mark77

Hi everyone,
I have read and read on this subject and don't know where to go. I have a '93 maxima with a VG30E. It has a couple of problems that i'm trying to get to the bottom of. When coasting at just over 1500rpms i get some "hunting" as the revs bounce up to 1700 and back down a few times. I beleive that this may be the torque converter locking/unlocking. The other issue is a "blip" in the idle which is quite obvious when listening to the engine. This may or may not be related to the first issue. I am concerned because i have read of this happening to people and then their tranny died. It seem strange that people refer to this happening to their cars but have not found any info of solutions.
I have done everything i can think of to try to fix these problems. I have changed plugs (NGK BKR6ES-11) and wires, cleaned throttle body, cleaned iacv, cleaned maf, replaced fuel filter, checked fuel pump, checked resistance of fuel injectors (all around 12-13) and cleaned corrosion off terminals, performed numerous idle relearns, replaced every vacuum hose i can find, tightened fuel hoses, replaced air filter, replaced dist cap, checked timing, replaced earth wires to distributer and alternator, adjusted throttle cable and ascd cable. Car has never thrown any codes. Only thing i can find that seemed maybe not quite right was when performing idle relearn and pushing the accelerator down to rev the engine up to 2000rpm, the revs seem to drop back down suddenly a couple of times before i can get them to hold at 2000.
I really want to get this car running smoothly as i have spent alot of time on it. The engine seems really good, plenty of power and no oil leaks. It has done 240 000 kms. I have had bad experience with auto transmission "specialists" in the past as they seem to be very expensive and in my case didn't solve the problem i had in a previous car.

Does anyone have any suggestions on how to fix this problem? I really appreciate your help.

Cheers,

Mark77

internetautomart

when you cleaned the MAF did you check how it ran with it diconnected

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mark77

I inadvertently seemed to solve the problem by attempting to drive the car with the TPS (not CTPS) unplugged?! When trying to do this, the car wouldn’t run properly at all and after about 100m I plugged it back in. The car behaves completely differently now and the previous problem is gone.

But now I have other problems that I feel may relate to the TPS and I am reluctant to just go out and buy a new TPS with out being sure that it can’t be fixed by adjusting something. I have read countless threads where people have stated “I replaced the TPS but it didn’t fix the problem”, usually prompted by mechanics to do so.

Since trying to drive the car with TPS unplugged, I have performed 2 idle relearns and adjusted the timing slightly. Incidentally as part of the procedure for adjusting timing that I found, it stated to unplug the TPS and rev the engine a couple of times for 1 sec before adjusting. As I mentioned previously when the TPS is unplugged, I cannot rev the engine past a bit over 2000RPMs. Not sure if this is normal. The engine just bogs down and “chugs”. Also when measuring resistance on TPS, I only get 7.4 kOhms at WOT not 9 as sated in FSM. I confirmed that the CTPS has continuity at closed throttle and resistance when opening throttle slightly.

The main problems that have appeared now are:
a) the car misses when it’s first started in the morning for a few minutes
b) the idle seems to change i.e. sometime 1500rpms in N(causing it to “clink” into Drive), then next time it is started it may be 700rpms in N.
c) there is a cycling fluctuation to the idle speed. i.e. tacho needle constantly goes up and down at idle.

I have read that the IACV can cause some of the symptoms above but I haven’t touched it during all this.

Has anyone had similar problems that they managed to fix - with or without replacing the TPS??

Thanks for your help

JNCoRacer

You might want to try cleaning the IACV. Also check around for any vacuum leaks.

mark77

Hey thanks,
Last night i think i put myself back to where i started from. I cleaned the IACV not very long ago. I checked all around the engine bay and i think the idle problems where being caused by the air filter element not being seated properly and letting air through. Bizarre because i hadn't touched it. Has anyone else had this problem? Anyway the idle is alot better (stable and correct) after i performed relearn again. Only thing is now the bouncing revs (coverter locking/unlocking) while coasting at 1500rpms is back! Arrhhgg. Any advice for me? Could TPS be doing this despite it testing ok?

JNCoRacer

It is possible.