musubk Posted June 10, 2018 Share Posted June 10, 2018 I''m having trouble with my EJ22 swapped BRAT that I can't seem to figure out. The engine is from either a 1990 or 1991 FWD automatic Legacy. It has ran great for a couple of years, but when I brought it out of winter storage this year it had this new problem. Upon first starting it for the day, it will drive normally for anywhere from 10-30 minutes, then suddenly it will start 'stumbling' heavily if I give it any more than around 1/4 throttle. It happens out of the blue, and feels like it's running out of gas or pulling a bunch of timing or something. It can barely make enough power to run 10mph when it's happening. If I stop and put it in neutral, if I put the gas pedal to the floor it revs to around 3000rpm then bucks and starts dying, drops to 1000 rpm then seems to bounce off a 'floor' there. The moment I let off the throttle it returns to a normal smooth idle. If I turn the car off and back on, the problem is gone, but will come back in a few minutes of driving. I first thought the MAF sensor might be going bad, but I tried a different MAF and it hasn't solved the problem. The car has never has a check engine light hooked up, but I went and jumped an LED bulb off the proper ECU pin to see if it would give me a code. With the black 'read connector' connected, ignition on, engine off, the light just flashes seemingly forever, about one flash a second, always the 'short' blink that's supposed to be the 'ones' position in a trouble code. I counted more than 100 flashes with no changes in length or frequency before I gave up. I'm kind of running out of ideas. Does anyone have a suggestion for what I should check? Link to comment Share on other sites More sharing options...
musubk Posted June 10, 2018 Author Share Posted June 10, 2018 testing the resistance on my throttle position sensor by the procedure detailed here: I find that between pin 2 and 3 I have 9.5kOhm, when this says I should have 12kOhm, and between pin 2 and 4 it varies from 0.1kOhm to 9.8kOhm where this page says it should vary from 1kOhm to 4.3kOhm. It does vary smoothly with throttle position, though. Am I doing something wrong with the testing or is this the problem? Link to comment Share on other sites More sharing options...
musubk Posted June 10, 2018 Author Share Posted June 10, 2018 (edited) Okay here is my current theory. One of the sensors is bad - maybe the throttle position, maybe another. I'm leaning towards the TPS because of the resistances I just measured plus the fact that the car acts fine as long as I stay off the throttle. When you first start the car it runs in (I think...) a preset fuel map until it warms up. It's fine in that mode, and that's why the problem goes away for a bit if I shut the engine off and restart. Once it warms up enough, it switches over to a more dynamic 'learning' mode where it tries to lean out for better fuel economy, but that's where it starts screwing up because it's basing the 'learning' off bad data from one of the sensors. Does this make sense? Edited June 10, 2018 by musubk Link to comment Share on other sites More sharing options...
el_freddo Posted June 10, 2018 Share Posted June 10, 2018 Have you looked into a weak fuel pump, blocked fuel filter or pickup in the tank? The constant flashes of the ECU is the unit designation. It'll tell you which market it's been designed for. Eg USDM/JDM/AUDM etc. So your ECU does not have any stored codes which is a good thing. The only other thing I can think of is a dodgy O2 sensor that's not yet throwing a code but is upsetting things. Cheers Bennie 2 Link to comment Share on other sites More sharing options...
montana tom Posted June 10, 2018 Share Posted June 10, 2018 I agree , check fuel pressure. Sounds like pumps heating up and barely working. Nice that Bennie understood the flashing ECU at least you know you have no codes yet. 1 Link to comment Share on other sites More sharing options...
musubk Posted June 11, 2018 Author Share Posted June 11, 2018 Okay, that's good to know about the ECU flashes. I was worried that I had wired something up really wrong. I thought about fuel pump and fuel filter, but I wasn't sure if that could cause the off/on nature of the problem. I'll swap in a new filter anyway, they're cheap enough and it couldn't hurt. I guess I'm kind of dancing around the fuel pump because it's a nice Walbro inline pump and I don't want it to be going bad, lol. But if the filter doesn't fix it I'll get a fuel pressure gauge and see what kind of pressures I'm getting. Thanks for the ideas. 1 Link to comment Share on other sites More sharing options...
el_freddo Posted June 12, 2018 Share Posted June 12, 2018 Pull the pump anyway to at least inspect the mesh filter on the flow IN side of the pump. This may be blocked/particularly blocked with crud from the fuel tank. Cheers Bennie Link to comment Share on other sites More sharing options...
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