New member here. I have a couple issues with my daily driven 1999 crew cab dually with 454 automatic.
The first issue is an intermittent high idle. It does not seem to be related to temperature, the A/C being on, or anything else I can figure. I tried changing the IAC motor, and it seemed to go away, until a week or so later when the idle went real high and it threw an IAC circuit code, so I put the old motor back in, and started dealing with the intermittent issue again.
The second issue is when cruising on the highway, it will start missing. It doesn't throw any codes, but this seems to be more prevalent when it is warmer, say over 70° F. Today, I noticed on the live data when this was happening, the timing would drop into the mid teens. When it was running good, the timing was up in the high 20s, but never more than 30° when cruising at about 3000 rpm. Are the knock sensors going bad and pulling the timing back? I don't hear it pinging. It just starts breaking up. Today was the worst it's been. It seems to pull fine accelerating at part throttle and at WOT.
The upstream oxygen sensors are only a couple weeks old. I changed them after I got an O2 sensor code a few times, usually coupled with a rich code (P0174 if I recall correctly). The long term feel trims just before that were pretty high negative, but they seem to be back in order now.
Plugs and wires are a few years old, replaced with OEM type wires and AC platinum plugs of the OEM number.
I've had the truck for about 8 years, but didn't drive it daily until about six months ago. It has about 165k miles on it.
Any help or ideas would be greatly appreciated.
Thanks in advance.
The first issue is an intermittent high idle. It does not seem to be related to temperature, the A/C being on, or anything else I can figure. I tried changing the IAC motor, and it seemed to go away, until a week or so later when the idle went real high and it threw an IAC circuit code, so I put the old motor back in, and started dealing with the intermittent issue again.
The second issue is when cruising on the highway, it will start missing. It doesn't throw any codes, but this seems to be more prevalent when it is warmer, say over 70° F. Today, I noticed on the live data when this was happening, the timing would drop into the mid teens. When it was running good, the timing was up in the high 20s, but never more than 30° when cruising at about 3000 rpm. Are the knock sensors going bad and pulling the timing back? I don't hear it pinging. It just starts breaking up. Today was the worst it's been. It seems to pull fine accelerating at part throttle and at WOT.
The upstream oxygen sensors are only a couple weeks old. I changed them after I got an O2 sensor code a few times, usually coupled with a rich code (P0174 if I recall correctly). The long term feel trims just before that were pretty high negative, but they seem to be back in order now.
Plugs and wires are a few years old, replaced with OEM type wires and AC platinum plugs of the OEM number.
I've had the truck for about 8 years, but didn't drive it daily until about six months ago. It has about 165k miles on it.
Any help or ideas would be greatly appreciated.
Thanks in advance.