idle drop/jump + shudder??
 

I have a 92 GXE vg30e, when coming to a stop the idle drops to almost 400rmp, jumps up around 1100rpm, then drops down to about 400-500rpm and shudders, then returns tonormal. Also when turning (while @ idle), or holding the power window switch @ the top or bottom of the track it affects the rpm by about 100 and causes the shudder as well (although no idle jump occurs).

Ive replaced the distributor + cap/rotor, plugs, o2, cat and alternator, set timing to 16,set the base idle, tested the battery, alternator, had a meter on the battery and the only drop is less than 1v????

I thought IACV or MAF but I switched'em withworking ones and no change. Im thinking a wiring or ground problem...any ideas?????

RE: idle drop/jump + shudder??
 

I'd clean all relevant connector pins from IACV via SMJ to ECU. Then check for vacuum leaks, then clean the IACV being used (see pages 6&14, clic link below). SMJ's can be found after dismantling drivers side fuse block.

RE: idle drop/jump + shudder??
 

Hmm, It sounds like a vacuume problem because the lower sputtering idle and then it returns to normal is usually a vacuum problem. If its a hose, i know some quick fixes until you need to buy a regular hose.
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RE: idle drop/jump + shudder??
 

I tried the smj behind the fusebox and the ecm/tcm, cleaning all contacts and using small amounts of dielectric grease...no change. I cant seem to find any vacuum leaks and tried a smoke machine through the pcv borrowed from a friend and saw nothing. I would think its related to the iacv but as mentioned switched it and no dice. I was trying to research the root cause.. any ideas??

RE: idle drop/jump + shudder??
 

IACV has to be clean: swapping dirty valve to dirty valve cant hlp...
The half inch supply hose leak can cause this; use liquid sealant in hose seatings.
Minuscle IACV gasket leak can cause problems. That is why cleanin is 'forbidden' for nissan techs :(
Try re-sealing the whole assy.

Check TPS and the zero pos sw adj, see p6
Distr Cap may be faulty - I mean the new one... 75% chance to get faulty... Redo the gnd as suggested on page10, see link below

RE: idle drop/jump + shudder??
 

i had this problem before where the rpm fluxuates and returns to normal and it ended up being a simple stuck pcv valve a $5 part if it was a vacuum leak it would never return to normal idle also check for any holes/cracks in the intake behind the MAF its pretty much a unmetered air leak into the motor. good luck keep us posted

RE: idle drop/jump + shudder??
 

Flexin airleaks can cause unsteady/varying flow/idle.

When flow changes or as load is added, limited IACV response causes lag in ECU correction adj - resulting in intermittent rpm drop: Dirt, worn bearing(s), bad contacts limit stepper motor torq, reaction time.

RE: idle drop/jump + shudder??
 

OK, So I ended up buying a set of rebuilt injectors and using a head gasket kit and did the whole nine.... head gaskets, valve seals, etc,etc.
My shudder coming to a stop has dissapeared which I attribute to a missing cap on the #6 injector (which must have cracked and come off then burned up in the cylinder) and the #2 tested at 27ohms. But now when I come to a stop the idle still bounces twice and returns to normal (no shudder now)

I replaced all the gasket related to the IACV + cleaned/dielectric greased all connectors sealed all leaks and used actuall clamps on hoses.Also swichted with a known MAF...no change???