2006 E-350 5.4L First symptom - cruise control would only work intermittently at highway speeds. Seemed to be associated with the brake, as it would work, but if you pushed in brake (slow traffic) and then tried to reinitiate the cruise, it wouldn't work. Over time, cruise worked less and less frequently, until now when it basically doesn't work ever.
Second symptom - about 3 months later (cruise control loss is frustrating, but not a killer... ), every once in a while, the engine would lose power while accelerating while merging into traffic on highway. At least one time the engine light came on. After up to speed, it didn't have problems and engine light would go off. Most times, merging/accellerating wasn't a problem.
Third symptom, and likely unrelated - about 2 weeks before the power issues started, we noticed the AC fan would not blow out the vent while accelerating to merge into traffic. The fan would be blowing, just not coming out the vent. Sometimes you fould feel it blowing out at your feet when this happened.
I took it to a repair shop today, and they said issues 1 & 2 are both the same - the throttle body needs to be replaced. They said the cruise control worked at lower speeds (35-45), but not at highway speeds. I've never used the CC at those lower speeds, so I didn't notice that.
My question - does that make sense? I just don't know enough about the throttle body and it's role to know if it could impact it in those ways.
On item 3, they said the vacuum resevoir was losing vacuum. They also found an unidentified issue in that the AC system pressure was too high, apparently from suspected pluggage. They said they have to pull out parts of the AC to get the vacuum reservoir fixed, so it'd be easy to fix it at the same time, but that they'd have to replace the drier and tubing.
Question - again, does that make sense? What are the risks if I don't fix the AC right now? Does the vacuum system deal with anything more critical than AC vent control? Financially, I don't know that I can get that fixed right now if it's not critical.
Are these common problems in these vans, or is this just one of those things where everything happens at once?
One other thing - he said they tested the battery and it was weak as well. Could that contribute to any of these problems? It seems that the problems are mechanical and not electrical, but I'm not sure. I know my old lumina had a cruise control problem when it had a weak battery.
Thanks for any help you can provide!