91 Dakota 3.9 Idle Issues
Thread Starter
|
Registered User
Joined: Jun 2010
Posts: 3
Likes: 0
91 Dakota 3.9 Idle Issues
Hey guys, New here ,been a reader for a while, just never registered.
Anyway, I have a 91 3.9 TBI.
I CANNOT for the life of me figure out this random idle misfire / shake.
I've replaced : Plugs, Wires, Cap, Rotor, Checked timing chain for slack, Done a compression test (140's across the board), swapped fuel injectors, checked for vacuum leaks...
It drives absolutely fine, but the idle is just unbearable. Sometimes you can definitely feel the misfire at idle, but MOST of the time, it shakes the whole truck at idle. I understand these aren't the smoothest of motors, but this is ridiculous. Sometimes it will idle perfectly smooth, and other times its a constant shake, unlike a misfire.
It's difficult to describe, but i'm running out of ideas here.
Anyway, I have a 91 3.9 TBI.
I CANNOT for the life of me figure out this random idle misfire / shake.
I've replaced : Plugs, Wires, Cap, Rotor, Checked timing chain for slack, Done a compression test (140's across the board), swapped fuel injectors, checked for vacuum leaks...
It drives absolutely fine, but the idle is just unbearable. Sometimes you can definitely feel the misfire at idle, but MOST of the time, it shakes the whole truck at idle. I understand these aren't the smoothest of motors, but this is ridiculous. Sometimes it will idle perfectly smooth, and other times its a constant shake, unlike a misfire.
It's difficult to describe, but i'm running out of ideas here.
Registered User
Joined: May 2010
Posts: 42
Likes: 0
Some aftermarket PCV valves that you buy new have a annoying buzzing sound though, which I learned the hard way just last year, you might just be better off taking some throttle body/carb cleaner spray such as this: http://media.photobucket.com/image/t...s/DSC07718.jpg to clean out your existing Positive crankcase ventilation valve.
If doing that doesn't fix your problem, I suggest taking out the idle air control sensor from the top rear of your throttle body and also cleaning it out with that spray. The spray also works ok for the EGR valve after you scrape the carbon out of the valve, the spray should get rid of the rest of the carbon dust and buildup.
It could also be things such as your ignition timing is off a little bit or maybe you have a weak, broken or loose wire on a fuel injector, it could be a lot of things. Your best bet might be to just call up a good mechanic that has a diagnostic computer and throw him a couple bucks to plug it in and see if any error codes come up, if it doesn't point you to the exact problem, it should point you to a general area. And while your there he could also check your ignition timing with a timing light if he has one. You don't need to go to a mechanic to try and resolve your problem, but in the long run it might just be faster and possibly even cheaper to just go.
If doing that doesn't fix your problem, I suggest taking out the idle air control sensor from the top rear of your throttle body and also cleaning it out with that spray. The spray also works ok for the EGR valve after you scrape the carbon out of the valve, the spray should get rid of the rest of the carbon dust and buildup.
It could also be things such as your ignition timing is off a little bit or maybe you have a weak, broken or loose wire on a fuel injector, it could be a lot of things. Your best bet might be to just call up a good mechanic that has a diagnostic computer and throw him a couple bucks to plug it in and see if any error codes come up, if it doesn't point you to the exact problem, it should point you to a general area. And while your there he could also check your ignition timing with a timing light if he has one. You don't need to go to a mechanic to try and resolve your problem, but in the long run it might just be faster and possibly even cheaper to just go.
Last edited by MagnumMan3.9; Jun 20, 2010 at 09:15 AM.
lol.