I just got done doing a stock bottom end rebuild, a CC-306 cam install (which was already in the car when the bottom end spun a rod bearing), and put some stage 2/3 Jordon Musser LT4 heads on my car. We also had a monoblade TB on it, but have since took it off. The car also has a 12-bolt, 30# SVOs, G2 intake, Madwolf PCM tune (but not tuned with the new heads/TB). The car also has a ported stock MAF, which we never had a problem with. The car is also a 6speed with a centerforce clutch.

We went to the speed shop today to pick up the car. The tech (who we know) met up with us and said it wouldn't hold an idle at all. All the speed shop did was measure pushrod length, install new pushrods and adjust the valve lash/roller rockers. The car would not drive at all with the monoblade on it, period. So we pulled the car over and installed the stock 48mm throttle body and that is it. It sounds a lot smoother, but when the car comes to a stop at like a stoplight, you have to stay on the throttle to keep the car running. Also when we were driving it home, as soon as you throw the car into 6th gear it would stall/die while cruising. We had to keep it in 4th at like 60-65mph. Sometimes the SES light would come on and when the car was running it would get smoother while driving. Sometimes coming to a stop it would die, but sometimes coming to a stop it would lope low and keep the idle around 800rpms.

Any ideas guys? Ion from madwolf said he didn't believe the tune would have a cause of this problem because everything is the same except for the heads/throttle body. Taking the Monoblade off really helped the car out. When sitting their idling with the monoblade on, the car would rev up to like 3500rpm on its own. While driving it home, on deacceleration with the 48mm my little brother would hear a slight "whistling" sound coming from the engine bay.

 

1. Since the SES light came on, why not scan it, rather than guess?

2. Is the IAC valve connected? Have you ckecked to verify it is working correctly?

3. Did you verify the valves are adjusted correctly?

4. Did you check the monoblade to verify the cable was letting the blades close completely?

5. What was done to the IAC passages when the manifold was opened up for the monoblade?

6. Please post LT1 questions on "LT1/LT4 Engine Tech". I'll move it there for you.

 

Did you have the exhaust on it?

 

any vacume leaks, is the cai on properly, is the elbow have any tears in it and getting un meatered air after the maf, that was my problem after i picked it up from a shop one day, it barely wanted to hold an idle and i found out that the bottom of the elbow wasent even on the tb correctly, as soon as i fixed it... problem was solved, check for air leaks

 

Yes. It had the Longtubes and then it ran through a y-pipe and that is it. We had to remove the catback portion because it was interferring with the driveshaft.

 

I was thinking vacuum leak also. So far, I haven't noticed any. I will check the intake tubing for proper fitment.

Should the codes, since the SES light came on and went off repeatedly, be stored in the PCM? Or does the light have to stay on constantly to get a reading?

 

The codes will remain stored even when the light goes off.