Ok guys, trying to race Sunday at info. Just got my car going from this winter. I got a built trans, and de pinned the connectors off my mil spec harness to clean some things up. Also added a fat house fab catch an. Haven't touched the tune.

So now I go to put a few miles on the trans. The car under med throttle goes completely lean around 3k, it will choke and sputter, then the computer over compensates by dumping in too much fuel and it goes straight pig rich on my web gauge.

Checked for boost leaks, none
Swapped out my cop with a known working cop, nothing
Plugs are fresh from last fall, took a look at them, nothing out of the oridinary
Checked all my wiring, all wires match according to the Evo shop manual and looking at a friends Evo.
No loose connections
Injectors just got back from fic, tested and cleaned
No cels

Any ideas what would be causing this? I drove the car in December and it had no issues, before I took the trans off and redid the harness.

I'm puzzled and am wanting to race on Sunday!

 

Cleaning the injectors changed the fueling a bit probably. It happened on my car with my old injectors. I would have your tuner take a look at it if you know everything is good. Maybe trying switching out the front O2 sensor.

 

It would be a good idea to switch out if the 02 sensor went dead or froze. Datalog the Evo as it idles to see if the Front 02 is reading.

Also there could be a missing ground or blown fuse.

 

thanks for the replies guys.

the o2 sensor is almost brand new. i replaced it last year around september. all my grounds are in the same spot they were last year. As for fuses, I guess i could look through my fuseboxes and see. I did check the ignition fuse, its good.

As for the injectors being cleaned. Ive had them cleaned multiple times with no difference in the way the car ran.

 

What trans did you have in and what trans is in it now?

 

just a basic rebuild of my old trans. evo 8 3-4 gears and all new synchros

 

Oh ok. I was going to say if the final drive or gear ration changed the load cells also changed and you would need a retune for that. At this point, get a data log and see whats not reading properly. Could be map or tps related.

Also check the ground that bolts to the trans and into the block. If the trans is painted, you may have a poor connection there.

 

Im starting to think its fuel related or something to do with a voltage issue cause the fuel to drop.

Its so consistent. At 3k rpm, my wb just shoots to lean, then after a few seconds of staying in the throttle, something goes on and it dumps the fuel in. I can hear the fuel pump high voltage relay(or whatever its called0, click. I have relocated that into the cab last year. I can hear it click, so I assume its working.

One thing I did do last night, I had the car idling and I revved it under the hood, my gauge on my fpr would rise, but then slowly fall back to idle pressure. Im not sure as to what rom I was at as I was under the hood, but to me, fuel pressure should rise as I rev the motor?? maybe cause their wasnt any real load when its just sitting?? Idk

 

No. Load is based on airflow (MAF) or manifold pressure (speed density). My car required no tuning changes when I changed the final drive

 

Gear/RPM or whatever it's called is the only table I would think would need changed. You would likely over boost some or be having to use downward correction otherwise.

 

Fuel pressure should follow manifold pressure. So connect a manifold pressure gage and see if the two coincide.

 

I was thinking the same thing. Initially it rises, but then falls a bit.

 

To know if that makes sense you need to know what manifold pressure is doing.

 

Just to update this thread. I was in the process of swapping out sensors from a buddies running evo. I just had finished swapping the map sensor which did nothing. I was in the garage revving the car in nuetral cause it stuttered just revving right around the 3300 mark.

Thats when my buddy and I heard a pretty nasty rattling/grinding sound coming from the trans. Seems like my input shaft bearing is bad. I just had the trans rebuilt by a friend who is a master tech for Acura, it was a synchrotech kit.

I am tearing the trams back out this week and were gonna take a look at it.

Im kinda hoping that the input shaft bearing noise was causing the knock sensro to freak out. Cause the noise it was making was right around the same rpm as it cutting out. I heard it before, but it was very faint, I just figured it was an exhaust sheild or something.

So Ill update this thread once the new bearings are in and the trans is back in.

 

ok, back to this issue now. So I got my reverse idler in and the noise in the trans is gone, which is good news. I am however still dealing with this fuel issue.

Basically at around 3500, no matter what load, the car goes lean for a few sec, stalls out and then fuel is dumped in and the car chokes it out and goes normal under boost.

I got into ecuflash and changed my open loop values to essentially make the car run into open loop all the time. This eliminates the front o2 correct? Thus if it was my front o2, by making it run in open loop, it would "bypass" the front o2 and run fine, if the front o2 is bad?

Well, it still goes lean at 3500, so I am assuming the front o2 is ok then?

Where else can I start looking for this?

I also checked the crank pos sensor while the car was down last week. No issues there as well.

Ive swapped out a map sensor, nothing, and an exhaust cam angle sensor, nothing.