connect 5 volts to the O2 and the 3K hesitation is gone
 

I have been screwing with this for a long time. I have grounded everything, rewired all the injectors with 14 gage and set up a relay off the main relay to run power to the injectors and the only thing that is acceptable is connecting a 5 volt signal to the O2 going to the ECU.
Its clear if I want this "thing" to run smooth throughout all ranges a Power FC and a tune will be installed.

So what you're saying is to bypass the O2 sensor and input a 5V signal to the ECU, or just disconnect the O2 all together and do nothing else? I thought O2 sensors output a voltage between 0-1V.

when i got my car it didnt have a o2 sensor in it, i later purchased one and installed it and noticed absolutly no change in the car.

this was on stock ecu

im not quite sure what your saying?

My 3K hesitation went away completely when I installed the PowerFC.

-Max

More details, please! The stock sensor is a 0-1v setup. I'm not sure how you can put 5v into that and have it work. That's terrific that that 3k hesistation is gone! :beerchug:

Sonny

My problem started only after It came out of storage. Never had this issue before or after new engine, trans, turbos, exhaust, hoses. I'm thinking my battery isn't keeping up its charge or I've lost some ground somewhere. We'll see.

Sorry its a .5 volt or 1/2 volt input. I just did that and the problem is gone. The computer sees this and seems to feed the engine OK. I surely don't recommend it. I have a volt meeter on the 02 and a cheep engine management system tweaking the map sensor input and its doing the job well. I do run rich in some areas but I haven't trimmed other than idle ranges. I have a ported engine and with out the .5 volt input the thing was a drag to drive at night or when the fans were on. I really did add a ton of grounds and created a new circuit for the injectors, power and ground sides. It took a lot of time and didn't do a thing. As for the other post which the problem started after storage the battery would be my first thing to test/replace. I also would wonder about the injectors. They could be restricted. I think the computer leans out the system or it is a bit shaky at 3k but don't know for sure. It might be something else. I wondered about the throttle settings, where the secondary plates open. If its not adjusted correctly it may be a factor. I am a efi specialist and it's got me for now. Shit happens

What are you using to supply the .5 volt input?

Sonny

Well there it gets compacted. The basic idea is to use resistors to drop down the system voltage to attain the .5 volt. I used a old general motors computer but you could connect a number of resistors together and drop the current/volts down to where you want it to be. Since the system is not going to (Ecu) draw a load of current by design it seems to work fine.

J.S.J, did you find your hesitation was only occuring at part throttle acceleration? I'm curious, because the O2 sensor signal is supposedly disregarded at larger throttle openings.

I notice my car has a slight surge when going from 3000 to 3200 rpm with a slow steady acceleration, say at a vacuum signal of -10 inches. The vacuum will sit at -10 through 3200, then surge to -4 or so, and the car surges forward slightly, and the engine runs "smoother". All with NO change in throttle input. I'm assuming this is of course the secondaries coming on, and I thought it was because the ECU has a hiccup in the primary to primary+secondary transition, where it shuts off the primaries breifly (well, reduces duty cycle, anyway). I don't know if the O2 sensor is still calling the shots at this point, though. You are basically telling the ECU that the exhaust is at stiochiometric with the 0.5 volt input, right?

my hesitation only happens at part throttle

Id be Hesitant to try this... Sounds like a long shot + some ...

Here are the true fixes:

1. Get a Power FC.

2. Replace O2 sensor.

I talked to my buddy about this. He's the weenie behind a couple of little gadgets like the SMC 500 (Simple MAP Controller -- allows you run big injectors on the stock ECU...mainly for Hondas) and the O2SIM (allows removal of the 2nd O2 sensor on OBD2 cars).

Is there a "filtered" tach pulse signal somewhere? (ie, that feeds the tach). It'd be simpler than having to derive the RPM using individual igniter pulses. The O2 sim box that he has could very easily be modified to piggyback a 0.5 volt signal only at the hesitation point. My car has extensive additional grounding, but the 3k hesitation is still there.

