I've been noticing a problem with my '03 Evo for at least 6-8 months now that I can't figure out, and now it's really starting to annoy me. When I'm cruising on the highway (or in town) and I let off the throttle I notice my afr's will go from ~14.7 to ~12.4 and just hang there while the motor decelerates. If I blip the throttle again real fast it will catch itself and drop to 22.4afr like it normally should when the injectors cut off during a decel situation. Why does it do this? I've tried a number of physical parts things to see if they were the cause (such as swapping back to stock intake piping, stock diverter valve, etc.) and none have made any difference at all. When I first got the car it never did this, and even after I stuck my UICP/LICP/Intake on it still didn't do it...except for within the past year or so. The only changes to the rom I have was the addition of the old Tephra mod patch for knock-cel only, but other than that it's still the same 94170015 rom I started with. Has anyone else experienced this or found a fix or cause for this situation?

 

Under certain conditions (notably when taking your foot off the gas after open loop driving), the ECU will continue to operate the injectors during decel. Usually the AFR still goes completely lean though. Have you tried monitoring IPW to see if the injectors are still being commanded to operate?

 

my car does this too since e85 switch ( or more noticable) car stutters under light driving when you lift. i will try to log ipw and see what its doing.

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I haven't logged IPW yet, I'll do that on my next run. I switched diverter valves and it helped a little with this for some reason, but still does it on highway travel. In my prior logs it usually shows IPW for a hair past getting off the throttle before the afr's go to a lean decel (injectors off), but they never stayed on for this long before. I'll see what comes up, thanks.

 

I logged IPW and a few others today, yesterday the car didn't do it as much, but today it did it every time I let off the throttle. A little strange I think. Anyway, I found that for some reason my TPS never drops below 13%, not sure if this is normal but I've never seen it go below that since I bought the car used. In my experience though usually TPS percentages are supposed to show ~0% when completely off the throttle. So far on the log the lowest I see the IPW read is 1.26ms when the TPS reads it's lowest of 13% with a 12.495 AFR. Of course, it still reads the same IPW when the AFR slides up to 14.4 as well, so it's possible that my maf could use some rescaling? My idle trims are almost 10% off (but with the other trims within 3%), so I wonder if that adds into the equation.

 

13% TPS is normal. The scaling in EvoScan is not correct. Did you get the 1.26 ms IPW when you let off the gas while cruising?

 

Had the issue forever after my cam/head install. Bugged the heck out of me. What it ended up being is I had the throttle cable to tight on the bracket. One way to check this is on decel put your foot behind the gas pedal and lift up slightly do the AFR's go to normal lean. Thats your issue



There are two bolts behind the valve cover that hold the throttle cable to a slide bracket. I loosened them up barely slid it to the right a little and good to go.

Too loose though will effect your throttle response drastically. You'll find a happy medium if this is your issue

 

Yes, and pretty much at every other point on the log as well where I was in some type of decel situation. There are a few points though right after the throttle blip that the IPW spikes down to a flatline (22.4+AFR) before jumping back up again to the 1.26IPW.

 

Check it out yet

 

Lol, sorry...I didn't see my post jump over yours. Yeah, I've checked that already, my old Honda's were notorious for sticking throttle bodies and that used to be a quick way to check if TPS voltage was correct or the cable was too tight/sticking butterfly.

Either way it didn't make a difference, plus I just took some slack out of the cable 2 weeks ago but left enough for the plate to close fully with some deflection.