1994 pathfinder erratic engine with no check engine soon light

[robertoquintana]

I HAVE A 1994 XE PATHFINDER A/T 2WD VG30E V6 ENGINE. STARTS AND WARMS OK. WHEN DRIVING AFTER REDUCING SPEED WITHOUT STOPPING AND YOU PRESS THE PEDAL TO GAIN SPEED AGAIN THE ENGINE BOGS DOWN OR STARVES FOR A FEW SECONDS BEFORE PICKING UP SMOOTHLY. wHEN YOU STOP AT A RED LIGHT AND GO THERE IS NO FAILURE. THE PROBLEM APPEARS BETWEEN 1000 AND 2000 RPM IN SECOND GEAR AS YOU ACCELARATE. ABOVE 2000 RPM THE ENGINE RUNS OK. THE SES OR CHECK ENGINE SOON LIGHT HAS NOT TURN ON. IDLE IS ALSO FINE.THE DEALER HAS CLEAN THE GAS TANK, NEW SPARKS, PURGED THE THE FULE LINES, CLEAN INYECTORS, CHANGED FUEL FILTER AND CHANGED THE THROTTLE POSITION SENSOR.NEED HELP TO PROPERLY DIAGNOSE.

[elwesso]

welcome to NICO!

Let me ask did tihs problem start or has it always been this way???

[robertoquintana]

This problem started about a year ago. Let me give you some history. A year ago the engine without warning simply jumped to 1400 revs for a few minutes in idle. Only after turning the engine off for some time or running it above 3000 revs for some time did it go back to its 750 revs idle. This happened randomly. Dealer was unable to diagnose or fix (just guessed) as there was no SES light. From then on idle was slighty rough. Otherwise engine ok.Later on idle began to be rough when hot and at last the SES went on. Valve clearance and tune up were diagnosed. Done engine ok but weeks later idle slightly rough with the added problem of bogging at +1000rev.SES light on again check AAV, fuel preasure, oxygen sensors. New AAV, fuel system cleaned thoroughly including injectors, preasure check ok and engine ok for a few weeks. Same problem appears again. No SES light. Latest guesses Mass air flow sensor may be the problem or the TPS. New TPS great improvement but not complete.