Idle problems.

[Av8ferg]

I was hoping someone on here can help me resolve my idling problem.  

So this engine was recently brought back to life (sat for many years)  and now I’m trying to get it running properly. 

Here is what has been done up to this point,

1. New plugs and wires

2. Valve adjustment 

3. New thermal vacuum valve

4. New AFM boot

5. New PCV

6. New Oil Pump

7. New fuel injectors

8, new fuel filter

9. Cleaned and resealed fuel tank

10. Replaced ECU and fuel pump relay

So here is how the engine runs.  It starts up easily and right away with no hesitation.  Once stated and foot off throttle it idles very roughly at about 500 RPM.  Sometimes it dies unless it’s warm then it might hold the idle without me intervening.  Adjusting the idle screw has not affect of the idle.  I tried adjusting the timing by moving the dizzy.  Moving it counter clockwise kills the engine and moving it clockwise all the way helps the idle very very slightly.  Thinking I had a bad vacuum leak, I hooked my tester to the intake manifold where the brake booster connects  and while holding the idle at 800-900 using my hand on the throttle linkage I was getting about 6 psi on the vacuum.   

So I don’t know where to start this problem.   To add more suffering to my problem I also noticed I have coolant leaking from one of my freeze plugs.  Not sure how difficult this will be to fix. ?  Another odd thing I’ve noticed is sometimes when I rev up the engine I’ll hear a “ting” sound from the engine as it revs back down.  My initial thought it was then timing chain rapping off the cover or side.  I say that because when I adjusted the timing chain it recall that a similar sound as I was working in there. 

I don’t know where to even start so any advice would be appreciated.  

 

 

 

[Zed Head]

8 minutes ago, Av8ferg said:

So here is how the engine runs.  It starts up easily and right away with no hesitation.  Once stated and foot off throttle it idles very roughly at about 500 RPM.  Sometimes it dies unless it’s warm then it might hold the idle without me intervening.  Adjusting the idle screw has not affect of the idle.

 Thinking I had a bad vacuum leak, I hooked my tester to the intake manifold where the brake booster connects  and while holding the idle at 800-900 using my hand on the throttle linkage I was getting about 6 psi on the vacuum.   

Bad vacuum leak seems likely.  If the intake system and crankcase are properly sealed you can kill the engine just by closing off the idle screw.  And raise idle speed by a couple hundred RPM with a single turn.  Check the PCV hose under the intake manifold and the EGR system.  Common leak areas.  The valve cover and crankcase are connected to the intake system so even a leaking oil filler cap can cause a big leak.  Injector o-rings are another common leak area.  Spraying carb cleaner at various spots is a good way to find a leak.  Idle speed will change.  Beware though, it will eat paint.

Intake vacuum is usually measured in inches of mercury though.  Not sure what 6 psi means.

[Av8ferg]

ZH, thanks.  

Idle screw as zero affect on the idle speed.  It does nothing.   

When I put the valve cover on I didn’t use any RTV just a gasket.  I also have one broken bolt.  Broke it trying to tighten the valve cover thinking this is where the leak might be from.  

I checked the PCV hose and it seems good.  

Here’s where the needle hits at idle on my vacuum gauge. 

[Zed Head]

That's inches of vacuum, a 0 - 28 scale, in mercury (Hg).  A very low number.  Looks like a big leak somewhere.  Just stare at the engine and all of the various hoses and fittings on the intake system and the engine's crank case.  Wiggle things while it's running, squirt some carb cleaner.  You'll find something.  Post a picture and we'll mark it up with places to look.

At least it runs.  Once you get the leaks sealed up the idle screw should work.

[Av8ferg]

Thanks ZH. This pic of the engine compartment is a older than the current status but it can still help me find the spots. Of note: currently the clamp on the hose to valve cover is now on and tight and the hose to the TVV is also connected. The attached photo doesn’t have those corrections made. This is the only pic I have right now.
I’m not near the car tonight but will return in a few days. Doing my research now so when I get there I can turn to making the fixes.


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[Patcon]

What about plugging the vacuum booster line or some of these other lines to try to isolate the issue?

[Captain Obvious]

I'm in agreement with the theory of vacuum leak(s). Your vacuum at idle should be well into the double digits. Hopefully 15 in Hg or higher.

I'm also in agreement that simplifying the system to try to isolate the leak is a good idea. Pull and plug the brake booster. Pull and plug the EGR system. Pull and plug the HVAC system. Pull and plug the carbon canister system.

Carefully inspect the PCV tube on the underside of the intake manifold.

[Av8ferg]

Okay, good plan. Should I pull and plug all and the same time or one at a time? Seems like it would be easier to do all and then add one at a time back to isolate to bad line. Thoughts?


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[Captain Obvious]

Yup. All at the same time.

Plug everything you really don't need and try to isolate the issue.

[Av8ferg]

Great, thanks guys.  Once I do that I’ll report back my findings.