reving problem!! have any ideas??

[blackonblack]

i just swapped in a dohc into my 89 240 and evrythings all good...but i just started noticing that it idles kinda rough and when the car heats up to operating temp it hits a rev limiter at like 3000 rpm...anyone have an idea what it could be?? thanks

[Eikon]

3000 rpm's is usually the magic number for MAF problems.

You might want to check your wiring or test with another maf.

[blackonblack]

ur good! i cleaned off the connector and stuff on my maf and now no more rev limit but it still runs REEEEEEEEAL rich and idles a bit roungh and i have a new 02 sensor i just put on...also the car has no egr or any emissions stuf...could that be the running rich problem? should i try a new maf?

[Eikon]

If your idle is still rough and you are running rich.. you might want to try checking for vacuum leaks.

If you can rev over 3k rpms.. your maf should be fine now. just to be safe however, you might want to make sure the wiring to the maf is shielded properly.

Is the TPS sensor hooked up and working? How about the IACV?

[blackonblack]

iacv is good but im not so sure about the tps...wen i unplug it nothing changes and also wen i unplug the new 02 sensor nothing changes...and wen i take the fuel pump fuse out the car revs up and stays up and takes like 5 minutes to cut off

[rogoman]

How did you do the DOHC install? Here are the steps that need to be performed:

-The accelerator cable needs to be changed. The sohc cable is shorter and doesn't have enough travel.

-The power steering lines need to be changed over.

-The tachometer will need to be changed out to a dohc s13 unit. the signal is different between the two. The tach can be removed from the cluster, or the whole cluster can be changed.

-The dash gauge water temperature sensor from the SOHC engine needs to be used. For some reason the resistance is different. If you use the stock sensor from the DOHC engine, it will register on the gauge as being higher than with the SOHC unit.

-Go ahead and remove the coil assembly from the car. the SOHC one won't work on the DOHC engine.

-The engine wiring harness and ECU will need to be replaced with one for the DOHC engine. The dash connector will need to be cut off the SOHC engine harness (where it meets the dash harness), and soldered to the DOHC engine harness in the same location. There will be wires that are left floating so don't worry. All the wires that need to be connected will be color matched. For example: just put red to red, and white to white, ect.

-The mafs from the DOHC car will need to be used. the SOHC mafs won't work with the DOHC ECU.

-The s13 ps pump has to have s13 ps lines.

[blackonblack]

i followed all the steps and im just running really rich and i need to tune it up...its running real rich making the idle rough and bogging when i floor it

[rogoman]

Check the ECTS which may be bad.

[blackonblack]

i tried that it stil runs rich with the new one...im kinda lost

[carman50]

i have an 89 nissan 240sx and i would like to bypass or disconnect the rev limiter how do i go about this

[Eikon]

why do you want to do this?

Your rev limited is there for a good reason.

You need to buy an electrical module designed specifically for that task. Search the NICO forums for the answer. Or check ebay for something.

But, please be careful... if you miss a shift, you could destroy your engine!

[rogoman]

i tried that it stil runs rich with the new one...im kinda lost

You may have leaking fuel injectors. To test them, unbolt the fuel rail from the intake manifold and pull off the entire assembly. Keep the fuel hoses still connected and don't remove any individual injectors. Also keep the electrical connectors on the injectors. With the assembly now away from the intake, turn the ignition key to the run position WITHOUT STARTING THE ENGINE. Now observe each injector to look for leaks. There should be no drips.

Make sure you have at least 4 spare insulator rings for the injectors in case some are damaged during rail removal.