[ahuf]

I replaced some extremely nasty (I'm guessing factory) spark plugs the yesterday. I did a quick startup and let it sit at idle till it warmed up to regular operating temp 200-210(normally 200).
Today I go to take it out with my son and it has an extremely low idle jumps about 50-200rpms.
I proceed to take the newly purchased spark plugs out to inspect them and check the gap again (gap is .035) on all so good to go. I put them back in, not in the same order and it runs like it should. I drive it around the block and it still sounds good.
I then let it sit for about two hours and take my son who had just woken from his nap(he's 2). I go to start my Jeep and it sounds ok. rpms are idling around 600-800 now. I drive about half a mile and stop at a stop light and the engine just goes back to how it first started off. Low rpms idling around 50-100 now. Light turns green and I press on the gas to head on my way. While driving(cruising or on the gas) it's fine. As I'm slowing down it's fine. As soon as I stop it drops it's rpms.

I bought RC12ECC number 438 Champion copper plugs.
I noticed with 2 of the NEWly purchased plugs that two of them had silver tops and not a darkish copper type of look. Went back to exchange them but the other ones at autozone were the silver top as well.(see pic below)




I went to Checkers/O'reileys and bought some new plugs tonight but haven't been able to test those out.

The Jeep was running great before I touched the coil rail and spark plugs. So, Unless I touched something else which I'm positive I haven't I'm guessing I have a bad plug or a bad coil rail or both.

What do you think?
Do I need to replace the spark coil rail at all? If so how many miles?

I am 13 miles off from 60,000 miles on the odometer.

edit :: I also found out that every place I went I could not get Champion truck plugs p/m 4412 ( everyone said they aren't being made anymore and that they don't carry them. I asked pepboys, autozone, checkers/O'reileys, napa.) I was going to try these instead of the RC12ECC.

edit edit :: I torqued everything down to spec as well. 30ftlbs for the sparks and 20ftlbs for the spark coil rail.

[Holder350]

Remove the battery cable for about 30mins and let the computer reset

[ahuf]

Originally Posted by Holder350

Remove the battery cable for about 30mins and let the computer reset

doing it now.

[Holder350]

After you hook it back up, on the first drive the computer will "relearn" the idle circuit and params....

Hopefully this is all thats wrong....your motor is to use to running with crappy plugs.

BTW, I dont recommend doing the drive tonight....too many drunks out there....

[robsjeepxj]

Sounds like a dirty throttle body & IAC as well or the IAC is just going bad. You can also look at the area (around the spark plugs) when it's dark outside to see if you have any arcing from a bad plug boot or too much dielectric lube.

[ahuf]

I'll leave it off for 50 minutes and then reconnect it tonight and test in the morning.

[robsjeepxj]

It shouldn't take more than a minute or two to bleed down any stored voltage left in the computer, all you have to do is disconnect the battery cables and hold the negative terminal against a known good ground source.

[CJ7-Tim]

Clean the Throttle body and the Idle Air Controller. Make sure all the spark plug boots are correctly engaged on the plugs before you tighten down the spark rail.

Re-Set the Engine Computer/PCM, the strange idle should clear right up.


This very simple procedure will Erase the “Adaptive Memory” stored inside the PCM and allow a new “Adaptive Memory” to be developed.

After performing this procedure the PCM will re-learn and store into Adaptive Memory your engines new performance characteristics.

Perform these steps exactly as they are written, in the order they are written. This will cause the adaptive memory in the PCM to be erased and cause the PCM to go into Fast Learn Mode adaptive mode.

Disconnect the POSITIVE battery Terminal and touch it to ground ( not the battery negative terminal ) for 30 seconds. The engine block or the A/C compressor pump will work as a ground. (This is to discharge the PCM capacitors, which maintain the Adaptive Memory.

Reconnect the Battery Cable
Turn Ignition Switch to the “On” position but DO NOT start the engine
Turn Headlight “On”
Turn Headlights “Off”
Turn Ignition Key “Off”


The PCM Adaptive memory has now been flashed, or erased from the PCM.

When you start the engine it will be running off a set of pre-programmed tables that come with the PCM from the factory.

When you get the engine up to operating temperature the PCM will start to collect data for the “Adaptive Memory”.

The PCM will collect data for Adaptive Memory for the first 50 Warm-up Cycles.

[robsjeepxj]

Well there you go.

[GregB_00XJ]

What CJ7-Tim said.



I also have a 2000, installed the exact same plugs in place of some Bosch Double Platinums that were installed 2 years ago (not by me) when the engine was redone. Followed this process, runs fine. All my plugs matched and were from the same box. Hope this works for you, let us know.

[ahuf]

update time.

So, last night I did the wait 30 minutes(i waited about 3hrs, playing monopoly) and reconnected the battery. I drove it around the block and it seemed to help. rpms were 400-600

This morning I did the disconnect the posi and ground it out for 30 secs and do the keys on, lights on, lights off, keys off. When I first started(cold) it up the rpms were around 750-1000.
As it warmed up the rpms dropped around to 650-750(warm).
I drove it about 10miles on the highway and roughly 5miles on street 25-45mphstreet signs.
Highway driving - rpms were 2000(warm)
Street driving cruising - rpms were 1000
Street driving stopped(idle) - rpms were 400-600

It seems to be driving fine. It doesn't seem to want to stall except for a few stops. The idle still seems a little low 400-600. Is this normal? I cleaned the throttle body(actually took it off and cleaned it up. I
m going to put some seafoam in it tomorrow to see if that helps at all. Never used the stuff but I planned on using it before just never have.

It runs fine at cold. I read some where that the engine runs off the computer until it reaches temp then transfers it over to the o2 sensor. I'll take a look at the sensors tomorrow and see if theres anything noticeable with any of them to require replacement.

Thank you for all the info Holder350, robsjeepxj, CJ7-Tim, GregB_00XJ. Really appreciate the help and info.

[Holder350]

In "warmup mode" the computer runs on some preset params...after its warm it reads A/F off of the O2 sensor.

The sensors can become slow to respond, and have a life of about 50-100k miles.

A IACV clean wouldn't be a bad idea either

[sbxj]

for future reference 2000 should use NGK plugs

[sbxj]

sfjfwlyd

[Holder350]

Originally Posted by sbxj

sfjfwlyd

Why, Yes I agree....and so does