1990 Legacy 2.2 MISFIRE

[artie b]

Hi, I have a 1990 Legacy L 5sp. I have a miss that is driving me nuts... It comes and goes smoothly, meaning gradually starts to miss then as smoothly as it starts, it goes away. Usually happens when you accelerate slowly or hit a small grade. I noticed it when I repaired the AC, but it can happen anytime, cold warm or at operating temp. usually warm. It may go 50 miles and nothing, then start it up within a few miles does it. I have shaked and tugged, and pulled connectors and the wiring. It smoothes out around 3200 or so rpm on a downshift. I have removed the thermostat with no change. I have replaced the knock sensor and used premium fuel no change. I can turn the engine off and coast and restart the engine no change. I have put new grounds on top of factory with the coil pack, ACV, no change. I put in new NGK plugs gapped @ .043 in. I have replaced the following coil pack, igniter module, plug wires, O2 sensor, All 4 injectors, fuel filter, MASS, gas cap, PVC valve, knock sensor, fuel pressure regulator ECM temp control sender, THE ECM. the same results. I have looked and felt, sprayed to look for a vacuum leak, no change. This has been going on for 3 months, and many tanks of fuel. When it's having this fit, it really uses the gasoline. I did notice when it was doing this, the fuel Gage would slowly go towards empty, and than drift back up, I out an extra ground on the electric fuel pump wire at the sender unit. I may have forgotten what else I did to this, and I'll be grateful to the winner of "Guess the Gremlin sweepstakes" Throw out what ya got! Thanks, Artie I have 2 codes stored in my ECM that I cannot erase, 22 knock sensor & 24 ACV valve. I have pinnout the knock sensor wire and that rang out. There is no CEL light on.

I still have the miss, Or I should call it a MISS-Fire. I pulled a plug wire of the good running Subaru and grounded a spark plug, the miss I have been describing is actuall a misfire. I am only partialy missing on the problem Subaru. The fuel pressure is smooth between 30 and 40, and reflects the change in vacuum. I hope somebody is still hanging in there with me. I have a very hard time thinking that the new spark plugs would miss in the very same manner as the ones I changed? I'm pulling my hair out on this rascal!!!! Any help me and my scalp would appreciate it! Any Subaru hotshots in NW Indiana?

[94Loyale]

Well, considering everything you have changed out, and checked already. Since it's easy enough to do on a 2.2. I'd run a compression test next and see what you get. And check the voltage while the car is running. Should have about 13.5 at idle, rev it up a little and make sure it doesn't go above 14.8 or so. Subaru's are funny when they don't get the right voltage.

[artie b]

13.2 idle and 13.8 at the highest.... I'm going to try some different spark plugs and I will check my compression, the misfire comes on very slowly and disappears rather quickly, faster than I can oull over, pop the hood, get out, open the hood, it already smoothed out. It will be a few days before I'm back into it, THANKS, 94 Loyale

[bosango]

This is a good one, artie b. Well, maybe not so much for you, but for those of us that like to add to our troubleshooting toolbox. Hopefully, you'll get to the bottom of this peculiar annoyance. Best of luck!

[daddycoolj]

I've had a coolant temperature sensor that was about to fail cause similar problems.

 

I unhooked the connector at the sensor. This puts the sensor in default so the ecu thinks the engine is hot. I drove around for the day with no problems.

 

I plugged the connector back up and the sputtering resumed.

 

sensor was $23

[artie b]

Thanks Daddycoolj, I traded that sensor, it's for the ECM, not the gage, and the same problem sufaced. I just know it will be something simple, if only I knew what it is. I just feels like a weak spark plug. Looking for more good ideas, thanks and keep throwing out ideas, Artie

[kickascii]

I have the same problem. Have you done the comp test yet?

 

I also have a noisy lifter that comes and goes. Could it cause a valve to not open far enough (or not let the valve close) to affect compression a little bit?

[Gloyale]

90 and some early 91 ECU's (ones with LEDs in them) A faulty IAC and it's associated code will make the ECU cut fuel to the #1 injector.

 

It does this when it determines it cannot otherwise propely control the idle though the IAC.

 

Try replacing the IAC. Make sure you get a correct one. in 90, MT models will use a single coil type (2 pins) and ATs and all 92+ models use a 2 coil type (3 pins)

 

Good luck if you have a MT model.