Ok, this problem has three stages it degraded to:
1. Truck started, but no cold temp high idle. Otherwise ran fine. It hadn't been used a lot over the summer, but had been driven a couple of times a month. (October is when the trouble started).
2. Truck would start as above, but then it would occasionally drop to ~500 rpm, then surge DOWN to almost off, then back to 500 or so. I couldn't increase the rpm above this, either with a simple press of the accelerator or by taking off (it wouldn't go -- no power).
Playing with the throttle would not usually kill it, but if I got in synch with the surge I could eventually get it to the base idle (800 rpm). Sometimes it would go back to 80 rpm on its own. Noticed that my engine check light was off (it is ALWAYS on for misc. missing). Strange. I would think this would be setting off more errors.
3. Drove to hunting camp (~8500 ft). Had to drive in 2nd/3rd (downhill in 4th) to make it (Eisenhower tunnel & Vail Pass), definitely lower on power as the trip progressed, kept the rpms above 4500, still slowed to 35 on moderate hills as the day progressed (~250 mile trip). MPG had dropped to 15 from my more expected 21-22.
At camp a few days later, wouldn't start (temps in the 50~65 range). Tried starting fluid in the intake hose in front of the air cleaner. Checked for spark on a cylinder. Adjusted distributor while cranking (no luck, returned to original position). Removed front two plugs, both wet, dark. Loosened fuel rail end plug; turned ignition on, had fuel. Removed distributor cap, confirmed no corrosion. Gave up, decided to tow it to the paved road.
While being towed, got it to start (bump start) if the rpm was above 2000. Got it to run and stay running (cold:4000 rpm) until it warmed up. Kept it in low range, was able to get down the mountain. Decided to look for vacuum leaks as best I could (wished I had the starting fluid, would have been easier). Pinched off a few lines (used a pair of pliers). Found when I pinched the bypass line to the IAC that would kill the engine. Restarted and noticed there was a high pitch/volume sound coming from this line that I hadn't noticed before. Drove the truck to the next town and back, didn't turn off the engine, did notice that power was definitely lower.
4. Pull started it to leave and go home. Mid-20's. Power worse, as going home got down to 2L and 15 mph on the steepest grades (11 mpg last stop). Also, pulled off for gas and liked to never have gotten off the city road into a parking lot. Truck stalled, then finally got it to start, then worked it to get it above the surge/500 rpm max to real idle. Slipping the clutch to keep it above 4000 rpm. Getting back on the fwy, I put it in low, unlocked. Still had to push it out of the road. Got it started and rpm up, then gunned it through the intersection and on the on ramp ("gun" is not the correct term: babied it across the intersection is).
Made it to Denver and had it towed home (couldn't accelerate once I stopped and within range of my AAA towing).
So, current troubleshooting status:
1. 1st attempt at starting, a very slight firing (a blip if you will, not eager). Nothing after this, which appears to work once in a day, not each time. Except for the bump start, this thing is DEAD.
2, Engine Check Light comes on when the key is turned to the on position.
3. Used my scanner, found no codes set, only 1 code pending (P0400, egr).
4. Going to inspect the TPS, anything else I can get to (crank position sensor, hoses, wiring). Plan to bypass/plug as many vac hoses as I can until it will start.
Any ideas?
Truck has ~190,000 miles, 235x15 tires, nothing else is modified. No new parts in the last 6 months.
