1991 F-150 XLT Lariat 4.9 rough idle - Need help!
11-30-2016, 05:45 PM
#1
1991 F-150 XLT Lariat 4.9 rough idle - Need help!
Hey everybody looking for some advice/help/etc:
My '91 F-150 i6 300 has started idling incredibly rough to the point that the whole truck feels like it's shaking. The tail pipe bounces up and down while parked and the exhaust note has changed pretty drastically (which I wouldn't necessarily mind if I intended for it to. It sounds almost like a V8 with a nice bassy lope).
As soon as I start driving over about 10 mph, the shake goes away and at 45 mpg, the truck is only pulling 1k rpm with no shake. My fuel economy has dropped from about 14 - 15 mpg to anywhere from 8.5 to 10, but I haven't noticed any significant loss in power. The truck only has 13X,XXX miles on it and has been maintained beautifully. All of my gauges read normal and the truck runs great otherwise.
Any advice, recommendations, thoughts, crystal ball readings would be greatly appreciated.
My '91 F-150 i6 300 has started idling incredibly rough to the point that the whole truck feels like it's shaking. The tail pipe bounces up and down while parked and the exhaust note has changed pretty drastically (which I wouldn't necessarily mind if I intended for it to. It sounds almost like a V8 with a nice bassy lope).
As soon as I start driving over about 10 mph, the shake goes away and at 45 mpg, the truck is only pulling 1k rpm with no shake. My fuel economy has dropped from about 14 - 15 mpg to anywhere from 8.5 to 10, but I haven't noticed any significant loss in power. The truck only has 13X,XXX miles on it and has been maintained beautifully. All of my gauges read normal and the truck runs great otherwise.
Any advice, recommendations, thoughts, crystal ball readings would be greatly appreciated.
11-30-2016, 05:48 PM
#2
Don't post duplicate threads, please.
12-20-2016, 12:47 AM
#5
Thanks for the input! We actually got it figured out a month ago - I dropped a valve into one of my cylinders. We're replacing the engine entirely. Thanks for the reply!
12-29-2016, 08:50 PM
#6
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Have you checked the injectors and the Harness For them,
My '91 F-150 i6 300 has started idling incredibly rough to the point that the whole truck feels like it's shaking. The tail pipe bounces up and down while parked and the exhaust note has changed pretty drastically (which I wouldn't necessarily mind if I intended for it to. It sounds almost like a V8 with a nice bassy lope).
As soon as I start driving over about 10 mph, the shake goes away and at 45 mpg, the truck is only pulling 1k rpm with no shake. My fuel economy has dropped from about 14 - 15 mpg to anywhere from 8.5 to 10, but I haven't noticed any significant loss in power. The truck only has 13X,XXX miles on it and has been maintained beautifully. All of my gauges read normal and the truck runs great otherwise.
Any advice, recommendations, thoughts, crystal ball readings would be greatly appreciated.[/QUOTE]
My '91 F-150 i6 300 has started idling incredibly rough to the point that the whole truck feels like it's shaking. The tail pipe bounces up and down while parked and the exhaust note has changed pretty drastically (which I wouldn't necessarily mind if I intended for it to. It sounds almost like a V8 with a nice bassy lope).
As soon as I start driving over about 10 mph, the shake goes away and at 45 mpg, the truck is only pulling 1k rpm with no shake. My fuel economy has dropped from about 14 - 15 mpg to anywhere from 8.5 to 10, but I haven't noticed any significant loss in power. The truck only has 13X,XXX miles on it and has been maintained beautifully. All of my gauges read normal and the truck runs great otherwise.
Any advice, recommendations, thoughts, crystal ball readings would be greatly appreciated.[/QUOTE]
