Strange Spark Plug issue

[Purv-Dawg]

I've been trying to eliminate any potential causes of pinging so I changed back to the plugs that allegedly were original equipment but it barely runs, backfires, and has no power. Does anyone have any insight into this? I've asked multiple people over the last twenty five years, trying to get some insight and no one has any answers.

My vehicle is a 1989 GMC C1500 5.7l. The plugs that every cross reference tells me are original equipment are CR43TS. They do not work for my application. I spent two years trying to figure this out twenty years ago and found out by dumb luck that the problem is those plugs. Although everything I read tells me it's not the plugs. It runs just fine on R43TS and R44TS plugs but I was trying to eliminate potential causes of pinging.

The only difference I know of is that the "C" in the recommended plugs stands for commercial. That tells me nothing. I can visually see that the electrode is larger on the commercial plug but most people swear by them on these trucks.

Any insight is welcomed.

[ralmo94]

I don't have any insight, but both cr43ts and r43ts both cross to the same NGK, both appear to be projected type, same heat range. I usually get NGK copper myself for everything, that's just me.

[Purv-Dawg]

I know a lot of people get good results with NGK plugs on these trucks and they are finicky about which plugs are used. I just can't be totally sure of false knock without eliminating anything other than the original plugs. I'm going to unplug the knock sensor tomorrow and see what happens. I emailed ACDelco and asked them for insight but I'm doubtful they will have any.

[ralmo94]

If you just unplug it you will get a cel and probably retarted timing if not disabled in tune. Do you have hardware to rewrite?I didn't see elsewhere that you posted?

[Purv-Dawg]

Initially I was using the stock ecm. Now I'm using EBL II and it's significantly worse now than it was originally.

[PlayingWithTBI]

Initially I was using the stock ecm. Now I'm using EBL II and it's significantly worse now than it was originally.

Maybe a little more history would help. Have you done the normal tuneup like, cap, rotor, wires? How old is your ignition coil and distributor? What heads are you running? What is your fuel pressure? Have you done very many VE Learns yet? Maybe your SA tables aren't dialed in?

Low fuel pressure, or lack of flow, can cause lean pops. Loose exhaust or a rattling Cat can cause KCs too.

Edit: How about throwing a WBO2 on it and logging with your WUD?