For about a year now I have had this problem at idle only with it throwing the ses light on my 95' Trans Am. Idles fine, just really rich, once you give it gas it goes off. I checked on my scanmaster and the map reading was around 24-25 then went down when it would rev over 2,000. Its a built 383 with a decent size cam, ported and welded intake with a twin 58mm. Anyone tell me how to fix it? Or what the deal is?

 

At idle, the PCM looks at the MAP sensor, and if the MAP is over 68kPA (exact number seems to vary from year to year?), it sets a code. If your cam is big enough, its possible your MAP is above 68kPa at idle.

You are indicating that ScanMaster reading at idle is "24-25" I'll assume that in inches of mercury ("Hg). That would correspond to about 80-85kPa, which would indicate a fairly radical cam. In effect, its telling you its only pulling about 6"Hg vacuum at idle. Check the vlave adjustment.

 

I checked the valve adjustment seems good. I do recall it didn't do this until I put my nitrous plate on. I have a 58 mm tb, nitous outlet monoblade plate, welded and ported lt4 intake. Has a monoblade opening. What's your opinion there?

 

Shouldn't affect anything as long as there are good gaskets on both sides of the plate.

What is "welded" on the intake?

 

Ill double check the gaskets. The runners are welded up on it. Llyod Elliott did the intake.

 

Made some new throttle body gaskets with some felpro gasket material and used some copper spray on the surfaces to make sure it sealed good. Still has a see light at idle 1100rpm and goes off at 1500ish. Anymore ideas?

 

Must be the cam. Has it been tuned on a dyno, or is it a mail order tune? That can affect the vacuum at idle.