Lower Intake Manifold q's

[gijoecam]

OK, I know that with the ooM12, the lower intake manifold o-rings were an issue. I *thought* my replacement motor in '00 came with both the revised tensioners and the revised o-rings, but now I'm not so sure....

On the first and only the first cold-start after a 6 hour soak (8-hours in the parking lot at work, or parked outside overnight) and the temp stays below 40 degrees, I get a rolling idle. It surges up to about 15-1600, then slowly falls back down to about 400 where it sputters, bucks, and hesitates, then it acts as though someone tapped the gas pedal, jumps up and rolls back down again. It does this rolling idle 4-6 times, then flattens out and purrs like a kitten until the next cold-soak. If I turn the key off while it's rolling and start it back up, the problem does not happen again. Subsequent restarts after the first one result in a perfect idle.

When the problem first surfaced, I replaced the IAC. That did not fix the problem. I was thinking that it was a sensor being out of whack, but have no easy way to check it. That all got me thinking about the lower intake manifold leak issue.... Sooooo.....

Could bad lower intake manifold o-rings cause the issue I'm having? If the o-rings were bad, wouldn't the problem occur all the time? Why only on a cold start after being VERY cold for an extended period of time?

I'm just trying to rul out the lower intake for my own peace of mind... I'm really still clueless on the issue...

-Joe

 

[Jakee]

I would think that if the O-rings were in fact bad, then the problem would repeat once you re-started it.

Have you tried resetting the IDLE by disconnecting the battery?

 

[Jakee]

ONe thing you can do to clear your mind would be to spray some TB cleaner where you suspect the intake leak. If there is a leak, the cleaner will be sucked in and you'll hear the difference in the idle.

Something changed but I'm not sure what. I wonder if your TB is dirty? You could clean that next. Maybe clean the MAF sensor after that? Once all that's done you could re-set the idle by disconnecting the battery for 20 minutes. Start it back up and don't touch the gas peddle. Let it idle for 2 minutes then turn the ac on full blast and let idle for 2 minutes. Then hold the brake, put in gear and let idle for 2 minutes. Next, turn the ac back off and let idle for 2 minutes. This should re-learn the idle. Maybe all these steps in order will fix your problem.

 

[gijoecam]

The system has been reset numerous times since the problem first started (working on other things). The TB has been cleaned on a few occasions both before and after the problem began. If it was a MAF issue, the problem wouldn't go away with subsequent restarts, or as the engine warmed up, but I forgot to mention that has been cleaned too.

As for the leak, when the lower intake manifold o-rings leak, where exactly does that come from? I've not followed it as I was always under the assumption that the new engine they put in had the revised parts... just not so sure anymore.

-Joe

 

[floydr007]

I used ether to check for the lower intake manifold gasket leak and found absolutely nothing. Then I had it smoke tested, and the shop found a very small leak. These engines are obviously very sensitive to vacuum leaks. My symptoms were EXACTLY the same. It only happened when the car was sitting in the cold, and once it warmed up there were no problems. This is because the plastic manifold shrinks in the cold, making the leak more apparent. Once it warms up, the problem typically goes away. The car would also have to sit in the cold for hours after being ran for the symptoms to show up again. Getting the 00M12 has made my '99 run better than when i initially bought it... Good luck, but i think your symptoms definitely point towards a vacuum leak.

 

[slpdave]

mine did the same thing for a year now it is a bear to start when it's below 40, once it warms up it's good until the next cold soak. I have come to the conlcusion that I finally have to replace the lower intake gasket, search for 00M12 and I think you will be enlightened.

Another user of the forums clued me into this (I thought it was my IAC, but I was wrong).

David

 

[dogfriend]

Could bad lower intake manifold o-rings cause the issue I'm having? If the o-rings were bad, wouldn't the problem occur all the time? Why only on a cold start after being VERY cold for an extended period of time?


-Joe

The reason that its worse with a cold start is because the o-rings will leak until the engine warms up - then the o-rings get warm, expand and close off the leak.

When its very cold, it will make the problem even worse. The o-rings will be at their smallest dimension.

From what I have read, your symptom is classic for the leaking intake o-ring problem.

 

[gijoecam]

That's what I was afraid of... Like I mentioned before, I *thought* that when they replaced the engine back in 2000, the engine came with the revised timing chain tensioner and I guess I (optimistically) was under the impression they would have used the revised gaskets as well... guess not.

Guess I'll chenge the tensioner too. The kit's only $40, and it's just 2 more screws to change the tensioner and install the volume reduction plug. I guess I'll see if those were the revised parts or not when I get to 'em.

Does anyone have the pictures of the how-to someone did on here bookmarked? I just ran a quick search and can't seem to find 'em. I thought they were stickied somewhere around here....

-Joe

edit: Found it!
http://www.explorerforum.com/forums/showpost.php?p=487634&postcount=33

For anyone searching....

 

[dogfriend]

http://www.explorerforum.com/forums/showthread.php?t=126608

http://www.explorerforum.com/forums/showpost.php?p=487634&postcount=33