The 10 worst things you can do to your car

[MERCMAN]

http://finance.yahoo.com/news/10-worst-things-car-141922919.html

[beantown mm]

#11 - Bring it to David Robertson / Donald Reyes / Damian Reese etc......

[NonaDAbove]

I'll agree with this response to #10 in the post:


I'll stop servicing my own car when dealers and retail car servicers stop charging $40-$50/hour just to do an oil change.

Granted, not everyone has the time, know-how, or common sense to service their own vehicle, but a little common sense, patience, and research will save you a chunk of change. And I've seen qualified shops (and mechanics I trust) make rookie mistakes. (i.e.: loose grounding screw on a new battery cable, or the Mercury dealer that left a Snap-On screwdriver on the cowl vent.)

At least if I made the mistake, I can usually retrace my steps and figure out what I did.

And I change my muffler bearings every 300 miles.:D

[SC Cheesehead]

"The old go-to rule for oil changes was to refresh every 3,000 miles. But most experts agree drivers should go by the schedule their car's manufacturer dictates instead.
"Frequent oil changes do not necessarily mean better performance or longer engine life," CalRecycle Director Caroll Mortensen told The Auto Channel. (http://www.theautochannel.com/news/2011/12/23/019198-how-often-should-you-change-your-oil.html).."

Yup. You wanna do it right, have your oil analyze and change it when it needs to be changed, based on the analysis.

[MrBluGruv]

Maybe I'm just clueless, but I don't really see how having a dirty intake filter will foul an O2 sensor...

[NonaDAbove]

Maybe I'm just clueless, but I don't really see how having a dirty intake filter will foul an O2 sensor...

A Dirty air filter will cause the MAF sensor to tell the PCM to adjust the air/fuel mixture to the leaner or richer side, (causing error codes P0171-P0174.) This may cause more carbon or unburned fuel to go into the exhaust, and foul the O2 sensors.

[MrBluGruv]

A Dirty air filter will cause the MAF sensor to tell the PCM to adjust the air/fuel mixture to the leaner or richer side, (causing error codes P0171-P0174.) This may cause more carbon or unburned fuel to go into the exhaust, and foul the O2 sensors.


But if the PCM is adjusting your fuel trim to keep the same A/F ratio, then how will it be lean or rich, no matter the volume moved?

[MyO4Rawdur]

But if the PCM is adjusting your fuel trim to keep the same A/F ratio, then how will it be lean or rich, no matter the volume moved?

Because if your restriction isnt allowing air in but the car is running lean then your car automatically sets a code and runs certain parameters which is basically dumpimg fuel because it thinks your maf took a dump. This extra fuel ends up on your o2 sensor. Basically if your maf is still giving a signal that is abnormal but its still working then your car wont die. Unplug your mad and the car will shut off.

[NonaDAbove]

But if the PCM is adjusting your fuel trim to keep the same A/F ratio, then how will it be lean or rich, no matter the volume moved?

If the mixture can be adjusted, it can be adjusted too lean or too rich. The problem is that the sensor will be misreading the the oxygen flow, therefore the mixture adjustment is incorrect. (Keep in mind that it doesn't adjust the air, just the fuel.)

This is actually a known issue with K&N filters. Some of the oil gets through to the MAF wires, coats them, and causes false readings. First thing I do with P0171-P0174 codes (or 188/189 on my '94) is clean the MAF. Almost always clears it up.

[MrBluGruv]

Because if your restriction isnt allowing air in but the car is running lean then your car automatically sets a code and runs certain parameters which is basically dumpimg fuel because it thinks your maf took a dump. This extra fuel ends up on your o2 sensor. Basically if your maf is still giving a signal that is abnormal but its still working then your car wont die. Unplug your mad and the car will shut off.


If the mixture can be adjusted, it can be adjusted too lean or too rich. The problem is that the sensor will be misreading the the oxygen flow, therefore the mixture adjustment is incorrect.

This is actually a known issue with K&N filters. Some of the oil gets through to the MAF wires, coats them, and causes false readings. First thing I do with P0171-P0174 codes (or 188/189 on my '94) is clean the MAF. Almost always clears it up.

So it's an issue with your MAF then, yes? Not the filter?

It seems to me we are assuming that the dirt IN the filter has actually caused direct damage to the downstream fuel trim components.

If the filter is clogged, but the MAF and O2 are still accurately reading the CFM of incoming air and the post-burn oxygen contents of the exhaust, why would it run rich or lean long term?

Isn't the entire point of a MAF/O2 system to accurately maintain a specific A/F ratio for emissions standards?

