Please help diagnose this problem

[Afunk]

Hey guys,

I just finished my NA-T where I swapped all the GTE electronics and manifolds and everything on to the GE block and head.

The problem is, the car hesitates at idle. The vacuum is around 11-13 @ 750 RPM so it is very low there but at around 1000-1050 RPM, the vacuum is around 18-19 which is on par. Sometimes the car will idle at 1000 because it doesn't really hesitate there and it is under ideal running conditions other than the fact that it is idling too high. Other times it wants to be where it is supposed to idle which is 750 RPM and the vacuum is non existant.

Before you say it's obviously a vacuum leak, please tell me what you think about this. I think that the TPS is off or something that is throwing the AF at idle off so vacuum is real bad but when it is out of idling range it runs perfect.

I am throwing no codes.

Thanks in advance,

Alex

 

[Supra Blues]

Check your ignition timing and that your ISC is working properly.

 

[rakkasan]

Hey guys,

I just finished my NA-T where I swapped all the GTE electronics and manifolds and everything on to the GE block and head.

The problem is, the car hesitates at idle. The vacuum is around 11-13 @ 750 RPM so it is very low there but at around 1000-1050 RPM, the vacuum is around 18-19 which is on par. Sometimes the car will idle at 1000 because it doesn't really hesitate there and it is under ideal running conditions other than the fact that it is idling too high. Other times it wants to be where it is supposed to idle which is 750 RPM and the vacuum is non existant.

Before you say it's obviously a vacuum leak, please tell me what you think about this. I think that the TPS is off or something that is throwing the AF at idle off so vacuum is real bad but when it is out of idling range it runs perfect.

I am throwing no codes.

Thanks in advance,

Alex

It is possible for the TPS to be out of calibration (although close) & not throw codes. It happened to me, but my accompanying symptom was engine surge while driving between 35-45mph. I would jump on the TPS first, then follow up with vacuum lines in needed.

 

[crf_rider]

To check for vac leak just grab a can of starter fluid as spray short bursts around the vac lines and intake manifold. Listen for any change in the idle. Dont soak your engine bay with it. That can be explosive.