Cefiro A32 VQ20DE - RPM move up and down during overdrive

millenric

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millenric

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Hi all Cefiro's sifu,

Just got my Cefiro A32 2.0 2 months ago. Changed the flywheel oil seal due to oil leak. However after that whenever I am constant on the gas pedal @4th gear (5% <-> 50% throttle), the RPM move down and up, repeating unless i let go the gas or press more to force it go down to 3rd gear.

Does anyone of you encounter the situation above. It is quite annoying and I'm worry continue use will either damage the valves or the gears.

P.S. I plan to use it as a highway car but now, it has become a city car (4th gear problematic). Can't imagine I have to drive this car with overdrive off... :(
Attached the consult RPM(series 1) vs Speed(series 2) graph. Sorry that I couldn't get the Scan tech nissan working (so i can read the TCM's data)
 

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12savefuel

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12savefuel

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Does it feel more like a gearbox or engine engine problem. Since you don't have the problem in the other gears it would presume a gearbox problem. If it is a gearbox problem and its only on 4th it looks like a lock up clutch problem. Looks like the clutch is locking (rpm drop) and unlocking (rpm up). Its could be the lock up clutch itself or it could be the lockup clutch solenoid. Or it could be a sensor or signal problem which is causing the lockup clutch to open and close. It could be the lock up clutch is worn also. So have to slowly check. easiest way to check is to get another gearbox and do a direct replacement just to check if the problem still there. If the 2nd GB also has the same problem that means the GB is got getting some signal from the ecu. Or its an engine problem.
 

millenric

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millenric

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Thanks for your advice, 12savefuel

I went to a few mechanics and each gave me different reason. @~@
Can't stand this anymore and I finally get the scan tech nissan working. Finally can read the A/T's data now. Refer to the graph I have attached(zoom to the point where RPM down up reproduced), like what you have said below, the RPM move almost follow the TCC SV's duty cycle. Looking it at the point when the RPM start dropping at gear 4(highlighted), I found that the RPM drop before the TCC SV duty drop abruptly from 70% to 43%. Did sounds like TCC is engaged around 70% and the RPM start dropping. Now the question will be, why do the TCM drop and push up the TCC SV duty repeatly? RPM drop when TCC engaged is expected right? is it caused by other sensors?

Before I get this data I was guessing the RPM down up is caused by the action in the gearbox alone (with the output of TCM normal), but seems like it is the TCM that move the duty cycle of the TCC SV down and up!!!

What do you think? I'm thinking to change another TCM and retry, should be easier than looking for another gearbox right? :-P
 

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12savefuel

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12savefuel

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RPM drop when TCC engaged is expected right? Yes. So the next question is, is the throttle position relatively constant when this is happening? TCC opens and closes based on throttle position rpm and speed. At the same time can you check that the throttle position sensor is set properly and the throttle switch is also working properly. You can see the throttle position and switch coupler both together near the throttle. If you need the procedure I have it for A32. Once you check that its working properly the next easiest thing to do is just plug in another TCU and try. Then plug in another ECU and try as well.
 

millenric

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millenric

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Yes, the throttle position is relatively constant during the "down and up" (17-16%).

Just to clarify, the throttle switch you mentioned below is it the throttle position switch? which is just beside the throttle position sensor.

Ok. If it is, yes, i think I'll need the test procedure. Thanks! Currently just referring to the Maxima's A32 service manual. Which mainly ask me to probe the voltage/resistance on both sensors.
 

12savefuel

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12savefuel

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Just to clarify, the throttle switch you mentioned below is it the throttle position switch? which is just beside the throttle position sensor. Yes correct. Will PM you instructions.
 

millenric

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millenric

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Checked the throttle position sensor - works according to the spec. no prob found
Checked the throttle position switch
1) closed TPS - both sensor and the wiring is good. sensor value from the consult is good too.
2) wide open TPS - sensor and the wiring to the TCU terminal is good but, consult's value is always ON no matter what is the throttle level. even still ON when I discon the throttle position switch. @~@

I think i will proceed to test it with another TCU. Do you know what is the part number of the TCU for this A32? Any chop shop you know around PJ/KL area?
 

12savefuel

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12savefuel

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There are many shops just a matter of whether they have or not. Maybe try the ones in subang near mydin or first.
 

millenric

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millenric

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Unable to find the exact model of my TCU. So I just plugged another TCU with the part number that I found online and is used on VQ20DE excimo.
Lockup is now engaged properly without fluctuation anymore. No abnormal/error code found on other gear(s). Phew.... job done.
Wondered what happen to my old TCU; The board is using the famous 68HC11 MCU. Time to debug it...
P.S. 1: Thanks 12savefuel so much for ur advices!!!
P.S. 2: Thanks to my dad so much that help me dismantle plastics on the mid console. :-P
 

doraemon98

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doraemon98

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Congratulation you have fixed the problem. I got so worry when I start reading your problem, and started to feels impressive on the troubleshooting. And so glad the problem has been solved!

Because of we have dedicated members here to help, I have good reason not to sell my ceffy!
 

12savefuel

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12savefuel

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Unable to find the exact model of my TCU. So I just plugged another TCU with the part number that I found online and is used on VQ20DE excimo.
Lockup is now engaged properly without fluctuation anymore. No abnormal/error code found on other gear(s). Phew.... job done.
Wondered what happen to my old TCU; The board is using the famous 68HC11 MCU. Time to debug it...
P.S. 1: Thanks 12savefuel so much for ur advices!!!
P.S. 2: Thanks to my dad so much that help me dismantle plastics on the mid console. :-P
No problem millenric.
 

deckerloh

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deckerloh

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Hi millenric,

I having the exact same problem that u have currently. Must be the TCU as what you have mentioned.
How much did you pay for the TCU, if you don't mind sharing?
Thanks.
 

marksmensrea

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marksmensrea

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Hey Guys, anyone can share with me the part no. for the TCU and where is it located in the car?
I humbly request help on this as I have 2 a32 2.0 with up down rpm issue at 70-80KMH tooo and its realllly annoying.

Thanks a million
 

deckerloh

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deckerloh

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Hi marksmesrea,

The tcu is located in the compartment behind the cd player, it's right behind the ashtray to be precise. As for the tcu part number, I'm not very sure, I just ask for an a32 tcu from the chop shop and just plug and play.