99 Explorer Idle Trouble

[bpopp]

Could a slipping timing chain cause a rough idle? The reason I ask is that on my 99 SOHC I had a horrible idle (esp. in cold weather) for almost a year. I tried most of the things here (new IAC, new MAF, plugs, WD-40 around the intake) and had no success. Eventually, my timing chain slipped a tooth and toasted my engine. I never knew whether it was the timing chain or the intake manifold that was causing that rough idle.

That was about 3 years ago. I'm now on my second engine ("low mileage" junkyard) and the rough idle has come back. It's not as bad as it was, but for obvious reasons, I'm taking it more seriously. Also, it's not consistent, but I think I've heard the notorious "death rattle" a few times at around 2500rpm.

By the way, on my dead engine and again on this one, I am getting P0171 and P0174 codes (lean bank 1 & 2)..

 

[chance942]

Change out the upper and lower gaskets. They have the set at Autozone for 15.99,fel pro.

Those codes mean your pump is weak. Single line set up?

 

[bpopp]

Are you saying the fuel pump is failing? I've been told lean banks can be caused by both not enough fuel (fuel pump/injectors/filter), bad ignition (plugs) or, more commonly, too much air caused by a vacuum leak of some kind. Would a fuel pressure gauge tell me whether it's a fuel pump problem?

And yes, I'm new to this. Trying to learn.

 

[chance942]

I had the same codes on mine and went all over it the vacuum sysytem. Replaced the upper and lower manifold o rings. It is possible that you have a leak but I didn't. The fact that it is on both banks points strongly to fuel.

Yes you can check the pressure with a gauge. Your fuel lines come up right behind the power steering pump resevoir and are right on the front of the left cylinder head.Pull off the plastic "sohc" cover and follow the line and you'll see I believe a blue screw off cover. Under that is the shrader valve to connect your gauge to.

Now how many lines do you see coming in at the location I mentioned? If it is two you can diagnose fuel pump issues easier from up top. If there is only one your pressure regulator is in the fuel tank. If you have one line the psi should be 60-65.

If you have 2 lines pressure should be 30-45

With pressure regulator vacuum detached, 40-50

Hold pressure @ 5 minutes should be 30-65

Max should be 65

Start with that. If you have a one line system and you don't maintain between 60-65 your pump is weak.

I don't know how to check the regulator operation if it is in the tank. I bought the complete drop in unit and haven't had ANY problems since. There are some very knowledgable people on here so have faith. I'm telling you from first hand expierence about having these codes and how I fixed it.

 

[bpopp]

Put a fuel pressure gauge on my ex tonight and got a reading of over 60, so I don't think I am having a pump/filter issue. I borrowed my dad's stethoscope and it sounded like I have a vacuum leak on two hoses going into the plenum. There's an L-shaped hose that plugs into each side of the plenum and then they meet in the middle with a t-connector. Both L-shaped connectors have a white plastic clip on them. Still haven't figured out where the other end of the t-connector goes. It looks like it goes underneath the thermostat housing and possibly down to some kind of sensor sitting underneath the battery (VMV?). When I plugged either/both of those holes, the truck idled much smoother. Maybe I should just buy some corks and be done with it.

 

[goahunter]

Thanks all for your different possible solutions. I've finally found out there the vacuum leak is. Turns out since the rough idle is intermittent Ive never noticed that the EGR valve is coming on while at idle and it shouldn't be. I finally caught it one time when it was idling rough and hoped out of the card quickly and pulled the vacuum line off of the egr valve. Idle instantly smoothed out and finger sucked into the vacuum line. Going to replace the EGR vacuum regulator tomorrow since a couple different times I've found this and the vacuum line doesn't seem to have the same pressure any time. Hopefully this fixes the problem. I hope if anyone else had this problem that it might help some. Will post with what this does.

 

[chance942]

Yes the VMV is down under the battery. That is where that tube ends up.

 

[gijoecam]

Change out the upper and lower gaskets. They have the set at Autozone for 15.99,fel pro.

Those codes mean your pump is weak. Single line set up?

I had the same codes on mine and went all over it the vacuum sysytem. Replaced the upper and lower manifold o rings. It is possible that you have a leak but I didn't. The fact that it is on both banks points strongly to fuel.

Assuming they're leaking, replacing the lower intake manifold gaskets will solve the lean codes and the cold-idle issue. Believe it or not, lean codes can be caused by either too little fuel or too MUCH air... That air can be coming from the gaskets.

 

[chance942]

yeah and throw a code for BOTH banks @ the exact same time. Not likely unless they're really bad all around. Mine was fuel.

 

[gijoecam]

yeah and throw a code for BOTH banks @ the exact same time. Not likely unless they're really bad all around. Mine was fuel.

Umm, yeah. The lower gaskets still surround all of the lower intake ports. It's not uncommon for more than one of them to leak, and even if one of them leaks, it still affects the airflow balance to the adjacent cylinders, which can and does cause a lean condition. The oxygen sensors don't tell you WHY it's lean.

Yes, a fuel supply issue can cause the same code, but in the OP's case fuel pressure all checked out, and the code persists. That points to a vacuum leak, and the most common cause of a vacuum leak that affects both banks on a SOHC that's still got the original lower IM gaskets is the lower IM gaskets.

 

[chance942]

Yeah still not buyin that.

 

[ERUSH97XLT]

Hello again,

I had similar problems with the same codes. Turned out to be ignition. Check out this link:

http://www.explorerforum.com/forums/showthread.php?t=225969

This might help, as other solutions are presented within this thread.


ERUSH

 

[bpopp]

This weekend I'm going to change out those two hoses going into the manifold and if that doesn't work, I'll change out the IM gaskets (upper and lower). I'll post the results.