp On 5sp?

[lizzard]

hey guys im new here and a proud owner of a 95 GTS and a moates QH
im a totally noob to the QH and just began datalogging. i got a strange reading from my T4M0: "trans oil temp" shows several times per second values between 150 und 170. i have a 5speed, no auto! and no former conversion from auto to manual. why does it show me the trans oil temp. should i bother? and: does it has something to do with my bad idle?
of course i worked through the surging idle checklist of jrichker, but i found nothing, no vacuum leaks, no bad grounds. i replaced a lot of stuff like IAC,MAF, ACT, TPS, rotor, dizzy, dizzy cap, coil, spark plugs & wires. fuel rails, FPR, PCV, EGR, fuel pump etc...

problem: i cannot bring the idle down to 650 rpm with IAC unplugged, 800 rpm are what i can get, not less, looks like i have mechanical issues. and when i release the clutch in first gear or in reverse, the engine dies.

any ideas?

 

[Noobz347]

Whomever actually set that car up is probably using the extra 5 volt reference for something else he/she thought they'd like to monitor.

For all you know, that 150*-170* that you're seeing is a 5 volt reference for say.... Blinker Fluid Reservoir Level.


Find out what it's actually doing and what the reference lead is really plugged into.

 

[lizzard]

thanks! yes, thats the point: i only dont know how to find out where the reference lead is plugged into, because i see it only in tunerpro in the item list

 

[lizzard]

 

[jozsefsz]

If I had to guess, the most common sensor to wire into an unused lead is a wideband (though usually people use the egr input, but if you have a functional egr they may have used the trans temp). Does your car happen to have one? The rapid switching you're seeing looks kind of like a nice o2 sensor narrow-band output. The software of course is just seeing voltage and converts that to a temperature reading.

As Noobz mentions, you'll want to find the pin / color of the lead coming from the ecu to trans-temp. Then figure out (physically) what's connected to that wire. Look for anything aftermarket, as I mention o2 sensor is a prime suspect.

For your high idle, you're correct, you should be able to get it down to ~650 with IAC disconnected using the throttle adjustment screw. If you can't, you might want to adjust the idle air bleed screw (allen screw under the plug on the throttle body, turn it in to give it less air). If still no luck, check to see someone hasn't drilled holes in the throttle plate. Otherwise, you're probably dealing with a vacuum leak (you mention you've checked, but the brake booster could be leaking, or you could have a pcv plumbing problem if someone['s added breathers, the evap bleed line is also commonly a problem on our cars), which could also explain a poor idle and those high-spots on the graph where the ecu is putting in more fuel because it thinks you've gone lean (assuming that's an o2 sensor output).

 

[lizzard]

thanks for you answer. when I unplugged the cable which is connected to MAF and ACT, it stopped up to 98% with this switching signal, another 2% are still switching somewhere else. so I have to go further with my examinations.
the other problem is, that I have a crank ok no start issue. maybe because I touched one of this 20 year old wires which are a real PITA.
but jrichker has a checklist I will work through the next days...

however, I wish u happy christmas!

 

[lizzard]

does anybody have a xdl-logfile of a nice & clean idle @650 rpm? I'd like to compare the data

 

[jozsefsz]

thanks for you answer. when I unplugged the cable which is connected to MAF and ACT, it stopped up to 98% with this switching signal, another 2% are still switching somewhere else. so I have to go further with my examinations.
the other problem is, that I have a crank ok no start issue. maybe because I touched one of this 20 year old wires which are a real PITA.
but jrichker has a checklist I will work through the next days...

however, I wish u happy christmas!

A very merry Christmas to you too! Just an FYI, if you unplug the MAF & ACT, closed loop is disabled, so you'll no longer see the o2 sensors switching (they'll remain at a steady voltage). I'd still bet you have an o2 sensor plumbed into trans temp.

jrichker's checklist is the best for crank & no-start, good find, and good luck!

I don't have an xdl logfile, sorry, hopefully someone else does (I replaced my QH with a Moates F3 chip until the next time I make hardware changes)..

 

[lizzard]

I'm sorry I forgot to say: I unplugged the cable with KOEO and cold 02 sensors. AFAIK the loop closes only with a engine running and when the o2 sensors are hot enough.

 

[Noobz347]

I'm sorry I forgot to say: I unplugged the cable with KOEO and cold 02 sensors. AFAIK the loop closes only with a engine running and when the o2 sensors are hot enough.

It is true that this circuit closes for the sensors but the EEC will not go into closed loop unless all measures are met (time, temp, MAF, 02, etc).

There should also be in your software somewhere, and indicator or flag telling you when the EEC enters into closed loop mode. In closed loop, ALL of the sensors on your EEC harness in the engine bay, are active and the EEC is accepting each of their respective inputs.

If @jrichker is on the forum today, I think he has a diagram that illustrates this.

 

[lizzard]

thank you guys for helping me
so, let's reveal the mystery of the trans temp oil data on a 5speed:
It ended up in pulling every wire from the ecu. I left only following 4 PINs:
1 keep alive power
20 case ground
37 vpwr
40 ground
no sensors, and even then it showed this strange signal!

so, I still don't know where it comes from, maybe from the PCM, the quarterhorse,ect
maybe the signal is of no further importance...idk

btw: the crank-no-start-problem turned out to be a fried TFI. But I was lucky and had a another TFI handy.
thanks @jrichker for your checklist!

...and I'm still chasing my idle problems, though the engine has no more vacuum leaks, it still dies very quick when I release the clutch...

 

[toyman]

thank you guys for helping me
so, let's reveal the mystery of the trans temp oil data on a 5speed:
It ended up in pulling every wire from the ecu. I left only following 4 PINs:
1 keep alive power
20 case ground
37 vpwr
40 ground
no sensors, and even then it showed this strange signal!

so, I still don't know where it comes from, maybe from the PCM, the quarterhorse,ect
maybe the signal is of no further importance...idk

btw: the crank-no-start-problem turned out to be a fried TFI. But I was lucky and had a another TFI handy.
thanks @jrichker for your checklist!

...and I'm still chasing my idle problems, though the engine has no more vacuum leaks, it still dies very quick when I release the clutch...

If you haven't done a smoke test for a possible vacuum leak you can't rule out that possibility. There are too many hidden areas that only a smoke test will reveal.

 

[lizzard]

I've done a smoke test, several times. my pcv and airbox, egr, iac and even tps were leaking, now the idle is a bit better, but still crappy. i heard there could be a leak from the lower intake manifold to the lifter valley, but idk if it's really possible.

question: when I'm coasting for a while in my car and step on the gas pedal I hear a decent "CLAC!" from the right side of the exhaust. Sounds like gas exploding. Do you know where it comes from? Bad combustion? Has it something to do with the idle-problem?