[Zeder]

Hello,
I wonder if any of you can help. I have an 83 malibu with a 305/th350. The car is bone stock. It has 44000 original miles on it. The engine sound pretty good with the exeption of a ticking lifter. What else is new! The car has developed a pinging noise only on one cylinder while under very light load, cruising on the freeway/highway. I goes away when I put my foot into it or take my foot out of the gas. Its really weird. I have set the timing to factory specs. It does the same thing. If I advance it 4 deg no change if I advance it 8 deg from stock(4deg) it pings like crazy. If I retard it to 2 deg It still does it. I don't know what is causing it. I lubed the vac and mechanical advance inside the distributer, no change. Put new plugs in it, no change. Any ideas?
Cheers
Zeder

 

[docvette]

Grade fuel

Doc hereimp:

What grade Fuel are you running? under 91?

You should run 93 or octane boost if your getting "Ping" or rattle on load...

You may also want to drop that timing BACK to the stock 4 degrees (W/ advance disconnected and plugged. 950 rpm curb idle, 650 in drive/reverse)...Had same problem on my Vette,

(yes , it's an 80 305.. What the heck were they thinking??, must be the same engineer's that were planning a 36 hp VW variant in a Porche for the economy package huh? 0 to 60...today...sometime...well it gets good mileage anyway...)

with diesel on shut down...I assume the detonation was just below my hearing range...(Mom was right...that Rock and/or Roll will screw up your ears when ya GET OLD AND DECREPIT....) Anyways went back to about 5 degrees and it ran fine.

I run 109 boost in mine with every 1/2 fill up and it hasn't let me down yet...

Doc imp:

 

[4 Jaw Chuck]

Check your EGR for proper function.

 

[troy-curt]

Sounds like there is a little carbon buildup. Use some water and clean it out.

Troy

 

[Robinson Robin]

Check your EGR for proper function.

This was my first thought as well

 

[Simo]

Hello,
I wonder if any of you can help. I have an 83 malibu with a 305/th350. The car is bone stock. It has 44000 original miles on it. The engine sound pretty good with the exeption of a ticking lifter. What else is new! The car has developed a pinging noise only on one cylinder while under very light load, cruising on the freeway/highway. I goes away when I put my foot into it or take my foot out of the gas. Its really weird. I have set the timing to factory specs. It does the same thing. If I advance it 4 deg no change if I advance it 8 deg from stock(4deg) it pings like crazy. If I retard it to 2 deg It still does it. I don't know what is causing it. I lubed the vac and mechanical advance inside the distributer, no change. Put new plugs in it, no change. Any ideas?
Cheers
Zeder

Sounds like gudgeon or piston slap,, i
spark timing will not help iff it is what i think it is.

That one cylinder will still give you good compression but ya gonna still get free run rattle(No load rattle).

 

[Zeder]

Thanks for all the feedback!
I will try the water thing, just a couple of tablespoons right? I will also look into the EGR system too. Good idea 4Jaw! I think the repair manual I have tells me what to look for!
I will let you know what I find out!
Cheers,
Zeder

 

[troy-curt]

I use an old mustard squirt bottle Probably 1/2 cup or so.
Run the throttle by hand high enough to keep it running good and slowly dribble the water in the carburetter, it will make a lot of smoke and stink, but it works.

Troy

 

[Brian Morency]

water?
does that really work i'll go try it right now in my car. but wouldnt carb cleaner work better? or does it to the same thing? i have used carb cleaner but never water, i thought it might be bad for it.

 

[troy-curt]

It cleans the carbon buildup in the cylinders. I don't think carb. cleaner will do the same thing.

