AEBS intake...IACV acts up when hot?
08-26-2011, 07:36 PM
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AEBS intake...IACV acts up when hot?
I recently bought a 96 hatch with a stock 99 si motor in it. Car had no cat, 2.5" exhaust, and a ebay short ram. Car ran good, except for once it got hot, the idle would surge slightly between 900-1200. I got a good deal on a AEBS intake and 68 mm throttle body, so I put that on. (I have a 50 shot on the car and plan on adding cams, just picking up mods as I find deals and trying to work out the tiny bugs). I had some problems initially, but adjusting the throttle stop/TPS sensor fixed those. Drove the car like this for about 3 days to work and back (it's about 15 minutes each way, I leave early in morning and get home late at night, no traffic, just back roads traveling about 65 entire time) so car never really got HOT. Car idled perfect, seemed slightly faster then before, I was pleased.
Saturday, took the car to do some errands, and after about 30 minutes of stop/go, car started missing really bad below 3 grand. I assumed bigger intake, stock tune, it was running lean. Pulled the plugs and they were white. Not TERRIBLE, but more then I was comfortable with. Car sat for a few days, I got a fuel gauge and adjustable fuel regulator.
Adjusted fuel to about 39psi vs stock 37psi and finally installed my wideband. Car ran about 14.5ish cruising, about 12.5 at WOT (a little rich for my taste N/A, but not extreme at all)
Car runs GREAT first 15 minutes or so. Long as I don't sit in any traffic, it idles smooth, it takes off, it pulls til redline perfect. If car sits and gets hot, it starts "surging" at idle between 1200-1800. When it's at 1800, wideband reads around 14.5...when it drops to 1200, it goes to about 12.5. I'm thinking the spark is cutting out and its getting too rich. Start driving, below 2500 it bucks and sputters like it's missing. From 2500-8200 runs like a champ when accelerating. Soon as I let it decelerate, wideband maxes out at 21.8, and if I touch gas car jerks back into acceleration. If I pull over for 5 minutes with car off, it'll go away for a few minutes until it gets hot again. The hotter it gets, the worse the miss, the worse the shake. I got stuck in traffic for over 10 minutes, and the surge went up to about 2k rpm, and I could barely get it moving again. Bucked until about 3500 and then ran great.
Today on way to work, started acting up, I pulled over, unplugged IACV (which looks brand new, and I was told was replaced recently. Looked very clean when I swapped it to AEBS intake from stock) and the car idled at about 800. Ran smooth. I still got the "jerk" when decelerating to accelerating (assuming the throttle closing off is choking out the motor, when I open it back up, it gets it's normal power back and jerks the car).
I decided IACV was most likely the culprit, realized they are 200 bucks, and decided to try and run car without it. I adjusted throttle stop until car idled at about 1200, and took it around the block. I still get the "jerk" when going from deceleration to acceleration. But no missing, no sputtering, etc.
Plugged the IACV back in (motor is still cold) and car runs like a champ.
I cleaned the iacv right before coming to make this post, and put a little dielectric grease around the sealing o ring. I'll find out tomorrow if it worked. I doubt it will because it was pretty clean to start with.
My question is, what could be causing this? Why did it start with the AEBS intake, I really doubt I need a custom tune over something minor like an intake. The AFR is good, the throttle blade itself is good, and car runs great until it really heats up. If I keep car at 2500, I can drive for probably an hour before it's a problem. If I sit in traffic, or beat on it, it'll act up within 5 minutes. Anyone have any ideas how to fix it? (besides a custom tune to have the IACV pwm adjusted).
I got one of those EBAY chipped ECU's (incase I do infact end up needing a custom tune)..and the guy gave me a base tune for my mods. It runs SUPER rich, and for some reason VTEC doesn't kick in until 6200. BUT I don't notice the "miss" or "jerking" , it surges real bad at idle once it gets hot, but I can almost deal with that, if the jerking will go away. If the problem is evident with the OBD1 chipped ECU, it takes much longer to show up. When it's cold, it runs great, and as it gets hotter, only thing I noticed was the surging.
Saturday, took the car to do some errands, and after about 30 minutes of stop/go, car started missing really bad below 3 grand. I assumed bigger intake, stock tune, it was running lean. Pulled the plugs and they were white. Not TERRIBLE, but more then I was comfortable with. Car sat for a few days, I got a fuel gauge and adjustable fuel regulator.
Adjusted fuel to about 39psi vs stock 37psi and finally installed my wideband. Car ran about 14.5ish cruising, about 12.5 at WOT (a little rich for my taste N/A, but not extreme at all)
Car runs GREAT first 15 minutes or so. Long as I don't sit in any traffic, it idles smooth, it takes off, it pulls til redline perfect. If car sits and gets hot, it starts "surging" at idle between 1200-1800. When it's at 1800, wideband reads around 14.5...when it drops to 1200, it goes to about 12.5. I'm thinking the spark is cutting out and its getting too rich. Start driving, below 2500 it bucks and sputters like it's missing. From 2500-8200 runs like a champ when accelerating. Soon as I let it decelerate, wideband maxes out at 21.8, and if I touch gas car jerks back into acceleration. If I pull over for 5 minutes with car off, it'll go away for a few minutes until it gets hot again. The hotter it gets, the worse the miss, the worse the shake. I got stuck in traffic for over 10 minutes, and the surge went up to about 2k rpm, and I could barely get it moving again. Bucked until about 3500 and then ran great.
Today on way to work, started acting up, I pulled over, unplugged IACV (which looks brand new, and I was told was replaced recently. Looked very clean when I swapped it to AEBS intake from stock) and the car idled at about 800. Ran smooth. I still got the "jerk" when decelerating to accelerating (assuming the throttle closing off is choking out the motor, when I open it back up, it gets it's normal power back and jerks the car).
I decided IACV was most likely the culprit, realized they are 200 bucks, and decided to try and run car without it. I adjusted throttle stop until car idled at about 1200, and took it around the block. I still get the "jerk" when going from deceleration to acceleration. But no missing, no sputtering, etc.
Plugged the IACV back in (motor is still cold) and car runs like a champ.
I cleaned the iacv right before coming to make this post, and put a little dielectric grease around the sealing o ring. I'll find out tomorrow if it worked. I doubt it will because it was pretty clean to start with.
My question is, what could be causing this? Why did it start with the AEBS intake, I really doubt I need a custom tune over something minor like an intake. The AFR is good, the throttle blade itself is good, and car runs great until it really heats up. If I keep car at 2500, I can drive for probably an hour before it's a problem. If I sit in traffic, or beat on it, it'll act up within 5 minutes. Anyone have any ideas how to fix it? (besides a custom tune to have the IACV pwm adjusted).
I got one of those EBAY chipped ECU's (incase I do infact end up needing a custom tune)..and the guy gave me a base tune for my mods. It runs SUPER rich, and for some reason VTEC doesn't kick in until 6200. BUT I don't notice the "miss" or "jerking" , it surges real bad at idle once it gets hot, but I can almost deal with that, if the jerking will go away. If the problem is evident with the OBD1 chipped ECU, it takes much longer to show up. When it's cold, it runs great, and as it gets hotter, only thing I noticed was the surging.
08-27-2011, 03:38 PM
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Re: AEBS intake...IACV acts up when hot?
care to elaborate? Have you seen anyone else have this issue with an intake manifold swap on stock motor? Did a tune fix it?
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ZedEx
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