Dealing with a high idle and light miss at lower rpm just bought the car has new Iac,fuel pump and injectors previous owner converted to 700r4 trans plug is under car vss is hooked up I unplugged egr vac line and idle dropped also the fans only work if I unplug mass air and set the light once it gets hot car won't start back until cool any help would be appreciated.

 

Year of car?

Do you have the ability to data log the PCM? It would be useful to see how the IAC “counts” respond to the high idle speed. Have you scanned the PCM for codes?

https://www.camaroz28.com/forums/com...95-lt1-874306/

There’s also a version for OBD-2.

What is the idle RPM with the EGR vacuum line still connected - in gear and in neutral? What does the idle drop to (in gear and in neutral) when you disconnect the EGR vacuum line? The word “high” means different things to different people.

What numerical temperature are you calling “hot”? Need numbers. Fans turn on at 226°F, and upgrade at 235°F. How they turn on depends on the year of the car and how many fan control relays it has.

Has any tuning been done to eliminate the 4L60E in the tune?

 

Car is a 95 z28 not sure if it's been tuned to eliminate the 4l60e it idles about 1800 rpm in neutral 900 in gear fans don't come on at all it will go past halfway on temp gauge still trying to locate a way to scan it when I pulled the vac line off egr yesterday idle dropped to 850 in park I've had the car for about 3 weeks so not sure what's all been done

 

Also need to mention that sometimes I hear a whistle sound the the air filter it kinda comes and goes there's no vacum to egr at any engine speed

 

Halfway (mid-point) on the coolant temp gauge is clearly marked as 210°F. The fans do not run at that temperature. Both fans turn on at low speed when the temperature reaches 226°F.

There should be vacuum at the EGR vacuum solenoid at all times. There will only be vacuum at the EGR valve itself when the PCM activates the EGR vacuum solenoid. Not sure what you mean by “no vacuum to EGR at engine speed”. The EGR system is not activated at idle. It is not used at WOT. Not used above ~3,500 RPM. EGR is only used when lugging the engine at low RPM - accelerating in the wrong gear, accelerating uphill. And when is does operate it isn’t switched fully on. The PCM “pulse width modulates” the vacuum, so the EGR valve only opens somewhere between 10% and 100%.

What EGR vacuum line did you disconnect that caused the RPM to drop? That’s just the opposite than what happens when you open a vacuum connection and allow more air into the intake manifold.

http://shbox.com/1/egr1.jpg

Fully warmed up engine, should idle at 650 RPM in neutral, 550 RPM in gear. Either the IAC valve is stuck open (yes, it's new, but what about the wiring?), the throttle blades are sticking open, or there’s a huge vacuum leak.

Is the SES light on?

 

No ses light went out with new iac temp has gotten close to the top of gauge still no fans and if I shut it off it won't start back until its cooled

 

Throttle blades seem fine

 

Little update found the pcv elbow below throttle body has a crack in it.

 

There is no diagnostic code for the IAC in OBD-1. No feedback to the PCM as to whether the IAC is working or not. If the SES light went out it’s just a coincidence. The IAC diagnostic codes were added in OBD-2, in 1996 models.

Cracked PCV elbow below the throttle body would be a signifivpcant vacuum leak.

 

I'm hoping the pcv was the problem got a new elbow and ect sensor ill update tomorrow.

 

I also noticed is there supposed to be a pcv valve on passenger valve cover?

 

No. The PCV valve is on the driver side of the intake manifold:

http://shbox.com/1/pcv.jpg

http://shbox.com/1/pcv_pipe.jpg

The line to the passenger side valve cover supplies clean, filtered, MAF measured air from the throttle body. That air is pulled through the crankcase by vacuum from the PCV valve, to remove the combustion gasses that get past the rings.

If you have excessive piston ring blowby, more than the PCV valve can handle, pressure can build in the crankcase, and the blowby vents through the line at the passenger side valve cover. Usually entrains oil mist, that ends up in a chamber on top of the throttle body, then drips into the incoming air flow, crudding up the throttle body and intake manifold.

 

Yeah someone has put a pcv valve there I'm assuming it's a plastic elbow that goes there.

 

Correct. There is a black plastic 90° elbow that pushes into the grommet in the valve cover (not real tight), and pushes into the hose from the throttle body. The PCV valve pushes into a grommet on the driver side of the intake manifold, as shown in the top link in post #11.

While the PCV valve inserts into the side of the intake manifold, it is not exposed to the intake manifold plenum. There is a sheet metal baffle on the bottom of the intake manifold, to keep hot oil off the bottom of the intake. There are holes in the baffle that allow the crankcase vapor to flow upward into small holes in the bottom of the intake, that are routed through an isolated passage into the inlet of the PCV valve.

 

I drove it still Has high idle around 1800rpm and misfiring