Time for a new oxygen sensor?
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Freshman User
Joined: Feb 2004
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From: Fairbanks, AK
Time for a new oxygen sensor?
My 95 F250 w/351 and 185,000 miles has developed a habit of coughing on start up when the engine is already warm. Basically, it'll turn over normally, catch, then cough real quickly and belch out a little bit of black smoke. It doesn't do this 100% of the time, more like about half the time.
I just had it tuned up a couple weeks ago and that didn't help the problem. So, is it time for a new oxygen sensor? Or does anybody else have some ideas?
I just had it tuned up a couple weeks ago and that didn't help the problem. So, is it time for a new oxygen sensor? Or does anybody else have some ideas?
Elder User
Joined: Jul 2004
Posts: 620
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From: Toronto, ON
This is just an idea for your consideration, but shortly after i got my truck, I'd start it up and it'd cough and shutter and blah blah, having a tough time trying to start. Eventually it would start though, and one running purred like perfection. I did notice that the interior lights would dim with the 'coughin' of the engine whilst trying to start up.
My father instructed that from those symtoms that it most likely would be the battery terminals. He cleaned them up with a wire brush tool and applied some dielectric grease to them.
From then on, it starts up perfectly.
My father instructed that from those symtoms that it most likely would be the battery terminals. He cleaned them up with a wire brush tool and applied some dielectric grease to them.
From then on, it starts up perfectly.
Posting Guru
Joined: Jun 2004
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From: Central NY
... but to answer your question, if those 185000 miles are all on the original O2 sensor, then you're about 125000 miles overdue ...
It coldn't hurt to change it if your unsure of the mileage on it either.
Cheers,
Popa Tim
It coldn't hurt to change it if your unsure of the mileage on it either.
Cheers,
Popa Tim
Elder User
Joined: Sep 2004
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The oxygen sensor will not affect starting or the first few seconds after starting. Not a bad idea to change it, based on age, but it is not causing this particular set of symptoms.
Other possible explanations include a failed fuel pressure regulator or a leaking fuel injector. That black smoke suggests an intake manifold loaded down with extra fuel. Do a fuel pressure test and pay particular attention to rate of leakdown.
Other possible explanations include a failed fuel pressure regulator or a leaking fuel injector. That black smoke suggests an intake manifold loaded down with extra fuel. Do a fuel pressure test and pay particular attention to rate of leakdown.
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From: Fairbanks, AK
Originally Posted by fefarms
The oxygen sensor will not affect starting or the first few seconds after starting. Not a bad idea to change it, based on age, but it is not causing this particular set of symptoms.
Other possible explanations include a failed fuel pressure regulator or a leaking fuel injector. That black smoke suggests an intake manifold loaded down with extra fuel. Do a fuel pressure test and pay particular attention to rate of leakdown.
Other possible explanations include a failed fuel pressure regulator or a leaking fuel injector. That black smoke suggests an intake manifold loaded down with extra fuel. Do a fuel pressure test and pay particular attention to rate of leakdown.
Elder User
Joined: Sep 2004
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A sticky valve lifter will cause poor compression, loss of power, a noisy valve train, maybe blue smoke in some circumstances. It will probably not cause post-start stumbling or puffs of black smoke.
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Freshman User
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From: Fairbanks, AK
Thanks for the ideas! If it is a leaking injector, what's the best way to go about fixing that? A fuel pressure regulator isn't too difficult, is it?
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The best way to deal with possibly leaking injectors is to prove that you need to. Run a fuel pressure test with a proper guage and look at the leakdown rate. The same applies to fuel pressure regulators, though they are easier to replace.
A stumble, cough, black smoke, etc directly associated with startup probably has nothing to do with the EGR system. A stuck open EGR valve can cause poor/no idle and general rough running. A malfunctioning sensor can set codes and cause excessive EGR (and driveability problems) under some circumstances. The 30 seconds after startup is not likely to be one of those circumstances.
A stumble, cough, black smoke, etc directly associated with startup probably has nothing to do with the EGR system. A stuck open EGR valve can cause poor/no idle and general rough running. A malfunctioning sensor can set codes and cause excessive EGR (and driveability problems) under some circumstances. The 30 seconds after startup is not likely to be one of those circumstances.
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Joined: Feb 2005
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Originally Posted by Popa Tim
... but to answer your question, if those 185000 miles are all on the original O2 sensor, then you're about 125000 miles overdue ...
It coldn't hurt to change it if your unsure of the mileage on it either.
Cheers,
Popa Tim
It coldn't hurt to change it if your unsure of the mileage on it either.
Cheers,
Popa Tim
Hmmm, just replace based on age? Not disbuting your info, but could you lead me to something that mentions why this is a good idea? I'm always willing to learn.
I guess this one has been in about 100K/6-7 years. IIRC I changed it due to poor running-but that problem turned out to be aftermarket wires and cap. I've kept her bone stock and do tuneups at 30K with all Ford parts/chg oil and filter at 3K etc and get 15MPG around town. No driveability issues. Come to think of it the fuel filter is due.
Tom
Tucson, AZ
Orig owner 95 F150 5L, 5 speed, 355 gears, 153K miles
Posting Guru
Joined: Jan 2001
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From: Nebraska
Originally Posted by tomandbeth
Popa,
Hmmm, just replace based on age? Not disbuting your info, but could you lead me to something that mentions why this is a good idea? I'm always willing to learn.
Hmmm, just replace based on age? Not disbuting your info, but could you lead me to something that mentions why this is a good idea? I'm always willing to learn.
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Joined: Oct 2004
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From: newberry mi
i usually leave oxegon sensors in till they give a code. around here the only time an oxegon sensor fails prematurly is from corrosion of the wire. also the o2 sensor does not have anything to do with startup becasue your motor is in closed loop system. fuel injected motors tend to do this till the motor builds up to temp then switches to open loop where it takes more info from sensors to optomize fule efficiency and delivery. somewhere else ya might want to look is a air intake temp sensor. sometimes if you get a little blow bye or crap in your manifold they will have an intermittent short that wil give a false reading and call for a rich fuel condition on startup like it is 10 below. had a festiva do this exact same thing.
Posting Guru
Joined: Jun 2004
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From: Central NY
Hey Tomandbeth,
Why bother changing your fuel filter, its not clogged yet and will probably work for a quite some time....
The same thought goes to O2 sensors. They are a wear item too and probably should be replaced every 60-70,000 miles. To my understanding they work by reacting with the exhaust to produce an electrical signal and this reaction/signal gets weak over time. I beleive it was FEFARMS that had an excellent post on it a short time back. Perhaps he can be persuaded to repost it once again.
Cheers,
Popa Tim
Why bother changing your fuel filter, its not clogged yet and will probably work for a quite some time....
The same thought goes to O2 sensors. They are a wear item too and probably should be replaced every 60-70,000 miles. To my understanding they work by reacting with the exhaust to produce an electrical signal and this reaction/signal gets weak over time. I beleive it was FEFARMS that had an excellent post on it a short time back. Perhaps he can be persuaded to repost it once again.
Cheers,
Popa Tim
Senior User
Joined: Feb 2005
Posts: 170
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Papa Tim,
OK, so I need to find his post or hope he just happens to see our exchange. What can I say, I never thought of an electrical sensor as a wear item. The fuel filter? yep.
Once again, I'm here to learn, laugh a little, crack a joke from time to time.
Tom
Tucson, AZ
OK, so I need to find his post or hope he just happens to see our exchange. What can I say, I never thought of an electrical sensor as a wear item. The fuel filter? yep.
Once again, I'm here to learn, laugh a little, crack a joke from time to time.
Tom
Tucson, AZ