Mach

Hey Guys,

I had some minor problems today. Let me explain and perhaps somebody can give me some idea of my next move.

Today at 2:45pm I was on my way to an appointment and after pulling out into traffic and running less than a block, my pony seemed choked up and died. I shifted to neutral (Automatic) and restarted. Once started it drop down to idle and die. The light changed, I restarted and ran down the street. While coasting in preparation for a turn into a parking lot, it died again. I noticed the "evil" check engine was on. I parked in the lot and got my tuner out. The code read "PO174 run too lean". Welp, I since I had not reflashed my tune since I got it 4 months ago, I thought I had nothing to lose to flash it again. Once reflashed, all seemed normal again. Idle ok, not overheating, yada yada... I went and did my appointment and then dropped by the car wash. When I fired it back up after the wash, I threw the same code again. Car seemed to idle ok and was not dying. I cleared code and drove it carefully home without incident or code reappearing.

Any ideas what may be the problem?

Should I reinstall stock airbox and run it into Ford? (it is warranty to 75K)?

What would cause a custom tune to run "lean"? If my air filter was becoming clogged (I do live on a gravel road), wouldn't that cause it to run rich? (from lack of air?)

Any help would be ummmm...helpful...

sycd

First make sure the intake is still tight under the hood and nothing came loose since you installed it.

If it worked for the last four months and is now starting to act up, I doubt it's the tune.

If that doesn't help you might want to go back to stock tune and airbox just to make sure it's not something else.

Just my $0.02

G.T

+1..
a loose CAI will allow unmetered air through.
it happened once to a friend with a K&N CAI.. his car was acting up, bucking and jerking, then it threw the code.
i wiggled the CAI elbow by hand and it came right off the TB, it was loose all along.

if it's not that simple, you might be looking at a fuel pressure issue.
try datalogging your Fuel pressure drop across injectors and see what that reads at idle and while driving.
you should be at 39PSI or so.
anything less might run you leaner

DarkFireGT

Doug told me the MAF sensor might need cleaning too. I'm running lean on my '05 and needed to check those two things also. Just haven't had time.

Mach

That the MAF would be fouled would make sense (especally with my dusty road)...what is recommended to use for cleaning? Rubbing alcohol? or some special cleaning solution?

Mach

Man...you guys ROCK!



I went out and checked and I'll be darned if the whole elbow was completly loose from the teflon sleeve. Easy fix to retighten up both elbow and to TB.

I will advise tomorrow if problem is resolved but my bet is "it's all is good"!

Two thumbs up!

bored out

Glad it wasn't the tune or worse bro!

RUgoinUp?

Glad it's fixed. I was going to tell you check the C&L Racer because over-tightening the clamp can easily bend the plastic on the racer thus leaving a hole under the clamp where air can enter unmetered. That's what happened to mine, resulting in the lean code.

Kryten

To answer this question, here is what I used recently. Works great and is formulated specifically for the task . Advance Auto is where I bought my can, should be availible at most auto parts stores I would think.

http://www.crcindustries.com/auto/co...x?S=Y&PN=05110

DarkFireGT

Ditto. That's what I've heard, and what I plan on picking up this weekend for our '05.

kevinb120

Heh as soon as I started reading thats the first thing I thought. It should actually be a pretty regular regimine to check that as it can be a big problem from one small clamp.

Mach

Welp, I drove my normal 100 miles today and am please to announce that all is good. No stalls, no codes, ran like a champ...

again, you guys rock!

ShowGT

Glad to hear, now bring on the weekend!

Francis

Newbie question:
I keep reading that running lean is really stressful on the engine, especially with forced induction. Why is that?

As I understand it:
Running rich - having more fuel in your air/fuel mixture, can't burn it all. Bad for emissions, bad for efficiency, but not actually harmful.

But if you're running lean, you've just got extra air that you're not using going in. In 2-stroke engines, this is bad, because the fuel is also used as lubrication. But why is this a big deal in a 4-stroke?

I'm told running lean tends to make you run hotter than normal. Why is that? The only explanation I can think of is that injecting fuel actually cools down your cylinder. But if you were to add more fuel, you'd have more combustion, and surely that would cause more heat than having some extra air in there.

I don't get it.

kevinb120

Running too lean can cause detonation, more of a hot flash-explosion rather then the normal proper burning of the fuel, and can burn out of time from where the motor is designed to burn it(i.e. pre-ignition before the pistion is in the ideal place). In a forced induction car (or very high compression engine) with even more heat it can actually burn holes through the tops of the pistons. As with anything mechanical, the more extreme the level of pressure on moving parts, the more dramatic the effects of something not being right are going to be. Everything happens in milliseconds with minute differences in temperature, but there is a distinct difference in what the proper speeds and temperatures the fuel should be burned every time it ignites in a given engine. If it is running rich then your first thought is correct, in a nutshell the unburnt fuel actually cools the cylinder temperature-but being too rich is also 'sloppy' and does not make optimum power.

Not to mention that different octane levels of fuel also burn at different rates, the higher the octane rating, the slower the burn, effectively becoming a 'cooler' gas temperature to work better in high-heat environments such as high-compression or forced induction. And to that you add the temperature the spark plugs ignite as well, as well as the timing of the ignition itself in the piston's stroke. Its all about the proper balance for any given motor of all the factors involved in burning fuel to make the most power while still being safe for the physical makeup of the motor's parts. And there is no one rule for every kind of motor, a setup designed to run on 'hotter' low-octane fuel gets no real benefit of higher octanes, and motors that require 'cooler' high-octane fuel can have severe problems with lower octanes.

When John's snorkel came loose on the throttle body, that little bit of extra airflow was causing the fuel to burn too fast for what the computer could tell the injectors to spray into the combustion chamber based on the tune's programing perameters, causing a potentially dangerous issue. It's that sensitive, even if its a gap so small a business card would have trouble slipping through. Modern computers are fast enough to notice the problem almost instantly, at least giving some level of protection and actually becoming instantly proactive trying to correct it. And older car would have burned dangerously hot hundreds of thousands of times before you knew there was a problem. Of course, the more extreme it gets in horsepower, the less chance you have of it not damaging a part, the slightest single glitch in a 8000 hp top-fuel dragster is pretty much total destruction.

RRRoamer

It's also a function of cylinder pressure. If you look at a function describing the probability of detonation, you would see several variables in it. Two of the biggest would be cylinder pressure and "air" (mixture) temperature. But right behind that would be A/F ratio.

Crusing around town at part throttle, your changes of dangerous detonation is pretty much zero. When the throttle is mostly closed, there just isn't enough pressure in the cylinder to cause it to happen. Needless to say, WOT with a supercharger forcing MORE air in there than normal is a much worse situation and it is MUCH more likely to detonate. Also, because there is so much air and fuel in the cylinder, when it DOES detonate, it can do a LOT more damage to the engine.

By running richer mixtures at WOT, you are actually using the extra fuel to do two things: drop the temperature of the mixture due to the heat of vaporization of gasoline and you are making the mixture harder to ignite (or detonate) simply because there is too much fuel hanging around. Of course, if you go too far, then the spark plug has a hard time lighting the fire (or, in the worse case senario, it CAN'T light it off!) and you power output drops like a rock. But at least you didn't blow up your engine!