Rough Idle

[Dick Berg]

1997 Explorer, EB, 4WD, 4L SOHC Engine.
I recently replaced the blown left side camshaft chain guide. I was able to do it without having to re-time the engine, based on a procedure by 2000StreetRod. Everything went well, the engine is smooth at speed, great gas mileage, no hesitation, etc. The only problem is the idle is a bit rough.
I checked for vacuum leaks by plugging all of the ports in the upper intake manifold, removed both intake manifolds, which were previously removed for the camshaft guide replacement, replaced both sets of almost new manifold gaskets, replaced the less than one year old EGR to upper intake manifold o-ring, and looked for any cracks in either manifold. I have also sprayed starting fluid all over the place with no change in idle. I also replaced the IAC valve, all with no change in the idle.
I just purchased a code scanner and will hook it up and monitor what I can.
Does anyone have any ideas what could be causing the rough idle? Are there any things to look for with the scanner that might give me a clue to what's going on?
There aren't any codes set. As mentioned, if not for the rough idle, the engine perfoms almost like it did when it was new.
Is there some sensor that could be outputting a faulty signal that primarily and/or only affects the idle?

Thanks for the help.

Dick

 

[my98nnj]

How was the idle before you did the work?
If it was smooth, then honestly I'd be looking at the camshaft timing again.

 

[janolsson]

I read an interesting thread about adjusting the TPS smothing out idle. IIRC you need to put a meter on it and check the variable voltage (one wire is ground, one is 5V reference and one is variable dependent on throttle position). Key on engine off you should get 0.5 - 1.5V off the variable line with the ideal setting being 0.95V.
Worth testing to see what your reading is at the mo.
Also What are the HT leads like and what plugs/gap are you running?
The other thing to check might be the PCV and associated tubing (at the back of the engine connected to the upper intake.

 

[mr2fix2it]

there is no way to do timing chains on this motor with out tools(and Get it RIGHT) it sounds like the timing is off there are no keyways and all bolts are torque to yield

 

[Dick Berg]

Guys - Thanks for the feedback.
When I did the left guide replacement, I very carefully marked the relationship between the sprocket gear and the camshaft. I believe that I put it back to where it was within a few thousandths, but there's no way to confirm that. The bolt that holds the sprocket gear to the camshaft isn't torque-to-yield. As I remember, the torque setting is around 65 ft-lbs.
Even if the timing was slightly off, wouldn't it have more serious driving indications than just a slightly rough idle? As I wrote, as far as I can tell, and I've has the beast since it was new, it runs no differently now than when it was new, except for the idle.
I should have added in my first post that the EGR valve was replaced a year ago, and was removed and sprayed with cleaner with no change in the idle. I guess it's not out of the question that it may have a small leak and is bypassing a small amount of exhaust gas at idle, but not enough to cause a code to be set. I did verify that there's no vacuum to the EGR valve at idle.
Jan - I'll check on what you suggested, it sounds interesting.

Thanks again to all who responded.

Dick