Thread: fuel trim problem

Ok so I got my pcm back from intense and the fuel trims were still in the negatives when i started it. So I drove it around for a bit and the fuel trims sort of mellowed out in the low numbers +/- 4 or 5. After I drove around abit longer the trims stayed in the positives and cruising and idle the trims are at +16.4 and driving it up to speed it would go to + 5-7. When I did get on it I got about 2-2.5* of knock. When I had problems from the pcm before I did a fuel pressure test and all the numbers were somewhat low but no one i talked to said they seemed to bad. On with out engine (48psi) Idle (44-45 psi) 2,500 rpm (48psi) and rev limiter (50psi). I wouldnt think my pump would be bad probly do need to change the filter its been awhile. Any ideas? Positive number means it has to add fuel correct?

If the trims are at 16.4 at idle you gots a vac leak.

thought that was only if it was in the negative?

+16.4 is vac leak.

it's trying to add fuel for mysterious amounts of air.

ok just checking. I was told on another forum back when I did my header install i had -16.4 and they said it was a vac leak

i realize that but if i had a vac leak wouldnt it always be a positive number? It ended up being my egr tube was ripped so i got rid of it and fuel trims were better after my headers

So i went and sprayed propane all over my engine and idle did not change I just changed the lower intake gaskets when i did and the gen v swap to the aluminum ones. Any ideas what it could be that would be leaking? No dtc's either

Originally Posted by Fivefingerdeathpunch

If the trims are at 16.4 at idle you gots a vac leak.

This isn't always true. People really need to look at the whole thing instead of just saying 16.4 equals a vacuum leak.

Mine are at 16.4 at idle and I know for a fact I dont have a leak. My cam is just lean at idle.

I had similar issues running no cat until I turned off cat test in the tune

Originally Posted by crazyguy03

I had similar issues running no cat until I turned off cat test in the tune

I have a cat still so that wouldnt be it. Did some more searching and found my hose from evap to throttlebody had a small hole in it. Replaced it and fuel trim seemed ok for a bit but on my way home it went back to +16.4 at idle or letting off the gas. Heard that the northstar adapter from zzp doesnt seal right all the time so maybe thats it?

Maf table or ifr table?

Evap still functioning?

sorry no way to get a table for you dont have anyone around me with a tuner or anything, and evap should be functioning i tapped the adapter for the evap to still function.

Did you get a tune with your n*? If not that's your problem.

yes i did

I meant a custom in car tune.

sent it to intense to be tuned so no i didnt dont have anywhere near me that can do it

Did you tell them you had a n* and everything or is it just a canned tune?

Told them n* and everything

Well after driving it for about 15 minutes, does it go away? Say your out driving for awhile. Do you notice it goes away?
Thats how I knew it was not a leak. I mean you really need to drive it. Short trips won't cut it.