Troy

__________________
If you don't make mistakes. your not doing anything.

69 SS/RS full custom Camaro 98 ISCA Grand Champion
69 SS/RS BB Camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 SS Chevelle BB conv.fresh frame off
26 T sedan street rod

 

[Brian Morency]

oooooo ic, i'll go do that then, cant hurt. i know i prolly have some carbon buildup

ok just went and slowly dumped 1/2 cup of water down carb while running and i held the throttle to an even running speed.

my results: i didnt get smoke and it didnt smell, it stumbled a little so i cranked up on the throttle a little more, and i only heard a sucking noise while it went down the carb, so i took it for a quick drive and i didnt really notice anything but i think the smoking from the breather is gone, maybe. i didnt let the engine warm up and i think thats when it smokes but i'll find out later when i go for a longer cruse.

 

[Zeder]

Hi Guys,
4Jaw you were right EGR issue! Thanks!
Well I tried the water thing. Did not make any difference. I then removed the EGR valve from the intake manifold. I fabricated a plate out of some 1/4 aluminum I had laying around and installed it in place of the valve. It seams to solved the problem. Or at least so I thought. I took it for a few drives after setting the timing back to 4Deg(Stock setting). The car ran great! No pinging. I also had to put a new heater core in while I was dealing with this other issue. So the test drive was nice a quite and warm! I went to sleep feeling all was right again! In the morning I took my dog down to a local dogpark,10 min away. The pinging had returned. Only when I put my foot into it though. I have a big hill to drive up on the way out of the park. I thought for sure that it was going to rattle my teeth loose on the way up the hill, but it didn't. The pinging had gone away, totally! I did notice that there is a valve on the passenger exhaust manifold, well right after it, and that the vacuum line that operates it goes to one of those temperature controlled valves at the water-neck where the thermostat sits. Does this valve (exhaust manifold) have to be addressed as well now that I have removed the EGR valve? Should I bypass the temperature controlled valve or just disconnect the vacuum line to the exhaust valve? By the way, We don't have any emissions test where I live.
Thanks!

 

[docvette]

EFE

Doc here:imp:

That Valve is an EFE Valve, It's purpose in life is to close the right intake manifold off during warm up, and reduce emissions during that time.

If you have a stuck one, It would run slightly hot, or if you put the Vacuum on a different source..I think Vacuum Closes That valve, lack of it opens it...controlled by the ported thermo~vacuum switch on the manifold..

If that were the case, I'm not sure, but I think the extra heat could cause pinging issues, It would have extra hot back pressure on the engine.

Check to see it's not stuck, or operating backwards!

Another Test you could try, is block off the Vacuum advance (if so equipped) and test drive it, to see if the ping goes away.

If it does check to see if it is on a ported vacuum source, or straight manifold vacuum..

If manifold, move it to a ported source, on a Q~jet, it will be the Left front of the carb,

This will only pull on 5 in Hg ..instead of holding it advanced All the time there is Vacuum present.

You may also need to re~weight the mechanical advance too.

Another Source of "Pinging" could be the A.I.R. (if so equipped)valve (s) at the Exhaust manifolds ...

these will oscillate loudly when malfunctioning or if the diverter valve is malfunctioning .

Pull the belt of the AIR pump and test drive it to test the diverter...If it goes away, get a new diverter valve or manifold valves, (or abandon the system since you don't have Smog testing) If it changes, look at the manifold valves..

Doc imp:

 

[Zeder]

EFE
Thanks for the info DOC, All the vacuum lines are in there stock position. I haven't changed anything on this car. My wife still doesn't believe me, I have a very bad record for implementing the "MORE POWER" thing with all my vehicles! I just removed the EGR valve, put a plate where the valve used to sit, and plugged its vacuum line. I am going to try and disconnect the line to the EFE and plug it too. I just want the valve to stay open, least amount of restriction. As far as re weighting the advance, I don't think I will go that far yet. Remember it's an all stock wagon! Right down to the 2.42 posi rear end! The car does not have an air pump so I guess the AIR diverter valve thing is out . I will let you know what happens,
Zeder

 

[Loki]

put the EGR back to stock it cools the temp in the cylider and lessens the ping, also GM makes a great top engine cleaner use it as the can says to clean stuff of the valves and pistons