98' 4.0
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Joined: Feb 2007
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98' 4.0
My son's wife has 98' explorer with 4.0 v6,to make a long story short it idles very rough when cold and surges,but when it it comes up on temp it seems to be o.k.We replaced plugs and wires,fuel filter and gutted the converters because it would make a bad rattling noise when started,we thought they were stopped up.Has anyone encountered this trouble,HELP PLEASE>>
Posting Guru
Joined: May 2002
Posts: 2,450
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From: Baltimore
Do a search on intake gaskets. There are lots of posts on that. What can happens is the gasket leaks while the motor cold which causes a vacuum leak and poor performance. As the motor warms up the gasket and metal seat better and the vacuum leak is reduced. Also, have you tried pulling the codes? There may be a code stored even if CEL is out.
Cross-Country
Joined: May 2004
Posts: 50
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Clean the IAC (idle air control) valve and/or replace it. Only takes a few minutes and is a common cause of idling problems on startup. Intake manifold gasket is also a possibility as noted in a previous post. Also a common problem.
4.0
Former ******
Joined: Nov 2004
Posts: 4,901
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From: Salt Lake City, Utah
We have some new converters for you. Good grief, why would you gut the converters? If there was something wrong with them, you would have had a CEL come on and tell you. I agree with the above posts, the IAC is responsible for the majority of idle related problems, and if it needs to be replaced, it is not too expensive. Vacuum leaks are very common on the 4.0L as well.
The cats to replace the ones you gutted and get your performance back and to turn the CEL off so you can get past inspections are not cheap. You really shouldn't have done that. Cats don't ever plug up by themselves unless you are talking about a motor home of something really large. Even then, the problem is tune up related.
The cats to replace the ones you gutted and get your performance back and to turn the CEL off so you can get past inspections are not cheap. You really shouldn't have done that. Cats don't ever plug up by themselves unless you are talking about a motor home of something really large. Even then, the problem is tune up related.
Cross-Country
Joined: May 2004
Posts: 50
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On a 98 SOHC 4.0, rattling cats are probably due to a loose heat shield. Common problem, and Ford has a fix kit for this, AKA a large stainless hose clamp. No sense in gutting the cats and, as pointed out, risking other performance issues (i.e., downstream 02 sensor readings). What's done is done. Good luck with the idle problem.
