RPM Needle Fluxuating

[ncburch22]

Started my truck last night and headed down the road. I got about a mile from home and noticed my RPM's rising and dropping rapidly from 1k-2k. I'm not sure what the cause is? As the motor warmed up it didn't occur as often or as vast as 1000-2000rpms. The needle would fluxuate at idle as well as cruising speeds.

 

[zulu]

I once in awhile have the same problem. only after morning start up but it will go away. I dont notoice it when idling.. I wonder if its the fuel?

 

[ncburch22]

From what I have gathered from other online sources is that it could be anything from water in the fuel, a broken part in the throttle body, a dirty mass airflow sensor, or a dirty air filter. I also read that the other LR3 owners had taken to the shop after experiencing this, but that the mechanics/techs did nothing about it because no engine light or faults were showing. I'll probably run by AutoZone and grab a bottle of fuel treatment.

 

[RobertY.]

You have to clean the throttle body, last week i did mine then calibrate it, problem solved.

 

[kwlr3]

I have inquired about and posted about this issue a couple of times in the past. My '05 does the same thing, only during warm up, low load and more pronounced the colder the weather. The dealer has no explanation, again because no codes are generated. The problem stops as soon as full operating temperature is reached. This started to happen at around 25,000 miles. I thought I could make a "safety complaint" out of it because my morning commute takes me through a 15 mph school zone just as the surging starts to happen. I didn't follow up, I live with it instead.

None of the possible cures seem to make mechanical sense to me so I have never tried to address it with my money. It would logically seem like something is happening to change the fuel mixture during warm up, maybe a bad air temp sensor or coolant temp sensor but I am told any of those would generate a fault code.

If you find the definitive answer, please post.

2005 HSE Java black and tan, 93,000 miles owned since new.