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350rs
12-30-2010, 12:36 PM
7 or 8 thousand miles on the rebuild of the motor. Still runs tip top, no leaks no nothing. However, sometimes when i hit the gas at highway speeds going uphill ( say to pass) i can feel it somewhat studdering a bit. Almost like a miss. That is the ONLY time it hints at any kind of a problem though. All plugs and wires are new to rebuild. Never throws a code. Without pulling the plugs im not 100% if thats even what im feeling. Could just be bumps in the road, but feels much more like a miss to me. I noticed today on the way to work it kinda did it on a right hand clover leaf style highway on ramp. Would this be at all fuel related? Such as pump, FPR, or a injector? Havent had 2 seconds of spare time in the last few months to breath, let alone look into this problem. 121k on the car itself, like i said 7 or 8 on the rebuild.

I tested the ignition module when it was apart, everything checkout out just fine. Im using NGK Iridium plugs, i know these motors are pretty picky about their plugs.. Would the delco plugs be better?

This may not be a problem at all, but i hate not knowing 100% whats goin on with my POS. ;crap

Edit: Also, have any of you tried the E3 plugs in this car? I put them in my 6.0 Silverado and it seemed to help a bit with mileage and towing.

dlineownzu4life
12-30-2010, 01:40 PM
Are you sure its not the trans shifting.... Also I believe there is a lag in the gas pedal to avoid going to WOT too quickly, so pushing it in 80% is only giving the engine 60% of its fuel compared to WOT. If that makes sense.

350rs
12-30-2010, 03:22 PM
no this isnt trans. It feels exactly like a miss. I never give it 100%. Only a little more throttle for a pass. Its kinda hard to explain it all, the best way i can think to describe it is a miss. Ill study on it some Sunday. Take some plugs out and see if i see anything that would do it. But since 99.9% of the time its fine, im sure the plugs are too.

Also, mileage has seemed to drop a bit. Not a HUGE amount, but probably 25 or 30 miles to a tank. Could be that im using the defroster and letting it warm up a bit too before i leave. only a min or two though. But i know that defroster puts a fair load on the alternator. Weather that translates to lower fuel cause the "strain" im not sure, but it makes since in my head. lol

350rs
12-30-2010, 04:32 PM
finally threw a code on the way home from work today. Not at all what i suspected. P0420. Replaced the cat 2 summer ago. Shouldnt be that. Replaced the upstream O2 a few months before that as well. Only other thought would be the downstream? Thats probably still OE.

However, my HG went out last summer... i guess it COULD be the cat itself.

Malaclypse
12-30-2010, 09:00 PM
A bad headgasket will kill a catalytic converter in short order. They're not meant to burn coolant.

The intermittent misfire likely isn't related to that code, however. I'd suggest its an ignition miss since it feels like a stutter. Fuel would cause a clatter or you'd richen up.

My thoughts are possibly a bad/corroded coil post, plug wires or the plugs themselves. Never hurts to check the plugs. I had the same stutter you're describing on a set of Delcos after 50k miles. When I removed them, the electrode was worn down to the ceramic.

Also, E3 plugs are a joke. Stick with Delco or NGK. I had a truck come in with those E3s at 20k miles... had a dead miss on #1. It was hell convicing the customer that his plugs caused it. Once I threw in a set of Delcos the problem went away.

350rs
12-31-2010, 07:23 AM
yea i know cats hate coolant. i changed the downstream O2 since it was cheaper and easier. Saw on here that the P0420 code tends to relate to the DS O2 if its not the cat. No luck. Dammit... Hoping that cat is still under warranty and i can replace it free.

I remember seeing a few slightly corroded posts on my coils. One was bad enough that i straight replaced it too. Id have to look at the others. Can someone clear up what came factory in a 01 3.4? Was it an iridium or a platinum???

I only have a few thousand on those E3 plugs. I run mid-grade or premium since towing is that trucks biggest purpose on this planet. And believe it or not.. it pulls better with a higher octane rating ( lets not start that overdone war here..) So hopefully i will not run into that same problem that your customer had.

Malaclypse
01-01-2011, 01:42 PM
I remember seeing a few slightly corroded posts on my coils. One was bad enough that i straight replaced it too. Id have to look at the others. Can someone clear up what came factory in a 01 3.4? Was it an iridium or a platinum???

They came with platinum plugs. Iridium should work allright though. Either clean the coil packs with some emory cloth or replace them. On my car I found the boots on the stock plug wires didn't fit very well on the coils. I ended up with MSD coils and Magnecor wires. Didn't have a lick of trouble after that. My old car was running strong at 120k miles.


I only have a few thousand on those E3 plugs. I run mid-grade or premium since towing is that trucks biggest purpose on this planet. And believe it or not.. it pulls better with a higher octane rating ( lets not start that overdone war here..) So hopefully i will not run into that same problem that your customer had.

You started it, brother. Higher octane fuel is useless unless you're tuned for it. It actually burns slower so if you're not adding spark you're just throwing money away. It may help alliviate some detonation problems you're having from those stupid E3 plugs but that's about it.

350rs
01-03-2011, 10:58 AM
A few days and a few hundred miles later.. the problem seems to have gone away. But the fact remains that burnt/unburnt coolant likely went through it when the head gaskets went. I called the parts store today, the cat has a 5 year/50k mile warranty on it. And its a direct fit. So im just going to change it to be safe. Since its free ( because the warranty) i might as well. Going to school soon and wont have the time to fix it like i do now.

Malac, have you heard from others about those E3 plugs being bad? I have read nothing but good things about them so far. And so far, have nothing but good things to say about them. Other than being a little costly. I will pull them before pulling season starts again to check them out. I pull a roughly 9500-10,000 pound camper with that truck and it never missed a beat last summer. Mileage improvement was minimal, but every bit helps these days.

Like i said, my car runs tip top now ( after what appears to be the second rebuild when i got into it). Other than this little problem which probably stems off the HG blowing. Nothing unexpected. Its about to hit 122k now. Hope the iridium dosent really effect anything over being platinum. I dont understand why it would, but im not super knowledgeable about plugs and these motors. More interested in just keeping it reliable and running strong for another 2 years or so.

350rs
01-12-2011, 07:02 AM
Not to bring back a dead post.. but its back. I didnt get off easy with changing the downstream O2 like i had hoped. I guess i will order in that cat and replace it this weekend, again. Anything else that should be checked while under there? Both O2 sensors are either brand new or less than a year old. No exhaust leaks anywhere either.

I like to update my posts for the folks who use the Search function.

350rs
01-17-2011, 07:08 AM
cat replaced, problem persists. Almost seems worse this time around. Ideas? Its limited to only highway speeds and when im getting on the gas. Say to get up a hill or pass someone. At least thats when its most noticeable. Still havent pulled the plugs, thinking that might be it. Not sure. Just really glad i didnt have to pay a dime to replace that cat this time around. Warranties are a great thing.