I posted about this here a couple of months ago, and the trouble had started a couple months before that (in December '24). My question https://www.yotatech.com/forums/f199...-22-re-319717/ got a good reply, but nothing i tried seemed to make the difference. I have been to three mechanics since. They don't believe me (seriously) that there is a problem! When they drive it, it's fine-- but i KNOW there's a big problem, and am going to a local, deep-thinking, long-time shade-tree mechanic next. I don't want to make him have to replace every single possible thing in a quest to find a problem that only occurs some of the time, so i thought i would ask here, ONE MORE TIME, if the problem rings a bell for anyone: a problem whose main feature is that it can hide for maybe 50 miles at a time, then show up! Then maybe 20 miles of bad running, 10 of good, then horrible again. The mechanics who looked at it did a few small things, then said, "She looks great, she sounds good, she runs like a top. Don't know what to do for ya." Then i drive away, and for sure, in 2 miles or in 50, she's rough again. Let me just recap:
1. Symptoms: (295,000 miles on odometer) Classic rough running in random circumstances. Nothing predicts this: not fast, not slow, not hot, not cold. The roughness is a hesitation, bucking, my hand on stick shift visibly jerking back and forth about a half-inch in each direction, small backfires from exhaust, dog in front seat tilting her head in puzzlement. Then randomly it disappears (after one minute or an excruciating hour) and she's fine. The other day, after the latest do-nothing professional shop in town, she did it at 65-70 on the flat freeway, then in first gear, going about 10 mph up an extremely steep hill, which made me so nervous i had to pull over and idle for a while, to recover my nerve, before jerking up the hill to my destination. (Note: Possible factor, just maybe... Seems she usually does NOT do this within the first 5 miles after starting up cold, that is, in the morning. However, if i turn her off for a minute then restart, she might. So i can't say that warm engine is a necessity, but cold engine is def. not a problem.)
2. What HAS been done or checked: Clean air filter and fuel filter. New gas cap (once she acted like this when i didn't realize someone had forgotten to put the cap back on). Timing as it should be at 5 BTDC. New spark plugs. Oil change. New intake air hose. Less than 2 years/15,000 miles ago, spark wires & plugs, distributor cap and rotor. Valves were last done almost 40,000 miles back (5 years ago).
3. What is advised now-- which of these would you start with, or eliminate, for a problem capable of disappearing for random long periods? (Things suggested to me by friends or online checking
Compression Check... Intake Manifold Gasket... Mass Air Flow... Idle Air Control Valve... EGR... Ignition system: coil or wires?, cracked distributor cap... Throttle Position Sensor... Crack in throttle body boot... Valve adjust/replace again.
THANK YOU FOR ANY HELP. Very frustrated that i go to mechanics and am of course ready and willing to pay money for the ONE JOB they might do, finding a problem... but since it doesn't occur right then, for them, they won't do anything. I really need to fix it. Was planning on a trip of about 1500 miles next weekend to visit daughter, but do not want it to finally hesitate too long, and die, while so far away from home!