I was playing around with a scan tool, and figured Id give it a shot attached to my 2K Accord V6 coupe.

First, the issue: Ive been battling the car not feeling right for a while now. Sometimes I give it gas, but it just feels like its not moving like it should. It will kick out of overdrive OK, but then it feels like there is nothing in 4th gear either, so it downshifts to 3rd. Sometimes after that its fine, but sometimes it REALLY doesnt go, and actually downshifts into 2nd.

Ive taken it to 2 separate Honda dealers, who seem to think its a tranny problem. They check the tranny and it checks out fine. After 2 separate opinions, I figured maybe its something else.

I also get an RPM drop when I accelerate gradually (i.e foot on pedal, pushing slowly). So I used the data logger to log what happens before, during, and after that "trigger". What Ive found is that the car goes from "closed loop" to "open loop (dri)" right around the trigger. At the same time, the "load value" goes from 30% to 12%, RPMs drop (of course), speed drops, and TPS goes from 17% to 9%.

Does this indicate anything? Eventually the RPM drop stops and the car "recovers" (load value actually starts at 60 at that point, speed starts going up, but RPMs end up higher than they were to start at the exact same speed).

Really weird stuff. The only things that I can guess are possibly an O2 sensor (should the car go into Open Loop during acceleration? I wasnt WOT-ing it, and I was only doing 55 mph), and/or the Throttle Position Sensor is bad (why go from 17% to 9% when I push the throttle down more? I dunno).

If anyone is overly curious and wants to help out, I can send a fully copy of the data in Excel.

Thanks in advance!!!
-Chris

 

I'll read the post again when I'm not tired, but I'm guessing general electrical problems... bad ground, maybe.

 

Wow that is really weird. Interesting problem though. I don't think it would be an O2 sensor though becuase the O2 sensor doesn't determine if it is in closed loop or open loop. Usually that is determined by the temp of the engine. So my question is what is the trigger for that the VSS sensor the TPS sensor or some combination of information? Your accord should have a separate computer for the transmission? If so maybe find out what sensors it uses for input and do a check of those sensors. Don't know but let us know what it is if you figure it out.

 

The only thing Ive been able to come up with about the open/closed loop thing is that Hondas (and maybe many other cars, nowadays) go into Open Loop mode A) when the engine is cold (we know about that) and B) when the engine is at WOT. I would have to assume that the TPS is responsible for telling the computer that its at WOT. Obviously, at 9% (or even 17%), we arent at WOT, so it shouldnt be going into Open Loop because of that. What I find odd, though, is the "(dri)" after the Open Loop. Does that stand for "Drive"? If so, is it possible it goes into open loop during conditions other than WOT? My guess is no.

If I remember correctly, the engine was warm. The scanner said coolant temp was 177 degrees. Is that warm enough? I think it is, but I could be wrong.

Now, what I understand about open loop is that it is sometimes used as a "limp home" method. Is it possible that the ECU is putting my car into "limp home mode" for no good reason?

Ive found a test for the TPS, just havent gotten the time to go out there and try it. Wonder if thats the source of the issue. I will also be changing my plugs during that time too, to see if that helps any (perhaps Im getting an ignition glitch from one of the plugs).

-Chris