AEM FIC + O2 Sensors = Stumble City??

[Cozmo]

It is entirely possible something isn't quite right. My TB is clean, my TPS is new.

I'm not sure about the MAP sensor though. Another possibility is throttle cable or the throttle plate out of adjustment I suppose.

The very light throttle problem seems to be that if I barely touch the gas (just to keep RPMs constant) I can sometimes (usually when pointed downhill) get it so that the vacuum reading on my boost gauge shows the same # as idle, and it goes nuts.

 

[angus]

Cozmo, I think your problem lies not in the FIC itself but somewhere in the car, you may have a problem that is only exaggerated by the FIC -

What you need is someone with a vantage scope (or similar) these scopes have preloaded software that contains info on the vehicle specific waveforms that are produced by all of the engine sensors (it knows what the outputs should look like) so if one (or multiple) of them deviates then you will see it.

Essentially, this tool will do what you are trying to accomplish by switching to the EMS (which BTW is going to really piss you off if you do it) - the scope will allow you to pinpoint the source of your trouble.

You need to find someone who:

A) Knows what they are doing.

and:

B) You trust and have faith in.

This way you can take your car there and get it fixed.

May the force be with you young Jedi.

 

[Cody@LoveFab]

Just food for thought and a relatively easy test.

Remove the F/IC. Replace the 440s with stock injectors. Drive around on the turbo kit, however, stay out of boost. Since your problem isn't boost related, it shouldn't be difficult to stay out of boost. Does the problem still exist? If so, than it's a mechanical or electrical problem with the car that will need to be diagnosed before the installation of the EMS.

If the problem goes away with the stock ECU/injectors than it's related to the F/IC tuning, the F/IC harness, or a combination of the two.

The next thing I recommend is to bypass the resistors in the Boomslang harness so that the ECU has full 02 sensor function. Try driving the car with the F/IC and 440's installed. If your 02 sensor map in the F/IC software was providing any extra fuel, you'll need to really pay attention and retune your primary fuel map.

Either way, a properly setup EMS is the way to go with OBD1 NSX's! Full boost control, fuel cut safety, adjustable rev limiters, the list goes on. You won't regret the EMS, you just want to be sure that the car itself is problem-free before you install the EMS.

 

[angus]

I fully agree with what Cody says, I think I did suggest this to you early on, I have done this in the past when troubleshooting vehicles.

The EMS is certainly a powerful tool for tuning and it is a benchmark in engine management, what I meant about the EMS pissing you off was that since it allows you so much flexibility (and since you love to play with your computer) you will spend the rest of your day (and nights) eternally tweaking your EMS...

 

[Cozmo]

I wouldn't need to mess with it if everything was good. Unfortunately I didn't get my stock injectors back when i got the turbo put on. I didn't know the boomslang had resistors in it.

I figured if there is something else wrong (map sensor etc) at least the EMS should make it easier to see.

The money isn't really an issue, I've already bought the EMS, and I have the tuning money set aside. Of course I don't want to waste my time and money trying to tune the car with things wrong with it.

I'm going to test the MAP sensor voltage later today. I checked all my vacuum lines just now to make sure nothing was leaking.

 

[Cozmo]

MAP sensor voltage is ok. I also cleaned the hell out of the idle air passage in the TB. I can get a few % of TPS movement before I get any vacuum from the port on the top of the TB. I don't know if that means my throttle plate is too tight or what.

I tightened up the throttle cable quite a bit too because it was way loose. From a quick test drive around the block I couldn't get the "such light throttle that it doesn't register on my boost gauge" issue to replicate. I'm not yet convinced it is fixed though.

 

[Cozmo]

I tightened up the throttle cable quite a bit too because it was way loose. From a quick test drive around the block I couldn't get the "such light throttle that it doesn't register on my boost gauge" issue to replicate. I'm not yet convinced it is fixed though.

I'm fairly certain now that I fixed this problem. I tried to cause it the entire drive home tonight and couldn't. Touching the throttle at all it now goes from -24 to -22 on my gauge no matter how slightly i push it. My throttle cable is almost as tight as it can get though because I'm almost out of threads to move it any more. I imagine it is pretty stretched out being 20 years old.

I still have some stumbling at part throttle though.

 

[Cozmo]

I managed to get my "almost no throttle hesitation" to happen on the way to work this morning. However it was down a steep hill in 2nd gear, and I had to try to make it happen. I think if I tighten up the cable a couple more threads it'll be completely gone. I could live with it the way it is now actually.

I logged some more driving too and might try adjusting my fuel map a bit more.

If i can get this working properly I probably won't use the EMS that is coming today. I can sell it for more than I paid and use that money + the tuning cash for a clutch.. woohoo.

 

[angus]

Wow.

 

[Cozmo]

Wow.

Yeah, who knew 2 tiny nuts were causing 75% of my problem.

My part throttle acceleration still isn't quite smooth though.

 

[ffffanman]

Going home to tighten my cable!
Trev

 

[angus]

Yeah, who knew 2 tiny nuts were causing 75% of my problem.

My part throttle acceleration still isn't quite smooth though.

Put the map that was originally supplied back.

 

[Cozmo]

Put the map that was originally supplied back.

I reset the ECU and tried that tune for about 3 stumbling blocks then I remembered that it is unsafe to run as it has no o2 offset map. Now that I can boost up a bit sooner and with less throttle, the chances of hitting some boost while still in closed loop are very high.

I switched back to my other latest tune and it was crappy again and I realized I'll be fighting with the fuel trims forever. The EMS is the right choice for my car, and now I have one. Worst case is I change back to the FIC if I really don't like it. I'd be out some money for tuning but I'll never know if I don't try.