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88 3.9L Pings like hell

1066 Views 3 Replies 2 Participants Last post by  toast9758
Alrighty. I've got a nasty ping that I've been fighting to hunt down for a good while now. I would just not worry about it because I've got another 3.9L motor that I plan on building for this truck, but that's for a later discussion, and I'd like to have this one last a bit longer.

Here's a general list of things I've done with the truck in relation to the motor:
  • Took off what was left of the EVAP system
  • Aftermarket headers
  • Open style air cleaner that was put on the truck by one of the 6 or 7 previous owners
  • Champion factory spark plugs
There's probably something I'm forgetting, but that's it for the most part.

In relation to the pinging issue:
- The dizzy took a crap somewhere around last year. The little metal crown/reluctor inside was just laying in the housing not connected to anything. I assume that there was supposed to be a little plastic piece to hold that attached to the dizzy. Where did it go? How did it stay running just fine for the 2 years before hand? No clue. you tell me.
Put a Carquest distributor back into just to get it back on the road again. This is when the pinging started. (I've got the initial advance dead on 8°, which is what I've read to be where it was set from factory)
- Fiddled around with with a 1 step colder heat range spark plug just to play around and see what it did. Spoiler alert: It didn't do much, if anything at all.
-
- Tossed in a spare computer I had from a previous repair that:
1. Didn't fix the pinging issue very much
2. isn't very happy when the motor's cold

I found that the pinging "gets better" when I unplug the 2-wire temp sensor on the right of the intake. I can only assume that it's the temp sensor that the computer uses to change the advance and what not. Don't get me wrong, it still pings a good bit when I give it gas, even with unplugging that sensor. The motor pings especially bad when it it's in 3rd or 4th on the highway, doing anywhere between 55 and 87 (can't decide whether the truck either has a 3 speed in it, I assume so cause the truck originally came with an 85 mph speedometer, or I lost 4th. Why do I think that? Cause I found a piece of the end of a snap-ring in the trans pan magnet about 3/4 of an inch long). Unfortunately I can't leave it unplugged cause the computer gets even more upset when motor is cold and tries to shut off on me.

Of course, I could just either keep running mid or premium in it. And I would be fine with that... If prices these days weren't so got awful. The other obvious fix is to "JuSt PuT a 318 V8 iN iT". If things don't go as planned with this new 3.9L I'm building, then yes. Maybe I will. But that's not the main plan for this truck, I've got an odd obsession with the forgotten son of the 318.

Anyways, I know I'm forgetting to mention something about the truck in relation to this, but I'll mention it later if I remember. I've got a feeling that I jsut got a crappy dizzy and getting a new one would fix my issue, butI'd like to hear some outside opinions on what on EARTH could be causing this ping. Thing's driving me up a wall and I'm heading straight for the moon at this point.
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Alrighty. I've got a nasty ping that I've been fighting to hunt down for a good while now. I would just not worry about it because I've got another 3.9L motor that I plan on building for this truck, but that's for a later discussion, and I'd like to have this one last a bit longer.

Here's a general list of things I've done with the truck in relation to the motor:
  • Took off what was left of the EVAP system
  • Aftermarket headers
  • Open style air cleaner that was put on the truck by one of the 6 or 7 previous owners
  • Champion factory spark plugs
There's probably something I'm forgetting, but that's it for the most part.

In relation to the pinging issue:
- The dizzy took a crap somewhere around last year. The little metal crown/reluctor inside was just laying in the housing not connected to anything. I assume that there was supposed to be a little plastic piece to hold that attached to the dizzy. Where did it go? How did it stay running just fine for the 2 years before hand? No clue. you tell me.
Put a Carquest distributor back into just to get it back on the road again. This is when the pinging started. (I've got the initial advance dead on 8°, which is what I've read to be where it was set from factory)
- Fiddled around with with a 1 step colder heat range spark plug just to play around and see what it did. Spoiler alert: It didn't do much, if anything at all.
-
- Tossed in a spare computer I had from a previous repair that:
1. Didn't fix the pinging issue very much
2. isn't very happy when the motor's cold

I found that the pinging "gets better" when I unplug the 2-wire temp sensor on the right of the intake. I can only assume that it's the temp sensor that the computer uses to change the advance and what not. Don't get me wrong, it still pings a good bit when I give it gas, even with unplugging that sensor. The motor pings especially bad when it it's in 3rd or 4th on the highway, doing anywhere between 55 and 87 (can't decide whether the truck either has a 3 speed in it, I assume so cause the truck originally came with an 85 mph speedometer, or I lost 4th. Why do I think that? Cause I found a piece of the end of a snap-ring in the trans pan magnet about 3/4 of an inch long). Unfortunately I can't leave it unplugged cause the computer gets even more upset when motor is cold and tries to shut off on me.

Of course, I could just either keep running mid or premium in it. And I would be fine with that... If prices these days weren't so got awful. The other obvious fix is to "JuSt PuT a 318 V8 iN iT". If things don't go as planned with this new 3.9L I'm building, then yes. Maybe I will. But that's not the main plan for this truck, I've got an odd obsession with the forgotten son of the 318.

Anyways, I know I'm forgetting to mention something about the truck in relation to this, but I'll mention it later if I remember. I've got a feeling that I jsut got a crappy dizzy and getting a new one would fix my issue, butI'd like to hear some outside opinions on what on EARTH could be causing this ping. Thing's driving me up a wall and I'm heading straight for the moon at this point.
How about checking the knock sensor and the headers may have leaned it out too much, I don't think that the 4 speed auto was available in '88 just the three speed with lock up torque converter which some people think is a fourth gear and that transmission was not computer controlled. Myself I like the 3.9 too I had an 88 with the 3.9 but mine was a 5 speed. I still have the engine but the rest is now gone.
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How about checking the knock sensor and the headers may have leaned it out too much
Did the 88 even come with a knock sensor? If it did it's news to me. I've had to change out the engine bay wiring harness a couple of times due to various issues and I've never seen anything that resembles a knock sensor
the headers may have leaned it out too much
That's what a couple of buddies of mine were thinking but even still, the pinging wasn't prominent, or even there in general, after the header installation. Still ran fine right after the headers were put on
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