I have a few problems going on so I attack them seperately.
When my car is cold and I start it, it starts right up, rpms climb to around 1500 then drop off and it dies...everytime.
The only way I can keep it running is to give it a little pedal when it starts to drop.
I only have to do this for 10-15 seconds then it'll idle.
I've watched my tuner to try and see what's going on with the afr and I noticed that the time it takes to get it to idle on it's own is about the time the WB o2 sensor heats up and begins reading.
Could the stock O2 sensor be my problem or is this a coincedence?
Anybody else have cold start issues?

 

I noticed this for the first time last night. It recently started getting cold here and I'm thinking it has something to do with the cold temps.

 

myne does that as well sometimes.


ERIK

 

I got the same problem with cams (272)

 

I put 17deg of advance and +7% fuel at idle and it's much smoother.
I found out something in the process. I had my palm logger hooked up. When I start the car without touching the pedal it starts in openloop fueling. It runs very lean (24:1 or more) and stumbles, if the ac or fans come on it dies.
If I rev it once or twice it will switch back to closedloop and idle fine at 14.7:1.
What could cause this? What can I do about it?

 

Anybody?

 

Yes, what your describing is the open loop cold start function, basically since its running open loop, the values in your 0% column are used, if its too rich, or too lean, you'll have to add or remove fuel accordingly.. Plus you may have to play with the ignition timing slightly.

This is perfectly normal, in fact in very cold weather, the car may run open loop for quite some time until the coolant levels start rising, and the O2 sensor warms up enough to function.

This is one of those "Weird" situations, in order to adjust open loop idle it needs to stay in open loop for as long as it takes for you to adjust it therefore you need to force it into open loop operation, I did it by disconnecting the front O2 sensor, but you'd have to clear the CEL later after your done..

 

Thanks alot, this is what I was looking for.
So do I have to use OLF to adjust the idle afr?
I've already adjusted my fuel and timing in the standard maps, (I just started adjusting my UTEC and haven't went to OLF yet).

 

Well, OLF for the ECU, and OLF for the rev 1.7 UTEC are two different things, but you can assume they both are generally active at the same time..

Therefore, you use your 0% column and the very low RPM's (0-1250) to compensate for all low load, low RPM conditions, if you need to force a static timing when in open loop, you would also adjust timing in that same column..

Basically it should run fairly rich when in open loop idle, if its too lean, or way too rich, you'll get a stumble when you give it throttle (a slight enrichment when the throttle is cracked to offset the sudden change in airflow, think accelerator pump on a carburetor)

Theres several ways to help your idle, with cams especially, you need to raise your idle so engine vacuum is a little higher, most of what you folks complain about with idle issues (and difficulty tuning) are due to either low engine vacuum, or alot of bypass air volume (Diverter bypass valve is open slightly at idle either due to a weak spring, or high vacuum if you have high vacuum, and a slight positive pressure in the upper intercooler pipe) It makes idle difficult to tune with a MAF sensor because differing circumstances can alter airflow simply because of air recirculating back before the turbo, or low engine vacuum.. you will swing wildly between a very rich, and very lean condition which becomes nearly impossible to tune.

Few suggestions to help your idle (Open loop or closed loop)

1) Adjust your open loop idle fuel/timing settings to get a decent idle, which is fairly rich
2) Adjust your BISS to try to get around 950rpm
3) Check your BOV/DV, make sure its not partially venting at idle, (take off the bypass hose and plug it and feel the DV to see if air is coming out.. IF it is, increase the spring pressure or adjustment slightly)
4) Decrease cam overlap if necessary, this will boost vacuum and raise the MAF readings slightly which will allow it to run more stable.
5) Check for leaks, vacuum leaks, very high vaccum, or very low vaccuum will affect quite a few vacuum controlled devices which could make getting a decent idle
6) Change your PCV valve! one of the most overlooked sources of idle problems is a leaky, stuck, or damaged PCV valve.. Most fuel systems take this "Controlled vacuum leak" into account and if its disconnected or stuck open, it could affect idle by running slightly lean, if its plugged off or blocked, it can run slightly rich.

Even things like the EGR valve can cause some troublesome and hard to trace issues.

FWIW, this is not exclusively a Flash or piggyback thing, it applies to any engine management that relies on feeback (closed loop fuel control) and/or suffers from low or high vacuum.

If you have a boost controller or other sources that rely on boost signal only, use a check valve that closes under vacuum on that line, it eliminates a potential mysterious vacuum leak that can affect idle.

 

So what happen when the car jump over to close loop? Will the adjustment to the 0% under open loop do anything when we are under close loop?

 

In closed loop you are relying on adaptive fuel trims and the O2 sensor.. What you end up setting in open loop, is a base tune that the trims will have less trouble adapting to, and shouldn't go out of scale or run out of adjustment (if you use an OBD-II logger, and see your fuel trims +/- 25% or so, your approaching a level where the closed loop system cannot adequately adjust (as mentioned in another thread)

Although I'm uncertain if the UTEC intercepts the signal and alters it for fuel injectors, or it just offsets the MAF frequency, the net value is the same..

Making your base adjustment in open loop will ultimately let the closed loop fuel control at idle to adjust correctly, trim faster, not hunt as severely, and not drop out of closed loop fueling (Resulting in a very rich or very lean idle which can cause stalling, you can hear a relay clicking when that happens if you listen closely)

 

WOah, you never fail to amaze me MalibuJack! You're the man! Thank you for the quick reply. Hopefully this thread will help owners with utec to idle their evo with aftermarket cams or whatever the case.

 

BTW, if you adjust timing in the 0% column, it should apply regardless of open loop or closed loop fueling is active at idle.. Keep that in mind since it shouldn't be necessary to adjust the timing in most circumstances, but for some, its just unavoidable that base timing (static timing with a timing light sound familiar?) needs to be altered.. since we don't have a distributor to adjust that you have very few options for adjustment, very few are mechanical and those aren't recommended anyway since it means fudging the sensor adjustments...

 

I tried to adjust my 0% fuel in OLF this morning. I watched my tuner and kept adding fuel, (I already had +7 in timing at idle). It was hard to keep running, I kept adding and adding. I ended up at +70% fuel before it would hang around 14-15:1 afr. By then it was fully warm and the afr went rich, around 11-12:1. I dropped the fuel back down to +50% and it was still rich.
I started looking into my scaling. I have 680cc injectors which my ECU is Dynoflashed for. I have 550 for stock and 680 for scaled inj, which should be correct since the stock ecu isn't referenced in OFL.
I'm wondering if I have another issue. I have suspected a bad injector for some time. It occasionally makes a very loud ticking and the engine runs rough. I have some 625CC inj coming and I'll send off my 680s for service.

I also noticd something the other day. I opened my oil cap with the engine running.I was supprized at the amount of air coming out. Not sure if it's blow-by or just the pumping of this engine. It was like haveing a hairdryer on low.

When I did a leakcheck (pressurized my system), I found a few leaks and fixed them, except the leak at the TB shaft.
Since it's at the butterfly of the TB, this could cause a vacuum leak. I don't know if the bushing is bad or if this is normal?

 

Hmm.. Don't know that its normal, however I suppose its possible, our cars don't have enough miles on them to wear out a throttleshaft bushing..

Swap your injectors and make adjustments.. Also, if your injectors are already scaled in the dynoflash, try setting the stock size to 680 and see if that helps any..

+70 offset just doesn't seem right.. either your getting really low injector duty (Maybe their not working right at very low duty cycles), or you have a major vacuum leak somewhere letting tons of unmetered air into the mix..