QuestionI have a 1984 FJ60 that is all stock, with 135000k miles. I bought it new and do all the work on it myself, so I am pretty familiar with its' innards.
Recently I have experienced a stumble/hesitation @ 2000rpm during cruise (40-45mph). During acceleration the problem is not apparent. I disconnected the EGR and the problem lessoned to some degree but did not dissappear.
I then tested the EGR and using the factory emmissions manual, it tested fine. I then removed the egr to clean and check for any carbon-non found. I then went through the 28 ft. of vacuum hoses and various valves. I replaced the EGR vacuum modulator, air pump, check valves(2), decel cut valve, tightened the manifold bolts, cleaned the air rail, and overhauled the carb. It still has the problem. My next step is to inspect the manifold gaskets and the ignition system. I also plan on connecting a vacuum gauge to see what's what.
Any ideas, 'cause I'm stumped!
AnswerI doubt if there is an intake manifold leak since this would also cause a rough idle, since the problem is there at cruising speeds at about 2000 rpm it woul eliminate an intake air leak. I remember a long time ago having kind of this same problem and it turned out that the intake manifold had a crack causing exhaust gas to leak into the intake, the two manifolds are connected with the exhaust manifold directly below the intake, remove the carburetor again and check the area directly below where the carburetor goes for cracks, if I remember correctly there may also be some sort of preheat tube in there that can also leak.
