I have a pretty complete setup (Full-Race twinscroll 3076, HKS 280s, FIC 850's, etc) and I have been fighting a lift-off stalling problem that seems to be getting worse. Basically whenever I lift off the throttle the rpm's fall to 400 rpm or so and sometimes it catches but most often it just stalls out.

I have bumped up all of the idles to the 1000 rpm range, added timing in the lower load sites (10* - no P300 code), done repeated vacuum leak tests, changed plugs, and even futzed around with the ISC Lookup Table (tried to add some ISC to the load sites where I'm lifting off or where it tries to idle to avoid the rpm drop) but I cannot get the thing to not stall when I lift off of the throttle. It doesn't only happen when I lift off at a very high load - it also happens when I'm stopped and blip the throttle. I have some datalogs that I'll sort through tonight if it'll help but if anyone has any flashing tricks that might help out, I'd greatly appreciate it (I hope the ISC motor isn't going out but I think that's my next thing to check)

 

Have a wideband? AFR flucuates at all?

How about your fuel trims? Sounds like a injector scaling issue. The FIC's scale a bit differently than other injectors from my experience.

Also, what BOV?

 

I had a similar problem (although not as bad) when it would idle very low or stall when getting off the throttle following right after a hard accell. Somebody suggested I should clean the MAF sensor, and that fixed it for me (used MAF sensor cleaner spray from Schuck's). Not sure if it's as easy as that in your case, but can't hurt to try...

 

Forgot to mention something - this is on 110 leaded fuel. The BPV is the Tomei version of the OEM Metal Valve set to recirc.

Scaling = 750

Latencies:
4.69 - 3.624
7.03 - 2.040
9.38 - 0.960
11.72 - 0.624
14.06 - 0.336
16.41 - 0.192
18.68 - 0.096

All of the Fuel trims (low, mid, high) as well as o2 feedback trim sit at 100. The wideband does jump around quite a bit - tends to go very rich and then I let off and as it the rpm's drop down below target idle it goes pretty lean. The funny thing is at cold start it idles just fine and even as it heats up it is fine - only when I touch the throttle does it start freaking out. Going back through the log the idle tends to be a bit rich (high 12's, low 13's). I cleaned the MAF once, I'll definitely give it another run. The weird thing is that it isn't only when lifting off after hard acceleration - happens even when still and I tap the throttle.

 

i have the same problem and i went through all the parameters as you did (Idle control).

it started when i replaced the injectors so i believe it is a scaling issue and maybe BOV has something to do with it.

 

the 9v/11v/14v/16v/18v latency is less than stock, there is your problem. More importantly the 14v.

if the fuel trims and 02 feedback just sit at 0 (or 100 in evoscan) then I would also check your 02 sensor. It will never be perfectly sitting at 0 (or 100 in evoscan) no matter what. Fuel trims are there for a reason.

I find mitsulogger to be much better at logging fuel trims.

Cold start better idle makes sense since it's in open loop until warm up.

 

The trims were actually setup with Mitsulogger (on another computer). I'll D/L it and give it another shot. Do you notice the o2 feedback to move around even at idle?

The o2 sensor was replaced when the turbo kit went in - the factory one was fused into the o2 housing. The one it was replaced with is an aftermarket version with the correct plug - I'll try and get it out and swap the factory one on.

Thanks a bunch all (wanna come visit AZ razor? ).

 

Use a torch on the O2 Housing and the sensor will come out like butter...

 

Yes, it will always be constantly adjusting. Shoot for trims to be within +/- 5 or so. Any less and you will just pull your hair out and chase your tail.

 

Boy don't I know about that chasing tail thing... I got too frustrated and dropped the stockers back in...

 

The full-race crew did when installing the kit and it still wouldn't come out! I figure my impact gun at full bore should do it.

Oh, and I'd love to drop the stockers in but they don't really have the flow for 30 psi

 

Bah... give it to Javier at Full-Race and tell him I sent you to get that shiz off...

Javier and I go back in my SR20 days when I lived in Phoenix from 98-05.

Anyhoot... yeah, you may get away with the stockers for oh... about 2 seconds at 30psi... :P

 

Have you tried adjusting the ISCV values? I'd suggest bumping up the two highest temperature cells by a few clicks each.

 

I believe I have done that on one flash - I'll give it a shot though. I'm going to go out and do a log with Mitsulogger right now. If the o2 feedback is stationary I'm going to assume that the front o2 sensor is on its way out.

As an aside, this is a non-OEM sensor with the correct plug that was a LOT cheaper than the OEM one. I wonder if that had anything to do with it going out so fast (the sensor has less than 1k miles on it).

 

this sounds like a problem i had tuning a stroked GM car. The MAF was scaled for the stock displacement, but it was getting much more air at let-off/idle than before, so it would run pig rich (8:1) at idle then subsequently stall out.

We bumped up the maf scale values on his tune and it helped smooth things out. (they tune by gal/cyl v. kpa on the idle table, and lb/min v. kpa on the VE table, a bit easier to understand, IMO...)

just a shot in the dark... *shrug*

the ISCV values that are posted in the thread seem to work pretty well. you might want to try that, also.