Guys that have had air leaks
05-02-2009, 09:39 PM
#1
Guys that have had air leaks
Give me some ideas on places to look.
I've already replaced the end of my fuel pressure regulator vacuum line (was cracked) but my LTFT's are still off by ~10% (via EFILive). I reset my long term fuel trims and let it run at idle and they went to about 6% right away and slowly worked their way up. LTFT#2 went to 11% while LTFT#1 stayed around 6%. I tried logging STFT's and they were fluctuating around 3%. I tried spraying some flammible spray around possible leaks (that I could safely spray) and it did not effect my fuel trims.
This air leak is causing my idle/start up to be miserable, and driving my truck is almost impossible anymore. Fixing the FPR vac line helped a little bit, since the LTFT's went down to ~11% from ~17%.
Any ideas? This all started after I swapped my new cam in. Could it be the EVAP motor on the top of the intake? PCV valve? Brake booster vac line? I'm trying to think of any of the things I removed for the cam swap, but none of them seem to be leaking. I did not remove the intake manifold when I did the cam swap. But I did recently install some 8.1 marine injectors, but the hard start/shitty idle has been present since the cam install.
I've already replaced the end of my fuel pressure regulator vacuum line (was cracked) but my LTFT's are still off by ~10% (via EFILive). I reset my long term fuel trims and let it run at idle and they went to about 6% right away and slowly worked their way up. LTFT#2 went to 11% while LTFT#1 stayed around 6%. I tried logging STFT's and they were fluctuating around 3%. I tried spraying some flammible spray around possible leaks (that I could safely spray) and it did not effect my fuel trims.
This air leak is causing my idle/start up to be miserable, and driving my truck is almost impossible anymore. Fixing the FPR vac line helped a little bit, since the LTFT's went down to ~11% from ~17%.
Any ideas? This all started after I swapped my new cam in. Could it be the EVAP motor on the top of the intake? PCV valve? Brake booster vac line? I'm trying to think of any of the things I removed for the cam swap, but none of them seem to be leaking. I did not remove the intake manifold when I did the cam swap. But I did recently install some 8.1 marine injectors, but the hard start/shitty idle has been present since the cam install.
05-03-2009, 03:21 PM
#4
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May seem kind of stupid, but did you check the connection for the intake tube after the MAF and at the throttle body to ensure you're not getting un-metered air in at those points?
05-03-2009, 07:24 PM
#5
Could a leaking header gasket cause this? My main concern is how much it is affecting my startup/idle/driving. I actually hate driving my truck now, it is that bad.
05-03-2009, 07:57 PM
#6
Check the vacuum hose from the back of the intake to the brake booster, Ive knocked that loose a couple times doing cam swaps. Id just take the manifold off all the way and inspect all the sensors and vacuum lines along with the intake gaskets. Definitely check out the intake tube. I know this all sounds elementary but the stupidest of stuff can bite us in the ***, I know all too well.
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05-03-2009, 08:16 PM
#8
EVAP motor is always kinda wobbly, if you look at the way its attached its not a very snug fit. You can always get plugs from the parts store and remove it then plug it to make sure. Id pull the EVAP motor out and make sure the little o-ring is still in good shape. 11% on the LTFTs isnt a huge leak but enough that a small cracked o-ring could cause. Check the brake booster hose, the map sensor and if you still have EGR. Check everything, pulling the intake off will be the best route IMO.
05-03-2009, 08:37 PM
#9
EVAP motor is always kinda wobbly, if you look at the way its attached its not a very snug fit. You can always get plugs from the parts store and remove it then plug it to make sure. Id pull the EVAP motor out and make sure the little o-ring is still in good shape. 11% on the LTFTs isnt a huge leak but enough that a small cracked o-ring could cause. Check the brake booster hose, the map sensor and if you still have EGR. Check everything, pulling the intake off will be the best route IMO.
I'm thinking about just getting my idle bumped up to 1100 for awhile
05-03-2009, 09:02 PM
#10
Yes it is enough to make start up crappy, my buddies h/c 5.3 had a leak on the map sensor and it would do exactly what you are talking about. His LTFTs were anywhere between 8 and 14 if I remember right. After that was fixed it ran fine once it warmed up a little bit. If it was me Id pull the intake and check everything on it, its got to be something post MAF causing it, and that only leaves the intake or a clogged cat but I dont think youre running cats right? Ive never seen leaky header gaskets mess up LTFTs before so I dont know if that could be the problem. Look around the gaskets and see if there is any carbon build up on the heads.