im having a little trouble with my 92 3.1 Camaro. im suspecting a vacuum leak somewhere in the car but im having a bit of trouble chasing it down. there are no obvious leaks or broken lines anywhere.

to make it short and sweet is the vacuum line running to the smog pump supposed to have a check valve on it? I can suck and blow through the line. is that normal?

 

anybody?

 

Flow on a check valve is supposed to be one way. If it's on a vacuum line, the flow will be towards the vacuum source. In this case, the intake. I doubt the check valve is causing the problem, though, unless it has a crack in it allowing outside air to get sucked into it.

Just because vacuum lines look good doesn't mean those are good. These get old, dried out, develop cracks, etc. If I suspected a vacuum leak, I'd trot on over to the local parts house and buy a variety pack of vacuum plugs to plug all the vacuum lines. The variety packs have various sizes that will fit various size vacuum ports. After I plugged all the vacuum lines, I'd reconnect these one at a time to see what happens. If you suspect a leak after all lines are plugged, get some starter fluid or WD-40 and spray it around the intake flange areas and see if anything changes. The intake could also be leaking.

Of course, after doing this exercise, nothing changes, then you have other things that are causing the problem. Exactly what is the engine doing? Also, are any trouble codes being thrown by the ECM?

 

i know a check valve only goes one way, I just wasn't sure if there was one on the smog pump or not. when I bought the car it wasn't even hooked up.
all my vacuum lines are brand new as the PO had them all hooked up wrong so I corrected it and replaced all of them. ive tried time and time again to find vacuum leaks in different way. (propane, carb cleaner, ear, etc) that's why I was thinking maybe its a defective check valve somewhere.

the car smells rich, idles low, runs good on the freeway but it bogs and wants to stall if im going lets say under 10mph. fuel pressure is good, injectors are good, the fuel pressure regulator isn't leaking. most of the parts on my car are new.
no check engine lights. (that's the part that throws me off)

 

You asked if sucking and blowing on a check valve is normal. I answered.
How old are the plugs, plug wires, rotor, and dizzy cap? Also, have you tried cleaning your throttle body and MAF sensor? Start with these. Ensure this is all good. Old ignition items can cause an engine to idle rough. You might try cleaning your EGR valve with some carb cleaner while you're at it.

 

haha I asked if it is SUPPOSED to have one. I appreciate the answer either way. i wasn't trying to step on your toes or anything.
in the 2 years ive had the car I've replaces, battery, alternator, fuel filter, intake manifold gaskets, valve stem seals, spark plugs are about 3-4 month old, wires, dizzy cap and rotor have been replaced, ignition control module, O2 sensor, CTS, and a couple other little parts I'm sure im leaving out.
the 3.1 doesn't have a MAF and when I replaced my intake gaskets I cleaned all the parts I had to pull off including the TB.

 

Lol ... I couldn't pass up an opportunity to answer the way I did.

If you are absolutely positive that your EGR is good and there are no other obvious problems, then I'd start looking at the ignition control module and pickup coil. There should be a procedure for checking those, somewhere. Also, when is the last time those injectors were cleaned?

Wait, you already said you changed out the ICM. I'd check it, again, anyway.

How many miles are on this engine?

 

If it smells rich, then it sounds like a possible air flow problem or possibly all the gas isn't getting burnt. If you are absolutely sure that it's not an electrical or fuel problem and that all injectors are clean and functional, then I'd probably want to do a compression leakdown test on each cylinder. (Different from a regular compression test.). It's possible you could have a burnt valve, blown head gasket, or rings going south.

Actually, what I'd do before a compression leakdown test would be to connect a vacuum gauge to the intake and see what it tells me. I'd check it at idle, revving it, and revving it while holding it at high RPM's. It's possible you could have a clogged exhaust, and a vacuum reading will show it. Also, if the valves or something else is/are having issues, a vacuum reading will show that, too. A compression leakdown test will confirm what the vacuum readings indicate.

 

the engine has 145,xxx miles on it. the new ICM probably has 100(not 100,000. just 100) miles on it, I haven't checked the pickup coil yet, its on my to-do list. brand new cat so I know the exhaust isn't clogged. I want to say my EGR is working correctly because im not getting any codes but im not entirely sure, it drives fine on the freeway.
there are a couple threads on here listing the same problems im having but not a single one has an answer to the problem.
I'm in the process of getting the good old California smog test. it tested high HC hence the new ICM and cat. I'm not burning any fluids I marked a line on my coolant overflow tank and it hasn't moved in months so I doubt my head gasket is leaking. the coolant and oil is clean, no over heating.
im just kinda going piece by piece checking everything. i was having this problem a while back and it kinda just went away on its own. now it started acting up again.

 

When you're on the freeway and when the engine is above idle speed, the vacuum being pulled is greater than it is at idle. Any vacuum leak will become unnoticeable. Also, if the EGR has a minor leak, it will be unnoticeable at above-idle RPM's as well. If the EGR is beginning to leak, or if some carbon deposit is intermittently making it's way around the valve seat, then it will cause the engine to not idle smooth. A totally bad EGR will make it idle rough to the point of stalling. Vacuum leaks are usually not intermittent, but a leaking EGR because of intermittent carbon deposits making their way around the seat can be intermittent. Wouldn't hurt to clean the thing with some carb cleaner and a wire brush. You're only talking the cost of a gasket to reinstall the thing. While it's out, check to ensure that a suction causes the diaphragm to open the valve. You can pull that suction with your mouth. lol. Not kidding, either. I've done it, and it works.

Usually, a "comes and goes" type problem like this could point to an electrical problem. Of course, intermittent carbon specs that are getting sucked around the EGR valve seat could cause this, too.

Only reason I mentioned a compression leak-down test was because this would be the next logical step if you were absolutely 100% sure that the problem was not electrical, not related to a fuel delivery issue, not related to injectors, or not related to the EGR valve being stuck open to some degree.

 

i will take the EGR apart and clean it again. however I have an electrical EGR so no vacuum to it. i'll see if I can get a compression test going when I can borrow the tester from my dad.

ive been able to get around this problem by giving it a bit of gas while im slowing down to bump up the idle. but I want to actually fix it rather than find a way around it.