I've been scouring the internet for weeks now looking for an explanation for my intermittent shaky idle. It's been there for some time now (I'd guess the last 30k miles or so), but only at idle, and it doesn't seem to have any regular frequency, though it will jolt slightly every 3-5 seconds or so. It feels like a tiny miss. It's not noticable to passengers unless I tell them about it and they feel for it. I idle my truck in the college parking lot for about an hour a day most days, and it's pretty annoying when I'm trying to catch a few winks.

A little background of other attempts to fix it and other symptoms before I get to my question. I use a little bit of coolant. Not much, but last time I changed the oil, I probably added about an inch to the overflow reservoir (50/50 mix of HOAT mopar coolant and distilled water). My truck has started to consume a small amount of oil the last few changes (running mobil 1, but plan to switch to royal purple next change). I go about half a year on synthetic between changes (~6k miles). I have seen very feint white smoke out the tail pipe before while idling at the lake, but it was odorless and could have just been condensation (humid day, but it was running about 15 minutes). I'm talking very feint, like line it up with a tire so you have a black background to see it feint. I've got a pretty good hemi tick going, that seems to have gotten worse over time. Hence the change over to RP next oil change. The build date on it is Dec. '03 (the truck is an '04), so I suspect I have the earlier hemi valvetrain (springs in particular).

I've cleaned the TB, replaced the EGR valve (reused the old gasket), and replaced the PCV valve at the same time about 20-25k miles ago. I've changed plugs last week with champion coppers, and probably 20-25k miles before that was plugs and plug wires (around the same time I did the EGR, PCV, etc.). I've got a valve cover gasket set with spark plug gaskets included sitting in the garage waiting for a cooler afternoon, and I'm not opposed to peaking around in the head while I'm there. I've also had the PCM flashed with the most recent update around that same time and it helped a little, but it's still been there. It's never overheated on me, and it's passed a hydrocarbon test (the NAPA head and block test). I feel fairly safe in ruling out a head gasket issue.

I don't have many engine mods, but I'm running a 180 JET t-stat and I've got an e-cutout if it matters.

So that brings me to this evening. I was googling around, like you do, and noticed someone mention O2 sensors being the cause of a misfire feeling at idle. My truck rolled over 100k about a month or 2 ago. I pulled out the upstream passenger side sensor and it's pretty white. Not pure white, but "10 years of smoke on white walls" white. I only managed to get the one sensor pulled as the downstream on that side was stuck on pretty good. I tried moving the truck into the garage to jack it up and get some leverage, but of course 5 seconds with the motor running needs 2 hours for the cats to cool off and it's 9:30 already. So I put the upstream sensor back in and only got it hand tight. I couldn't reach my ratchet and O2 socket up there because the cat was warm. I started the truck up and backed it out of the garage for the night. When I put it in park and set the parking brake, I noticed the "shimmy" idle was going more frequently. I gave it a little gas, and thought I could feel a slight hesitation. I then started experimenting a little with the gas pedal. When I BARELY (and I mean try 5 times to get a good one) touched the pedal enough to rev the engine, it would bog down and start shaking like an early stall. I held it there, and it dropped the idle down to around 500 rpms and started loping pretty well. I couldn't hold it there much because it was so sensative, but it's a new symptom I hadn't felt before.

I've got no codes, and I hooked up superchips to double check. Is there anything in the datalog section of superchips that might help me check the O2 sensors? When I get some time someday soon, I may try lightly sanding all the sensors and see if it makes a difference. I'm about 50/50 on driving the truck halfway across town tomorrow because the idle has become a bit more finicky.

Can a worn O2 sensor that's not tripping any codes cause a shaky, intermittent idle issue?



P.S. Sorry it's so long. Just trying to include as much info as I can.

 

I am just not flipping 80k and I just recently replaced both or my front O2s for maintenance/age and mileage reasons. I wasnt getting any issues. With you being at 100k I dont think it will hurt to change yours. Have you done a compression check to get a gauge on how worn your internal parts are?

 

I have not done a compression test. Trying to avoid buying a compressor. I've seen bits and pieces of information on compression testers that don't require a compressor, but haven't dug into it much. I think they involve tapping the starter to create pressure from the stroke cycle.

What O2 sensors did you go with weed? I have heard of problems from buying the one size fits all type.

 

Ive got a compression tested from Autozone from years ago and I guess it was around $30 or so. I was in Harbor Freight last weekend and seen them for $12.

I used Bosch sensors from Autozone (P/N 15504) and were $25 each.

 

Did you do all 4, and did they give you any trouble (installation, engine behavior, etc.)? Cheapest I can find online is $30 a piece plus shipping, so autozone sounds like a winner so far.

 

Dirty fuel injectors and/or sticky throttlebody. I doubt the 02 sensors will solve the issue but still need replacement for normal maintenance on upkeep.

 

In the 5 or so years I've been watching dodge forums, it's *******ly never bad injectors. I know I can't rule it out, but I just don't see it very often, and having a shop check their flow rate is throwing money down a the pit of diagnostic fees (which I really hate). I cleaned the TB with brake cleaner about 20k miles ago. It wasn't too bad then, but it definitely didn't hurt.

 

Hmm. Virt.ual.ly is a bad word?