ICE888

iTrader: (19)

I have a weird problem. Ever since I put in the UTEC, I have this idleing problem. Sometimes when I let off the gas, the car drops idle to very low, almost stalling, and has a hard time correcting it self until I blip the throttle (ie lightly tap it). I dont understand why it does this. I noticed during that same time, WB looks very lean, yet some times very rich. I am just stuck. Couple times it did stall on me. How would one correct this low idle, almost stalling problem? When I first put in the UTEC, I noticed that it idled very lean, so I added 10 to 0% column through 1500 rpm and it idles now at 14.3-8 when it idles correctly. Funny thing is, if I just regularly start the car, I dont get any idle issues, but when I start to drive it and let off the throttle quickly, is when it happens.

Also, how does one tune timing correctly. What I was told before is to adjust timing to what the ECU wants to see, but how do you know what the ECU wants to see? And when you do find that out, do you just enter those numbers into the timing colums?

Thanks again!

Alfred

djmikeymike

iTrader: (1)

my car does it too....but i don't have a Utec i just have a flash.....i think it might have to do with intakes and one of these days im going to put the stock intake back on and see what happens

MalibuJack

iTrader: (5)

Its likely due to an aftermarket intake.. The UTEC's signal is delayed ever so slightly, which makes the symptom show more frequently, but it would happen on almost any car.. Another thing to check is to make sure you don't have any vacuum leaks that could throw the fuel trims off...

Imprezd

This is due to the nature of your aftermarket intake. The reason it doesn't happen when you start the car, is because the ecu always enrich's fuelling at cold start and idle. You should use a scan tool to check your long and short term fuel trims. I would guess your ecu is probably adding a lot of fuel. If you can get these two values with +/- 10 your car will be a happier vehicle all around.

This is done by add fuel in the 0 percent column, from 750 about 1500 rpms to start.

Thanks,

Jermaine~

MalibuJack

iTrader: (5)

Another thing I noticed is check your long term trims after driving at highway speed for awhile.. then adjust it so its as close to zero as possible (+/- 10%)

Then let your car sit and idle for awhile and watch the trims, you'll see them drift higher or lower.. make a note of the alteration, then you now have the information to adjust your closed loop curve (0% column) to get a really happy AFR throughout the RPM range in closed loop fueling, what this will do is keep the car from shifting rich if you've been driving the car for awhile and its mid-rpm afr is a bit lean and it trims it to richen up.. or vice versa.. Trust me, it'll help alot with drivability..

EVO8LTW

iTrader: (41)

My car did that with a mail-in Dynoflash until I added 18% fuel at 900 rpm. I anticipate having to do something similar when I install my UTEC.

PDXEvo

iTrader: (4)

I have had this same problem ever since I put the UTEC in. My idle afr's are richer then normal at 14.3 to 14.5:1 but havent really put any effort into fixing it. I have read some other areas on this forum that say its caused by the low vaccum in our cars. The only time I see it is if I start on the gas then quickly let off and give it some brakes. Since our braking system runs off the vaccum system I believe this is what is causing my issue. Especially since it seems to be more problematic in the summer time when I have the AC on.

MalibuJack

iTrader: (5)

What your describing in your last statement is the classic issue with the MAF anomoly, when you load the car up, and then cause it to suddenly bypass through the DV, it confuses the MAF sensor, the difference is most cars handle it without stalling, some aftermarket intakes, filters, DV's can disrupt the MAF enough to actually cause it to stall..

However you have to look at your MAF reading at idle.. Its something nobody can really "measure" until you put something on it like an S-AFC or the UTEC, but at idle the car normally idles around 33hz or so at 900rpm.. If you use an OBD-II scanner, you have to look at your fuel trims.. The closer you can get those fuel trims to 0, the better quality idle you'll have under those circumstances.. Sometimes the closed loop fuel curve forces corrections at higher cruise RPM's which is slightly different than the idle airflow, which means that if your cruising around and getting a normal closed loop AFR, then come to a stop, the car will swing rich because the fuel trims are now slightly rich, the trick is to alter the idle settings a bit so the trims are consistent between your cruise RPM and your idle RPM, it will then give you a stable 14.7 afr (without load on the engine like the alternator/fans kicking on or a/c compressor) The trick is to try cruising around and watch your long term fuel trims, and then idling for awhile and watch your long term fuel trims.. once you have the curves consistent, you can make wholesale adjustments to the column so that the long term fuel trims are within +/- 10% and it'll run smoothly.. when a/c or load on the engine kicks in, it may swing lean as engine demand increases, it doesnt read any additional airflow, but it will eventually adjust.

PDXEvo

iTrader: (4)

The issue I have right now with setting fuel trims is that I am using an O2 simulator so the stock ECU isnt getting a real reading from the O2 sensor. I need to put a switch in on the O2 sim so I can actually set fuel trims then flip it on when I go through DEQ. I also dont use an aftermarket intake since they seem to be more problamatic then good. Idle MAF is 27 Hz at 850 rpms.

MalibuJack

iTrader: (5)

Actually that shouldnt matter.. Fuel trims are determined by the front O2 sensor..

If you dont have a functional front O2, then you have bigger problems to deal with

27hz is fine for your idle at 850, a little on the low side, but not unusual for a modded car. Mine with the stock Maf, Buschur Intake pipe and buschur intercooler and pipes was 30hz at the same rpm.. Now (with the blowthrough MAF) I have it set "Static" at 36hz and use the 0% column cells to drop it a tad if RPM's drop below 1000..

PDXEvo

iTrader: (4)

Where is the front O2 sensor located? Ive never noticed it before.

MalibuJack

iTrader: (5)

Its on the O2 housing attached to the Turbo.. if you peek up where your downpipe bolts up to the turbo you can see it..

PDXEvo

iTrader: (4)

Well thats good news.Thanks for the info.