Check engine light..........

J

junkman306

Registered
So I've noticed that my check engine light has been coming on after hot rodding around, but goes off after normal driving for awhile. I've also noticed that after hot rodding around, it smells like someone got a perm at a salon. So I'm going to put 2 and 2 together and hopefully someone has some input. My theory is that a cat is clogging, which would explain the smell, causing heat build up, which is causing the o2 sensor to get hot, causing the check engine light to come on. I'm also assuming that the reason it goes off after normal driving is because the steady stream of air is cooling the exhaust on the way home, allowing the light to go out.
 
Good a theory as any...but you ought to pull the codes. No more guessing. If the CEL came on, it's got a code stored.
 
budpytko said:
Good a theory as any...but you ought to pull the codes. No more guessing. If the CEL came on, it's got a code stored.
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It won't store a code unless the light stays on. It's throwing an intermittent code, but it won't lock it. I've tried reading it a hundred times, but to no avail.
 
junkman306 said:
It won't store a code unless the light stays on. It's throwing an intermittent code, but it won't lock it. I've tried reading it a hundred times, but to no avail.
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I've always understood that there could be codes without a CEL. Maybe I'm wrong but, have you tried a different reader?
 
Be2lose said:
I've always understood that there could be codes without a CEL. Maybe I'm wrong but, have you tried a different reader?
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I've heard the same, but I couldn't get my reader to work here at my work and the local ford dealership can't pull a code either. I've never been able to read a code unless the light stayed on. :confused:
 
The codes are indeed stored, you do not need the CE light on to see them.

Are you chiped or stock program?

By the way, the cats dont usually clog up unless your using lawnmower gas (non-premium) and not taking car of the car for a LONG time. Odds are its just the O2 sensors that need replacing.
 
unity said:
The codes are indeed stored, you do not need the CE light on to see them.

Are you chiped or stock program?

By the way, the cats dont usually clog up unless your using lawnmower gas (non-premium) and not taking car of the car for a LONG time. Odds are its just the O2 sensors that need replacing.
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Stock program and I'm pretty sure the previous owner has no idea what premium gas is or anything about maintenance. It only does it as described above which makes sense to me. I'm fairly sure a cat is clogging based on performance and smell. I'm pretty sure it's heat thats causing the o2 sensor to throw the light, but no one can read the code. :confused:
 
So pull the pipes behind the cats and ream them (it) out. Cheap way to see if it's the cat or the O2. Well, it sure isn't cheap if the problem is NOT the cats....which it prob is NOT!
 
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I'm gonna cut to the chase....

junkman306 said:
My theory is that a cat is clogging, which would explain the smell, causing heat build up, which is causing the o2 sensor to get hot, causing the check engine light to come on.
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Wrong....

junkman306 said:
It won't store a code unless the light stays on. It's throwing an intermittent code, but it won't lock it. I've tried reading it a hundred times, but to no avail.
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And wrong.


Your cats smells like that because they are doing their job by burning all the raw fuel you're pushing through them by hot rodding around. When your cats clog, you won't "smell" it, you'll just feel it.

Whenever a check engine light comes on it stores a code....EVERYTIME. Even if it shuts off.....its called a "history code" or "continuous history code". On 95 and older Ford/Lincoln/Mercury vehicles you have to run 2 different tests to get the codes. A KOEO test and a KOER test.

Here's a good rule of thumb....if your check engine light comes on...stop what you're doing and get the codes read. Don't theorize and continue driving it...you're just going to make things worse.
 
J said:
Whenever a check engine light comes on it stores a code....EVERYTIME. Even if it shuts off.....its called a "history code" or "continuous history code". On 95 and older Ford/Lincoln/Mercury vehicles you have to run 2 different tests to get the codes. A KOEO test and a KOER test.

Here's a good rule of thumb....if your check engine light comes on...stop what you're doing and get the codes read. Don't theorize and continue driving it...you're just going to make things worse.
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Ok. Second time I've said this (just not as detailed). Springfield Lincoln Mercury, Friendly Ford, Republic Ford, Oreilly Auto Parts (me), and Autojunk have all checked the codes on this car and there are none. I'm not theorizing because it's fun. I'm theorizing because it makes sense and I've been around the block once or twice. I've also never in my life, driven a car that smelled like a perm because the cats are doing their job. You will feel it when a cat clogs, but unless it just happens while driving down the road, you're probably not going to notice it as much. If it happens slowly as you accumulate mileage, it will eventually restrict exhaust flow enough to allow heat to build up in front of the cat, faster than the air around can cool, causing the o2 sensor to freak from the heat and inaccurate reading from the build up of the exhaust gases.
 
How did you run a 14.91 with this problem? I'll be taking mine to the track for the first time in mid June and would be happy with mid/low 15's. If your sure that's the problem I'll say it again "Exauast upgrade"
 
Be2lose said:
How did you run a 14.91 with this problem? I'll be taking mine to the track for the first time in mid June and would be happy with mid/low 15's. If your sure that's the problem I'll say it again "Exauast upgrade"
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It has just recently started this problem. On the 14.91 pass, I just planted the loud pedal and that was the result. :D
 
How old are the O2 sensors? They get replaced at 60k, but can often go longer to 100k+. If you milage is up there and you dont know, replacing may be the quickest test and you will also be sure you have a new set even if thats not the problem.

By the way O2 sensors detect oxygen, not heat.

By perm smell could you also mean rotten egg smell?

This would be easier with ODBII where there is a second set of sensors to make sure the cats are working! lol
 
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unity said:
How old are the O2 sensors? They get replaced at 60k, but can often go longer to 100k+. If you milage is up there and you dont know, replacing may be the quickest test and you will also be sure you have a new set even if thats not the problem.
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I doubt they've ever been replaced and it just rolled over 99,000. I may try that. I was just trying not to spend any more than I have to. ;)

By the way O2 sensors detect oxygen, not heat.
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This is true, but wouldn't a clogged cat cause a mis-read, due to excessive exhaust gas build up?

By perm smell could you also mean rotten egg smell?
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It's not a rotten egg smell, but I'll bet it's leading up to that smell.

This would be easier with ODBII where there is a second set of sensors to make sure the cats are working! lol
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I agree. I may just have to break down and go with aftermarket exhaust now. I'm planning on replacing the o2 sensors when I fab up my exhaust, that way they'll be new. :D
 
my vote is for the o2 sensors. even if they are not the problem, then a new set still wouldnt hurt. smoother idle, etc... i just repleced mine, on a 97 with 97k on it. so im sure yours could use the change!
 
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