LvR

Auto VG in pristine mechanical and electrical condition, good performer, "good" fuel consumption, regular services, "babied" most the time because my auto box now in standard guise has 240000Km on and still smooth as day one............

Till yesterday that is!

Strange thing is now happening:

1. only when the motor is warm
2. only on touching the brake (not actually applying any force - just moving the pedal by about 5 mm
3. only at speeds normally done around town - about 50-70kph
4. "seems" like it only happens with AC off
5. only with OD on

If I touch the brake pedal when it looks like I may be required to stop somewhere, its as if the auto-box kicks down a gear immediately (perhaps disengages the OD?) - you can see the revs jump by about 400-600rpm depending on the speed you travel at - the result is you get the same feeling as if you would jump on the brakes unexpectedly - very irritating indeed.

Thought it must be something with vacuum lines? .................... checked cannot find leaks or bad hoses anywhere.

Thought it could be earth or battery related - checked and cleaned (even though they seemed to have been in good condition anyway) - no go.

Anybody with the same experience and a possible solution or even ideas as to the mechanism involved in this strange behavior?

Any thoughts much appreciated...............

Wiking

Any: Tranny downshift is hard: some solenoid activated bands 'hits on hard'. I would think engine is just a receiver - in the end of trannyrope...

Tranny fluid level, color?

Solenoids ? ok, measure ohms, check the voltages they receive.

TCU getting soaked from leaking core or getting too hot and acting weird. Check how he is, is it too hot for it? Clean connectors.

How To Check Out: http://www.cardomain.com/memberpage/748507/15

LvR

Thanks for the interest Wiking

Just to report back:

Tranny fluid ?- normal level (max mark when hot and level) and a nice red color.

No heater leaks I can find inside, and coolant level has never needed a top-up in ....... 3 months (?). Checked actual radiator level when cold and it sits right at the top ready to run down the expansion tank downpipe.

Bit busy during the week, but I plan on doing all connections on some weekend anyway.

Perhaps one thing I have not mentioned is this:

If I touch the brake pedal, then things happen as I described - if I release the pedal (just that few mm travel) the box seems to immediately resume the state it was in before I touched the pedal and I can also see the rpm drop by about 400-600 rpm.

Wiking

This means gear change down to 3 and back to 4??? That itself sounds logical TCU control; how much the engine breaking effort should be, dunno. Normally at least it should be noticeable.

Some recommends driving in town - OD off... I dont, cause gas here is taxed 3x the US rate.

LvR

Indeed I agree.

Had to drive around some more this afternoon and some more strange things started to happen:

ONLY the left indicators would stop "flicker" when I slowed down and touched the brake pedal!

So this now that started to point to some obvious elctrical issue - so I slapped a voltmeter (Fluke) on the batt and drove around for a while - sure enough!

Eventually things started acting up and the culprit is batt voltage dropping below exactly 12V...............

So looks like its the alternator or wonky wiring between somewhere.

Will tackle it tonight - have to finish earning a living for the day first - will report back when all is solved.

LvR

Just to close up shop and give the answer found:

Charge indicator inside the car never came on - yet looking back at what was actually happening now, its rather obvious that is what the problem was.

Turned out to be a bad connection inside the alternator!. We have Bosch 90AH units fitted here in South Africa - When I started to look for the missing 2 Volts at the batt I traced back to the alternator output - same voltage there so it not the cable between the batt and alternator.

Out came the alternator, removed the reg/brush assembly and the problem was immediately obvious - ie - a "dirty/corroded" spring loaded contact between the diode plate and the regulator............

Cleaned it up, bent it to ensure a bit better contact, cleaned the commutator (still wonderful after 240000Km), brushes still less than halfway worn so that went back in, assembled and tested ok.

Back in the car the indicator problem on the left were not gone immediately! - and neither the kick-down thing - both now turned to "intermittent".

So yesterday I slapped a charger on the batt and left it for the day.

Today - all fine and back to normal.

Sat here studying the FSM diagrams for the indicators, and will be damned if I can figure why only the left-hand indicator would be affected and not the right................ who knows exactly what goes on inside the TCU, so that reaction could very-well be "normal" under those specific batt voltage conditions................


Even so - problem seems to have been solved and batt sits at around 13.9V constant (same as alt ernator output)

Thanks for the interest.

Wiking

Thanks for your input: I think this underlines the voltage problems with Nissan (most others also] thinnyskinny wirings. Gene Rally: If that 12V at battery is not enough for TCU to work properly, better triple the wiring capacity around all signals what the computer complicators handle.

relates to this thread:

http://forums.maxima.org/showthread.php?t=383651