So I posted this on my thread about my motor-truck build but recieved no answers. I think that people are just tired of seeing the thread. But I will repost this here because I really want to drive my truck.

So I am working out the issue I have been having with my truck. It wants to have a real iratic idle loaping up and down from 300-600 rpm when you let off the gas and coast, that or it dies. Also it runs rough under 2200 rpm.

New

IAC,TPS,Pcv.
No engine vacume leaks vacume is fine. Fuel pressure is fine, and all injectors are fireing fine. Fuel sync-distributor has been moved around and the problem still exsits just to a varying degree.)

The only things left to check are -

map sensor( my voltage checkd out ok and the snapon scanner did not pick up on anything-doesnt mean the vacume part of the sensor is bad tho)
engine coolant temp senosor
intake air sensor

So I will buy these as soon as I can and see what happens.

I am told my IAC count should be around 40-60 but I have no way of checking that unless I go back to the shop and hopefully there snapon scanner/computer can read this. And if its off then what buy a new one again and hope its right?
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Where are you located?

 

If your IAC counts are off the Snap on tool should be able to recalibrate it. Where you having problems like this with the original engine? I hate to see you wast money on replacing good parts.

 

Are the sensors you bought of good quality? Like not Duralast crap? And have you set or had the fuel sync reset?

 

tomorrow I am having the truck plugged into the snapon tool and hopefully they can recalibrate my IAC to 40-60 counts says hemifever. I ordered a new map senosr and that may be here tomorrow. I also installed a new engine temp sensor which didnt help. I am going to set the fuel sync tomorrow with the timing light.

And the parts that I am buying are the typical auto parts store stuff nothing out of the ordianry.

I didnt run the engine much before it was all tore apart.

 

You cant set the fuel sync with a timing light.... You need a good scanner..

 

That snap on will tell you your fuel sync, but the number will bounce a bit so you have to take an average 0 to +4 bounce is about +2, +2 to +6 bounce is +4, etc.

You'll want to set the fuel sync at 0 to rule out that as a problem. You can fool with moving it around after you found your problem.

As far as setting the IAC counts: You will need to ask Hemifever what he has programmed the target engine idle to be on the PCM. then try this to adjust the IAC counts:

remove air hat
turn on engine and warm up for about 5 min (full operating temp).
pull PCV tube off to create big vac leak, the IAC will close completely.
unplug IAC motor.
slowly reconnect PCV tube, try not to let the engine stall. Disconnect and try again if it does.
adjust idle set screw on TB to idle 125 rpms under the number hemifever gave you. This is the minimum engine idle. Get it as close as you can.
shut off engine, reconnect IAC, and reset the pcm by disconnecting the neg battery terminal and then turning the key over for about 10 sec.
reconnect the battery terminal and start the engine. Let it idle for at least 10 seconds before you touch the throttle. Take it for a test drive.

 

Fuel sync should be set with the engine spinning between 1000-1200rpms (need a constant rpm) especially with a loppy cam. That will show almost no bounce at all in the readings as long as the timing chain & gears are fresh. Last time I set mine with a snap on mt2500 it showed 0 to +1 at 1k rpms.

 

Thank you soo much guys going there right now. I know hemifever told me he likes the fuel sync at +4

 

well I went dowm to the shop and they plugged in the latest and greatest snapon diagnostic computer and everything showed fine. So after looking for a while he said do you want to set the iac to the factory settings?(counts were at 60) I said sure cant hurt anything and that did it! Runs great now!

When I get her broke in it will be bliss!

gave her 3/4 trottle at a stoplight with no brake and left dual marks all the way across all while trying to feather the gas to keep her under 4g! Nice!

Once I get 500 Mi I will change fluids and up my shift kit setting to the highest levels.