Moses Ludel

Moses, I made a video of the Snap-on MT2500 scan tool readings maybe this will help in the RPM issue. Here is some history of the 89 Jeep Wrangler YJ 2.5L.  I have what i call a hiccup when idling or driving every once in awhile. The engine is usually warm to operation temp and will hesitate or act like it dies ( rpm drop at an idle to 200 rpm or so) while idling in the drive way. Sometimes will die but will start right back up and there is days when it dose this hiccup while i am going 25 or 45 mph or what ever speed and has no rhyme or reason. Here is what I have replace or trouble shoot with a multi-meter (analog and digital meters), i check and replace vacuum hoses where needed and replace 4 small hoses on the TBI.  Clean the crank sensor, replace MAT sensor, installed MAP sensor but ended up not using so replace with original. I compression check each cylinder and had 95 to 100 psi per cylinder. I put Seafoam in each cylinder and let sit overnight. Did this twice to get rid of the blow-by and it hasn't consumed any oil in 1000 miles spark plugs look good too, light colored. The Plastic valve cover was replace with an new oil cap as well because of oil being push out thru the oil cap. After the Seafoam treatment I check compression and found it went up to 110 in each cylinder. The engine has no leaks and no noise of any kind that would point towards replacing it.  Also put Seafoam in the gas and poured some into the TBI. This seem to work quite will for smoothing out the idle and performance. I have real good acceleration. Previous owner replace the spark plugs, wires, rotor and cap, O2 sensor, belts, and change all drive train fluids to synthetic and oil change with Valvoline 10-30. I Check grounds under hood and they look great. The engine idles about 800 rpm. I borrowed a Snap-on MT2500 and scan it but really nothing stands out. When the jeep is running I wrote down the readings from the MT2500 and notice the ST Fuel trim 126 and LT Fuel trim 133 steady. I listen to the TBI with the air horn off and sounds like a hissing noise when the engine starts to hesitate or stall, but will start right up. Kind of out of answers other than the TBI needs replace and I have plenty of power on the highway and thru the whole power band from start to 80 mph. I removed the gas tank because the sending unit was showing incorrect gas level so I tested the gauge and the sending unit and found the baffle in the tank was the issue, so I removed it and check all the fuel lines and the vents and all is good and not plugged up. Gas gauge reads correct now and it seems to run pretty good today as I drove it for about 10 miles.  What is your thoughts, thanks.  

Moses, I made a video of the Snap-on MT2500 scan tool readings maybe this will help in the RPM issue. Here is some history of the 89 Jeep Wrangler YJ 2.5L.  I have what i call a hiccup when idling or driving every once in awhile. The engine is usually warm to operation temp and will hesitate or act like it dies ( rpm drop at an idle to 200 rpm or so) while idling in the drive way. Sometimes will die but will start right back up and there is days when it dose this hiccup while i am going 25 or 45 mph or what ever speed and has no rhyme or reason. Here is what I have replace or trouble shoot with a multi-meter (analog and digital meters), i check and replace vacuum hoses where needed and replace 4 small hoses on the TBI.  Clean the crank sensor, replace MAT sensor, installed MAP sensor but ended up not using so replace with original. I compression check each cylinder and had 95 to 100 psi per cylinder. I put Seafoam in each cylinder and let sit overnight. Did this twice to get rid of the blow-by and it hasn't consumed any oil in 1000 miles spark plugs look good too, light colored. The Plastic valve cover was replace with an new oil cap as well because of oil being push out thru the oil cap. After the Seafoam treatment I check compression and found it went up to 110 in each cylinder. The engine has no leaks and no noise of any kind that would point towards replacing it.  Also put Seafoam in the gas and poured some into the TBI. This seem to work quite will for smoothing out the idle and performance. I have real good acceleration. Previous owner replace the spark plugs, wires, rotor and cap, O2 sensor, belts, and change all drive train fluids to synthetic and oil change with Valvoline 10-30. I Check grounds under hood and they look great. The engine idles about 800 rpm. I borrowed a Snap-on MT2500 and scan it but really nothing stands out. When the jeep is running I wrote down the readings from the MT2500 and notice the ST Fuel trim 126 and LT Fuel trim 133 steady. I listen to the TBI with the air horn off and sounds like a hissing noise when the engine starts to hesitate or stall, but will start right up. Kind of out of answers other than the TBI needs replace and I have plenty of power on the highway and thru the whole power band from start to 80 mph. I removed the gas tank because the sending unit was showing incorrect gas level so I tested the gauge and the sending unit and found the baffle in the tank was the issue, so I removed it and check all the fuel lines and the vents and all is good and not plugged up. Gas gauge reads correct now and it seems to run pretty good today as I drove it for about 10 miles.  What is your thoughts, thanks.