Dirty/bad MAF sensor?

[I_H8_1.8]

Update in post #20...issue has returned!

Hey guys, it's been awhile since I've been on here, since I finished my EJ22T swap in my '95 Impreza.
I've had some issues lately where the car will just die while driving it down the road (bad & unsafe) or the highway (much more bad & dangerous)! When it dies, the engine basically loses all power and stalls once the rpms fall to zero, but I can sometimes stab at the gas pedal and get it going again, along with a nice after-fire/explosion and flames out the muffler! I'm kind of surprised the exhaust hasn't blown apart! If I stab at the gas pedal after it dies, I can hear the turbo spooling, but sometimes it will catch itself with the above mentioned effects, and sometimes it doesn't help. I can get it restarted, but it sometimes takes numerous tries before it will start and stay running. A lot of times it will start with an after-fire, then stall again. It seemed like keeping the rpms above 3k or so helped, for a bit, but that didn't really seem to make much difference after a while. Basically, it seems the fuel injectors keep giving fuel, but I'm losing either spark or air, just judging by the after-fire. I don't have a constant CEL, but I did check the codes tonight - I had 14, 15, 16, 17, 22, & 23. The injector codes have been stored in the ECU since I can remember, and I also had to replace the knock sensor shortly after my swap, so to my best recollection, the only new code is for the MAF sensor. I seem to recall a few threads on how to clean the MAF sensor, but didn't have much luck finding them. My Haynes manual pretty much just says to check for battery voltage in the harness to check the sensor, so I'm looking for any help on how to clean or better check the MAF sensor. Can anyone help out?

My car: '95 Impreza L AWD 5-speed, with complete EJ22T engine/ECU (except for air pressure sensor - have a Chrysler or GM one that Vikash helped me with), 2004 (?) WRX turbo, 1998 WRX intercooler, HKS WRX catless downpipe, 2004 STi muffler, Walbro 255 lph fuel pump, and I can't think of what else at the moment. To best of my knowledge, the engine is a 1991, and the ECU/harness is a 1993.

Thanks in advance!

[gijonas]

EJ22T engine/ECU (except for air pressure sensor - have a Chrysler or GM one that Vikash helped me with)

related???

[I_H8_1.8]

EJ22T engine/ECU (except for air pressure sensor - have a Chrysler or GM one that Vikash helped me with)

related???

I might think so, except that there were no codes stored in the ECU for that; the only "new" code was for the MAF sensor.

[wtdash]

Almost the same codes on my post HERE.
Replaced the MAF and no issues since.

TD

[I_H8_1.8]

Thanks, that's very helpful! Is there any way to clean/check the MAF to confirm that it's bad, or is swapping it out for a different one the only real good way to tell?

[cj91legss]

autozone has a spray can called Maf Cleaner, works pretty good... Supposedly it doesn't leave and resiue behind like brake parts cleaner... and it's safe for all electrical connections and sensors. Might wanna try that. 7-9 bucks a can

[gijonas]

Yeah ^

But then again finding another should be pretty damn easy too.

[asc_up]

Yeah, but the MAF cleaner is cheap and works, so why spend more money than you have to?

[gijonas]

Yeah, but the MAF cleaner is cheap and works, so why spend more money than you have to?

Cuz thats how things are done in the car world! Dont ask silly questions!

[Legacy777]

MAF cleaner will probably not fix the problem. There's probably an element or something cracked on the sensor causing the problem. I experienced similar issues back in 2000 or so. Got worse during warmer temps. It finally left a code for the MAF sensor.

Replaced it, and no more problems.

[I_H8_1.8]

So it's sounding like replacing it would be the better route, although I may try the cleaner and see if it makes a difference.

Next question is what did you guys that replaced the MAF do; did you find a used one, or get a new (remanufactured) one? I checked with my friend at Autozone, and the cheapest he could get one for me would be about $180...ouch! I'm trying not to spend that much if I can help it, but I want to make sure I get a known good one.

[Legacy777]

Get a used one from a junkyard or someone on the bbs.

[asc_up]

Get a used one from a junkyard or someone on the bbs.

IF the MAF cleaner doesn't work, then +1 to this.

[gijonas]

Oh and once again i have one thats good if you need it.I swapped over to a JECS when i got the revtronix chip.

[I_H8_1.8]

Thanks for all the replies so far; much appreciated!

Oh and once again i have one thats good if you need it.I swapped over to a JECS when i got the revtronix chip.

PM sent.

[scootledoo]

soo kind of old thread.. but did replacing the maf help ya? because i ahve having VERY simular issues and im kinda boned right now and need to get bak on the road.

[RJ93SS]

i got a maf too,

op how's your fuel pump ??

[I_H8_1.8]

I meant to update this thread earlier, but didn't get around to it. I got a MAF from gijonas and installed it a couple of weeks ago; it seems to have fixed the problem!

