Hey guys, I just recently finished building a f20c with inlinepro 2.4L crank, h beam rods, mahle 13.5 pistons, BC stage 3 N/A cams, supertech valvetrain and 640cc injectors, and a 700CCA bosch battery. I am on stock ecu at the moment, but I'm going to run AEM standalone, which I'm going to get next month. I decided to do the first cold start on stock ecu, as I have read cold starts with aem standalone can be a little rough. But I noticed a little issue. My car won't rev past 4krpm no matter how fast or slow i push the gas pedal. Is this normal because of the stock ecu and the mods or can it be something else? I want to sort all issues first before going to the dyno with the aem.

I will record a video this afternoon and will post it here.

Thanks!

 

Did you wait untill the car warmed up? The ecu limits the rpm untill the temp gauge reaches 3 bars.

 

Not a V-Tec 3 bar issue. Your ECM is in safe mode. It does not like a sensor input so the ECM is limiting the injector flow to allow you to safely drive it to the dealer. If you pull the OBD-II codes you can easily tell what sensor if misbehaving. You want o get any hard codes, pending codes, or freeze frame data. From you mods my educated guess is that you have an issue with one of three sensor connectors; TDC 1, TDC 2, or most likely CPK (aka Crankshaft Position). The engine computes engine speed from these reference sensors. The data is used to determine the time and amount of fuel injected. If there is a mismatch the engine self protects.

The CPK sensor is located on the fuel harness and I would clean and reseat that one first. Start at the Throttle Position Sensor as it's easy to find. It' on the throttle body on the inboard side (top connector on TB is MAP). Follow the harness back and the CPK is next in line (followed by a fork in the road with right fork heading to the starter and the left to the 4 fuel injectors). Clean, dry and reseat CPK Connector.

Beyond the injectors you hit another fork. The right fork (long) goes off to the rear of the intake manifold and has two connectors(Idle air intake and intake air temp). Stay on the left branch and the next short stub will be TDC1(2 pin); right at the next fork is TDC2 (2 pin). Clean, dry, and reseat.

Utah

 

I didn't know about the "safe mode" of the ecu I was guessig it had something to do with the crank sensor because when I was building the engine it catched some humidity, so I ordered one yesterday. I'll try reseating a couple times to see if that helps.

I have never ran the car with TPS plugged before the mods.... it gave me some revving issues. Whenever I stopped on a stop light the car would rev to like 400rpm then back up to 800-1k (Sometimes it would shut down), So I unplugged it and it ran fine. I'm going to check that out now, too, though.

P.S. the green sensor that is attached to the middle of the block under the intake manifold is broken. I have no idea what it does.

Thanks for the info, Utah.

 

Sounds like the knock sensor

 

Oh.
The owners manual doesn't tell what it is :/ Thanks. The one thing that sucks on this engine is the massive amounts of sensors and electronic inputs. At least it doesn't have 4 O2 sensors like some Mitsubishis.

 

Agree the center below mani is knock. Two wire connector, green sensor w/ black connector (red/blu). The ECM will usually bypass a bad signal by going into "fail-safe function". In this mode the car drives normally by defaulting to a factory base code. The ECM will ground out and set a MIL or pending MIL code. Most smog sensors have these factory bases which is why the pull your codes during a smog check. But timing codes are critical to prevent catastrophic failure. As such the ECM goes into "back up function " (aka fail safe or protect mode). CPK, TDC 1, TDC 2, Knock, and several others have no default as the are relative to other inputs. You need to get these squared away.........

Utah