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2002 1500 5.9 Quad Cab
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3 Posts
Discussion Starter · #1 · (Edited)
If you’re like me, you’ve tried everything and read everything about this dip/ stumble/ rough idle when stopped in drive and reverse (neutral and park seem smoother) —that doesn’t seem to qualify for a Check Engine Light...

This is my first post, and it’s about a solution reached with the help of this forum:

After a recent tune-up ( Autolite plugs + CRT Performance wires, distributor cap, rotor, hot coil (w/ .050 gap), I noticed a rough idle at operating temp when stopped in DRIVE and REVERSE.

the best way I can describe the problem is this: when I’d come to a stop in gear, the idle would initially look fine at 650. Then after 15-20 seconds I’d see a tiny drop in RPMs, almost unnoticeable. Then another. Then I’d get a stumble to 550-600, but it would jump back up. Then again. It got worse and more frequent the longer I sat still in gear.

and I tried EVERYTHING:

swapped the coil back to stock and reset plugs to factory(.040), changed IAC (x3), TPS (x2), removed and cleaned throttle body, cleaned and tightened all grounds, swapped for Champion Plugs, new DIE HARD SILVER Battery, silicon sealant and hose clamps on EVERY VAC LINE, PCM hard and soft reset so many times I lost count, re-routed plug wires, re-routed again, bottles of sea foam and Marvel Mystery...

read a really excellent and detailed forum discussion about a guy with the same truck (5.9)/ same problem who had it solved when he swapped the crankshaft position sensor, so I got out the 18” extension and did that... threw in the Cam position sensor (in the distributor) at the same time (because why not - the air hat was out)

then I bit the bullet and did the NTK O2 sensors (was up under there anyway to do the SUPER 40 with a 3” side escape in front of the right tire)

nothing worked. I read EVERY forum, tried EVERY suggestion...

(never went to a shop though because hate shops and I’m stubborn as ****. The Dealer might as well be on the moon for as likely as I am to go there)

and then said **** it, let’s just swap these plugs one more time for the NGK Coppers...

Went to unscrew the cylinder no2 plug and it broke free way too easily. Used my phone to look was down the steel tube protecting the plug/ boot, and saw it...

THERE WERE TINY PIECES OF CERAMIC IN THE SPARK PLUG WELL

The no2 spark plug was hitting the pieces and not fully seating.

Went and got the wife’s vacuum with the long, skinny attachment. Went around to every cylinder and vacuumed them out (used two fingers to cover the gap in the steel “plug protector” so the vacuum pressure wasn’t lost)

grabbed the NTK’s, gapped them, install...

Perfect Idle. No drop, no hesitation, now I believe it would idle through a whole tank of 87 without a hiccup.

Not saying this is definitely the problem with your rough idle, or even a common problem... but if you are like me and have tried EVERYTHING to figure out this mysterious rough idle... try doing a good deep clean of the spark plug wells.

these forums have taught me everything so far. Had to give something back. I hope this helps you with your rough idle problem.
 

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You didn't mention the plenum gasket issue. And you can remove the plug shrouds with vice grips.
 
2002 1500 5.9 Quad Cab
Joined
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3 Posts
Discussion Starter · #3 ·
You didn't mention the plenum gasket issue. And you can remove the plug shrouds with vice grips.
figured a vac leak would lead to a higher idle... not the other way around. Good call on the plug shrouds I’ll be removing those and cleaning again on the next long weekend.
 
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