I have a 1992 Chevrolet Camaro RS with the 5.0L TBI Engine and T-5 5 speed manual transmission. Here is a list of upgrades that I have done.

1. Rebuilt Engine w/ everything stock except for the following:
a. Melling MTC-1 Torquer Cam
b. March Performance Underdrive Pulllies
c. Hooker Competition Headers
d. K&N Air Filter

All of the sensors on the engine have been replaced. The computer was replaced with the a reman computer with the same GM service number. All of the Air Conditioning components were taken out of the car. There is no heater control valve and the vaccum lines are open still. They have NOT been plugged off. All of the vaccum lines have been connected to the throttle body and have been routed to all of the correct locations. The air cleaner temp sensor is ran from the throttle body to the air cleaner and the other side of the air cleaner temp sensor has been capped off. All of my wires are in the correct locations as well. All fuses are good as well.

Now that you have a complete layout of the car here is the problem.

According the the Chiltons Manual that I have the STOCK engine is only suppossed to idle at 600 rpm's. The engine is idling betweem 2000 rpm and 2500 rpm right when you start it up. I have been working on the car for over a year and just got it started today and it is timed just so it will start and run.

The original motor in the car was the bone stock motor from GM. The camshaft was a roller cam with a .350 int and .385 on the exh. The new cam is a hydraulic flat tappet cam with .420 int and .443 on the exh.

Does the cam have anything to do with it idling high???????

I need as much input as I can get. I need to have a complete checklist of what I need to check to solve the high idling problem.

Keep in mind, the car will start up and run but it has not been broken in yet and still has the cam break in oil in it.

Let me know as much info as possible.

 

When I start up my stock 91 305 TBI it idles at 2000 to 2500 when it is cold. Once warmed up a bit the idle will gradually drop down to where it should be so its probably normal if you haven't run it long enough.

It sounds like you need to address any vacuum issues and then look into tuning the computer since you changed your cam. Depending on what duration your cam is it will not be in an ideal state of tune. Your car will probably need more fuel pressure too.

 

When I start up my stock 91 305 TBI it idles at 2000 to 2500 when it is cold. Once warmed up a bit the idle will gradually drop down to where it should be so its probably normal if you haven't run it long enough.

It sounds like you need to address any vacuum issues and then look into tuning the computer since you changed your cam. Depending on what duration your cam is it will not be in an ideal state of tune. Your car will probably need more fuel pressure too.

 

I am going to call Melling and ask them about the cam that I put into it and ask them about the specific application that I have. I am going to check the intake for a vaccum leak and reseal it if needed. I know that I have to get an updated computer chip to tune the computer. Does anyone know anything about TBIchips.com????? I have heard that he is good but I don't want to waste any money if I don't have too. Also, is there anything that I could have done with the IAC sensor on the throttle body to make it be installed wrong???? I tightened it until it was snug and not overtightened. Every bit of input is very helpful.

 

Likely vacuum leak.

Visually inspect the IAC and determine if it is seating or stuck partly open.

 

2 thinks came to mind,
i had a loose prom and it idle around 2,500 with no check engine light


the other would be a vacum leak or as mentioned above the iac valve might be stuck open, remove it and pull the plug/valve outward, screw it back in.

 

The cam grind you have is an old one. Many companies make it, such as edelbrock, summit, etc. Its actually pretty good in TBI applications, provided you do some tuning. It was one of the first cams I used in my 350. Other than making the engine run rich on the stock tune, it wont have much of an impact on the idle. It sounds like you have a vacuum leak, or the throttle body or the IAC is stuck open.

It sounds like you have not broken in the cam yet. Break in the cam first, and then move onto the vacuum leaks, or whatever the issue is. With TBI, a vacuum leak will have little impact on the engine. Its no different than having the throttle open as its speed density, so its OK to run the engine briefly for break-in like that.

One thing you dont want to do is roll a lobe. So dont bother with the diags. quite yet untill its ok for the engine to actually run at idle speed.