surging 3vze

[classic55]

Greetings - driving '95 4-runner 3VZE auto/air. replaced motor after #2 son developed rod knock and parked it. Driving under normal conditions at a slight throttle especially if light grade and A/C on a surge is felt, if giving heavy throttle no surge felt - changed plugs wires rotor cap & rotor EGR valve & checked for vacuum leaks (none found). Been chasing this for 3 years and this is getting old. The other day it was suggested to disconnect the EGR valve and with the EGR temp sensor unplugged surging reduced (not eliminated but reduced somewhat), no changes with the vacuum line connected or disconnected and plugged. Does this give anyone a thought line to cure this problem???? There are no codes in the computer (except when I disconnect the temp sensor in the EGR valve). Also #2 son says he never noticed the surging but I do not think he had his foot out of the throttle long enough to notice

I need HELP

Thanks in advance

Classic55

 

[Indy4Runner]

This sounds familiar. I had a '99 Expedition that had this happen and only when the engine was lightly loaded and/or going up an incline. I tried everything I could think of (tranny fluid flush, spark plugs change, etc.) before finally taking it in to the stealership. The problem turned out to be the MAF. Evidently, it had just enough contamination/corrosion on the sensor to make it give off false readings, which in turn caused the computer to meter the incorrect amount of fuel--altering between too much and too little--to the engine and thus the resulting bucking and shaking I was getting.

Funny thing is that mine never threw a code either. Evidently it was just enough corrosion to affect the truck but not enough to throw a code. Any way, hope that is your problem.

 

[classic55]

Thanks Indy4Runner for the idea, only we crossed that bridge also several months ago with no change in symptoms. I plugged the EGR valve this AM and driving it to see how much it reduces the surging and I would estimate this got 80% of it out, enough that I can live with the rest if we find the cause of the problem. I have looked in my Haynes manual and it very vague on the emissions system to the point I have not found the EGR Modulator (I believe that is what controls the EGR valve vacuum) in a diagram or on the 4Runner.

Keep thinking and I am going to keep searching for a solution.

Classic55