F20c early limiter at 7000rpm ?

[m wirth]

I am new to ecu’s and computers so maybe someone has some helpful ideas. My F20c engine runs absolutely perfect up to about an hour of moderately fast back road driving, no vtec to scary on narrow twisties, but when there is a nice straight it comes up to 7000 rpm and goes flat, 180 temp, I have never run it up to the limiter when the vtec is working properly so I can’t compare. When the motor is just up to temp the vtec works properly. After it has cooled plugs are a perfect color the electrodes are square and there are no apparent cracks in the coils. Also maybe suggestions on proper code scanners and other proper electronic servicing tools.

Thanks

mike

[BusaNostra]

You need to warm up the engine approx 2 to 3 bar or you are limited to 7,000 rpm.

Also check the oil level.

 

Possibility your thermostat stuck open and the gauge is reading it incorrectly?

[WestTexasS2K]

M worth a brother trials rider I see.

 

Have you ever been able to get the car to go to 9k rpm? Does the vtec kick in when warm? Are you sure your tach is corretly calibrated? It is possible that it has a limp mode code in the ecu. Get the car warmed up. Then turn off the car. Remove power to the ecu. You can do this by removing the battery + terminal or disconnect Connector A on the ecu. It will be the connector with the fewest wires. Sometimes by turning the battery cutoff will not remove the power to the ecu. It depends on if the red wire on connector A is connected to battery power or thru the switch. Reconnect and then see if it will go to redline and Vtec. If not then check to make sure the blue wire with white strip on ECU connector A is in the correct location. It should be in pin 9 check picture below to see correct pin location. The drawing is from wire side view of the plug. This blue wire connected in the wrong spot will creat a limp mode issue which will limit rpm.

 

Other things that can cause limp issues are oil pressure and water temp. Water temp to high or low will keep vtec from engaging. Low oil pressure can cause vtec problems. If you are getting vtec for more than 2-3sec then you are hitting the rev limiter (that last few thousand rpms goes by fast). Your tach is off calibration. If it doesnt go into vtec it should be very obvious. It is like hitting a nitros button or powerband on a two stroke motorcycle. If you dont get vtech you have a bad vtec solenoid or a wiring issue or limp mode in the ecu. Low oil pressure can cause vtec failure too. You would most likely have something more noticable going on. Call me and I will help you get that issue resolved. 325 650 7049.

connector A 2.bmp

Edited May 16, 2011 by WestTexasS2K

[Mondo]

Mike,

I have a 2005 motor (F22 I think) and never could get the stock ECU to work properly concerning the VTEC. You should get a cheap code scanner. It will tell you all the fault codes... some won't matter (no smog pump etc..). Mine would rev all the way maybe 3-5 times and then it would cut out around 7 grand. Turn off car/battery switch, start back up, and it would do the same thing again.

Does the idle change by a few hundred rpm at times? I would remove all the trouble codes (with the scanner) and start the car. My idle went up when the VSS trouble code came on.. also any misfires. Seems the ECU couldn't read/process the speedometer signal from the transmission. Finally went with an aftermarket ECU to solve the problem.

Edited May 16, 2011 by Mondo

[WestTexasS2K]

The AEM has no limp mode so it will fix the issue. It usually is a wiring issue. I have done 5 of these and they all worked great with stock ECUs. I suspect you have a limp mode hung from the blue/white VSS signal on connector A. I bet it is plugged in the wrong spot. Removing the power will reset the ecu. Or if you have the obdII plug on your car a scan tool will reset the ecu.

There was some confusion in the factory manual as to which view of the plug was used in the drawing pin side versus wire side. My previous instruction will show the correct view.

[m wirth]

Thanks for the replies all, I will try the remedies mentioned, when I get more than one day in a row without rain. Yes it has been to 9000, ye ha, on a narrow tree lined road it's like warp drive with eye ball over load. I'm sure it has the OBD port so I will get a scanner, is it proper to leave power to the ecu always on.? that is the way mine is. Mondo is correct the way mine goes, revs all the way, I only go to 8200, several times and then after an hour or so I try to go up again and it cuts at 7000 but my idle stays constant.

thanks again, you guys are great

I will keep you informed, and yes trials is still my main vice, licking some non trials wounds and getting in shape to show the kids how it's done.

mike

[WestTexasS2K]

Just sold my GasGas 320. I hope to get another bike incrhe future my son is in a very active Boy Scouts troop so my weekends are pretty full and not enough time to ride.

[WestTexasS2K]

I bet the blue white wire is the problem. If the ecu is on all the time then it will keep all codes saved. If you hook it to the battery switch it will reset the codes when you cycle the battery. I had the same problem on my first car. It turned out that it was getting a VSS code putting int in limp mode blue/white wire should fix it.

[m wirth]

Thanks Loren, I took the ecm out and checked the wire, it was in the proper hole but it was not pushed all the way in, the connector was distorted so it was wider than the slot and not making contact with the pin, or so I think. Only got to drive it for about half an hour but when I asked for vtec it obliged. We will see on a longer hotter drive.

thank you kind sir

mike

[Sevnn]

I had similar behavior from my car. I could get into VTEC but it would randomly go into limp mode and would require a battery cut-off reset to get it running right. Loren pointed me to the blue and white wire. I checked and nothing was ever hooked up to it (my car was purchased used/built). After hooking it up I've never had the problem again.