'91 4.0L intermittent sudden drop in RPM - Jeep Wrangler Forum

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Old 01-14-2010, 08:27 PM
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Join Date: Jan 2010
Location: Spotsylvania County
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vthokie87 is on a distinguished road
'91 4.0L intermittent sudden drop in RPM

About 2 months ago, had a very intermittent hesitation (sudden drop in RPM) at 2000+ rpms and check engine light would come on intermittently as well. Replaced the plugs and wires and symptoms seemed to go away. Its been very cold here in central VA for the past month or so and decided to check the coolant level before leaving work yesterday. Once home, added water and coolant to the radiator and reservoir and ran the engine until warm to make sure a good mixture of old and new. The trouble started the next morning. Was very difficult to start, but got it running and off to work. A couple of minutes before arriving at work, intermittent hesitation came back, and check engine light back on. Ran the codes and got 12 (battery disconnected), 33 (A/C relay - no A/C in the Jeep), and 41 (Alternator field open or short). After work, hesitation was still there (check engine back on after a few RPM drop-offs) , but was able to drive most of the 35+ miles back home with no issues, but just before I got home, hesitation was back. Shut off engine and went to restart. Struggles to restart but can get it to start.

Very confused about the coincidence of bringing coolant level back to full and adding to reservoir and now all of a sudden this hesitation problem is back...

Any ideas???
Virginia Tech '87
Ut Prosim: "That I May Serve"
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