tbi pinging

[bp71k5]

If you haven't been following my earlier threads, my issue now is that the engine pings under moderate to high engine load on 91 octane gas. No engine codes are being shown. My BLM data is now good with the higher fuel pressure according to TBIChips.

Brian at TBIchips is sending a new chip with a milder timing curve in an attempt to fix it.

Base timing is at 0.

I also want to drive this k5 1000 miles to moab in one week. If the pinging isn't gone, no moab.

Anyone have any options to get rid of my pinging if this new chip doesn't quite do it? Gas additives, fancy spark plugs, cooler thermostat, etc?

 

[dyeager535]

Need to really know engine specs. Wild stuff that I have seen though for one, is Vortec heads with the wrong plugs, and of course too high of timing.

I'm sure this has been covered ad nauseum, but can you give the basics on the motor? (compression, heads, pistons, etc) What I'm getting at is if you are running compression high enough to require 91 octane or not, in the first place.

 

[bp71k5]

What I'm getting at is if you are running compression high enough to require 91 octane or not, in the first place.

I actually don't know specifics, but 4x4High built it and it's a near stock 1971 350 with a TBI cam, iron heads.

After driving it this morning, I'm starting to wonder if I even know what pinging sounds like. Can valve train noise sound similar? The web sites I've read say it sounds like marbles rulling around in the motor. Mine sounds nothing like that. It's more like "whistling" when the engine is under load.

 

[syclonekid43]

how many miles on the motor? could be maybe the timing belt is streched and timing is not 100% cause of it

 

[dyeager535]

Pinging to me KIND OF sounds like metal tapping metal. Nothing like whistling at all.

It's not the "roar" that you get when you flip the air cleaner lid on a carbureted motor? If you are hearing pinging, you will likely see knock counts.

 

[bp71k5]

The motor is a new rebuild with almost 500 miles on it. Im still breaking it in. I did a TBI conversion to a carbed motor so I'm trying to tune it.

I do see some knock counts in the 1200rpm range when I datalog it, but the ECM doesn't report any errors with the ESC. One thing is that there is no EGR system on it which is supposed to help with knocking.

 

[dyeager535]

Any throttle at all, other than cruise, EGR has absolutely no play. If it's detecting knock, but not all the time, then its working fine. But you shouldn't see much knock being detected. A small amount to me would be acceptable.

Sounds like you're hearing something else.

 

[80 Chevy K20 4x4]

Have you done some extensive vacuum leak testing to find the "whistle sound"?

Have you put a vacuum gauge on it to see what it does at idle and at throttle openings?

 

[bp71k5]

Maybe whistle is not the right term.
The marbles description I've heard makes it sounds like there's just random popping. It does sound somewhat like very light metallic "clicking" , but it's not random at all. It gets faster as the motor turns faster and slows down when the motor does. It also only happens when I have my foot on the gas and the truck is in gear. If it's just idling in the driveway and I step on the gas the noise isn't there at any engine rpm.

The noise also goes away when I'm at freeway speed and I'm just feathering the throttle. Once I get on it, the noise comes back in any gear.

I may try and drive it up to see if Scott can confirm what it is.

 

[bp71k5]

But you shouldn't see much knock being detected. A small amount to me would be acceptable.

Do you have any guess at what would be "small"?

 

[4X4HIGH]

You should drive it up here one evening and let me drive it and see if i can figure out whats going on.

 

[4X4HIGH]

Dorian, i built this engine for Brian. It is a basic 350 chevy with a 1989 TBI cam and compression ratio is close to 9:1. I don't keep specific info on the engines i build but at the time i told Brian we needed to keep the CR as close to 9:1 as possible to avoid pinging issues and having to run premium fuel.

 

[bp71k5]

You should drive it up here one evening and let me drive it and see if i can figure out whats going on.

Are you around today\tonight?

 

[dyeager535]

You checked your flexplate for cracks or loose bolts? From what you are describing it would have to be really bad to make sounds when you describe, but it's possible. Probably replaced when the motor was put in?

Powerbraking (lightly) or climbing up a steep incline even at slow speeds usually results in flexplate noise if it's broken.

 

[bp71k5]

You checked your flexplate for cracks or loose bolts?

Manual tranny. It's not a loud noise at all. I can't even hear it when the engine gets above 2500 rpm.

I did just notice the knock sensor wire wasn't hooked up.But after connecting it, no changes. I wonder why the ECM wasn't complaining about it not being hooked up and how could I get knock counts in winaldl with it disconnected?

I'm now noticing the idle is surging up and down a little. I wonder if I somehow am missing a vacuum leak...

 

[bp71k5]

Alright so I did a nice long datalog after hooking up the knock sensor. It is picking up a single knock at 3 or 4 different points on the map but nothing else while driving even when I'm hearing what I thought was pinging. I've attached the knock and BLM numbers here. If anything it's running a little bit rich now but it's much better than before.

It does pick up a lot of knocks (200+) when I start the motor or turn it off but I'm assuming thats normal. I'm going to let Scott look at it and be the final judge.

 

[Thunder]

Flex plate bolts loose?
Was the torque convertor fully seated in the trans?
Check to see if the fuel lines are contacting the firewall anywhere. If they touch the firewall you will hear the injectors click as they open and close. the firewall metal will amplify the noise. It sounds similar to what you describe.

 

[bp71k5]

Flex plate bolts loose?
Was the torque convertor fully seated in the trans?

I don't have either of those.

The fuel lines do come in slight contact with the metal brackets in a few places. I'll have to check that too. Thanks!

 

[dyeager535]

IMO, anywhere fuel lines come in contact with ANYTHING metal, they need to be either securely clamped so there is NO movement, or they need to be covered in rubber hose (split lengthwise to go over the fuel line) THEN securely clamped down to ensure they don't move and abrade the metal.

This does apply to rubber as well, but personally, I use no more rubber line than absolutely necessary, which in my case was 0.

Another ridiculous thought (which did happen to me actually) is to ensure that all your pulleys are properly secured. A loose crank pulley will make all sorts of racket, I assume any other loose pulleys would be equally noisey.

 

[bp71k5]

IMO, anywhere fuel lines come in contact with ANYTHING metal, they need to be either securely clamped so there is NO movement

Agreed. I have a couple small metal tube clamps that are not totally tight so the metal lines can slide in and out a bit. Since I'm still messing with stuff around there I just haven't totally cinched everything down just yet.

A loose crank pulley will make all sorts of racket, I assume any other loose pulleys would be equally noisey.

Everything seems to be tight. I'd assume those would be noisy with the tranny both in gear and not right? This noise is definately related to engine load.