Well I fired the new motor for the first time last night and it would only run with the throttle almost all the way open. It won't stay running without WOT or come close to idle.

What should I try???

 

Check timing to minimum of 6 degrees, set the TPS and IAC.

Try adjusting your fuel pressure up a little at a time.

Someone else may have better ideas

 

Thanks, I was thinking about the fuel pressure ... how do I set the IAC???

 

If it doesn't want to idle, it's just probably tuning issues. You may have to adjust your throttle plate open more, if you've recently done mods. You can look at your iac counts. If there over 50, open your throttle plate more. If your iac motor is working, make sure it's not lean at idle. If you adjust your throttle plate open more, you need to recheck your tps voltage.

 

It won't start or stay running unless the throttle is almost fully open, then it won't rev either.

How do I set the IAC and throttle blade?

 

There is a "how to" for setting the TPS and IAC in the C-4 Tech section done by Lars.

 

Are you SURE that the TB blades are even moving? In other words have you pulled off the bellow, with the motor off, had someone look inside and you press the gas to the floor. This should put the blades perfectly horizontal(fully open). My bet is at 100% throttle your blades are just barely opening. Otherwise when you started it, it would have probably went to 5000+ RPM.

Its not unlikely that you will have to give it some gas on the initial startup to get it to go. What people do not always see is by giving it "gas" your actually giving it air. Most of the time with larger injectors, there is tooo much fuel being delivered at startup for the engine to effectively start up. On all my chips I usually remove fuel at startup to assist in this.

As said above, MAKE sure your IAC and TPS are set CORRECTLY. I always shoot for about 20 count on the IAC for idle to begin with, then back it down to 0 counts from there. I have written many things on this, but in the nutshell, what its doing is at 20 counts, the IAC has some control over idle. With our larger cams etc, the IAC tends to"hunt" for the set RPM. WHen you take it just down to where the IAC hits zero, that eliminates the IAC from controlling the idle speed this sends all the air through the TB blades. And the idle will be nice and steady. The key here is just to hit zero barely on a warm motor. That way when needed, the IAC can open and still alter the idle. If you go too far open with the TB blades, then you essentially eliminate the IAC having any control. Not the best scenerio. If your just getting started a IAC count of 5-8 is proabably best to start with. Then SLOWLY back it back down till it just zeros. You will see a HUGE improvement in idle quality.

Also after getting the zero counts on the IAC, then go back and make sure the TPS is at .054 Volts.

This is probably the #1 thing people have wrong on their cars and causes them to have idle problems. This is why on the stock TBs, the adjustment screw is blocked off. GM knew they would probably have all sorts of people with claims of bad idle if that screw was easy to tinker with.

Just think of the IAC as a controlled intake leak. Under all normal idle conditions it should be shut. zero counts. That means warm motor, no A/C on, no accessories, good charged battery, etc. Only when needed should the IAC open a little to raise the RPMs.

Hope this helps you out.
:cheers:

 

It sounds like your problems are much more severe than adjusting the TPS or IAC. Sounds to me that it's deprived of fuel, air, compression or the spark timing is completely outa whack. Make sure the TB is opening as jesse mentioned. Make sure you have FP at the fuel rail.....since you have a mini ram it's easy enough to pop up the injectors and see if they are firing fuel. Then if you have air and fuel...check to ensure you have compression....maybe your valves are too tight. If you have compression, air and fuel, then your spark timing is whacked out. Recheck the timing and firing order. Good luck

 

I had a similar problem and found that my distributor was off one tooth!

 

Thanks for all your help!!!

I'll try those things and see where it takes me :D

 

*UPDATE*

Fuel pressure is 43 psi ... so I'm going to check timing now. Any more ideas???

 

Without being there, my best guess would be timing is out of phase, second guess would be valves too tight.

 

Ralph is right. It's not a throttle blade adjustment, or tps adjustment. If it won't rev up at all... you have the timing way off, tight valves, or some sort of other problem. Is it smoking or backfiring? Have you double checked the firing order. It's kind of hard to say without being there.

 

My nearly stock L98 did EXACTLY the same thing that you are describing just after I washed my engine. The throttle position sensor got wet and was reading 4 volts (near wot) at all times. It ran like crap until you revved it up to match the airflow to the fuel flow. You may have a bad TPS. Make sure that the voltage goes smoothly from .54V to 4.5V without any jumps or anything.