Hey guys! Picked up a 2008 accord V6 auto sedan with 245,000 miles a few months ago, and it has been an absolute headache with this one issue I’ve been stuck on. When driving it, it won’t accelerate past about 3500-4000 RPM. In neutral at a standstill it’ll rev freely, but when driving and flooring the throttle in any gear, it’ll get to around 3500-4000RPM and stay there until I let off the throttle and then it shifts (pretty roughly) into the next gear. At first I thought maybe a limp mode, but there are no codes at all. When I bought it, the trans fluid was extremely low (dipstick was DRY), but I filled it and it still did the same. Took it to a mechanic friend who hooked up a snap on scan tool to monitor activity while driving, and he didn’t see anything out of the norm. He thought the trans was just burnt up from being run without fluid and that it needed a new trans.

replaced the trans with a lower-mile junkyard trans (but reused most of the old sensors aside from the shift solenoids and a few other bits) and of course it’s still doing the same thing. For background, I started off thinking it was an engine issue so I made sure the VTEC solenoid screens were cleared, replaced gaskets on VTEC solenoids, changed oil, checked spark plugs and coil packs. I’m thinking it could be one of those sensors is bad, like maybe the fluid pressure sensor or the clutch pressure control switch, but I’m just sick of throwing parts and effort at it, and everyone I’ve talked to is stumped on it. Does anyone have any idea??

 

Without codes in this case, I'm not sure what is the root cause. I'd start with some basics to see how the engine and transmssion are working to start narrowing down potential causes. If you still have access to the snap on scanner, I think you can scan all the modules where there is a tree of all the modules. Let us know if any are off-line.

I'd also use the scanner to monitor short and long term fuel trims on bank 1 and bank 2 at idle and at high rpm (4 data points x 2 rpms would be 8 values). Also montior to ensure you are in closed loop when doing the test. Fuel trims will jump around a bit, so an approximate value will work, say your bank1 sensor 1 short term is 10-13, just report an approximate averat of 12. This will give you an idea of how the engine computer is managing fuel ratio.

I'd drive the car with the scanner and see if the snap-on can tell you what gear the transmission is in. I'm pretty sure this has 6 gears. When you get to 4000 rpm, see what gear the PCM thinks you are in. When the hard shift happens, see if the PCM went up a gear. You'll need an assistant to monitor the scanne or drive while you monitor the scanner.

 

I’ll get access to that scanner again in a few weeks, so I’ll try it again then. My mechanic friend was watching it and said he didn’t see anything out of the norm. The PCM was always reflecting the correct gear, even when it was stuck around 4000rpm. It read correctly in gears 1-5. That’s what made him think the trans might be shot altogether, because everything seemed normal and he said it felt like the trans was slipping. To me it feels more like a soft limiter (almost as if the car is in limp mode) but I took his word, as he’s the professional lol

I’ll check fuel trims when I have access to the scanner again, I appreciate the insight!

 

Not sure if you already got this fixed, you might want to chk to make sure air filter is not plugged ,also chk the MAFS ( mass air flow sensor )

 

I've been looking all over for someone with the same problem and would love to hear the fix to the issue if you have solved it thank you