I bought this car from JM Automotive(great guys) about a week and a half ago, for the first few days it idled great and i had no issues but recently in the last couple days its beginning to have a real rough idle at cold start and 50% of the time when its warm. It feels almost as the car misfires for a couple seconds then it raises the idle to about 1800(on cold start) and it goes away but when warmed up if it does this it idles up to about 900 but when it drops it almost stalls out, but it saves its self. Jesse told me to check for vacuum leaks and i couldn't find any, the vacuum stays at about -21psi on my boost gauge as well so I'm stumped. I looked on nasioc and some people said it could be a clogged fuel filter which ill probably try next. Just looking for some insight if anyone else has had a similar issue. Thanks! edit: i don't know if this helps but the mods on the car are 3" inch catless turbo back, aftermarket header/upipe, tdo5 turbo, turbo inlet, and an FMIC.
I see you mentioned nothing about a tune? Find out from JM what if any it had, if none? Get a tune on it. Maybe if you have a compression tester, get that done for piece of mind.
Jesse had it tuned right before i bought it from Devin @Medic_538. It doesnt miss or anything under load, but i will still try to do one for piece of mind.
Have you tried to reload the tune or reset the battery? I know my car starts rough sometimes (maybe twice a month) but it last about 10 seconds and then I can feel and hear it smooth out. With regards to your tune, I have a few tunes and one of mine (alt E85 tune) acts like what you describe with the almost stall and then rev up again. I had to have that tune adjusted due to some misfiring issues though. Fuel- What are you running>
It's open sourced, maybe the tune needs a couple tweaks. It's tuned on 92 octane, but I run 93 octane from BP. I've read up some more and talked to Jesse at JM and he said to clean the maf, if that doesn't work, clean the idle air control valve, if that doesn't work then I'll probably change the plugs. If none of those work, then I'll probably bring it to Jesse and see if Devin will tweak the tune.
Just a bit of advice on the iac be ready to spend at least $350 for the part from a auto parts store. It doesnt really sound like a iac cause mine was bad and it would just hold the rpms at 1500 at idle and drop down to like 1100 when warmed up. Plus if you do the iac the screws holding it were a pain to get out and we had to drill one out and get a whole new set of screws to hold it down
Update: cleaned the MAF and put in a new fuel filter and its still doing it, not as much though probably only 50% of the time now. I will be cleaning the IACV this next weekend once my new gasket gets here. If that doesn't work then I'll be putting in new spark plugs.
You can clean your IACV and bypass the coolant line from it, run without a gasket until it comes. The only reason for the gasket is to keep coolant from getting in the intake. Also, unless they changed things the screws on the IACV are very soft. Use a light impact driver with large flat head screwdriver insert to work them out then replace with a allen head bolt (5x20mm? 8.0pitch?) Finally, one more thing to check is the crank position sensor, it's ~$25, just replace it.
I found the write up on NASIOC on how to clean the IACV and i'm just going to wait until my gasket gets here before playing with it. If cleaning the IACV doesn't work then ill change my spark plugs, and if that doesn't work then ill change the crank position sensor, if none of this works then ill bring it back to JM and have devin play with the tune.
Agreed the screws are very soft. I had to drill one out cause the head got stripped so badly and I didnt really do much to it and they stripped. I put regular screws in there so if I had to take it off again it would be a lot easier. They seem to be working which is nice.
