legacycentral bbs

The Check Engine light wasn't intended to tell you when the engine is running incorrectly; it's only supposed to tell you when the ECU is having a problem with one of its inputs or outputs. Excessive knock, and the subsequent boost limiting and timing retard, isn't a problem with an input or output.

So why does the light blink on other Subarus when an issue is taking place?

I've noticed my car running with 5psi boost about 5% of the time since "fixing" it. I'd like that to be 0% of the time but its sure hard to troubleshoot when there is no indication of what causes it.

I am going to try a another Italian tune up, new fuel pump and fuel filter in case pressure drops at time causing a lean/knock condition.

The light blinks on other OBD1 Subarus when an issue is taking place?

well guess what..no CEL, bossting at 5lbs again this week. subaru select monitor worked last time. gonna use it again to fix this

well stoopped at SIP.

plugged the select monitor in . no active or stored cels, reset the computer anyway. voila back to normal again.

what is going on!

Hmm, that's strange....

well lasted a week, back at 5lbs no cel

still resetting the computer once a month when it acts like a bitch .

thinks its time i look for a replacement ecu.

Yeah, that may be the only thing left to try unfortunately.

well replaced my ecu

once again all is fine then a few weeks later im back @ 5lbs, no cel.

i have revscan and it shows no codes. I cant find a way to facotry rest the ecu with revscan, must i use the SSM?

if anyone has any input on this ill take it? is it possible for the factory bcs to be doing this without throwing a code? this is my only guess to the problem as it has to be electrical/sensor but not the ecu.

If the ECU detects overboost or excessive knock it will limit boost to wastegate pressure. If the Octane Factor (like IAM in newer Subarus) goes too low it will limit boost to wastegate pressure. The ECU has a "high" and "low" advance table and it uses the Octane Factor to adjust the timing between the two maps based on knock.

That being said, are you having any overboosting issues? Do you have a good knock sensor and a new knock sensor wire soldered from the plug to the ECU to correct the possibly faulty stock wire?

None of this behavior will throw a code. As Josh said before, the CEL is only lit when the ECU detects a problem with an input or output. The CEL flash you speak of on newer cars is required by the OBDII standard, and is required to signify only a severe, repeated cylinder misfire, not an issue like this. On a newer Subaru, even with IAM at minimum value and knock events occuring you will not get a CEL.

RevScan and a laptop can be used to check on your knock retard, Octane Factor and many other things. Do you have a laptop and an SSM cable? I can get you the latest version of RevScan if you do.

sounds like you are dead on

usually its 10psi driving around. i did notice right after factory reset i would get some posp/cutou @ boost spikes while it was still learning, then be solid at 8-10psi, hten a few weeks later retard to 5psi

i have revscan but unsure of what the values should be as i dont know too much in that area, i guess i could data log and email it to you?


knock sensor is good to my knowing but maybe i should replace it and do new spark plugs too?

Just tell me what your Octane Factor is in three states:
1. after a reset
2. with the car running right after a good drive for it to learn a bit
3. with it limiting boost to 5psi.

Also, if you could post two screenshots of your Learned Knock Correction table from the left-hand menu after steps 2 and 3 above.

Yeah, it takes the ECU a couple full throttle runs after a reset to keep the boost spikes in check, especially if you have a TD04 or something it's not tuned for. I don't what turbo you have. Still a VF11?

If nothing is readily apparent from the above tests I may have you go drive it and do a datalog of some parameters as well, but we can hold off on that for now.

thanks for the tips ill get my ecu reset with the subaru sm as i cant see anyway to reset it with revscan. as far as the screenshots are you refering to the " memory knock counts" in the left menu?

as far as my motor goes, its mostly stock. perrin pulley, desnorked & silencer removed intake, catted 3"dp and 3" catback

With RevScan you can reset it by right clicking the "ECU" heading in the menu at the top left of the screen. At least I believe that's what it says. I don't have RevScan available to me right now. It's the heading that expands to show all the sub-options like logging and stuff. If you right click on it you can reset the ECU.

Yes, I think "Memory Knock Counts" might be what that one is called. I am out of town right now so I can't check it out 'til next week. If it fills a table up at the bottom of the screen with a bunch of numbers then it is the one I am thinking of.

k reset the ecu just now, first pic is before hand @ the 5psi issue, octane factor is (-1%)

2nd pic is just after reset octane factor (50%). after i drive it today ill do one more

Thanks, can I see the Memory Spark Advance as well after your drive along with the Octane Factor?

The -1 in the OF cell means your car is knocking enough to cause this problem (or thinks it is). -1 basically means use the failsafe timing table and limit boost to waste gate pressure. The 50% reading after a reset is the default. In a perfect world, that would slowly increase to 100%. Those screenshots pretty much confirm my theory. You are using at least 91 octane gas, right?

By seeing the spark advance memory after some driving I can offer a little insight into what the problem may be.

thank you so much for helping on this, im at work but will scan the car tonight. i always use 92 oct gas. gonna try to get new plugs and wires on monday too

scaned it this morning , OF is at 6% now. here is the screenshots

back at 5psi so i scanned today



afterward I installed new plugs and wires, cleaned the air filter, and dumped in half a gallon of 108oct gas. reset the ecu so lets see what happens now

That is lame. I suggest that you remove and carefully inspect your knock sensor for cracks. Also check where the knock sensor plugs into the car harness right there at the bellhousing. If the harness side wiring is broken you need to replace it with high quality shielded microphone cable. If the knock sensor is cracked it needs to be replaced.

Let us know how those two items look.

cool, just gonna go ahead tomorrow and replace the knock sensor, ill put some miles on it and report back

This is interesting stuff. I'm surprised the cars are just designed to put up with running shitty and never let you know about it. Some newer GM cars tell you if they're running reduced power with a "REDUCED POWER" light, I'd think they'd want to let you know something like that so you can take it to a dealer to have it diagno$$$ed.

Just curious, are you guys with the issue running 91 or 93 octane? I know when it was stock my TW didn't have quite as much pep if I filled it with 91 (that was before I had a boost gauge though), so for the past few years I've always went out of my way to get 93.

well folks...... plugs and wires seem to have been the problem from the begining

after i replaced them and did a reset the car has not gone back into "safe" mode. no knock counts and the OF is actually starting to rise. its at 69 right now and I imagine the more i drive it , the better the ecu will tune

Great! How did the old plugs look?

When OF hits 100% you know it's good to go. It should drive better and better until that happens.