99 I30 Transmission / Deceleration Issue

[ejohanss]

I have owned my 1999 Infiniti I30 for three years now and it has been an exceptional car! But it has always had a minor eccentricity that I would love to fix. Any suggestions? --
This seems to happen mostly at lower speeds - let's say between 25 and 50mph. When I am cruising along at a steady speed and let off on the gas, there is an abrupt deceleration similar to what you would experience in a standard transmission car. This is an automatic, of course, and typically an automatic kind of "coasts" under these circumstances. I do not have it in the sport mode, as a matter of fact, it seems to do this less in the sport mode!
Anyway, this is a minor thing, but I would sure love to cure this problem. I have driven several other I30's and Maxima's with this same engine and none of them do this, so I know there must be an adjustment or part replacement that would make this wonderful car 100% instead of 99%!
Thanks in advance for any suggestions...

[Nahkapohjola]

Originally Posted by ejohanss

I have owned my 1999 Infiniti I30 for three years now and it has been an exceptional car! ...

Maybe it shifts to 2? Anyways, the tranny solenoids are computer controlled; start by checking your charge voltage at batt, then TCU etc... check the Favorite Links at left plus read here what could it possibly be:
http://www.cardomain.com/ride/748507/14
http://www.cardomain.com/ride/748507/15

[dfownz]

I have a 96 I30 right now and it does that from time to time. Check your tranny fluid, mine was starting to look bad so I replaced that and now its fine.

DF

[ejohanss]

Anyone else had this issue with their I30 or Maxima?

The guy at Jiffy Lube said it didn't sound like something that a transmission fluid change would fix...so I didn't do it.

(By the way, should I change the filter and screen or do fluid only when I finally do the tranny service?)

[Nahkapohjola]

Originally Posted by ejohanss

...do the tranny service?)

Yes, and those detailly depicted repairs have corrected it.

As far as I know, the screen is for life. Right; fluid does not control gears, it delivers power.

[ejohanss]

I talked to Infiniti today about this issue.

The service manager seems to think it is related to the torque converter.

Per him, the computer senses throttle position, wheelspeed, and other things and makes a determination as to whether or not to keep the torque converter engaged or to "freewheel".

That sounds all fine and dandy, until he indicated that there is not likely anything that can be done...unless programming has gone bad.

Is this a plausable explaination?

[Nahkapohjola]

Originally Posted by ejohanss

.... a plausable explaination?

Partly true; problem is that typically their electronics edu is thin, if nicely put.

3gen TCU/ECU's have got eprom's, their programming is done once and does not go corrupt. The newer cars may have this problem, and around the corner await Microsoft viruses. (Is this programmability true in 99, I think not. Try to find a factory service manual. If it is, reprogramming can correct a corrupt program.)

TCU uses minuslce signals for input which are easily corrupted via connector oxidation. The program uses [sometimes corrupt] inputs to decide output. Then TCU outputs control solenoids in the tranny. Solenoids control the tranny valves which control oil flow. Torque converter is a dummy in the end of this chain, it is either ok -or- dead. You may affect only to the input, which are the TPS, temp, and rev sensors.

The whole computer process uses electricity: make sure charge voltage is ok [at TCU]. If u repair/replace TPS http://www.cardomain.com/ride/748507/6 and clean all related connectors as already suggested (DIY), I guess your problems are over.

Principally the signals are like this (maxima chart):

[dr-rjp]

It is definitely due to a combination of the torque converter and worn clutches. I have the same problem, but was able to minimize the annoying "clunk" by not abruptly taking my foot off the gas pedal (and modulating the pressure instead) and by turning off the O/D whenever travelling at 30mph or slower.

When I first got the car, it drove me crazy. Now, I've learned to live with it.

I'd also recommend using Mobil synthetic transmission fluid to help smooth out your shifts.

[Nahkapohjola]

Originally Posted by dr-rjp

It is definitely...

Definitely U cannot say definitely about an issue u have not corrected. U may say: "it may be..." and cont to live w/o repairin the issue.

[ejohanss]

Anybody else used Mobile synthetic tranny fluid?

[Nahkapohjola]

Originally Posted by ejohanss

Anybody else used Mobile synthetic tranny fluid?

Do not ever use any other grade than what mfg suggest, or better. AT fluid if AT tranny. Read manuals for the requirements.

There are some snakeoil additives; I guess no harm done testing - if total repair is the other alternative. Some claim theyre great, I would not use them in functional tranny.