Forester random missfire

so i have a 1998 forester with a 2.5ts a 5sp it has almost 200k on it. i have replaced the fule pump fule filter along with the plugs whires and coil and i am still having an issue with the car having a ****ty idle and it will missfire under load under 3000RPM

Ideas?

 

Have you checked for boost/vacuum leaks?

 

its NA, but yed i did check for vacume leaks, and i came up with nothing

 

What cylinder? Find out which cylinder, then try moving an injector to the opposite bank, see if it follows. If that doesnt work then try a compression test.

 

misfire is on 2/4

 

What kind of plugs?

 

NGK, i was told they where the OEM plug

 

I meant the number, as a 99 would get a different plug than a 98.

 

even with the same motor?

 

'98 is DOHC, '99 is SOHC

 

98 is a DOHC, 99 is a SOHC. They aren't the same motor, and they do each take different plugs.

 

ok ill take a look at the box when i get home

 

Depending on if you got the NGK standard: NGK Part # 2382 {#BKR5ES11}
or V-Power: NGK Part # 6953 {#BKR5E11}

Text me Mo, if you want me to swing out tonight and help diagnose

 

NGK pn# PFR5B-11 is what you're supposed to have in it. Subaru part number 22401aa570.

 

Did Laser Platinum plugs come stock in the 98 Forrester?

 

They were platnum, yes. IDK they must call them "laser" in the aftermarket world. The part number I gave is for the NGK number that is standard in the 98.

 

i checked the injectors, they all ohm from 14.5-13.5

 

You probably have burnt valves or dropped exhaust valve guides. Drop the exhaust from the heads, look up and see if the guides are dropped down.

 

i would bet on it being droped exhaust valve guides. its happend on my forester!

 

This is a 98, its more likely a burned valve, I've never heard of a DOHC dropping a guide, however, 99-2007 (sohc) or so, drop them like crazy.

 

did a head gasket, while the heads where at the shop they did a valve job with new seals and now the car is good to go!

edit, the misfire was back just a few days later getting worse and worse

 

How are your grounds? If you take a multimeter around the engine bay, any metal to metal point should read a solid 0 ohms. After some time, the wiring can get pretty corroded and create poor grounds. This can cause problems in time.

Does the behavior vary between dead cold startup and after the engine has warmed? Does it vary with throttle position? Basically I'm curious if it varies between open and closed loop operation. If you can stab the throttle and rev through the rpm range happily but have miss and hesitation at lighter throttle and even idle, it's a good sigh the air/fuel sensor is going out. As it gets worse, the symptoms get worse to the point where the car cuts quite heavily at partial throttle and almost won't idle without dying unless you give it a bit of throttle and keep some revs. That's on the far end of the spectrum though. Regardless of degree, it's always dependent on the open/closed loop switch which is a dead give away.

 

so i replaced spark plugs because of the miss fire, then wires, then coil, to find that one of the new spark plugs had a crack in it, poped a new one in there and i was good to go!