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Last Saturday I cleaned my 6 year old K&N filter that came with my Callaway Honker CAI for the first time in preparation for my annual oil and fluid change. I followed the cleaning instructions, didn't over-oil, allowed to air dry etc. and then buttoned everything back up. The car sounded and performed fine as I enjoyed a spirited, back roads breakfast cruise the next day (Sunday). On Monday, while driving to the dealership for the oil/fluid change, the Check Engine light came on. I told the tech and he checked the codes and told me I probably have a loose hose or other air leak. Since, my appointment was for an oil/fluid change only, I would need to set up a second appointment for a full diagnostic check so he cleared the code and told me to recheck my Callaway Honker connections when I got home.
On the drive home, the Check Engine light came on again, however the car was running fine, idling fine, etc. so I decided to take off the CAI and clean the MAF as perhaps I had some K&N oil pass through the system. I used CRC MAF cleaner, waited for everything to dry and then reassembled everything back up to the throttle body making sure all the connections, hoses, clamps, etc. were tight. Now this is where it gets weird. After cleaning the MAF, there is a higher pitched air sound coming from the engine. Almost as if there is some kind of air leak. At first I thought it was a loud belt, but why would that happen after cleaning the MAF? I had noticed prior to any of this maintenance work, that there was a subtle whining noise during acceleration, however thought that was just the 14 year-old fuel pump showing it's age.
Anyway, the Check Engine light has come back, even after pulling the MAF sensor connection and disconnecting the negative battery cable to reset the ECM.
Before I bring it back to the dealership for their plug-in diagnostics analysis, is there anything that I'm missing that I should check? As mentioned, all clamps, hoses, etc. seem solid.
The codes are P0171 - Fuel Trim System Lean Bank 1 and P0174 - Fuel Trim System Lean Bank 2.
I would revisit every connection and component between the MAF and the throttle body for any signs of cracks or misfit of connections and tightness of the clamps.
If that doesn't resolve the issue (you may need to clear the two codes and drive the car after touching anything) I would inspect the PCV lines on the car end to end. The rubber lines typically dry rot and create leaks over time that will set these same two codes. Basically any air leak after the MAF will cause the O2 sensors to sense a lean condition because of the unmetered air.
Thanks. That's what's so confusing is that the leak would be after the MAF and the increased air sound occurred only after the I cleaned the MAF sensor. I did not disconnect any PCV hoses/lines when I disconnected the CAI and air bridge or when I cleaned the MAF sensor. Plus, with the Callaway Honker, the MAF is relocated right in front of the Throttle Body.
If I can't find anything and bite the bullet and have the dealership plug in their diagnostic tool, will the tool tell them exactly where the leak is?
Hi !!
Yes, P0171/0174 would be indicative of an air leak that is affecting BOTH banks...like an air leak downstream of the MAF sensor...since you had removed your CAI that gives you pretty good "direction"....you can spray Brake Kleen or even a squirt bottle of water in that area and see if the cars RPM changes or with the water you'll hear the water getting sucked into the engine...LOOK CLOSER !!!....and NO their scan tool will not tell them where the leak is !!...the only thing they will be able to see is fuel trims change when they find the leak....save your money !!
p.s. Here is a good video on finding those vacuum leaks by my friend Paul Danner....the "Jedi Master" of Engine Diagnostics !!
^^^ Thanks. I wish there was a similar video for the LS1 specifically as my MAF lines up right next to my Throttle Body due to the Callaway CAI. I also read you can use the MAF cleaner spray as well to test for leaks vs. water. I just don't know where to direct the spray.
^^^ Thanks. I wish there was a similar video for the LS1 specifically as my MAF lines up right next to my Throttle Body due to the Callaway CAI. I also read you can use the MAF cleaner spray as well to test for leaks vs. water. I just don't know where to direct the spray.
Yes, you can use MAF cleaner...I personally use a propane bottle I have with a long nozzle on it...just spray the MAF cleaner all around the MAF sensor where the bellows fits up to the TB...you most likely have a thin hairline crack somewhere...take it apart again and LOOK CLOSE...or give it a good shot of Brake Kleen...dump that water on it like in the video...you'll find it !!
P.S.... I'll probably be retiring to the Sunshine State in a few years...you can look me up...I'll be your personal Corvette diagnostic Technician...LOL !!
Yes, you can use MAF cleaner...I personally use a propane bottle I have with a long nozzle on it...just spray the MAF cleaner all around the MAF sensor where the bellows fits up to the TB...you most likely have a thin hairline crack somewhere...take it apart again and LOOK CLOSE...or give it a good shot of Brake Kleen...dump that water on it like in the video...you'll find it !!
P.S.... I'll probably be retiring to the Sunshine State in a few years...you can look me up...I'll be your personal Corvette diagnostic Technician...LOL !!
Originally Posted by 8VETTE7
Never said you disconnected PCV lines. If they are the problem and they could be, the codes are a coincidence with what you did with the cleaning. I would STILL examine the PCV lines. Heat, and oil are the reason they dry rot. You can use the MAF cleaner or propane on those just like the other areas.
Thanks. This is proof again that no good deed (proactive cleaning of the MAF) goes unpunished.
