kawi10r998cc

Got a problem I can't quite nail down...recently went forced induction and of course had it tuned with an AEM EMS. Ever since the tune I've noticed that cold starts are great, it cranks right up, idles perfect, reaches temp fine, and continues to idle fine. If I've been driving for awhile, whether "spirited" or "normal", and I shut off the engine and go to start it back up the car will run VERY lean...normally my wideband (have UEGO with the EMS and a serial datastream gauge hooked up) on a hot startup will peg out at 18.4 (which is where I assume it will not read any higher). Normal idle hovers right around 14.5-15.2 AFR but when I start it after it's already warm it goes lean. If I try to let it sit until it smooths out, it idles very rough, not cutting off but cutting out a bit. If I blip the throttle the AFR goes to a normal range, but then rises again to 18.4+ as soon as I let out. This lasts for almost a minute, then the idle AFR returns to normal. If I drive the car AFR is normal except for when I shift, then it drops straight back to 18+ AFR until the time has passed when it will idle normally. Temps when this happens are between 178-195 so startup enrichment tables should have nothing to do with it since they cut out at 158 or so and if I "enrich" the startup any at a higher temp than the mix would be rich all the time b/c the next step up for the startup enrichment table is getting into the normal running temps.
My next thought would be to raise the time for those temps on the "Start Extra Decay Table" and raise fuel compensation percentage for those temps on the "Start Extra vs Temp Table" (both under FUEL > ADVANCED FUEL > FUEL TRIMS) but that just doesn't seem like it needs to be done since the tables seem ok...here are the tables:



And here is a link to the picture in case it isn't big enough to be read here on the forum: http://i387.photobucket.com/albums/oo316/k...reencapture.jpg

I have searched and racked my brain to figure out what is causing this but I haven't found much. Only real thing I was looking into was IAT and ECT temps being incorrect as I've read the cal tables are off, but it was tuned with these cal tables and I haven't changed them so I wouldn't think that would effect it. Also, all the posts I've seen on the cal tables being 15-20 degrees F off are old and I've checked my cal tables against the newer tables and they match so maybe AEM fixed the problem? Or my tuner knew about it and fixed it before the tune. Anyway my mods are in my signature if that helps! Any suggestions would be greatly appreciated!

candymanjl

more than likely your tuner put in the coolant temp cal floating around on the AEM forums. that's not 100% right but it's closer than the default AEM settings.

do you have the built in UEGO or the external one connected to the AEM? in either case make sure it's calibrated correctly and start from there, make sure your reference isn't off.

do you have good voltage at idle? if the primary injector battery offset isn't dialed in perfect the battery voltage will mess with all kinds of stuff at idle.

kawi10r998cc

I have the built in UEGO. I just checked calibration a few days ago (unhooked sensor, O2#1 volts were at 3.93, gain was at 1.28). I'll have to check voltage at idle, haven't thought of that one, but you may have something there. I'm running the PC680MJ to save space and if it is hot under the hood the battery may not have as much voltage after having to start the engine and maybe when the engine begins to idle ok it's b/c the battery has been sufficiently charged as to be at the right voltage. Primary injector battery offset would affect idle all the time though wouldn't it? ...if it were incorrect? I think I"m going to check voltage on cold start and hot start and see if the pri inj batt offset helps...thanks!

kawi10r998cc

Ok I just compared my Batt Offset Primary Table with the table given to me with the injectors from T1 Race Development and none of the figures are exactly on par with the table given to me, but they are close and they are all for fuel pressures between 43.5psi to about 55psi. But I don't have a fuel pressure gauge so how would I go about measuring to make sure the numbers in the table are accurate?
The figures in the Batt Offset Primary Table are: 6V= 2550 7V= 2550 8V= 2550 9V= 2100 10V= 1780 11V= 1530 12V= 1360 13V= 1200 14V= 1050 15V= 940 16V= 810

On the T1R table 8V at 43.5psi fuel pressure = 2595, 10V at 50 psi fuel pressure = 1740, 12V at 50psi fuel pressure = 1360, 14V at 55psi fuel pressure = 1045, 16V at 43.5psi fuel pressure = 810

Any suggestions? I need a fuel pressure gauge don't I?

kawi10r998cc

Voltage at idle is just under 14 and stays pretty stable. I also raised the fuel compensation and time it is in effect under Start Extra Decay and Start Extra vs Temp and hot starts are not perfect but much improved. Still wanna get it pinned down though

candymanjl

voltage effects how the injector flows, that's what that table is compensating for, it was worth checking. honestly there's a so many variables it's hard to know where to start. email me your cal and I'll see if I find something wrong. candymanjl@yahoo.com

it's probably stuck in a loop, two conflicting variables working against each other. I've done that by accident with the idle, it's frustrating.

300sx

[QUOTE=kawi10r998cc,May 24 2009, 12:13 PM]Voltage at idle is just under 14 and stays pretty stable.

kawi10r998cc

Modifying the "Start Extra Decay Table" and "Start Extra vs Temp Table" (both under FUEL > ADVANCED FUEL > FUEL TRIMS) has almost entirely fixed my problem. Still needs a bit of fine tuning...I'd recommend taking a look at them 300sx...FYI I set my calibrations for those tables much higher than AEM's defaults...the temps you have to set are 156, 178, 194, 212, etc. I matched 178 to 156 on time and compensation, and decreased values by 2 climbing up higher in temp. That seemed to work. Candymanjl is taking a look at my map so if he finds anything else that may cause it I'll PM ya and let ya know so hopefully it will help you!

kawi10r998cc

Thanks for the reassurance Jeff...that's exactly why I wish I could've made it 13 hours north to have you tune my car...you've been a big help with making sure I got everything I needed to make the engine management side of my install work! I just can't believe I was right about this problem (so far)...LOL looks like I may be figuring this whole turbo thing out! Now to purchase and install a new knock sensor...mine all of a sudden started reading a flat .02V on my logs I've been running after showing normal voltage for the first few, and I already checked the connections and it's hooked up...but it's a pain to get to! It never ends

300sx

This thread gave me the motivation to play with mine a little lol.

Definatly seems alot better now. I just started my car up and watched the temp and waited for it to cross one of the breakpoints and shut it off and started it back up. Then made adjustments from there. And so on for every breakpoint.

Here's what I've got on Start Extra vs. Temp Table from 158 to 212...

20.5078125 - 19.53125 - 14.6484375 - 9.765625


And here's my Start Extra Decay Table from 158 to 212...

13.34765625 - 13.34765625 - 13.0859375 - 10.73046875




Nice to have some real EMS tech talk going on around here!