I have a 2004 ford ranger with a short history of problems...the engine is v6 3.0L OHV.
1) It died 2 summers ago, stopped right in the road, around noon in the middle of July. I live in Tucson so it was pretty hot. The car had been shaking at low rpms for two weeks, and the engine light was off and. I had it towed and the folks replaced the fuel pump module assembly. It was working again.
2) Last summer, it began to shake at low rpms again. The shakes would come in waves, the engine light was on for a few days, then off for a week. I took it to a shop (different than the first) and in their notes they wrote "no active codes, but confirmed customers concern regarding vehicle running rough at idle. Tests determined engine has a misfire due to spark plug wires arking. We removed and replaced plug wires and spark plugs with new. Vehicle appears to be operating as designed." The shaking had indeed stopped.
3) Fast forward to this summer, as soon as the 110 degree days began hitting (3 weeks ago), the truck has been taking 5-10 seconds of cranking before it starts... BUT only during the daytime (sometimes there is a terrible metal-shredding sound during startup, but before it has actually started). Once the temps are below 95 for an hour, the truck starts right up. Then to my delight, the engine light has come back on (2 days ago) along with the rough shakes at low rpms. It used to idle around 1 krpm, and now the truck is very quiet and idling around 1/2 krpm. I got a code reader and the code is p0506 - "idle air control system RPM lower than expected".
So my first thought is, this hot weather just can't be good for the truck. Does anyone have any ideas about this? Is the heat causing all of these problems or is it unrelated that the same/similar symptoms begin showing up like clockwork around the hottest days of summer?
UPDATE: I took the car to a mechanic where they performed a smoke test to detect vacuum leaks. Two leaks were detected, the first was in the air intake hose, and the was coming from the throttle body. The idle air control component looks to be directly connected to the throttle body, hence the p0506 code.
The hose was fixed. They recommended replacing the entire throttle body and then doing another smoke test. For $900 I told them i would replace the throttle body myself... hopefully it won't be too difficult!