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Evo GeneralDiscuss any generalized technical Evo related topics that may not fit into the other forums.
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Hey guys so I was out driving the car and tuning then I started noticing weird things happening. Car would try to die at idle, afr on the leaner side at idle and cruising. I got on it a bit to see wot and as soon as in got into boost I saw 12.8 - 13. I let off right away. I loaded an older map that I know works and same thing. I’m thinking fuel pump right away but it’s a year to 2 year old 255 and this car doesn’t get driven much. I stop to flash the car and the car would not turn on. Tried everything. It would just click like a starter issue. Connect jumper cables to it and right away car turns on. Go to oreylls and they said alternator and battery are good. So now I’m pissed. I know this shouldn’t be done on these newer cars but I was so mad and said screw it. I pulled the negative battery cable with car running and car died. In the old days this meant bad alternator. Now out of nowhere car continues to turn on no problem and afrs at idle are back to where they should be. I haven’t tried wot again and don’t want to until I figure it out. I noticed last summer or the one before in the day time a similar thing happened. Afrs would be more on the lean side when it was hot as hell outside. This is what made me change the fuel pump back then because you could hear it get loud. Any ideas? Can an alternator work on and off or do they just go bad?
corrosion can build up on the terminals and cause electrical problems. The fact that it got better after you took off the cable and put it back on makes this seem even more likely. You could start by cleaning the terminals, and check the Engine to Chassis, Engine to Battery, and chassis to battery grounds to make sure they look good.
I put a multimeter to it after i got home and afr were back to normal. The readings checked out. Car idling 14v. The battery is in the trunk and the terminals look new. I guess i can check the grounds and make sure theyre ok. What gets me is every summer it seems to do something like this. As if heat has something to do with it. Checking some of the logs one evoscan battery voltage is usually in the 13s. Ive always had a lean take off issue and nothings fixes it. I notice in some logs around that area ive seen voltage as low as 13.1. Can an alternator fail slowly or when they fail they fail and thats it? I mean maybe fuel pump is going bad again but damn this would be the 3rd one i think would be going bad because of similar issue. It cant be. I havent done the pump rewire. Maybe it needs that? idk i just think its weird specially when i disconnected the negative battery cable and car turned off.
I put a multimeter to it after i got home and afr were back to normal. The readings checked out. Car idling 14v. The battery is in the trunk and the terminals look new. I guess i can check the grounds and make sure theyre ok. What gets me is every summer it seems to do something like this. As if heat has something to do with it. Checking some of the logs one evoscan battery voltage is usually in the 13s. Ive always had a lean take off issue and nothings fixes it. I notice in some logs around that area ive seen voltage as low as 13.1. Can an alternator fail slowly or when they fail they fail and thats it? I mean maybe fuel pump is going bad again but damn this would be the 3rd one i think would be going bad because of similar issue. It cant be. I havent done the pump rewire. Maybe it needs that? idk i just think its weird specially when i disconnected the negative battery cable and car turned off
You should try measuring resistance between your battery chassis ground point and the alternator case. Sometimes chassis grounds when you relocate the battery don't turn out to be very good. What are volts doing when you are having issues? If you can associate lean/rich afr with different voltages then you need to adjust the Injector Battery latency comp table for that associated voltage.
Your not suppose to pull the negative because it can damage the electronics in the car. The Alternator is controlled by the ECU so it would make sense for the car to die.
Yeah i know i was just mad. I know in the old days it worked but not sure how it compares to now. Thing is car would run just fine a week ago at wot. Nothing has changed. It is on stock injectors and latencies have never been touched. I can add fuel 100 load and up sure but i want to know why this is happening when it was running just fine on this map. Only thing would be the alternator theory, grounds, or fuel pump. Im not the greatest with electricity so can you explain how i can check battery chassis ground and alternator case resistance if the battery is in the trunk? What should the readings be?
Very good video! Super informative. Thx for that. If it was a ground issue wouldn’t the problem be constant and not intermittent?
Not necessarily, sometimes grounding issues only show up when something starts drawing current, and sometimes things draw different amounts of current at different temperatures etc.
There is normally a very large ground wire going from the back of the engine/transmission area directly to the chassis and then to the negative battery terminal. When you relocated the battery did you leave that cable attached to the chassis ground?
I bought the car with the battery relocated. So when I turn the car on cold voltage reads 14 - 14.05. Now after driving a bit it’s 13.8 ish and i took a video where you can see when the fan turns on it’ll drop to 12 for a second and pick back up to mid 13. Don’t know how to post it. I guess I should check over all grounds but I’m also thinking this can be fueling issue some how. This car is going to drive me crazy.
I bought the car with the battery relocated. So when I turn the car on cold voltage reads 14 - 14.05. Now after driving a bit it’s 13.8 ish and i took a video where you can see when the fan turns on it’ll drop to 12 for a second and pick back up to mid 13. Don’t know how to post it. I guess I should check over all grounds but I’m also thinking this can be fueling issue some how. This car is going to drive me crazy.
That's not good, you do have some kind of issue with that kind of voltage drop. Voltage across the system effects everything, how fast the injectors open and close, the fuel pump etc.
Yeah something else I noticed is the tensioner starts jumping back and forth when fans turn on and rpms drop. Don’t know if that’s normal or not. Since it wasnt acting up I went for a drive and did a pull and afrs are good. 11.3 - 11.4. Something is up and it’s intermittent. How can I post videos?
Yeah something else I noticed is the tensioner starts jumping back and forth when fans turn on and rpms drop. Don’t know if that’s normal or not. Since it wasnt acting up I went for a drive and did a pull and afrs are good. 11.3 - 11.4. Something is up and it’s intermittent. How can I post videos?
Thats probably from the alternator getting loaded up.
Jun 1, 2019, 04:40 PM