If it doesn't work in this fashion, then simply driving your car to place with a higher or lower air density should effectively cause your car to run catastrophically lean or rich; why on earth have a computer calculate fuel trim on the fly if it can't even compensate for a slight drop in total CFM of air into the engine?

[MyO4Rawdur]

So it's an issue with your MAF then, yes? Not the filter?

It seems to me we are assuming that the dirt IN the filter has actually caused direct damage to the downstream fuel trim components.

If the filter is clogged, but the MAF and O2 are still accurately reading the CFM of incoming air and the post-burn oxygen contents of the exhaust, why would it run rich or lean long term?

Isn't the entire point of a MAF/O2 system to accurately maintain a specific A/F ratio for emissions standards?

If it doesn't work in this fashion, then simply driving your car to place with a higher or lower air density should effectively cause your car to run catastrophically lean or rich; why on earth have a computer calculate fuel trim on the fly if it can't even compensate for a slight drop in total CFM of air into the engine?

No its the filter. If you have a jam packed filter you get crappy gas mileage. If you dont believe me go throw it in some dirt and leaves if you can find some. Your maf only knows what it sees. If the air coming through tje filter is going to slow and the maf sees it as a restriction it basically hits that failsafe. The maf wouldnt know why its losing air. Theres something that is on older cars thats called a barometric sensor that its now combined in your vacuum system. Map sensor or in the maf. Your car knows the density of the air and adjusts based on that. If you ever had like an olddd carb car then youd have a baro sensor.

[NonaDAbove]

So it's an issue with your MAF then, yes? Not the filter?

It can be either. A dirty/clogged filter or a fouled MAF sensor can throw the reading off beyond the system's ability to compensate.


If the filter is clogged, but the MAF and O2 are still accurately reading the CFM of incoming air and the post-burn oxygen contents of the exhaust, why would it run rich or lean long term?

If that were the case, then it would be possible for a completely blocked intake to still allow the car to run, since you could just adjust the A/F accordingly. Obviously, it wouldn't.

[MyO4Rawdur]

So it's an issue with your MAF then, yes? Not the filter?

It seems to me we are assuming that the dirt IN the filter has actually caused direct damage to the downstream fuel trim components.

If the filter is clogged, but the MAF and O2 are still accurately reading the CFM of incoming air and the post-burn oxygen contents of the exhaust, why would it run rich or lean long term?

Isn't the entire point of a MAF/O2 system to accurately maintain a specific A/F ratio for emissions standards?

If it doesn't work in this fashion, then simply driving your car to place with a higher or lower air density should effectively cause your car to run catastrophically lean or rich; why on earth have a computer calculate fuel trim on the fly if it can't even compensate for a slight drop in total CFM of air into the engine?

You could also tape up the filter covering half of it and youll see codes I believe. When I was working at toyota I had a car come in that was dragging during accel and had no shot of runnimg with the a/c on. Checking the throttle body I found a plastic bag in the air box covering most of the filter.

[Bigdogjim]

Just common sense on the list. D'oh. Good lits never the less.

[MrBluGruv]

It can be either. A dirty/clogged filter or a fouled MAF sensor can throw the reading off beyond the system's ability to compensate.



If that were the case, then it would be possible for a completely blocked intake to still allow the car to run, since you could just adjust the A/F accordingly. Obviously, it wouldn't.


But then this is the core of it isn't it? Even if it can't produce enough power to turn itself over, it should still be able to maintain a constant A/F ratio while it tries, shouldn't it?

The bottom line is that these modern cars aren't carbureted, and should be able to handle fuel trim adjustments much better.

I don't see the reason why the vehicle wouldn't be able to run at a specified A/F ratio all the way down to not even being able to produce enough power to crank purely because the CFM of air has dropped. I could see going lean because you are forcing far MORE air into the motor than the injectors and fuel pump can keep up with, but I don't understand how it should be a problem long-term with less air.

Does the PCM just give up and run a fixed injector cycle table?

I get why running outside the normal window of A/F ratio can cause issues, but I don't understand why restricting the total CFM ALONE would be the root cause, outside of inferior programming...

[NonaDAbove]

I get why running outside the normal window of A/F ratio can cause issues, but I don't understand why restricting the total CFM ALONE would be the root cause, outside of inferior programming...

Because it's possible to restrict the air flow beyond the PCM's ability to adjust the fuel to match. It is an adaptive system. Hence the meaning of the codes:

P0171 System Adaptive Fuel too lean on bank 1
P0172 System Adaptive Fuel too rich on bank 1
P0174 System Adaptive Fuel too lean on bank 2
P0175 System Adaptive Fuel too rich on bank 2

Maybe this will help, too:

P0171 FORD Description
With the Air/Fuel Mixture Ratio Self-Learning Control, the actual mixture ratio can be brought closely to the theoretical mixture ratio based on the mixture ratio feedback signal from the heated oxygen sensors 1. The Engine Control Module (ECM (http://engine-codes.com/articles/ecm.php)) calculates the necessary compensation to correct the offset between the actual and the theoretical ratios.

