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LT fuel trim 49.2% Posted by JerseySaab [Email] (#666) [Profile/Gallery] (more from JerseySaab) on Fri, 14 Apr 2023 10:28:49 In Reply to: Re: 1997 CSE sudden rough running, stalling, JerseySaab [Profile/Gallery] , Fri, 14 Apr 2023 09:37:46 Members do not see ads below this line. - Help Keep This Site Online - Signup |
I found that with a cold start the engine would be rough for a few seconds then settle into idling. Then after the engine warmed up for a while things took a nosedive when the system entered closed-loop mode, rough running and threatening to stall. Feathering the gas kept it running while I checked data on the Tech2.
Long term fuel trim is a whopping 49.2%. (It was zero last time I checked months ago.) Short term trim is also positive but only by a few percent. So it looks like over time the computer has been adding lots more fuel to compensate for a lean condition. O2 sensor readings looked good (heaters OK, upstream sensor varies in voltage, downstream is steady). Time to replace that fuel filter and look more closely for vacuum leaks...
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