Problem with heater/vaccuum??

Oct 30, 2006 4 Replies
J

Hi All,



I have a 97 XLT with 4.0 SOHC. I have a problem when I move the heater into the defrost (upper vent) position. At idle, when in this position I hear a loud click and the engine bogs down to about 400 rpm then recovers. Three seconds later the cycle repeats. When the heat selecter is in the floor/defrost position the problem still exists, but it doesn't seem to bog down so badly.



Any suggestions on what might be causing this? FWIW, I do have the infamous blend door problem.



Thanks for any input you can offer.


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A

The AC is enabled in any positions that include the defrost vents, and I would guess that's what you're hearing -- the compressor kicking in and out.

Why the engine is bogging down so much? Don't know.

Perhaps the infamous MAF (Mass Air Flow) sensor in the air intake is acting up and screwing up the engine management system. That happens.

Alan Moorman

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J

Hi Alan,

Thanks for the reply. Should the compressor be kicking in and out so much (every three seconds)? It seems somewhat excessive.

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A

That's been talked about here, before, but I don't remember the outcome.

Perhaps Jim Warman could weigh in on this??

Alan Moorman

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O

Cycling frequently is usually because low on Freon

As for engine bogging down, slow responding and/or dirty IAC valve ???

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