Punchy

92 pickup manual 3.0
The truck is a manual conversion and the engine and trans from my 92 4R with 300+K mi which I put most the miles on.
Truck blew HG a little while after I got it so swapped.

This one totally eludes me as I know the 3.0 very well.
No ping or knock during hard acceleration or even lugging it but as soon as the engine is unburden or just a slight lift of the gas peddle I can hear all cylinders pinging litely.
Other then that everything works great for some miles now.

I do have a O2 gauge and its showing no lean outs at all.
Tested EGR and works fine, Also disabled and same problem.
No miss fire no backfiring.
Only parts not from 4R are the wiring harness and distributor which is in great shape compared to the old 4R distributor that had like 1/8 shaft toggle play and still ran.
Timing is between 10-12 btdc at the moment.

possibility:
Am wondering if the O2 sensor has gone a little flat and not detecting O2 as well as it should and therefore leans the engine more but does not ping during Acceleration due to open loop with more fuel being pumped in.

Opinions, Thanks.

rworegon

How old are the plugs and wires? A small crack in a vacuum hose? Dirty fuel injectors?

O2 sensor could be the issue.....some resources say they last 90,000 miles or so before become slow to respond. And, only use a Denso O2 sensor or one you pick up from the Toyota dealer. These engines often don't play nice with Bosch or other brands.

Punchy

Agree 100% with Denso.

plugs and wires are in good shape, No vacuum leaks.

The O2 sensor was the used after the previous HG blew (Only water was in the cooling system), Might have affected it.

Team420

I'd say it's 99% likely it did affect it...

That being said... what grade fuel, and where do you get it? If I go to the little 2 pump place down the road that dosent get fuel delivered very often, my motor pings, but if I get it at a bigger place that gets fuel deliveries twice a week, it dosent... Also maybe try high octane to rule that out.

Punchy

I get the cheapest gas I can find, Never had pinging what so ever except a station near Vegas that was overpriced and pinged madly.

O2 sensor on order.