i had the swap done years ago on my expedition. recently, the intake/intercooler was removed to be cleaned. the mechanic said i should put new intake gaskets on, as the 1st set didn't look that good anymore. i gave him L ones instead of expedition ones. the truck has been to the dyno the last 2 weekends to be re-tuned. it's not pulling numbers anywhere where it needs to be. first we thought there was a bad plug or coil, so i had all 8 of both replaced. no change next time down. then the fuel pump was going crazy. we dropped the tank and found the pump sitting too close to the bottom of the tank. we raised it up, and it sounds much better, and it's getting the proper fuel pressure across the band, but still no power. gonna have a compression test done today. if that passes, only thing i can think of is a vacuum leak. thoughts?

 

is the vacuum lines hooked up properly?

what boost are you seing?

 

Id bet my engine its not intake gaskets.... a vacuum leak wouldnt cause a power loss at WOT... Its probably a tuning issue

 

Sorry to hijack but are the intake gaskets for an L the same as the regular 5.4? Reason I ask is that I have a new spare set that I want to use when I do my swap.

 

we've been tuning this on the dyno for a few weeks. this guy is L experienced, and has had several himself. a/f is right, timing is right, fp is right, just has no top end. under normal driving, truck runs mint (even w/less hp). should i have used the expy gaskets or the l gaskets?

T.I.T.S.

 

let me add the the l's use the same intake gasket for both sides, whereas the expedition specifies rh and lh.

also, based on live fuel trims, the truck is a little leaner on bank 1....about 5% or so consistently. he said that could just be an o2 sensor.

 

Again I thought gaskets where the same!

There are a lot of vacuum sources on these applications, but I would have thought you would problems at idle.

 

gaskets are the same, you can throw a vacuum leak out. does power drop off or does it just not make as much as you think it should? can you post a dyno chart?

 

power way down. i don't have a chart avalable, but it is down significantly (give or take 100 rwhp). runs fine around town and such, and up to about 5-7 psi, but then it has nothing. sounds like an air hole.

here is a post on another site with more info....so as not to type everything again!!

 

so it sounds like its blowing air out somewhere? If that is so, then you should have a noticeable vacuum leak at idle and throw lean codes. So just to be sure, none of these problems happened until the intake was pulled to clean the intercooler? If that is the case, pull it all back off and check over everything.

 

to tell you the truth, i assume thats when it happened. i drive normally 99% of the time, and the truck runs great. but on the dyno, it has no juice anymore. the mechanic who did the intake cleaning is taking it back tomorrow night to check everything over. it has repeatedly thrown lean code after the cleaning, but i attributed that to the new aem intake, as the tube is much bigger than stock. even after the tuner made the tune rich, i was still getting lean codes, both banks. now i have rich codes, which kinda makes sense, cause it's tuned rich to be safe.