2.5L
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2.5L
I have a 99 ford ranger with a 2.5L 4 cyl. 2wd. auto. step side. reg cab. I am getting a check engine light with a code of bank 1 running lean. I have replaced both O2 censors, fuel filter, plugs and wires but not the 2 coil packs. I replaced the air filter, and even did an oil change even knowing it didn't need it just for giggles. I tried doing the at home air leak test by just spraying brake cleaner in the areas to see if the motor would bog down and got nadda. So I am at a loss of what I could try next. Please help. 
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Joined: Jan 2004
Posts: 13,851
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From: SW Va
Welcome to FTE.
Coil packs, plugs & wires don't affect fuel trim, fuel filter & maybe the air filter might if they're grossly plugged.
If the upstream O2 sensor switching range or speed were at fault, you'd also likely have codes for it & the downstream/after cat O2 sensor doesn't affect fuel trim, it just tattles on how well the cat converter is doing its job, so lets think about this some more.
A number of things can cause a lean condition, like a vacuum gasket, seal, hose, or part. So, an acting out stuck open/deposit clogged PCV valve, or dry rotted rubber plumbing to it, all being down stream of & thus not monitored by the MAF sensor, can corrupt fuel trim lean, as can loose intake manifold bolts, or faulty gasket, dirty MAF sensor, low fuel pressure from a weak fuel pump, clogged or crimped fuel line, or clogged fuel filter, but you've changed the fuel filter, so unless it was faulty, belongs low down on the suspect list, are some of the things that come to mind.
Post All pending, or set trouble code Numbers you have, including the one you say you have for bank one, the lean code number, as they can offer up good trouble shooting clues, to help focus your troubleshoot.
Coil packs, plugs & wires don't affect fuel trim, fuel filter & maybe the air filter might if they're grossly plugged.
If the upstream O2 sensor switching range or speed were at fault, you'd also likely have codes for it & the downstream/after cat O2 sensor doesn't affect fuel trim, it just tattles on how well the cat converter is doing its job, so lets think about this some more.
A number of things can cause a lean condition, like a vacuum gasket, seal, hose, or part. So, an acting out stuck open/deposit clogged PCV valve, or dry rotted rubber plumbing to it, all being down stream of & thus not monitored by the MAF sensor, can corrupt fuel trim lean, as can loose intake manifold bolts, or faulty gasket, dirty MAF sensor, low fuel pressure from a weak fuel pump, clogged or crimped fuel line, or clogged fuel filter, but you've changed the fuel filter, so unless it was faulty, belongs low down on the suspect list, are some of the things that come to mind.
Post All pending, or set trouble code Numbers you have, including the one you say you have for bank one, the lean code number, as they can offer up good trouble shooting clues, to help focus your troubleshoot.
Logistics Pro
Joined: Jan 2002
Posts: 4,907
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From: suburban atlanta
I would connect a scan tool and observe what the system is trying to do, and what the system is 'seeing' from its sensors.
Excess air or lack of fuel can trigger the code, but a misfire can do so, too. Unburned mix will have excess O2 molecules which the O2 sensor(wonder what it senses..?) will report as 'lean' because the O2 was not consumed. Leaks into the intake after the MAF can also make the mix 'lean', beyond what a 'trim' can correct, apparently.
tom
Excess air or lack of fuel can trigger the code, but a misfire can do so, too. Unburned mix will have excess O2 molecules which the O2 sensor(wonder what it senses..?) will report as 'lean' because the O2 was not consumed. Leaks into the intake after the MAF can also make the mix 'lean', beyond what a 'trim' can correct, apparently.
tom
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