Yes, I know a standalone will eliminate this, but standalones are not for everyone. I've used 2 of them (Hondata and Haltech E6K). They offer wonderful control and are perfect for more hardcore apps, but if a simple module can be made to fix this problem, that would be wonderful!

Sonny

As far as I'm concerned, the Power FC is made for everyone - UNLESS you're using a dedicated standalone like Haltech, TEC-II, MoTeC, etc.

Once you go PFC, you will *never* go back to the stock ECU. It's just plain better.

clayne: I see a PFC in my future someday, but not right now. I don't put anything in my cars unless I feel that I have a good understanding of what's going on. I tune my own cars. Having said that, I don't have the time or money right now to learn another standalone. It is true that once you've learned a couple, learning the others are easier, but honestly, I don't feel comfortable enough yet with the amount of rotary knowledge that I have.

If I could spend $50 and have this problem fixed (even if it is a bandaid), that would work in the short term. Even if it is a "black box" kind of mod (which I generally frown upon), it's interaction is minor enough that I'd be willing to experiment. Basically, we'd try to inject a 0.5 volt signal into the ECU's O2 sensor input whenever the rpms are between 2900 and 3100 and the ECU is in closed loop.

Cheers,
Sonny

Idle and WOT, IRRC....

Any way you look at it, it's still a hack and a patch for a flawed OEM EFI configuration.

Also, the hesitation should only really happen when cold. If it's all the time, the O2 sensor should be replaced.

You really do not need to know how to tune the fuel maps in a PFC in order to install the PFC. The base and mod maps are plenty adequate for a mildly modified vehicle. When it boils down to it, the PFC is safer than the stock ECU.

clayne: I think you're trying to get me divorced. ;) I will pursue a PFC someday, but I don't wanna give up hope in this 'little' fix just yet.

Sonny

I never had a 3k hesitation before the PFC...But then again maybe I was too dumb to notice...Is this something that everyone suffers from?

Not everyone with a stock ECU experiences this. I am one of them -- for the most part. It happened to me twice when I first got the car, but never again. Hell, it may have been a bad tank of gas. ;)

I believe JSJ is only telling us this for informational purposes. He didn't suggest anyone else do the same. On a side note, applying 1/2 volt to the ECU isn't going to hurt it, electrically (very high impedance input). I'd be worried about driving the O2 sensor with too much voltage though.


From what I've gathered from other threads over time:

-The smog pump changes states around this RPM range as well, depending on load.

-The stock ECU, in general, is a black box. There's nothing to indicate exactly what the box is "up to" at any given moment. It seems, all we have is empirical evidence, such as this thread. Those that have actually reverse engineered and dumped the stock ECU ROM are the only ones who would know exactly what's going on. As far as I'm aware, none of them have posted any info on it, either. ;)
The line between "open" and "closed" -loop modes is a blur, and not necessarily just for our own stock ECU. For us, at least, it seems the O2 sensor has an effect on partial acceleration; perhaps even before (relative to RPM) dithering occurs?

My point from these random thoughts is that several band-aid fixes have been prescribed, despite the fact that no one is quite sure what the cause is. I guess I'm getting tired of seeing glib answers like "Add 0000-gauge grounds!". Sure, a particular "fix" may work for some people, but obviously it hasn't helped everyone, assuming these fixes are performed properly. It seems as if there are many causes for the same set of symptoms.

I'm not trying to crap on your ideas, Sonny & JSJ. It would be useful, at least, to know if it worked for some cars.

Obviously, a "brain transplant" with a tunable PFC will fix the problem. But, like sonny pointed out, it costs a lot. What about guys like me who are happy with the car the way it is, for some minus hesitation (and minus stock AST ;))? I, for one, am not planning any power modifications.

Speaking of which, has the PFC alone w/out other mods given anybody problems with california smog? Aside from the CEL?

come awn Dood! you've been down on yourself for awhile now!?!?!?! is it cause your baby isn't at home and will be getting manhandled soon???

she'll be back, I promise ;)


oh, about the O2...unplug the danm thing. :D