Hello everybody, need some help with a misfire I’ve been chasing for two years. I have a 97 montero sport with only 2.5k miles on the engine( I have a remanufactured engine) and ever since the installation I’ve been having a misfire on cylinder 5. I have tried swapping coils, fuel injectors, spark plugs, and have even put in new intake gaskets. I know it has a vacuum leak due to the fuel trims going back to normal when the vehicle is moving. I have a rough idle. Would appreciate any help. I’m thinking maybe a stuck valve or misadjustments.
LTFT BANK 1:-10.2%
STFT BANK 1:8.6%
LTFT BANK 2:10.2%
STFT BANK 2:0.0%
If your fuel trims are good while driving but not good at idle, then there is an air/vacuum leak somewhere past the MAF sensor. While driving, the air leak becomes obsolete because the engine demands more air at driving speeds. But at idle, a small air leak can cause issues since the engine needs a precise amount of air and fuel to idle perfectly. Did you have the engine remanufactured or did you buy the vehicle like that? I agree there may be a maladjustment on cylinder 5 if you tried everything on it.
From your fuel trims, bank 1 (where cylinder 5 is) seems to be having either an air restriction or too much fuel injection (fuel subtraction long term). Bank 2 on short term is good, but long term it's needing to add fuel, so either too much air or not enough fuel being injected. From my experience, cleaning the throttle body and MAF sensor helps with rough idling (assuming the fuel and air system are good). However, I would look into addressing cylinder 5's misfire first.
@razmigb
I have tried swapping the MAF sensor but it was the same thing, even cleaned both also. Cleaned the throttle body when I had changed the gaskets for intake. Also I had bought a remanufactured engine for my truck since the original motor had the heads blow up.( not my fault, previous owner used tap water). Had the work done by a local mechanic, so I will more than likely take it back to him and let him figure it out. The engine has warranty and this is my “third” engine, so either they never swapped it or it’s something else. The engine is from Surefire, so I want to have someone from there to come down to the shop and have a look at the motor.
Did you check the headgasket leak?
@yaser
Highly doubt it’s the gasket, doesn’t smoke, oil looks good and full, and the coolant is still green and full
"Had the work done by a local mechanic, so I will more than likely take it back to him and let him figure it out." .......... It is best to have a poor mechanic keep working until he falls on the correct fix.
"The engine has warranty and this is my “third” engine, so either they never swapped it or it’s something else." ........ My guess is "something else". Time to look for money back. Three times? You have more loyalty than they deserve.
@jimz
I have a second mechanic work on my sport and he recommends swapping the engine. I have brought up the fact for a refund but the mechanic told me I couldn’t since the engine has already been in use. Don’t know if that’s true or not, will try to call Surefire and ask them myself.
Fix the vacuum leak. If the misfire persists, then do a compression test. You may have a valve issue.
@mountainmanjoe
I have checked the entire area of the intake for a vacuum leak. The only thing I can think of is maybe the exhaust flange gaskets since two of them are leaking before the o2 sensors, so it would make sense for the fuel trims to be off. The only thing I don’t get is why the fuel trims are complete opposite, one negative and the other positive. If it was a vacuum leak wouldn’t the fuel trims be the same on both sides?
Bump