My 90' w/ auto, 4.0, has developed a stumbly miss at idle only. About 1110 rpm's miss is gone. Kinda of stumbly off the line until it hits that rpm range. Miss is a random bump, bump bump, bump. No pattern to the miss, sometimes its 2 bumps or 3 bumps in a row or none at all for 3 seconds. Idle speed seems normal aswell. Has'nt stalled out at idle either. Just got back in town from a 500 mile trip, around 20mpg. Lots of power, 65 up cabbage hill, did'nt miss a beat. Plugs, cap n rotor newer, aswell as o2 sensor. Had some loose manifold bolts searching for problem, not the first time. No change after re torque. I figure if it did not reseal gasket then off idle and gas mileage would suffer aswell ? Tell me if my thinking is wrong. Ran the tests on the 3 EGR componets, all working. Throttle body squeeky clean. Did the back pressure test per FSM, no blockage. Was suspicious of the temps about 5 degrees warmer, have to chalk that up to the warm weather recently, we hit 80* once again.:laugh2: That test goes through some vacuum measurments at idle and 2000rpm. Idle is about 16 and 2000 rpm is 22 of vacuum. Anything suspicous of the 16 at idle ? I can see the miss in my vacuum reading, vacuum would fluctuate 1/2 up or down to the miss of motor. Idle motor cleaned when I did the t-body. TPS per my scanner reading is acceptable range, actually right where I set it last time. Usually tranny will tell me my TPS is acting up.
Thats about it in a nutshell. Searched til my eyes bled, nothing quite the same. Throw me a bone, something I'm missing here.
Thats about it in a nutshell. Searched til my eyes bled, nothing quite the same. Throw me a bone, something I'm missing here.