RJ93SS, my fuel pump seems to be fine as far as I can tell.

[scootledoo]

well my cars not running right now and ima have to run to the junk yard today after work with some friends.. any chance yall might have a maf i can buy?

[I_H8_1.8]

Looks like RJ93SS says he has one. ^^^

[I_H8_1.8]

Hate to say it, but the same problem returned a few weeks ago, when it was pretty hot out; probably high 80s to low 90s with high humidity. On my way home from work, come to a stoplight, and the car stalled (A/C was on). Get it started again on the first try, light changes, and ~200 ft. later, if that, it stalls again as I'm moving; no warning or anything. Took numerous tries to get it started again, and got a bunch of explosive sounding after fires in the process. Still no CEL. I pretty much got the car home and parked it, and haven't touched it since aside from checking connections and such.

I wanted to get the ignitor checked, but Autozone can't check it with their equipment. I will check with Advance and a few other parts stores this weekend, but is there any way I can check the ignitor and/or MAF sensor on my own if one of them can't? I really don't even want to drive the car with it acting like that, as it's unpredictable at best; I've been contemplating selling it as-is or parting it out, because I'm tired of dealing with it.

Any ideas/advice/etc.? Want to make sure I've pinpointed the problem before driving it again, and I don't have the money to, nor am I comfortable with just throwing random parts at it in hopes that it's fixed without knowing for sure.

[Legacy777]

It really sounds like a MAF. I had similar issues several years back. It wasn't AC related, but I would lose power all of a sudden, car would stall. Sometimes it would start back up, other times I had to sit for a little bit.

Did you end up replacing the MAF?

[I_H8_1.8]

Yeah, I did replace the MAF with a different one; my first thought when it happened was that it was the MAF again. I got a "known good" used one from gijonas; it seemed to fix the problem for the most part for awhile, although there was a "hiccup" for lack of a better term, every once in awhile while accelerating. I certainly don't think he sold me a bad one, but I can't help but wonder if the one he sold me ended up going bad for whatever reason. Given that that the one he uninstalled and sold me due to going to a JECS (?...Not familiar with that) was working fine before he removed it, I question if it just went bad or if there is another issue. What I'm really after is a way to check the MAF and/or ignitor on my own, to confirm the problem before I replace either. My local junk yards don't seem to have many Subarus, unfortunately.

Something I thought about after I posted earlier and after looking in my Haynes manual in the Troubleshooting section: could this have anything at all to do with the timing? I had the water pump and timing belt replaced at a local shop that I'm not sure I trust anymore due to unrelated repairs, but I basically took their word for it that it was set right, and although I don't remember the exact time frame right now, I do recall that I never had this issue until after that. I also only have a Haynes manual and not a Chilton's, although I think I do have the FSM saved on one of my hard drives. Hell, it could also be a fueling issue for all I know at this point, although it doesn't act like it with the sometimes massive after fires. I guess I should really do some more troubleshooting, but I'm extremely hesitant to drive the car at all at this point, and it seems there's only so much I can do with it sitting in one spot.

One last thought: if I disconnect the MAF and start the car, the CEL will come on and stay lit, but it will still stay running and default to a preset setting to compensate for no real time input. Why would it just stall with no CEL prior to stalling if the MAF is bad, i.e. the ecu not getting a proper reading from it? How is that different? Thoughts like that make me think it may be something other than the MAF, such as maybe a fueling or timing issue, or something else.

I swear I'm not trying to write a novel, but I am trying to include as much info in my posts as I think will help, plus I'm kind of thinking out loud...through my keyboard.

[Legacy777]

MAF's can be kind of tricky. The problem I had was intermittent, and only left a stored code I think twice over a year period. The problem typically has to be present for a certain amount of time. That's why it may not throw a check engine light.

As for your comments regarding timing belt. That may very well be a culprit. If you suspect the shop, I'd double check it. It's not too difficult to pull crank pulley and then timing covers to check things out.

[I_H8_1.8]

Ok, so I realize this is in the wrong section, but this problem is still ongoing. After getting 2 different MAFs from a junkyard on eBay, I'm starting to think this is not a MAF issue, and could possibly be a fuel pump issue. I currently have a Walbro 255 lph pump in the car. Would I be ok to swap in my old Impreza L 1.8 liter fuel pump just to test the car to see if it stalls with no warning signs after a few minutes of idling? I may also have a stock fuel pump from a '98 Impreza 2.5 RS, but I haven't found it just yet. I'd like to try a different fuel pump first before buying a new one blindly, as money is pretty tight. Thanks in advance.

Worth mentioning: after my last battery disconnect for a few days before installing the "new" MAF to clear the ECU codes, then installing the "new" MAF and having it still stall with no warning, I checked for stored codes; there were none.

I would equate the whole issue with having your computer just randomly shutting off instead of blue-screening...very frustrating and no real troubleshooting direction given!