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Rough in gear idle

40K views 39 replies 10 participants last post by  the_Big_dill 
#1 ·
Hey all,

I recently changed my alternator, belt, idler & tensioner pulley, the car runs as quiet as new while in "park" or at a higher speed in "drive".

However when i put it into drive, reverse, low or 3, it starts sounding rough with consistent vibration patterns. What is causing that noise and how would i go about dealing with it?

Cheers,

Phil.
 
#4 ·
Could possibly be a bad motor mount, or a dirty throttle body when I took mine apart to replace my valve cover gaskets mine was completely covered with carbon cleaned it up and the van idled and accelerated smoother at low rpm's, you could take it to a shop and have an induction service performed on it, that would clean up the throttle body and intake plenum, also maybe a partially clogged fuel injector or line, just some ideas.
 
#5 · (Edited)
I guess I will just clean the throttle body myself and see if that helps. Should I actually take off the plenum and clean in there, or is that negligible?

Is carb cleaner a decent replacement for throttle body cleaner? Because I have some of that, while throttle body cleaner I will need to buy.
 
#9 ·
I've noticed with dodge instrument clusters in full size and minivans is that you're best off to replace all your illumination bulbs at the same time. I can't explain why, but installing one or two new bulbs tend to burn out the old ones you left in once you reinstall the cluster. You won't need to change the bulbs for indicator lights.
 
#10 ·
I placed an order today for 8 new PC 74 bulbs.

Looking to fix the idle, i took off the air duct and could see and feel a black hard substance on the edge of the throttle plate! At least a few millimeters from the edge.

After some research, i found out the 3.3L has no mass air flow sensor and no EGR valve. Why no EGR?

Also, i am going to seafoam the car this weekend, i took out the break booster vacuum hose, and the revs started building, to my hesitation, i plugged it back in... is the rev building normal?
 
#11 ·
By taking the hose off, you gave the intake another source to pull in air. The computer is going to add fuel to accomodate the extra air going in to maintain a certain air/fuel ratio. So, yes the RPM will go up when you pull any vacuum hose that attaches to the intake manifold.
 
#12 · (Edited)
Yep, when i went to sleep, it kinda hit me that im opening another source of air to the manifold XD

So why is there no EGR valve on my engine? i am assuming not having one is a good thing, since its just to control emissions?

EDIT:

I looked closed into the idling and as it turns out it isn't steady on the revs.

Once the engine settles its at about 900RPM then after a few seconds it will drop down to 700RPM and idle roughly, sound and vibration, but only lasts for a second or two before the engine goes back to 900RPM and repeats this.
 
#13 · (Edited)
I don't have an answer for your EGR question. I've heard that sometimes cam profiles are set up to retain some exhaust gases; thus, doing the same job the EGR used to do. I know that varaible valve timing engines are set up to retain exhaust gases and eliminate the EGR valve too.

I always wondered if the EGR valve, or the lack of, tied to whether or not the engine is flex fuel. The reason I wonder is because some engines do have EGR while others don't even in the same model years. I've had a thousand chances to ask smart people about that myself but i keep forgetting. I've got a head that's like pouring water through a collander. It'll retain something for a little while but it's always going to wind up empty again.
 
#16 ·
When you replaced the alternator, did you use one with the Lutens decoupler? If not, there's a good chance that the low speed roughness is being caused by an incorrect clutch.
 
#32 ·
How many times does the CEL blink? 10 times and then stop, or does it continue "forever"??


A possible reason for the PCM flashing the MIL light with just the Key in the ON position Engine Off (KOEO) is because the I/M readiness monitors are not ready for testing. The reason they are not ready for testing is because of the previous fault code that has been set and the engine hasn't had the run time necessary to allow these I/M monitors to run - OR - codes have been cleared and all the I/M tests have not been run. Once all the I/M tests have been run successfully, the light should cease its blinking routine.

This MAY be the normal operating charecteristic for the MIL light under the circumstances that you find yourself in.

This is something that was introduced with the 2002 model year in response to federally mandated emissions regulations.

Look for "pending" codes with your code tool.

As far as your rough idle goes, I suspect that you may have a severe misfire condition. The blinking MIL sometimes is telling you that the engine is having a severe misfire condition. Under these conditions the integrity of the cat is at risk. These misfires sometimes do not show up as matured codes. Sometimes they don't even show up as pending codes.

Once misfire conditions are corrected, and the I/M tests are done, the light should return to it's original operation.

There is a good Autolite misfire diag video on YouTube youtube.com/watch?v=K_uJ2aLcnzQ that addresses rough idle and misfire problems.
 
#20 ·
Yea, I meant MIL :)

That actually is the only culprit left with this rough idle, as all else has been dealt with, yet this has been an issue longer than I knew anything about the car.

Regarding the inlet air temp. sensor: I was told it has been replaced without any positive outcomes. I checked the connector to the sensor and it was clean, i even blew it with compressed air, but that did not help.

Did a true fuel economy test and am pleased to say that on a full tank of gas I can do over 700 kms, which is 9.4L/100km.

Also noticed a funky smell coming fromm the exhaust, is it dirty catalytic? I do know that the car burns oil, so that may also be it.
 
#21 ·
Here is an update regarding the P 1192 code (low voltage for IAT sensor):

The sensor works properly, it is something to do with the wiring.

When the engine is cold, the wire reads exactly 5V.

Once the engine is turned on, within a few seconds, the light is back on with the same code.

Checking the IAT sensor wire, i get 0.12V... If i use the the multimeter ground with the ground wire of the IAT wire and the positive of the multimeter with the positive battery post, i get ~12V, which (i think) means there is a GOOD ground.

I then plug in the positive multimeter to the incoming wire for the IAT sensor and the ground of the multimeter to the battery negative, and get an abnormal reading, something like the 0.12V. Is the ECM bad?
 
#25 · (Edited)
Well, the engine code is not connected to the rough idle, as the problem persists even in the small intervals where the voltage on the sensor is correct...

I do think it is the torque converter... As when i am idling on an incline, the car seems to struggle, like a consistent on and off for power, like a Slipping clutch.

Changing the transmission fluid is one solution i have read online, but i have never done it and don't know how to do it, never has been done since 190000kms... and who knows how long before then, heck, the original factory wires were there until 260000km.

Any assistance in changing the ATF fluid would be appreciated, i heard ATF +4 is the only one this transmission will accept.
 
#26 ·
Hey again, i have been reading up on sensors recently, and much of the symptoms are relating to a possible bad crankshaft position sensor, what do you guys think? This is related to the Rough idle i was talking about.
 
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