Hey, Scotty! I've got a 1988 Honda Civic LX Automatic with 142000 miles. The car struggles to go uphills. On a flat road, it responds fairly well but struggles when trying to overtake another car. When it is at a standstill, the car revs up all the way as how it is supposed to, but when driving, it responds normally until about 3000 rpm. After that, it struggles to rev up no matter how deep I press the pedal. On a fairly steep hill, it won't respond at all, again, no matter how much I press the pedal. The engine won't die or make any sputtering sounds but will just hang in there. One strange fact to me is that the check engine light isn't turning on (it does turn on momentarily when turning the key on, so the light itself works). Also worth pointing out is that the car idles normally (about 750 rpm), and when turning on lights or AC, it adjusts without issues.

The car has had this problem for years. The engine was rebuilt a year ago, but the same problem persisted. I found out about two months ago that the fuel pump had weakened. I changed it, and performance improved but very slightly. The distributor cap, plug wires, and air filter were also changed recently. I checked the fuel pressure; no problem there. I took the spark plugs out a couple of minutes ago and noticed they were pinkish in color. Do correct me if I am wrong, but I understand it means that the car is running lean. I thought it could be the oxygen sensor, so I took my DMM (a pretty basic one) and after it reached normal operating temperature, it displayed 300 millivolts when idling. As far as I understand, it should be oscillating between 100 and 900 millivolts, but I don't know if such a basic multimeter can pick that up. When revving at about 4000 rpm, it displayed about 850 millivolts, sometimes dropping to like 240. I have a hunch that the oxygen sensor is malfunctioning, but why the check engine light won't turn on if that's the case? I thought, well, perhaps a vacuum leak is the cause, but I didn't find any. I have thought about everything, but I cannot find any reason why the car is behaving like that. I'd appreciate it very much if you or anyone can help me out here!