G50: Trans issue - Can anyone help?

[AZhitman]

OK, got the Q back today with her replacement engine... She's running strong.

Got a strange trans issue, which I am inclined to believe is electronic in nature - Here's the symptoms:

1-2 shift is HARSH. Like, almost violent, especially at mild acceleration. On hard accel, it's delayed and slow, but not as harsh.

Once cruising speed is reached, and the accelerator is released (ie, "coasting"), the RPM's drop to idle speed. Almost like a manual trans car being placed in neutral while coasting.

If you then press the accelerator while "coasting" to accelerate, it takes a second to "engage" but then seems to function fairly normally.

Any thoughts?

Fluid was flushed 4 months ago, level is correct, and filter is new.

[elwesso]

its probably not a trans issue... did you wire up the neutral/WOT switch on the TPS (the other connector)... is it shifting where it should?? or does it not shift unless you let off the gas?

its probably a TPS issue.... are you getting a TRANSMISSION MALFUNCTION thing?

[Jesda]

I agree, sounds like TPS to me too, not trans.

[PopPop]

I agree, sounds like TPS to me too, not trans.

Greg has an new TPS that he purchased from the dealer along with the R&P line that he needed to complete the swap!

[elwesso]

Greg has an new TPS that he purchased from the dealer along with the R&P line that he needed to complete the swap!

well then its the jerry rigged wiring!!!!!!!!!!

[3Q Jay]

glad to hear Quella is back. did u check the shift solenoid bypass resistor?

[AZhitman]

I will check both -

Where is the resistor?

[elwesso]

glad to hear Quella is back. did u check the shift solenoid bypass resistor?

are you talking about the dropping resistor... if so its mounted on the frame on the passenger side kinda by the battery.

[AZhitman]

Hmmm... Will do - How is that tested?

[elwesso]

we were thinking it was unplugged... the resistor itself is prolly OK...

[3Q Jay]

yes, the dropping resistor. if Quella has TCS, you will barely be able to get to the resistor (blind feel) under the tcs reservoir bracket.it has one of the 2 wire connectors similar to the rear brake pad sensor harness connector (the one about 12 inches inboard on the lower arm).

[Q45tech]

IS IAC set correctly at 10% duty cycle?

[rotorimp]

Duty cycle on the IAC was not checked. Full throttle and closed throttle were wired correctly. When I went to adjust the tps--in order to get the closed signal I had to adjust it a bit below Nissan spec .6 instead of .7 Ohms. I am sure that the wiring is spot on. the CAS on this motor (JDM Motor) has a additional plug coming out the bottom of it and the wiring harness from Gregs car only has a provision for one connection. motor idles great and runs strong--just has that shifting thing?

BTW is there a secret to getting the nut on the long bolt for the alt???

[elwesso]

Jason

Is the car throwing a "TRANSMISSION MALFUNCTION" code??? That would really be helpful... Any ECU codes either??

You dont want to adjust based on ohms, but on volts at the ECU.... probe the ECU at the appropriate places and adjust to .4-.44 volts...

[maxnix]

BTW is there a secret to getting the nut on the long bolt for the alt???

Scoth tape for some.

[AZhitman]

Wes - I do get a trans malfunction code at startup.

Man, who'da thunk 3 years ago I'd be counting on my little buddy for Q repair tips?

[elwesso]

Its called 23,000 posts and unthinkable hours...

Do the trans diagnostic thingy...

Youll wanna do the transmission diagnosis... Here is what you do.. Put the car in drive (engine not running), then turn the ignition off... Turn the trip reset thing counterclockwise, and while holding it turn on the ignition.... IT should then display AT CHECK on the display.. Then, move the shifter to 3, and press and release the accelerator fully.... move it to 2, and then to 1, and then press the accelerator down all the way and release it (when its in the 1 position)... Give it a minute, and if theres a problem with the electronics, it will show up on there... Tell us what the codes are and I can look them up in the FSM... If everything is fine, it wil display OK...

note that the engine has to be warmed up (gauge in the middle) or the test WILL NOT work!!!!!

[AZhitman]

You rock brotha. Much appreciated.

Will post up in the morning, thanks Wes!!!

[Jesda]

Man, I cant wait to see that beast rolling again!

[AZhitman]

Mama drove it today for the first time in a few months... I detailed it yesterday, and had forgotten how in love with that car I'd been...

