darkstormcr

I have a 93 DX with a D15B7. I just put this motor in, so little by little all my issues have been ironed out. My last problem is configuring the warm idle.

On cold start, the FITV pulls air before the throttle body and the IACV remains closed. The idle is around 1500 and slowly drops until the motor is warm. The FITV spring is screwed in all the way and all components were cleaned prior to reassembly.

Now, once the motor is at normal operating temp., the idle sits just over 1000. If I cover the port in the throttlle body leading to the IACV, the idle drops to optimum 650-750 range. Unfortunately that port is not supposed to be covered in normal operation.

I followed the procedure in the factory service manual to set the idle. This involves, with the motor hot, unplugging the IACV. With the IACV unplugged, the idle speed drops slightly but not a lot. The CEL turns on.

At this point, I can set the idle screw, but it is screwed all the way in and still at just over 1000. I can increase it but not decrease it.

Afterwards I turn off the car, reset the ECU and plug the IACV back in. CEL is off but idle is still the same (obviously) because the screw position did not change.

So, my question is: is my IACV bad? If not, how else can I go about lowering the idle? Do I have a small vacuum leak somewhere? Not enough vacuum somewhere?

Former User

With the engine warmed up and idling, if you put your finger over the port leading to the FITV, do you feel air flow and does the idle speed drop?

Have you cleaned the FITV and IACV?

darkstormcr

Yes

...and yes...

Former User

There should be NO air flow into the FITV port when the engine is warm. That's your problem. Clean and adjust the FITV again - click link in my signature.

darkstormcr

I'm sorry, I read that wrong. There is no air going to the FITV port, there IS air going to the IACV. The idle drops if I put my finger over the IACV port. No change if I cover the FITV port.

Former User

Given that the FITV port is not pulling any air, covering the IACV port in the TB should drop the idle speed to about 450 rpm. Since this does not happen, you have an intake air (TB or IM gasket) or vacuum hose leak.

ThatRicerDaniel

Throttle cable too tight?

Former User

This^ is another possibility that I failed to mention. There should be about 1/2" of slack in the cable.

darkstormcr

Cool, thanks for the help guys. I will look at these possiblities when I get home.

darkstormcr

Throttle cable is OK, I checked the mounting and gaskets on the TB and IM and those are OK (brand new gaskets, too). So I guess I'm searching for a vacuum hose leak. Any ideas on where to start, or how to pinpoint the source?

When I mounted the fuel rail, the studs were missing so I just bolted it in. There is a slight gap (less than 1/4 of an inch) between the rail's mounting points and the intake manifold. This was due to the bolts being too long, however the injectors are fully seated and won't go in any further. Could I have a leak at the injector seats?