New cat, can we compare trucks? need help now!

[97LowRanger]

Hey guys i just installed a new cat, also have a scanner and at idle the long term fuel trim is at 12-14 and short is around 5 really high correct? as soon as i rev it the long term comes down to 2-4% and stays while running and as soon as i let go off the gas its back to 19% Lt......vacuum leak?
the problem i see is that my O2 reads rich here is what i got
LT FTRM1(%) : 13.3
O2S11(V) : .810
O2S12(V) : .785
so i understand the cat is not doing much maybe is topped off as far as it can clean if i had a vacuum leak my O2 would read lean wouldn't it?

PS thats what the scanner reads im assuming it means O2 bank 1 sensor 1, and O2 sensor bank1 sensor 2?
its a 2.3 L
Really need help asap i don't want to blow my new cat

 

[adsm08]

Those trims are high, but not extremely.

Take these readings and do some math for me...

Take long and short trims at idle, add the number (if short is negative subtract, eg LT12, ST-2 = 1, LT12, ST5 = 17)

Then take the same numbers at 1500 RPM.

Take the two results and subract them. If the difference is 15 points or more it's a vacuum leak, if its less than 15, and that's right up to 14.9, it is probably the MAF.

 

[97LowRanger]

Thanks

Thank you for the help its a little late but i will check tomorrow and im just worried not to shoot out my cat, and i have cleaned the MAF but will do again tomorrow it cant hurt.

 

[BRUTUS_T_HOG]

That looks like a vacuum leak to me. Carefully spray starting fluid around the intake/hoses. If yu see fuel trims dip down way negative you've found the leak.

 

[adsm08]

Thank you for the help its a little late but i will check tomorrow and im just worried not to shoot out my cat, and i have cleaned the MAF but will do again tomorrow it cant hurt.

But cleaning the MAF won't help if it is bad, rather than dirty.


Another thing to try is resetting the computer, and see what the fuel trims do. If they shoot up quickly that is a vacuum leak. If they creep, it's an electronics problem.

 

[97LowRanger]

But cleaning the MAF won't help if it is bad, rather than dirty.

Another thing to try is resetting the computer, and see what the fuel trims do. If they shoot up quickly that is a vacuum leak. If they creep, it's an electronics problem.

Right, is there an easy way to test the maf? also if it was a leak it would show at idle and the truck idles perfectly no shaking or anything. and at 1500 the long term is around 18 and short term between -3 to 4. and what is the process to reset the computer?