RomRaider

maybe you guys can help me out.

I am getting a P0171 CEL. I made a boost leak tester to find my vacuum leaks and was able to locate some of them. I used to get the cel after a 100 miles but since i fixed the major leaks I am now getting the CEL at around 200 miles.

more details of my problem can be found here:
http://www.iwsti.com/forums/2-5-liter-litre-factory-motor/233120-first-time-pressure-testing-help-me-find-my-leak.html

"AF Learning #1 A" is stuck at 15% so that that there is still a vacuum leak somewhere.
my only thing is that my AFRs are in normal range at idle and while driving.

I have yet to try the carb cleaner test so i will try that.

If your fuel trims (AF correction/AF learning) are higher (adding fuel) at time when manifold vacuum is high (at idle) you will probably find that the leak is coming from some place after the throttle body. A boost leak test is usually the easiest way to find the leaks, but carb spray/propane can work to find it as well. Engine speed should change a little when you get close to the leak if using carb spray/propane.

Good luck

thanks ill check that area out. so when you say after the TB do you mean towards the intercooler or towards the IM. ill check when i get home from work. From reading this post i do not really need to reset the ecu. It should fix itself if i fix the leak. I just have to run the car for a little while so that it could adjust itself.

You shouldn't need to reset the ECU, because the AF learning (long term fuel trim) will adjust based on the AF correction (short term fuel trim) over a period of time. It may take some time for the AF learning to change, so if you want to see if a change you made has effected it you CAN reset the ECU to see it right away, but you should be able to watch the AF learning to see if a change you made has had an immediate effect.

When I say AFTER the throttle body I mean- inside of the intake manifold (anything that has vacuum pressure inside of it).

i did not have time to do the carb test today. Is it bad that i have been driving it with this problem?

It shouldn't be a problem as long as your fuel trims are actually adding enough fuel... if you are maxing out your fuel trims and it is still too lean then it could definitely be a problem.
Do you have a wideband o2 sensor that you can use to compare the reading of your stock o2 sensor to?
The "System too lean" code is set because your fuel trims have stayed positive over a long enough period of time to set the code, the possible reasons for this code to pop up are either:
1. Your car is too lean because of un-metered air entering the intake tract after the MAF sensor
2. Your car isn't getting enough fuel (could be low fuel pressure, bad injector, etc.)
3. Your o2 sensor is going bad- if it thinks the air/fuel ratio's are too lean it tells your ECU to inject more fuel (fuel trims), but if the mixture really isn't too lean, say it's actually good, or too rich, and the sensor keeps reading that it is too lean it will keep telling the ECU to inject more and more fuel.
I've seen a truck that was injecting so much fuel that it was literally raining black soot when the engine running (the truck had stacks like a semi )

It has to be 1 or 2. I have already replaced the front O2 sensor thinking that was the problem. And i know for sure the car is actually running lean because I saw the white chalky residue on the old O2 sensor.

When i previously did a boost leak test I was not able to find any audible air leaks. That is why I need to resort to the carb test.

But here is the thing before all this even before the check engine light, I have always had to prime my car to start it(put it on the on position for a second or so). I don't think my car is hold pressure when it shuts off. its been like this for 75k miles(car has 150k now). I changed the fuel pump to a walbro to see if if it would fix the problem but it did not. It has been running fine since just starting it was bad. I just got the tactrix cable recently to diagnose the CEL. Do you think my fuel trims have been out of wake since i started experiencing the starting problem? Maybe bad injectors?

Hopefully I can get to doing the carb test today.
A few more questions?
What parameters can I look at in the ECULogger to check if my injectors are working properly. Also is the tank fuel pressure correct in the ECUlogger? If it is what pressure should it be at?
What other parameters can help me narrow the possible issues?

Thanks 02rexwi,

You have been a lot of help.

If you think it is fuel related I would T in a fuel pressure gauge onto the line coming from the fuel pump between the firewall and the fuel lines on the engine. You should see about 43.5 psi when you cycle the key without the engine running. The fuel pressure should come up to 43.5 and stay there, if it doesn't then there is either something wrong with the fuel pump or the fuel pressure regulator. When you start the car the fuel pressure should drop. It is a 1:1 regulator, so if you're at -10 psi. vacuum then your fuel pressure should drop 10 psi.

When you did a boost leak test did you get the system to stay pressurized? I usually try to get the boost gauge to read 20 psi, and if the system is sealed up well it shouldn't drop from 20 to 10 psi in less than about 5-10 seconds.
If you can't get the boost gauge to read more than 5 psi. you are either using too small of a compressor (doesn't have enough flow) or you have a very large leak.
If it is a very large leak you will be able to find it with carb spray fairly easily.

-Mark

Sorry i forgot to add my FPR is new as well. I need to to put a gauge on my boost leak test adapter that i created. I only used it to see if can here anything. I have a big enough compressor to constantly put 20psi into the system.

Ill also do the fuel pressure test and see that could be an issue as well.

So I wont be able to find any small leaks with the carb test?

Thanks again.

-bradley

You do not want to measure pressure right at the boost leak tester, because there could be a pressure drop from the tester to your intake manifold, and you will not see it. You want to measure the pressure in your manifold. How many gallons is your compressor tank? Out of curiosity.

You can find small leaks with the carb/propane test, but leaks will typically be more pronounced and easier to find by listening or by using soapy water when doing a boost leak test. The fact that the engine isn't running (noisy) and everything isn't hot makes a boost leak test much more desirable, but in a pinch the carb/propane test works faster.

its a 1000psi tank.

Where would be the best place to attach a gauge? At one of the nipples? Im trying to figure out how i can attach it and what kind of gauge i can use.

i think the carb test will at least point me to the right direction because i can hear any air escaping at all.

http://www.oreillyauto.com/site/c/detail/EQU1/3640.oap?ck=Search_pressure+tester_N0665_1432600_3186&keyword=pressure+tester&pt=N0665&ppt=C0103

can i use this to test pressure for vacuum? I just have to plug one side?

You can rent a fuel pressure tester from autozone or most other auto parts stores. You will T the fitting/gauge into the supply line from the fuel pump.

As for your 1000 psi. tank- it is not the pressure that I am concerned with, but rather the flow of air. You need a large volume of air to be able to fill the whole intake manifold/intercooler system (especially if you have a FMIC). Just because it is a 1000 psi. tank does not mean that it can flow enough volume to adequately fill the system. I recommend at least a 20 gallon air compressor tank... You should be looking at flow (usually measured in CFM) instead of pressure.

Im sorry it's 120 gal. with a reg that's adjustable for a content flow between 10 -150 psi. Sorry for some reason I was thinking max pressure.

Also autozone did not have the one I need for rent. I'll try another place.

As for monitoring pressure in the intake manifold- I like to use romraider on the graph view. That way I can set my laptop under the hood and watch the graph of manifold pressure while I operate the boost leak tester and look for leaks.