Engine Rebuilt still pinging

[heedicus]

So I have a 91 Landcruiser and I am in the process of rebuilding the engine. I got this rig from a friend with 250,000 original miles on this engine. It originally had low compression in the number 4 so we decided to rebuild it. I have had the stock engine professionally rebuilt but when I got it back and it had a strange pinging noise, i basically would ping at idle and when driving so it turns out I then had 4 point piston failure. They then took it back and rebuilt it again, we replaced the mass air flow sensor and rebuilt the fuel injection and today I drove it again for the first time the same pinging noise is back. I have not removed the engine yet (just got out of the truck) to have it checked.

My questions are.
Is this a common problem because of the old engine block itslef?

Is there another engine I could put in it that would be more powerful and reliable?

Is there any value for the old engine block.

We are in month 10 of operation fix up my cruiser and my wife is running out of patience. This is sopposed to be the daily driver for the family.
Thanks,
Tren

 

[CJF]

Have you tried running premium?

Have you tried backing off the timing? Even if it's set to spec., why not, for information purposes, see how far it needs to be backed off to stop the pinging?

Here's the one that worked for a friend with a 3FE rebuilt by Robbie (powderpig on this forum): Pry into the AFM (air flow meter) and loosen the spring a half dozen clicks or so, which makes the ECU think more air's coming in, causing it to richen up the fuel mixture. Let me know if you're interested in trying this, and I'll dig up more info. on it.

Curtis
91FJ80

 

[heedicus]

Yes,
I have ran premium no change, and I will try backing off the timing. And I am interested in the AFM idea so shoot me whatever info you think may help...
My concern is last time I heard this noise ,I ended up with 4 point piston failure. If i back off the timing and this pinging stops we can assume this time the pinging was a different issue?
Thanks,
Tren

 

[CJF]

Why does it need to be a different issue?

 

[CJF]

AFM adjustment info

Go join the 3FE Yahoo Group, and then look here:

http://autos.groups.yahoo.com/group/3FE/files/Lessons%20learned%20and%20fix%20tips/AFM%20tuning/

Also, feel free to introduce yourself to the group and to stick around; that's my other home in addition to this one. ;p

BTW, we sign off with our real names over there, as I do here.

Good luck,

Curtis

 

[ElJefe]

...
My concern is last time I heard this noise ,I ended up with 4 point piston failure.

This would concern me a little bit... OK... a lot! These engines started life as a copy of an already revered design, and then went through 30 more years of refinement and improvement by Toyota. The 3-FE may be a dog but it as close to bulletproof as an engine gets. I have a friend that has a 91 that has been happily and CONTINUOUSLY pinging for the last 270,000 miles without incident.

If you had the engine rebuilt which resulted in a cracked piston during break-in... something went DRASTICALLY wrong during the rebuild. Look at your second invoice, I have seen 2 engines that had pistons come apart while running, both needed to have that cylinder bored and sleeved. The fact that it is still making sounds that are not normal leads me to believe that the machine shop threw it back together with a bandaid over whatever they screwed up the first time.

 

[heedicus]

Ok
Thanks all for the replies, I do have a few more questions... I have some more info/
So i am having the 4 point piston failure on 2,3,4,5. does anyone know what the tolerance is sopposed to be between the piston and the sleeve? I think what could have happened was he bored it out to big and used a piston that was too small. also I have been told I have to use geniune toyota parts (pistons) is that true. I had him bore it out to 50mm and left the compression stock.
thanks for all your help.
Tren