Idle drops when auto shifts in or out of second

redbullet

YJ Enthusiast
Joined
May 11, 2021
Messages
268
Location
San Jose, CA
1993 2.5L with auto transmission. Recently my Jeep has been having an intermittent issue that now won’t go away. It is starting/running fine in first gear, but the moment it auto shifts to second the rpm’s drop and it shakes like a banshee. I then stop and the idle returns to normal. I tried cleaning throttle body, replaced sensors (IAC, TPS, MAP and crankshaft position sensor). Also has a recent distributor change, but was running fine after that. Last month when this happened I was able to disconnect the battery overnight and it resolved…not this time. Any ideas.
 
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…was able to fix the issue by having the computer/“ecu” refurbished by SIA electronics found on eBay. Pretty cheap fix: $125. Two capacitors were burnt all shifting problems are resolved and Jeep is running smoother than ever:

 
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Why are ecm's for 2.5s soo expensive? Everybody pulls the 4 banger and "upgrades" the engine. You would think 2.5 ECMs would be cheap and plentiful. I'm venting because I'd like to pack a spare computer on the trail ...but at $400 for a used one, sheesh.

Anyway, glad you figured it out. What led you to the ECM?
 
I am hoping to track down a cheap spare someday too, as I plan on keeping my yj forever and it would be nice to have a spare one. To answer your question, all mechanical portions of the trans looked in good order and the intermittent nature of the issue led me to believe it might be the computer…lucky guess.
 
The problem is back…tested fuel pressure and it is good with no leaking from injectors. Replaced cheap battery that died, checked spark plug gap, no fouled plugs and now trying oxygen sensor when it arrives in a few days. This time it happened after I got back from a 150 mile wheeling trip and washed it. Fortunately it crapped out in my driveway. Any ideas?
 
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