Rough Idle Questions

[rpenner54]

Rough Idle Questions (Now with Video)

Okay all, I will post a video Tuesday of what this thing is doing. For now I will try to describe it. I have a 1995 4.0 OHV with 187k miles on it. Here is what has been done.

Spark Plugs/Wires
Fuel Filter
Air Filter
EGR Valve
Upper and Lower Manifold Gaskets
IAC
Both 02 sensors
Vacuum is tested to be around 16 which I am told is good here for Colorado.
Fuel Pump
Fuel Filter
TPS

It is still running really rough. I would say it's rompy like up and down real good. I need to get a meter and test the TPS but I figured with 187k on the clock I should probably just replace it. However I have already swapped it with the one off my '93 and still had the same results. I am not sure that one is even good anymore as the motor it came on is gone.

Here is what is left,
MAF
???
???
What else?

Thanks!

 

[littlezell]

let me know what you figure out I am having the same issue... its only the first few seconds of running.... I have changed sensors and even cleaned the intake..... still havent figured it out..... its like its idling way to low and causing a miss..

 

[rpenner54]

Okay replaced the TPS now. Still the same thing. Cannot figure it out at all. Looked at the MAF the diodes or whatever is in there looked good and all looked real clean inside. Also I guess the fuel pump was done too I forgot about that.

Here is are two separate videos.

http://youtu.be/pxUlA0K7EyM
http://youtu.be/Xt9as11fhGM

Any ideas what I need to do now?

 

[KillerKidd42]

mine has similar problems (subscribed)

 

[Rick]

How did the plugs look that you pulled out? Any fouled plugs??

I take it it was running this bad before the plug and wire change? Did you check the wiring order just to be sure there are no wires going to the wrong plugs?

Could also be a BIG vacuum leak, possibly a blown power brake booster? Or... I have had an issue with the fitting that goes into the booster, and I have even seen the hose going to the brake boosters completely deteriorated on the underside causing a vacuum leak.


Just throwing out some ideas...

 

[rpenner54]

Rick,

It's run somewhat bad for a while. CEL on and all that. The plugs were changed just cause my kid thought that would help her. It's her car and she drives it all the time I am just trying to get it running right for her.

I was looking at that connection the other day and it could move a lot at the brake booster side. I am going to have to take a better look at that. I wonder if I could just plug that for now to test it.

I need to get a ODBI reader, and a vacuum tester I think. I just keep throwing parts at it due to its age more than anything else.

 

[rpenner54]

Oh yeah, checked the wiring order all was good. Will check the plugs again this weekend. Not enough daylight left. Just went out and checked the brake booster. Pulled that line and got a real good hissing noise and then a pop once I pulled it out. I am assuming that means I had good vacuum built up. It also did not change anything once I pulled it.

 

[kindred4x]

Sounds like a huge vacuum leak. Have you tested fuel pressure at the manifold? My rig hesitates alot and I narrowed it down to the fuel pressure regulator on the fuel manifold. I am reading low pressure at idle. My motor hesitates like that also for a little bit, but doesn't die. Might be worth a shot to check fuel pressures

 

[Rick]

I had good vacuum built up. It also did not change anything once I pulled it.

Did you pull it and then plug the hose??

 

[rpenner54]

I did plug it but just used my thumb. Maybe not good enough? I will do a good plug on it here Thursday afternoon. I will also get some tools and report back my findings on Vacuum and fuel pressure.

 

[rpenner54]

Just swapped my coil pack and ICM off the '93 on to it and it still had the same result. Arg.... I just got to walk away till I get some tools I guess.

 

[mrboyle]

From the sound of that first video, you have a major vacuum leak.

 

[swshawaii]

Do you have the PCV elbow in post #21?
Throttle body cleaned, PCV valve replaced?

http://www.explorerforum.com/forums/showthread.php?t=241110&highlight=bad+idle+pcv

 

[Rick]

I did plug it but just used my thumb. Maybe not good enough?.

Thumb should work fine. Guess that wasn't it.

 

[rpenner54]

Looks like I am going to have the search for the leak. I have pulled and checked all the lines to the top of the motor so far and saw no cracks. However I am sure that this has to be the problem like you all are saying.

I just had this problem on our aviator and had to replace the hose at the backside of the motor. That was easy, I only wish this was as easy.

 

[Rick]

Intake manifold leak... spray some carb cleaner around the manifold where it meets the cylinder head and see if it changes the engine rpm.

 

[rickybobby]

if you do the intake manifold, pull the fuel rail and replace the gasket under that. there is a TSB for it. not sure what years the tsb covers as i found it while diagnosing a 97 mazda B4000, but it should apply to all of the 4.0 ohv with a paper gasket in there which is all of them up to 97

 

[swshawaii]

Here is what has been done.

Spark Plugs/Wires
Fuel Filter
Air Filter
EGR Valve
Upper and Lower Manifold Gaskets
IAC
Both 02 sensors
Vacuum is tested to be around 16 which I am told is good here for Colorado.
Fuel Pump
Fuel Filter
TPS

Replaced?

I need to get a ODBI reader, and a vacuum tester I think. I just keep throwing parts at it due to its age more than anything else.

Agree.

 

[rpenner54]

Yup, did both the upper and lower intake gaskets. I will re-check the torque settings on them though. I went off the article on here that was saying it was all in-lbs and not ft-lbs. Somewhat confusing this is what I went off of http://www.explorerforum.com/forums/showthread.php?t=171819 . I am questioning my torque settings now.

 

[swshawaii]

Yup, did both the upper and lower intake gaskets. I will re-check the torque settings on them though. I went off the article on here that was saying it was all in-lbs and not ft-lbs. Somewhat confusing this is what I went off of http://www.explorerforum.com/forums/showthread.php?t=171819 . I am questioning my torque settings now.

The link shows 17 ft/lb. If you used the inch/lb scale they would be VERY loose. (1 foot pound = 12 inch pounds)