[rotorimp]

I will back probe it at the ecu to set the TPS----

I had to wire that nut onto the alt.----I think Engineers should be made to work on their own products from time to time. I don't think that there is any other way unless you evacuate the ac system and put it on outside the car.

[AZhitman]

Well, trans diagnostic procedure didn't work - are we certain it has to be at operating temp?

It displayed "AT CHECK" and all steps were followed. The only thing I saw on the display is the orange box on the left side of the screen lit up for a few seconds after the test.... Never gave a code or message.

[elwesso]

Well, trans diagnostic procedure didn't work - are we certain it has to be at operating temp?

It displayed "AT CHECK" and all steps were followed. The only thing I saw on the display is the orange box on the left side of the screen lit up for a few seconds after the test.... Never gave a code or message.

Yes

Im thinking its the closed position sensor circuit... Attached is the pinouts for the TCU and the page from the FSM that is relavent... DO this and report back and we'll see where we go from there...

[AZhitman]

Spectacular.

Thanks Westchester.

[FarFetched]

I've found something interesting. Just a theory of operation, but might shine a ray of light on your problem!Quote »In response to a signal indicating the present throttle valve opening degree detected by a throttle valve sensor and a signal indicating the present vehicle speed detected by a vehicle speed sensor, a lock-up controller determines whether a lock-up clutch should be brought into the operatively connected state or it should be released from the operatively connected state, and on completion of the foregoing determination, the controller outputs a certain signal to a solenoid valve. In the case that the lock-up clutch has been released, this state is maintained. On the contrary, in the case that the lock-up clutch has been in the operatively connected state, the controller determines whether maintains this state or selects a lock-up clutch releasing pattern depending on the present throttle valve opening degree. Specifically, the controller selects a pattern in such a manner that the operative connecting force of the lock-up clutch is quickly reduced at the time of coasting of a vehicle, it is slowly reduced at the time of an intermediate throttle valve opening degree, and it is appreciably slowly reduced at the time of a large throttle valve opening degree. With such control, a driver does not unpleasantly feel a stifling shock at the time of coasting, and moreover, acceleration behavior of the vehicle is enhanced at the time of a large throttle valve opening degree. [/quote]

[AZhitman]

Nice. That sounds like what's going on, especially when "coasting" - the trans appears to disengage completely, with the tach reading idle and re-acceleration take a split-second while the trans "re-engages".

[carlosinseattle]

WOW!!!

That was a mouthful. Do you think this condition could also cause a shimmy in a 91Q? I have what I think is a "Chuggle" as described on other posts. I did the full flush with Mobil 1 ATF and filter change, but I still have the chuggle problem. When I'm coasting sometimes the car begin to vibrate and it feels like an extremely quick engaging and disengaging of the lock up on the torque converter. Could a faulty TPS cause this?

I'm in Seattle, so whoot me an email at [email protected]

Thanks

[maxnix]

I did the full flush with Mobil 1 ATF and filter change, but I still have the chuggle problem. When I'm coasting sometimes the car begin to vibrate and it feels like an extremely quick engaging and disengaging of the lock up on the torque converter.

Did that include 6 oz. of Lubeguard Red?

[Q45tech]

AGAIN THE IAC IS SET INCORRECTLY

The IAC acts like a dash pot and steps [it maintains] the engine rpms when you let off the throttle............when costing it [ecu calculates an rpm just below normal [minus 300 rpm] for speed at 60 mph IAC keeps engine at 1700 instead of 2000 to allow a normal coast down, at 55 mph =1530 at 50= 1350................always about 300 rpm LOWER than would be at steady speed..............progressively drops in 5 mph steps.

Why setting hot idle IAC duty cycle at 10-15% is so important without IAC operation the engine will immediately drop to idle rpm 650 as the torque convertor slips and cannot reverse spin the engine UP to the appropriate RPM when you are in 4th gear........ in 1st or 2nd or 3rd the mass of the Q can couple backwards enough torque to overcome TC slip and drive engine rpm higher.

The CONSULT is your FRIEND.

[rotorimp]

IAC is set at 8% right now, ECU is seeing the closed TPS signal and the TPS voltage is a little low at full throttle. When we hooked the consult up last night the first thing we noticed was the timing---it showed 40 degrees at idle- which was almost 900rpm. The CAS that is in there is from a earlier 95? with 2 connectors--gregs harness only has a provision for 1. We will set the base timing with the other cas from gregs original motor (they are both Hitachis)