Rough Erratic Idle...Getting Worse!
 

so i bought my car a little over a year ago and it has always had a "shaking" problem....replaced plugs (ACD Pro Iridium), Wires (BWD), MAP sensor (Delphi), and the lower motor mount, LIM and UIM, hoping these would fix the issue. While they did seem to help at first, the shaking always comes back.

Over the last few months i have noticed small drops in RPM while sitting at stop lights, from 750 down to just above 500 rpm at first, and it didnt happen very often. Now, however, the car is becoming more rhythmic in these rpm drops, and theyre becoming worse, like down to 400 and back up, which creates a very noticable shudder.

im thinking TPS, or some fuel related issue like maybe the sending unit. but it cant be the rail or the injectors because i went through all of those when i did the LIM UIM.

NEED HELP!!

thanks in advance

Hi `Aaron,
How many miles on your 3.9L ?
Have you had a codes "Engine Light" ?
Did you do the previous work on your engine ? or was it someone else ?

How's your MPG's ? >the same average or worse ?
What gas are your using ?
It could just be a bad sensor or some bad fuel ?
Have you tried any fuel addictive's ?
I've found that ethanol can cause many problems : (

I like seafoam & you may want to check it out...
Good Luck `Aaron :thumbsup:
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124k miles, no engine codes, not even in the history, ive done all the engine work since i bought it....its probably some finicky little issue like a sensor or vacuum leak, etc. i need to investigate

Sounds like a vacuum leak, check your rubber intake gaset connecting to your intake, and also I would recommend cleaning out your throttle body, and cleaning your MAF, and changing your air filter and cleaning the box. Thats where you want to start at.

@Hiroska, all of that has been done lol

UPDATE....Car had no problem going home yesterday or coming in to work today, and it only did it once last night after leaving the gym...guess ill just have to keep watching it

Hmm is there a custom tune? Have you had your belt checked? Pulleys all good?

no tune, i havent done the belt yet but ive done the water pump and checked pulleys before, nothing loose then, maybe ones getting funky...idk do you think it could be a power distribution problem? Its the original alternator and i had to splice in a new pigtail connector on the backside of it once, ive always kind of wondered if the alt is on its way out....

You would know if it would be, your lights would be really dim, and also car would basically lose power if driving. So I doubt its the alt. One thing that causes a shake, but also comes with a noise, is the Harmonic balancer, its something that goes bad on our cars very often. It caused my car to idle a bit weird. Do you hear any noises?

um not really, the other day it was making a random loud tick every now and then, but not consistently

ill let the car warm up and look at the pulleys after work