After resetting the ECU my idle dips after pressing the clutch in and coming to a stop. The problem goes away after a somewhat short "learning" period (maybe 20miles) so I don't think its a big deal, but I have been having issues with a P0300 lately so I was wondering if anyone else had similar problems.

 

anybody?

 

After you reset the ECU, your Evo cycles through fuel maps to "learn" trims. It is totally normal.

 

Normal the idle will relearn in a couple drive cycles

 

I have had this same issue recently. I wonder why.
The car didn't use to have this issue...

w evo, did you change the intake air filter or the intake pipe or had any mods to the stock air box??

 

Yeah, I remember the idle being choppy initially after resetting the ECU but it seems to take a much longer time to pick the right map.
The only intake mod I have is a drop in panel filter. I cleaned the filter and the MAS and that didn't seem to help much. The issue appeared to pop up after installing a mini-battery oddly enough.

 

The best way I've found to reset your ECU is to do the ECU reset, start car, turn on all accessories (AC, fan on high, radio) and then drive to operating temp without any boost.. very lazy driving for 10-15 minutes or so, the idea is to keep the engine in closed loop mode. Any heavy footing will make your AFR go lower than 14.7 - drive easy. Once the engine has warmed up, stop the car and turn off the engine. Now restart the engine and you can drive like normal. Doing this method will reduce (not eliminate) the 'hunting' for 14.7, as the first time the ECU is turned on I believe it sets the base fuel trims.

 

do you have cams or cam gears. I never had any problems with the p0300 code til I got tuned recently.

The tuner did several pulls with no code. We adjusted the cam gears and the p0300 code popped up. Well After a day of driving I noticed the idle was set a little low for my liking. We adjusted the idle and cleared the code. I havent got the code since.

Try deleting the code using a code reader or ECU flash tool instead of disconnecting the battery. maybe the idle being low is causing the code to come on. I understand you were having the p0300 before disconnecting the battery but its worth the try.

 

Thanks for the advice Mr. Evo IX.

No cams or cam gears yet. I started to throw the p0300 after having the timing belt replaced. I have tried to delete the code using a code reader but it came back while cruising. I am a little stumped at the moment. I am thinking about getting a Creader and forgetting about it. Everything feels great at WOT so I'm not overly concerned. Its just extremely annoying.

 

The only way to get rid of the P0300 is to stick in a Ceader, or get an 05 ECU, but then you will have to get new key s with it also! The P0300 seems to come on when aftermarket clutches are put in or eng parts are changed out. It doesnt seem that you have much changed to ur car, i would start by changing the plugs! Hope that helps...

 

Yeah I am thinking the Creader is the best bet right now... I changed the plugs (gapped to 0.025), checked and cleaned the coil packs and wires, cleaned the EGR and check the hoses, checked the PCV, cleaned the injectors and nothing really changed although the car is running really well in general.

 

The P0300 can be caused by excessive ignition timing at idle, its common for tuners to bump up the timing on bad idling cars with cams, OR ~1000 other things wrong with the car and/or the tune. The best thing to do is check the freeze frame data and find out the conditions when the code is being triggered, that's as good of a starting place as any. The Creader is where you end up when you've checked and rechecked everything and nobody can figure it out.

 

Thanks, I am in the process of getting evoscan right now so I will check the data from the instant the light is triggered/the shudder during cruise occurs. I'm hoping I can track down the source of the potential problem so I don't have to go with the Creader!

 

Back to the idle issue after ECU reset, the single biggest contributing factor is ISC position. It has both short term and long term trims, just like fuel trims. When the ECU is reset, the long term trim goes back to a default centered value, which is likely incorrect for your setup, especially if you've programmed a different idle speed. The short term trim is left to do all of the work until the long term catches up (adjusts slowly), and in transitional situations the ECU makes some incorrect assumptions and you get stalling and other issues.

The best way to set this is the way we do it with DSMlink. We know the "target" long term value, so we simply adjust the BISS to achieve this value. I don't have these values for EVOs, and I'll bet the only thing available to read it is a mitsu scantool. Some loggers may have it, I'm not sure.

If this can't be done, the next best thing is to get the car up to full operating temp (best is after a decent drive), reset the ECU, start it up, wait 30 seconds or so for things to settle in, and set the idle for your programmed target idle speed. The short term trim is still arsing about with ISC position, so this isn't an exact science, but it can get in the ballpark enough that a reset ECU doesn't aggravate the **** out of you for 2 days and your long term trim is more likely to be more centered.

This is more of an art than a science without the right tools and information, so YMMV.

 

Thanks for the information! ^^^