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I have a 1999 Dodge Ram 4×4 with the 5.9L V8 engine and it’s really rough at idle. When I bring the rpm’s up to 2000 she smooths out, but as soon as you take it back to idle she’s rough again. I did look at live data, but didn’t freeze frame it cause not sure how to get the data from the scanner to my computer. Anyways my Short Term Fuel trim on both 1 and 11 (i’m assuming this means 2, not 11) are both hovering around -10% to -15% at idle which indicates a rich condition and it’s trying to take fuel away. My Long Term Fuel Trim on both 1, and 11 are at 0%. When I rev the engine up to 2000 RPM, both Short Terms are still around -8 to -10% again both Long Terms are still at 0%. I also looked at my Oxygen sensors and the bank one seemed to be alternating between 0.8v and 0.1v which seems normal to me. The Bank 2 oxygen sensor was hovering around 0.8v to 0.7v the entire time. Also yes the truck was completely warmed up when I took these readings. What and where should I start to diagnose this problem to get the truck to idle better? Thanks.
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Welcome to the wonderful world of owning a second gen ram ( I have a 95 same setup as yours ) pull #8 plug and check the condition. remove air cleaner box and open throttle plate and take a look inside the intake. if you have oil pooled at the bottom of the intake then the lower plenum gasket is blown. this causes all kinds of drivability probs with the rams. if you have to do the plenum go to hughesengines.com and get the plenum upgrade kit so it is a one time fix.
Another place to check regarding the rough idle is the idle air controller ( mounts to the back of the throttle body ) also a part that goes bad on the rams.
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