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Miss At Idle

akorna

NAXJA Forum User
My recently purchased '99 XJ Auto 4.0L 4X4 with 109K runs great, but has slightly rough idle (miss). I replaced plugs, wires, cap, rotor, fuel injector cleaner, removed and cleaned throttle body and IAC. The TPS checks out according to spec for idle voltage, but when I connect my auto xray scanner it shows a 15% throttle opening at idle. (It shows 0% on my other OBDII cars, both GM) Cleaning the throttle body/IAC did get rid of an off idle stumble. Air filter looks almost new. Any other ideas?

Thanks!
 
Injector cleaner, always seemed to help my, idle some. Sometimes took a repeat to get it right. Most times the miss at idle turned out to be the cap or injectors.
 
Thanks - just wondered if someone else had a OBDII scanner or could verify TPS signal at idle and WOT. Mine shows 15% throttle opening at idle, 78% at WOT (I would expect 0% at idle, 100% at WOT!) Voltage at with Key On is 0.78 volts at idle, and 4.8 something at WOT.

No trouble codes, MIL is off.
 
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