Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
I'm new (finally getting around to) learning new and advanced diagnostic techniques. This place looks awesome so far. I've started going through the videos and materials but hoping to maybe get a jumpstart/ pointed in the right direction at least. I drive my truck all day long delivering mail and the fuel economy has been killing me more and more lately..
I've noticed my current fuel trims look good at idle but seem to get worse the further I open the throttle when driving. (15-20 long-term) then back to bouncing around zero rather quickly when throttle is closed. Performance has been getting better but still very sluggish. Ive done the WOT test and o2's stay rich so not likely fuel pressure (if I understood that section correctly) or maf iirc.
so far I've replaced all four oxygen sensors a couple weeks ago. (Two were dead and one was acting weird). Just replaced Egr valve last night (leaking with smoke test, need to perform another). Only code in PCM is readiness test not complete. I've seen nothing dtc's related for rich/lean conditions in weeks
I have a launch x431 for scanner and I'm dealing with a 2000 Mercury Mountaineer 5.0 in South West Michigan.
Air filter visually looks good, blew out at last oil change ~30 days ago.
Truck is at 110k original miles. Bought at 69k 6 years ago and don't think it's ran right in a long time.
Purchased truck with bad fuel pump. Installed llt bosch from azone. Have warrantied two of them now. Trying to do it the smart wAy but maybe I should still put a fuel pressure gauge on fuel rail?
Recommend you get specs from ford for your year and make. Mitchell 1 for my truck - 2007 Ford Ranger V6 has LTFT-20 to 20 and STFT -10 to 10 driving 55 mph down the highway. I think if you had a fuel trim problem to be worrying about, the check engine light would be on. My personal opinion only. If you want to rule out any low power problem, do a back pressure test on exhaust system. Further peace of mind, check your maf voltage and g/sec at wot. Your previous run suggests all is well, but not sure if you checked them pids also. Thanks.
Last edit: 1 month 2 weeks ago by bills4065. Reason: addditional info.
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