Hey guys,

I just purchased a 85 IROC, it has a fully built 350 and I am having some idle trouble with it. The car also has a manual transmission FYI.

When the car is up to temp, and I hit the clutch or come to a red light, the rpms will drop to about 500 then spike up to 1500 then drop back down to 500, sometimes it will stall out and sometimes not.

There is also a switch on the dash for the rad fan, if I turn the fan on at idle, it will always kill the engine.

I thought it may be the IAC or TPS, or a dirty throttle body. I haven't checked anything out yet. I was wondering if anyone had any guidance on how i could troubleshoot it?

 

Clean the TB and check for vacuum leaks. Iac and tps are a good place to start. I would also look at the O2 sensors too. Sounds like since it is only after it warms up it is a closed loop issue. The O2 voltages should also give you some insight on what the mixture is doing.

 

I would second the previous posters suggestion. From the fan perspective, sounds like its switched direct w/no relays......switching that on shouldn't put that muh od a load on the system.

 

Hey, thanks for the reply's greatly appreciated.

So all I have done so far is clean out the throttle body with a shop towel and increase the throttle setting 1/4 of a turn. I haven't had any issue with stalling at a stop even with the rad fan on but the idle is too high now, around 1200 RPM. I only had a chance to drive it a couple times before I had to put it in storage for the winter (Winnipeg, Canada) so I didn't adjust the throttle cable back 1/4 turn to see if it was just a dirty throttle body.

When I get the car back on the road from winter storage, I will re-adjust the throttle cable back to where it was and see if that makes a difference with the idle without stalling, fingers are crossed.

Another problem I am having is that the previous owner installed a high volume oil pump and the car is leaking very small amounts of oil after driving it. I believe the issue is that the oil pressure is waaaay to high, the pressure gauge it basically maxed out. The previous owner also told me that if the car was driven really hard, it would push oil out (not really sure where, and I can't tell where it's coming from). Anyways, the prev. owner told me he had planned on converting the valve cover breather to a PCV valve.

Does anyone know if converting oil breathers to PCV will reduce the oil pressure, or is this even possible to do with a 350 TPI engine...and if it is possible, how would I do it? I will post this on a new thread because I am guessing no one will see this post, thanks in advance for the advice and guidance.

Cheers,
Mike

 

Oil pressure is internal and isn't going to cause an external oil leak, but a poorly vented crankcase will. Hook up a PCV valve to one valve cover, and leave a breather in the other. Doing this will have the PCV sucking out crankcase pressures, instead of it blowing out naturally on its own. Some people view the PCV as an unwanted emissions item instead of something that's actually good for the engine to have.

 

Thanks, I will try that in the spring. Does it matter if it's the left or right side breather converted to PCV?

Sorry for asking this, but I just don't know the answer; can I get a PCV valve push in contraption (kind of like the breather) and where would I hook the line up to with the TPI, somewhere around the throttle body or does there need to be a hole drilled somewhere (I hope not) and this is an easy conversion?

 

Doesn't matter which side is to what. Yes you can get a push in PCV/breather combo, I have one on my engine that I got at the parts store. Yours originally had a PCV valve in the drivers side valve cover and the hose connected to manifold vacuum on the intake manifold somewhere between the two sets of runners. The passenger side valve cover had a vent tube but I would have to cheat and look up a vacuum schematic to see where it went. But you can use a push in breather instead if you prefer.

 

That would be me,,, dirty blow by air can stay out of my nice clean intake.


"Fully built" is not a spec, if there is modds done to the motor that have not tuned into the ECM then you will never get it to idle right. Any idea what year the motor and fuel injection came from? The 350 TPI was not offered in the 85.

If this was a stock engine the first thing I would check was the IAC port and the IAC itself for carbon build up. The ports can be blocked up and really slow down how fast the IAC moves. This will cause an over reactions (RPMs up and down). Also the IAC itself can slow down with age and cause the same issue. It is real easy to see with a scan tool. The ECM tries to speed up the RPMs but the RPMs don't rise for several seconds. Also a leaking EGR valve can send the RPMs up and down but on higher miles cars there are a lot of things that can do it.