I'm really new to the forums but here's my issue..

I have an 03 evo 8. My cars is having idling issues really bad I have done so much research and found that the IAC could be the problem. My car literally needs me to pump the gas and hold the idle for it to stay on. My mechanic changed the IAC sensor and it was all good started up nice.. Until I came to a dead stop at a stop sign. Car dies on me and when I try to turn it on again it struggles again with the idle? But when I start it up at a cold start it starts up fine I'm so confused and cannot find the answer to my problem anywhere. 3 mechanics I've paid to fix it and nothing. I've tried boost leak tests, search for vacuum leaks, new spark plugs, even went to my tuner and he cannot find out why it's doing this. So the iac did fix my startup but once it dies on the road, the startup is the same as before I changed the iac it's so weird. I've changed the fuel pump twice already so I doubt it's that. I even swapped out the MAF and BOV to see if that's my problem.. Nothing. Someone please help!

My mods are:
Hks 272 cams
Walbro fuel pump
950cc injectors
Forge bov
Tuned using evoscan by Turco

I don't have any crazy mods done

 

did you ever adjust your BISS during tuning? are you using a Tehphra map? if so, i'd bet your trims are way off and adjusting the BISS would help.

 

My car is currently doing the same thing after an aeromotive 340 install. I went back to the walbro and it still won't stay running. I hope you find an answer I need one too lol. What do your afr's look like when it dies out on you? Does it go full lean right before it dies?

 

Did this just start out of nowhere or did you just have parts installed/ tunning?

 

I would pull the battery cable and let it sit resetting the ecu...see if that changes, it will take a while to get it to adj but could be worth it.

 

what plugs are you using and what are they gapped too? It may be tune related, but if you gap them a bit smaller it may help you get you driving until you get your tune/issue resolved. I swapped in larger cams, and when I gapped my plugs to .028" it would want to stumble and die at idle every so often. I re gapped to .025" and its much better, at least to get me around until I get retuned.

 

Also, check and make sure all your injectors are firing. If you put your hand on the injectors, you can actually feel them "Tick" as they fire. If one or more are not firing, then change your injector resistor box.

I just had this same thing happen to me.

 

The car runs fine it's just the idling. We ajusted the BISS when we tuned. Plugs are gapped to .25 everything is normal this problem just came out of nowhere!:/

 

have you double checked the trims after adjusting the BISS? the only reason i bring it back up is because i THOUGHT i had mine set until i realized i wasn't waiting long enough in between adjustments LOL.
plus.. i can't think of anything else it could be without having the car in front of me

what does the A/F do right before it dies, go rich or lean? the fact that it only does it in closed loop is helpful. but then you gotta figure out if it's a sensor or the tune.

have you tried flashing different ROMS? seems like if it were a sensor it would do it the whole time, you would have weird AFRs or something that catches your attention.

do the datalogs show anything weird?

when in open loop, does the car hunt for idle at all while warming up?

 

Id check the biss screw again

 

Hey guys sorry so here's the update.

Turns out my idiot mechanic didn't "calibrate" the IAC Sensor. So now the car won't die. But the idle still drops down to 500 at times. Me and my tuner are stumped he's tried so many things and while he's experimenting the car starts up great, once I'm home and try starting up from a cold start, I have that problem where it won't turn over until I pump the gas pedal. So basically my main problem now is my startup and not so much the idle drop while driving. We've checked the biss screw and everything. Any ideas?

 

I didn't think the Evo IAC's had to be calibrated. He probably took out the IAC and manually adjusted the plunger in it so that the vehicle would idle. I have seen this situation before on a different brand vehicle, turned out that the PCM wasn't commanding the IAC to do it's job. The fix was a PCM and IAC replacement.

 

I think its the maf sensor

When you statt modding it I think it throws everything out of whack and you have to rescale everything compensation, scaling etc

When i converted to speed density it runs like a charm would never go back to maf again

I had the same issue but with more modifications

 

Can you check what ROM the car is running and report back?

 

the MAF is fine. modding your car will not adversely affect it unless your airflow is overloading it.

what procedure did you use to adjust the BISS? i only ask because i was given correct info, but with a key point or two missing.. and if you did yours how i first did mine, it may not be right LOL.

if someone messed with your IACV then that would suck. there is no need for that to be touched. but if they did.. then nothing you can do is going to make up for it. well, except replace it, i guess, as you don't know exactly what he did.