Nice thread title, huh? So I'm tinkering with my 2002 F150 4.2L manual 5 speed. The main reason is that it's intermittently doing some weird things. Some of the things it will do from time to time for some unknown reason: -Idles pretty fast. about 1400 RPMs when cold... generally about 1200 when warm. But occasionally it will idle smoothly, around 800 to 900 which I would assume is more normal. -The thing it has liked to do lately... meaning once every few days... is the engine surges when I push in the clutch to shift... or when you push in the clutch to stop at a stop sign. The RPMs will sometimes go up to 2400... and stay there for about 5 seconds, before slowly quieting back down to 1200 or so. (I suspect the IAC) [B]This is probably my biggest annoyance currently, and I'd like to figure it out.[/B] So if you have any suggestions, I'm all ears. -The intake vacuum is usually running steady at about 20 in-Hg. (when the idle is fast- 1200-1400 or so) But once when I was working on it and it was idling normally at 800-900, it all the sudden started surging, and the RPM's started to fluctuate by about 100 RPMs and the vacuum pressure dropped to a steady 15. (suspecting the coolant temperature got to a certain point and the computer mistakenly triggered the EGR duty cycle, which about wanted to kill the engine.) But it only did that once that I know of. Of course, it's never handy to test it when driving and it's doing this... or else I'd unplug the IAC power or unplug the EGR vacuum to see if it makes a difference. Course sometimes I don't think of that until later. :wall: It's throwing the P0171 and P0174 lean codes from time to time, which usually you would suspect a post MAF vacuum leak. (of course, the MAF could be messed up too, despite having cleaned it several times) If I clear the codes, I can sometimes drive it for a couple days before it will throw the code again. City driving seems to do it (more deceleration more often?) If it's all highway driving, it seems to not throw the lean code, at least not until I get to the city... My B1 & B2 Fuel Trim is pretty high (>+30 or +40) when the engine is cold at idle, and at low RPMs, and maybe that's partly normal, partly the computer overreacting to the lean codes. They are very good on the highway when the engine is warm. (ranging from -3 to +3) It also from time to time throws a P1131 and P1151 code (Lack of HO2S-21 Switch, Sensor Indicates Lean) which could also be a stuck or leaking EGR (which would explain the very low 15 in-Hg vacuum and surging). I need to do a leak test on the EGR but don't have a hand vacuum yet. I'd like to check fuel pressure soon to rule that (and the fuel filter) out as a problem. I've gone over the vacuum hoses with a fine tooth comb, and have replaced anything even remotely suspicious. I probably need to have a mechanic perform a smoke test to be sure and rule out a vacuum leak. The O2 sensors seem to read okay on the OBD-II Live Data graphs. The ones before the C/C range from .1 to .7 and the ones after the C/C are usually a steady .5-.6 on the highway. MAF ranges from .01 to .12 from cold start to highway driving. Not totally sure what's normal. Anyone know?

I have a 07 suburban 15005 4x4 5.3. I replaced the battery and still had a slow hard crank. Had the starter tested and it was weak so I replaced it. Now nothing. I have 11.5 volts on the thin lead at the starter 12.8 on the thicker one. I don't know what to try next.