In case the amount of the compensation value is extremely large (The actual mixture ratio is too lean.), the ECM (http://engine-codes.com/articles/ecm.php) judges the condition as the fuel injection system malfunction and light up the MIL (2 trip detection logic).

[MrBluGruv]

Because it's possible to restrict the air flow beyond the PCM's ability to adjust the fuel to match. It is an adaptive system. Hence the meaning of the codes:

P0171 System Adaptive Fuel too lean on bank 1
P0172 System Adaptive Fuel too rich on bank 1
P0174 System Adaptive Fuel too lean on bank 2
P0175 System Adaptive Fuel too rich on bank 2

Maybe this will help, too:


So basically yes, whether it can literally adapt or not, it reaches a point where it chooses not to try any more and runs off of a fixed fuel map.

I'm still curious to see at what CFM of air the computer interprets as "must be a malfunction" and gives up.

[NonaDAbove]

And the fixed-fuel map is not a "best case" scenario. It doesn't allow the adaptation to run the leanest fuel mixture with the best power output.


I'm still curious to see at what CFM of air the computer interprets as "must be a malfunction" and gives up.

That's a more technical question than I would have the answer to, probably would be in a Ford OBD-II spec or 4.6L spec manual.

I enjoyed this conversation, though, it made me think through the process a bit! :coolman:

[MyO4Rawdur]

Basically if you try to force air in to a car with a 80mm throttle body then its not going to matter because the throttle body is restricting it. Cant force more than a certain amount of air in unless your car is stuck at wide open throttle. Youre using ideas that are just far fetched so dont over think it. Too much air isnt possible unless the fuel supply is being restricted. There will always be enough fuel and enough air but theres times when either side will get restricted and newer cars will auto correct for those. The mar sensor would stop working if the car thinks that it is malfunctioning. The basic fuel table is used to prevent too lean or too rich conditions. Also the car changes timing as far as I know to prevent too much or too little air to go in.

[MrBluGruv]

And the fixed-fuel map is not a "best case" scenario. It doesn't allow the adaptation to run the leanest fuel mixture with the best power output.



That's a more technical question than I would have the answer to, probably would be in a Ford OBD-II spec or 4.6L spec manual.

I enjoyed this conversation, though, it made me think through the process a bit! :coolman:

Same here, I enjoy a good mind stretch every now and again. Cheers :beer:


Basically if you try to force air in to a car with a 80mm throttle body then its not going to matter because the throttle body is restricting it. Cant force more than a certain amount of air in unless your car is stuck at wide open throttle. Youre using ideas that are just far fetched so dont over think it. Too much air isnt possible unless the fuel supply is being restricted. There will always be enough fuel and enough air but theres times when either side will get restricted and newer cars will auto correct for those. The mar sensor would stop working if the car thinks that it is malfunctioning. The basic fuel table is used to prevent too lean or too rich conditions. Also the car changes timing as far as I know to prevent too much or too little air to go in.

As for the too-lean conditions, I was thinking more about boosted applications, specifically going from a factory N/A setup to an aftermarket forced-induction setup where you could quite easily force more CFM of air into the motor than your fuel system can keep up with.

Boost opens up an entirely new can of worms though, and consequently would be traveling pretty far off our original point of discussion. lol.

[MyO4Rawdur]

Same here, I enjoy a good mind stretch every now and again. Cheers :beer:



As for the too-lean conditions, I was thinking more about boosted applications, specifically going from a factory N/A setup to an aftermarket forced-induction setup where you could quite easily force more CFM of air into the motor than your fuel system can keep up with.

Boost opens up an entirely new can of worms though, and consequently would be traveling pretty far off our original point of discussion. lol.

Yea youre right about that haha boost is like a world of its own when it comes to computers but thats why there are boost gauges and tunes. Too much air and things go boom. To much fuel and things go boom bang haha hopefully this helps you stay n/a ;)

[Shaijack]

So it is like putting a plastic bag over your head. Engine dies and you die....

[MyO4Rawdur]

So it is like putting a plastic bag over your head. Engine dies and you die....

Haha sure.

[Vortech347]

#11, letting a girlfriend drive. Learned that early on with my Fox. I don't care how damn hot she is.

[Motorhead350]

Not following Zack's advice.