Rough idle in gear 1990 Mirage throttle position sensor or idle speed

Had (supposedly) valves checked and adjusted. Could this be a gas cap problem? Mine is a little rusty with some crystallization but seems ok otherwise. It is the original cap.

When I give 15 seconds of ignition w no start then crank the ICS SEEMS to recalibrate meaning I get searching rpms again. Everytime it seems to search less and less. Should I just give it a week to try and sync? Someone also mentioned programming the (new ECU) any ideas around these two issues. Thanks again.

ISC is new from mitsubishi. Only a few months old. Wandering rpms are self resolving but I am getting a little random rpm surge when stopped in gear post MAF replacement. Vibration is still a problem still rough in gear at operating temp. Something is not telling the engine to lean out? Or increase rpms? While in gear at a stop. Its almost backwards meaning out of gear no ac rpms increase and idle is smooth in gear w or w/o ac rpms increase a little but not enough? And I get a steady shake through the steering wheel - shake stops as soon as i'm out of gear. Is throttle position sensor a possibility?

Could use additional information on MAP location - but can not find it or any reference to it on 90 mitsu mirage.

Mounts are maybe 3 months old. Reset idle again by ear. The car wants and does for a moment, run smooth in gear but then shaking starts and exacerbates I also hear some puffing like exhaust leak ( but had that checked )as idle lowers and shaking starts most noticeably when I first go in to gear.

Replaced all 3 motor mounts and 1 trans mount. 3 months ago

Setting idle higher doesn't seem to help.

I know. The idle surge has resolved / is gone. Suggestions to read RPMs? I have no tach installed

Your last comment might be the answer. Even though the mounts were bought from RockAuto less than a year ago the vibration never resolved. I can see the engine "jump/move" more than an inch when in gear and out. Does this sound like a bent center support? I have not inspected it lately but will tomorrow. It did take some muscling to get the front mount in and adjusting to get it to line up.

This problem manifested itself one day years ago. It just appeared. It was mom's car perhaps she did hit something or run over something.

The only other weird part to this is that when the engine is cold there is no vibration in gear. But as soon as it reaches operating temp the vibration is there when in gear. I am also noticing a tough start in the morning, the engine idles very low and then the ISC kicks in and rpms come up - but not right at start up.

Thanks for your continued advice/support.

Please see the attached video pics. I can not tell if its "bent" or not but obviously took some damage. Re Center Support - is that, scratched, rusty bar running font to back it? The front of the car is to the right of the screen.

I suspect the ISC is dirty / other since I have pulled it, connected, unconnected, reconnected it many times. Suggestions on cleaning it?

I did have a guy adjust the valves - I believe he got creative on setting them to resolve this problem-to no avail-do you suggest another valve adjustment/job? The car does run rough (quite) at cold start up, and will stall if I drop it in to gear, if the ISC has not engaged.

Would additional video help nail this down? Im pretty sure we've got it ID'd but would like to be quite sure before I drop it off for another attempt to resolve.

Thanks again.

Well Im stumped. I replaced the center brace, got the ECU rebuilt, replaced all fuel injectors, timing belt, had valves looked at and anything else I could think of. The good news is the ECU rebuild fixed the ISC fail/sporadic behavior. The rpms are high at cold start up and adjusts as the AC compressor kicks in and out and temp comes up and I have no vibration in gear. But as soon as the engine is warm the vibration in gear is back and is exacerbated as AC, lights, brakes or steering are engaged at normal op temp. It idles smooth as silk out of gear and warm but starts vibrating in-gear under any kind of load but only in gear.

Ive notice the head lights dim as AC is put on when in gear. Idle has been set with code scanner (no code - no check eng light) to factory specs.

Could it be a sensor or switch in the gear selection housing? Or the alternator? It happens in every gear and I mean as soon as I shift into a gear (auto trans). Sometimes it smooths out a little - usually when the AC compressor kicks in or if I put it on a high setting (more blower) and rpms come up.

Engine temp sensor checked out ok. The only other thing Ive noticed is despite a new thermostat the temp gage still shows the normal op temp running a little above the normal hash mark. I am at a loss for what to do next. Thanks again.

That (mounts) was the first thing I did in April of last year. I just replaced two more this week with no improvement.