I just went out, started the car and sprayed the MAF cleaner all around the hoses, connections, bands, etc. and didn't notice any change or stall in the idle. I guess next step would be to remove the Fuel Rail Covers and see if there is anything there that may be loose. I had replaced most engine hoses with the braided hoses four years ago so they should still be in pretty good shape. What I did notice is that there seemed to be more exhaust moisture vapors and water on the tail pipes. Not sure if it's related.
Thanks. This is proof again that no good deed (proactive cleaning of the MAF) goes unpunished.
I just went out, started the car and sprayed the MAF cleaner all around the hoses, connections, bands, etc. and didn't notice any change or stall in the idle. I guess next step would be to remove the Fuel Rail Covers and see if there is anything there that may be loose. I had replaced most engine hoses with the braided hoses four years ago so they should still be in pretty good shape. What I did notice is that there seemed to be more exhaust moisture vapors and water on the tail pipes. Not sure if it's related.
NOT related !!...try using water this time once you get the fuel rail covers removed...might be easier to hear it !!!...You can be pretty liberal with the water....just not try to get water on those coil packs/wiring or fuel injectors/wiring...try removing the MAF connector again and make sure those connections are clean since you had it disconnected and it's seated all the way when reconnecting it...keep us advised !!
p.s. I don't know if you have a multimeter but maybe we should check the wiring...if you don't know how to check them I can give you some guidance...the MAF is 3 wire and the IAT are the other two.Does the engine feel like it's running a little rough at idle ??
After cleaning the MAF, there is a higher pitched air sound coming from the engine. Almost as if there is some kind of air leak.
The codes are P0171 - Fuel Trim System Lean Bank 1 and P0174 - Fuel Trim System Lean Bank 2.
Any help is appreciated.
You have a big enough vacuum leak that you can hear it inside the car? Use a cheap tool store stethoscope to locate the leak. (You could cobble something up with a funnel & length of hose.) I'm guessing PCV conn.
NOT related !!...try using water this time once you get the fuel rail covers removed...might be easier to hear it !!!...You can be pretty liberal with the water....just not try to get water on those coil packs/wiring or fuel injectors/wiring...try removing the MAF connector again and make sure those connections are clean since you had it disconnected and it's seated all the way when reconnecting it...keep us advised !!
p.s. I don't know if you have a multimeter but maybe we should check the wiring...if you don't know how to check them I can give you some guidance...the MAF is 3 wire and the IAT are the other two.Does the engine feel like it's running a little rough at idle ??
It feels like it's running a little rougher than normal at idle. However the biggest change after cleaning the MAF sensor was how loud the air intake sounded afterwards. As mentioned, I thought it was a bad belt. Since the MAF is relocated right next to the Throttle Body due to the Callaway Honker CAI design, it's pretty straightforward in terms of reconnecting it back up. It only fits in one way and I pushed it into the rubber connector for a snug fit into the Throttle Body before tightening the aluminum bands.
It feels like it's running a little rougher than normal at idle. However the biggest change after cleaning the MAF sensor was how loud the air intake sounded afterwards. As mentioned, I thought it was a bad belt. Since the MAF is relocated right next to the Throttle Body due to the Callaway Honker CAI design, it's pretty straightforward in terms of reconnecting it back up. It only fits in one way and I pushed it into the rubber connector for a snug fit into the Throttle Body before tightening the aluminum bands.
Well as I had mentioned maybe it's a MAF wiring problem now...I can tell you how to check the sensor wiring if you have a multimeter...does the car run smoother at higher RPM ??...say around 2500-300 RPM ??...a vacuum leak will smooth out at increased RPM...without a scan tool hooked up I can't give you any more direction...since this issue started after removing and cleaning the MAF sensor I would concentrate on that area if I were you !!
Time to update this thread with the fix. First, I want to thank all the members who helped and offered suggestions on the probable cause, fix, etc. That's one of the reasons why this Forum is so great.
Onto the resolution. After double checking all of my connections, reconnecting the CAI, cleaning the MAF sensor, re-securing the hoses, etc. I retraced the project after stepping away from the car for a few days due to a short business trip. The time off must have cleared my head because when I retraced my steps to the initial step before I cleaned and oiled the K&N filter in the Callaway Honker CAI, I had emptied my catch can.
Yep, I forgot to re-tighten (counterclockwise down) the pet **** valve on the bottom of the catch-can after emptying the oil. That was the air/hissing sound I heard after cleaning the MAF. The pet **** valve works in a counter-intuititive way as you close it by turning the butterfly handle counter-clockwise so the handle is at the bottom of the valve stem when fully closed instead of the top and I had turned it clockwise towards the top thinking I had closed it. I had reached underneath the catch-can and noticed a little oil on my fingers which prompted my "ah ha" or "duh" moment.
Paying this forward in hopes of saving someone else the aggravation I went through.
07-12-2018, 01:43 PM
Ugh - Can't Clear PCM Codes
The pet **** valve works in a counter-intuititive way as you close it by turning the butterfly handle counter-clockwise so the handle is at the bottom of the valve stem when fully closed instead of the top and I had turned it clockwise towards the top thinking I had closed it. I had reached underneath the catch-can and noticed a little oil on my fingers which prompted my "ah ha" or "duh" moment.