Thats right.... I found out today fer sure.

While reading another post of a misterious misfire I went to look for possible sources of leaks into my Exhaust manifolds....and then while I was checking ARGHHHHHHH! Right infront of my eyes there it was.... the Airpump check valve nicely bolted to the exhaust manifold... as soon as I saw it, it hit me!! This are one way valves... What if they leak!!! read on guys....


It ocurred to me they allow air right from the Air pump into the exhaust manifold in one direction only but what if the airpump allows fresh air into the check valves while the pump is off?? This possible malfunction could be creating a lean condition and sending the PCM into injecting more fuel..what if the airpump leaks fresh air or even if the other check valve leaks exaust back into the pump?? are this two engine banks interconected?? one leaking valve could send a rush of exhaust into the other bank.... (split fuel trims came to mind)


Are this two smog check valves interconected?? Chiltons diagram shows them clearly interconected and then conected to the smog pump. then It ocurred to me again... what if... just what if one of them leak exhaust back into the hose??? it will go straight to the airpump *and* right into the other check valve too. Since the other check valve accepts incoming air into the manifold in one direction then I figured it would accept the blowby into the other exhaust bank and possibly throw the mixture out of whack in that one bank.... (split BLMs was ringing in my head again).

So.... today before work..... I unplugged the driver side hose conected to the check valve with the Engine on and there was a lot of exhaust noise coming out.... I held a piece of paper against the Driver side Check valve and the exhaust was creating a vacum and held the paper agains the valve...no that much of suction though... However.. the Rubber Hose!!!! it had a rushing (exhaust?) air out!!! the air was vibrating at the tone of the exhaust manifold tune.... blowing air out that I am sure its going right into my driver side bank since the check valve accepts the air in that direction.

Now the pump was off so obviously the OTHER check valve is leaking exhaust back into the smog pump hose and is rushing it into the drivers side manifold!!! I plugged both ends shut (hose and check valve) and the Short Term fuel trims moved up two notches closer to 128 (ideal) on the other hand, my vacum dropped one notch lower..(?) The idle neither improved nor got worse.... on the other hand, I remembered it takes time for the PCM to adjust to the changes... so if the extra exhaust is throwing the oxygen readings off in one or the other bank... (more flow in one bank and less flow on the other bank) it may take time for the PCM to adjust the balance and run the engine better. Its only a theory of mine right now but I will Scan my car at idle with everything conected then save the log... then I will plug both Check valves shot, drive around town for a few days, then scan the Short and Long Term Fuel Trims again for signs of improvement... checking to see if they get closer to the ideal 128.


Currently At idle they have been around 117 to 118... and holding steady. I hope I am onto something good here... if this fixes my BLMs it *may* hopefully it may be the fix for those of you who have chased a missfire or even re-programed the PCMs to get the perfect fuel trim levels.

I know many of you have deleted those valves but for the rest of us I am hoping this one step closer to finding that Fuel Trim problem fix that we have been looking for a very long time...

Wish me luck. I wanted to share my findings with the rest of you guys and gals.

Please share your opinions in this post... so we can keep track of progress.



Marvin

 

Normally, when the valve is broken, the rubber hose melts from the heat.

 

Ditto on a bad check valve causing problems with that rubber hose. I had the passenger's side check valve go bad on mine. http://web.camaross.com/forums/showt...hreadid=175747

Thomas.

 

Will you be able to hold your finger in the hose closing it shot while holding your finger on the valve opening to hold any leakage while the engine is at idle and coolant temp is at 216.50*f? The air coming out of the hose was not hot at all. Idle problem? perhaps. Car idled for about 10 minutes before I did the test. Maybe my problem is so minor is of no consequence.


The hoses at both ends are in good shape still. My vacum dropped a couple of notches and the my BLMs and Integrators moved up a couple of points closer to 128 at the same time.

Im thinking for as long as the rubber hoses hold, the vacum leaking from one valve to the other one is of little consequence since the presure will eventually even out between the two manifolds. Like I sad before, I did not notice any difference in the way the engine idle when I did the test. Only difference was in the scanner and the vacum gage but very minor.




Marvin

 

Stoopalini, did you notice any idle problems when your Check Valve went bad? did it have any effect on your RPMs or fuel Mix?

I just read your post and realize I dont do WOT runs except for one two days ago.

I am only trying to figure out if a leakage on one of those valves affect the fuel trims.


Marvin

 

I didn't notice an idle difference when that valve went bad, or after I replaced it. Although, I have been chasing a small stumble at idle/intermittent misfire under load for a while, so it's hard to tell. I'm not sure if it had any effect on the fuel mixture as I didn't scan the PCM before replacing the valve.

If both of your check valves are leaking, I can't see how the rubber hoses wouldn't be effected? Maybe the valves aren't leaking bad enough to cause any serious problems with the hoses yet .....

When I bought the new check valve, I blew through both sides to see how they worked. When I blew in the hose side, air traveled through unrestricted. When I blew through the manifold side, air would pass through when blowing lightly, but when I blew harder it would close up. Seems to me the valve is made to close up with increased pressure.

Thomas.

 

My passenger side is the one leaking exhaust but it wasnt that much.. it was more like a constant vibration coming out and blowing some air too. The one on the Driver side on the other hand it sucks air in. I held a piece a paper against it and just held it in place.. very slight vacum.

I had the scan hoked up and a vacum gage too. When I plugged both ends the Integrators move up closer to 128 and the Vacum actually fell down a notch or two.

Did it several times to make sure and each time it did the same thing. Didnt see any change in idle speed or engine smoothnes.. maybe is of a very minor consequence I guess... I am thinking to plugging the valves and drive her for a few days and compare the scan results with those I have now...


Marvin