yet another pinging 360

[SVO42]

I looked through some old posts about it, as well as the article in the tech section. My problem seems a little odd. The 360 in my Wag is stock, and I'm assuming never rebuilt, with 148K miles, recently rebuilt 2150 carb, and K&N filter.

I've mainly been driving it around town, with a little highway driving, and haven't had a problem with detonation using 87 octane. My girlfriend and I took a trip last weekend, and it started pinging when going uphill under load. I figured it was just because it was loaded down, so I used 91 octane and the ping went away.

After getting back and filling it up again with 87, it's still pinging around town (always under load, like uphill acceleration) on 87. It wasn't doing this before. I know the likely candidates are bad/leaky vacuum lines, EGR valve, CTOs, and worn distributor advance springs. What is the most likely candidate for it to start doing this so suddenly? I don't have a lot of time and money to just start throwing parts at it.

FYI, last I checked (about a month ago), the vac lines were all good and hooked up properly, with the exception of not having the charcoal canister lines hooked up since I'm waiting on a new can. I have the purge signal line plugged, and the vapor line near the PCV valve plugged. The bowl vent and tank lines are still hooked to the can.

Thoughts, guys? This sucks since my SVO is overheating (or has a bad gauge-planning to work on both of these this weekend).

[brad_fsj10]

Could be carbon on the valve plunger. Pull it and make sure the plunger is seating properly.

Also, I once had a Cherokee WT that had a starter bolt that would loosen up. The loose bolt would allow the teeth of the starter to vibrate against the TC flywheel teeth. It sounded EXACTLY like spark knock pinging and usually happened under load or while going up hills. Mine turned out to have stripped threads in the tranny bolt hole.

Just a thought.

[89grand]

I've got a pinging problem too that only shows up when the weather gets hot. I'm still trying to debug the problem. So far, I have a lot of new vaccuum hoses, a new distributor, fixed a sticking heat riser, retarded timing a few degrees and nothing I've done yet has cured it. I'm running 91 octane right now which does minimize it, but something else is wrong, I shouldn't have to run 91 octance with retarded timing just to get it to stop pinging. I haven't really done anything to the EGR or the CTO's. I think that'll be my next adventure. I also run kind of hot in the summer too, not over heating, but hotter than I'd like it too, and that's even with an electric pusher fan added to it.

I don't really get all of these problems a lot of us have. I'm sure in 1989 when the original owner took off from the dealer with mine, it didn't get hot or ping. I don't know why they are doing it now.

[ June 04, 2004, 10:17 AM: Message edited by: 89grand ]

[carrotman]

I think there are only a few things that could make the engine ping. Mechanically, the timing chain could be stretched causing the cam to be retarded. Would run better at high RPM than low RPM.

If the initial timing is set correctly, I would plug the vacuum advance and see if it ran better. If it's the same, I would check the EGR. Pull the vacuum hose and plug. If it runs better, check out the hoses and CTO. If it runs the same, you may have to do like Brad said and clean out the carbon on the pintle on the bottom of the EGR.

[Ralph Rogers]

Steve, I've had the same problem too, although I don't run hot even with 110 like yesterday. Fresh water in the overflow tank is only 183.
I have noticed that it has a lot to do with where I buy gas. Trying to cheap out on prices, like it's that big of difference.
I've gone back to brand name gas and the problem is gone.
Where does your dist advance come off of? Is it straight from the carb, or does is go through all that other smog crap? Try running it straight from the carb. Could also be a bad dist.
Put the timing light on, see where it is on the pully then rev the engine and see if it moves, and where it moves to.
Ralph

[SVO42]

I did a little listening on my way to work today. The ping still only shows up near highway speed under load (going uphill), but it doesn't start until the engine's warmed up.

Except for my trip, I always get my gas at the same Phillips 66 station near my house, so I doubt it's the quality of the gas. It's right off of an interstate exit, so I know it doesn't have a chance to get old.

The ambient temperature doesn't matter. There were hotter days here before my trip and it wasn't pinging.

I had my Wag in the shop about two months ago for some work, and also had them go ahead and finish fine tuning my carb after I rebuilt it. I don't have a timing light or tachometer to really set things right, but I'm hoping to get a timing light for my birthday in a few weeks. The shop set the carb up well-it's never ran better until now. They also advanced the timing a bit, but again, since I don't have a light I don't know what it's set at. My vacuum advance comes through all of the smog CTOs and non-linear valve. I've been trying ot get it set up just like stock before I modify anything. I don't have to pass a tailpipe test, but we do have visual inspections here, so I need to keep it all. I have a feeling none of that stuff has been changed, so it might be a good idea to replace the CTOs and EGR valve anyway. I don't *think* they'll be too expensive.

Thanks for all your input, guys. Any other ideas would be great. Hopefully I'll make some progress this weekend.