Engine is out of 1999 Explorer. 5.0, A/T. I built this truck by scavaging the parts from a wrecked vehicle. All new plugs and wires, after about 10K it had a bad miss but no codes. Finally tried pulling plugs and a couple no longer had the tang on the ground electrode. The parts house said I needed a cooler plug.

After about 10K it is missing again and pulling the wires off the coils one at a time while running there are two with no noticeable change and one with ever so slight a change in sound. I did not want to start pulling wires because the last time I did the ends pulled off and stayed on plug. I will pick up spare stuff tomorrow.

Just wondering, what is the best plug to use on a 1999 5.0 with 87 octane gas?
Or should I use different gas?

This is first time it has a O2 sensor code. Not sure what direction to go.
I mostly have been working on Diesels last couple years.

 

If you had an issue with the spark plug wire ends staying connected to the plugs and the wire pulling out of the terminal end, then the wires might be your problem rather than the spark plugs. You may want to go up a grade or two in quality of spark plug wires that you're using. Is there anything with this engine you're aware of that is not stock and may require a colder plug? If not, are you using the stock spark plug? I don't recall if the '99 calls for a copper or a platinum, plug, but I have used both platinum and iridium plugs and have been very happy with both. I know there are multiple folks who will caution against using platinum or iridium plugs in an engine that doesn't call from them, but I've had good experience with both. I avoid the plugs with marketing hype on special electrode geometry, etc. so I'm unable to comment on those.

Do you recall which diagnostic code in particular you were getting? There are a lot of codes related to the oxygen sensor readings and performance, but very few that actually state the sensor itself is bad. A code that an oxygen sensor is report lean or right might actually tell you quite a bit about where you should be looking for the issue with the way the engine is running, especially if you do not have a misfire diagnostic code.

-Rod

 

I will have to check when I get back but the current plugs are Motorcraft and supposed to be as listed for stock 5.0 Explorer. It is in a 1996 Ranger, using ‘99 Explorer ECM. The first set I installed as part of my swap were NGK I think. The original vehicle was actually owned shortly before I got it by a little ole lady. The dude I bought it from confessed to dropping his phone and while diving for it came up in time to hit a pole. In disassembling for swapping there was no indication it was not factory, though if it had been tinkered with the techs were very neat.

The O2 codes are P0155 “O2 sensor heater circuit Bank 1” and “P1127 Ex temp out of range O2 tests not completed”. These were not stored codes but from KOER. There were no applicable stored codes for running or drivability.

I used the scan tool to check a couple things for live data and on “Short term fuel trim Bank 1” the numbers were fluctuating between 7.0 and 14. When I clicked on “Bank 2” the meter was froze at “28.00” until I gave it a little Rev and then it was compatible as far as
the range of numbers and fluctuations.

Thanks!

 

With positive fuel trim numbers, that would suggest the ECM thinks the engine is running lean and therefore it's holding the injectors open longer to let more fuel in. What were the long term fuel trim values? It seems like you maybe should be looking for a vacuum leak, leak in the intake air tubing after the MAF sensor, or possibly and issue with the MAF sensor. Since it seems both cylinder banks are tracking each other, the issue is probably something that would effect both cylinder banks.

If this were a spark/ignition issue I'd expect a misfire code but also a negative long term fuel trim value due to unburned fuel in the exhaust looking like a rich condition.

-Rod