Rough Idle Update

[irishblessing]

yeah its usaully a vacccum leak can i ask whats rough about the idle

 

[Blackedge03]

I thought I had it figured out yesterday when I found a spark plug wire with a bad boot.
I replaced the wires(plugs replaced last week) but it still has the rough idle. I would describe it as a "quiver" sort of like a vibration almost. The dealership said they don't have this problem out of the 3.0 engine but have seen it in the 4.0
They said it is "lean" but they don't know why. They couldn't get past the bad reading from the MAF. Put two MAF's from Advance auto on the truck. It still showed a reading like the truck was in the Himalayas. I am ready to give up and trade the thing. NOTHING
I've done so far has made a difference. My hometown mechanic told me that he had a guy bring one in that had to have the heads replaced and a valve job and that it had always had a "quiver" to it. After the job was done the idle was smooth. Crazy.

 

[irishblessing]

i have a little quiver it comes and goes nothing big but its only when im in park it used to shake around a little in drive but i replaced the plugs and wires and coil pack and now its just in park i took it to my mechanic he didnt even notice it i dont think mine is anything serious though

 

[GMWIGGS]

I've been following this seeing what you have done to try to fix this problem. I'm starting to think a bad fuel injector, or maybe a partially clogged injector. If one cylinder was not getting enough fuel to ignite properly, wouldn't that result in a lean condition? I'm starting to lean away from the vaccum hose possibility. Most mechanics know this and will search like heck for it, fix it and charge you for a part...... J/K! Anyways just a thought to add to your mystery, hope you get it fixed!

 

[Blackedge03]

I have been thinking about the fuel injectors also. Not sure I want to tackle it myself or not. I am going to do a little more research on how to go about it. My mechanic can't look at the truck until Tuesday at the earliest. I doubt I can go the whole weekend without tinkering with it myself. If anyone has any advice on this I am all eyes. It's tough when the thing doesn't throw a code or CEL. Thanks

 

[aeraceranthony]

If your going to see the mechanic Tues, then I highly suggest you get the injectors flowed while it sits for a few days. It should be around $25 an injector ($150 for all). This will help out a lot, but may not be the probelm. I think its a vacuum hose.

 

[Rearanger]

If you can determine if the roughness is coming from one cylinder then you could switch out it's injector with one from another cylinder and see if the problem moves to the other cylinder. To do this I think you'll need to pull the entire fuel rail - sooo, maybe just do as aeraceranthony says and get all 6 flow tested and corrected if necessary. I used http://www.witchhunter.com/

 

[Blackedge03]

If your going to see the mechanic Tues, then I highly suggest you get the injectors flowed while it sits for a few days. It should be around $25 an injector ($150 for all). This will help out a lot, but may not be the probelm. I think its a vacuum hose.

Thanks for the advice. I'm not sure what I'm going to do just yet. I sprayed all around the hoses and intake gasket again today to double check for a leak.
Still haven't found one. I even pulled one of the hoses off and barely stuck it on the nipple and sprayed that just so I could show my wife how the engine would rev up...LOL.

 

[Blackedge03]

If you can determine if the roughness is coming from one cylinder then you could switch out it's injector with one from another cylinder and see if the problem moves to the other cylinder. To do this I think you'll need to pull the entire fuel rail - sooo, maybe just do as aeraceranthony says and get all 6 flow tested and corrected if necessary. I used http://www.witchhunter.com/

Thanks for the link. I checked it out. Those guys seem like they know injectors. Lots of good info there. I'm going to think on it for awhile. I'm not sure what I will end up doing. I don't want to get in over my head mechanically. It doesn't seem like it would be too complicated though.

 

[Blackedge03]

By the way, in an earlier post I said that the idle at cold start was fine. I realized later that it seems to make a difference what the outside temp is. When I start it for the first time to go to work at 2:30 in the afternoon the cold idle IS rough. When I start it up to go home at 11:30 at night the outside temp is much cooler and the cold start idle is MUCH smoother. Does this tell me anything?
Also, I replaced the downstream O2 sensor today- made no difference.Thanks

 

[Blackedge03]

yeah its usaully a vacccum leak can i ask whats rough about the idle

It is a pulsating/quivering idle. It feels rough then a little quiver then rough some more then another shake or two and so on..

 

[Rearanger]

When I start it for the first time to go to work at 2:30 in the afternoon the cold idle IS rough. When I start it up to go home at 11:30 at night the outside temp is much cooler and the cold start idle is MUCH smoother. Does this tell me anything?

Engine coolant temp sensor (ECT) will cause richer mixture when engine
cold(er), so in cold weather/cold start it will mask lean burn condition until engine warms. Your year does not have an IAT (intake air temperature sensor). I can't find testing specs in my Haynes as you could test it without removing it. The electrical resistance changes with temperature. It is located on top of the intake manifold next to the upper rad hose connection to the manifold and will have two wires going to it. I don't think it's very expensive. You'll need to drain the rad first and either use teflon tape or liquid sealant (I prefer) to install the new one. If your mecahnic could give you the temp/resistance specs you could get engine to full operating temp and test it.

 

[Blackedge03]

Ok, I took the fuel injectors out. Checked the resistance with the meter and all checked within spec. I used a 9 volt battery to "cycle" them and heard the click noise so none were stuck. I cleaned the tips with a toothbrush and some gas. Cleaned the orings. Put everything back together and I want to say the idle has changed but I am not sure. I know it is not smooth but it seems different. I drove it around for 15 or so miles and followed the idle relearn procedure in the owner's manual. I don't have another ride so I can't send the injectors off for cleaning/testing right now. I think for all they do at
witchhunter.com it is well worth the money. The only question I have is how common is it for injectors to be bad on a vehicle with only 46k on it? Was thinking I will see how it does tomorrow and maybe put some more seafoam in the gas tank. Any thoughts on this? Thanks

 

[Blackedge03]

Engine coolant temp sensor (ECT) will cause richer mixture when engine
cold(er), so in cold weather/cold start it will mask lean burn condition until engine warms. Your year does not have an IAT (intake air temperature sensor). I can't find testing specs in my Haynes as you could test it without removing it. The electrical resistance changes with temperature. It is located on top of the intake manifold next to the upper rad hose connection to the manifold and will have two wires going to it. I don't think it's very expensive. You'll need to drain the rad first and either use teflon tape or liquid sealant (I prefer) to install the new one. If your mecahnic could give you the temp/resistance specs you could get engine to full operating temp and test it.

I'll try to find some specs on it myself and test it. Still not sure I will get it to the mechanic. I am starting to wonder what he can do that I have'nt already tried. Of course, he does have more experience and I am not even close to being a mechanic...LOL

 

[Rearanger]

On thinking about the ECT some more I can't see how it would give lean burn. It can cause warm engine to run rich but I doubt there is enough range to go the other way. You can check it in the vehicle but I wouldn't drain the rad and remove it, I just don't think that's going to be the problem.

Ask your mechanic if the engine has a barometric sensor. It adjusts mixture depending on air pressure. I think it could cause lean burn - if that is the cause of the rough idle.