AC fan and engine mis @ same time....

[DCauffie]

This is a 2001. The ac fan will stop and the engine will mis all at the same time. Happens at random. Did wires, plugs, and cap. Dealer says to just do a tune up everytime this happens. Is this a vac problem? Where should I look First?

[dingusc]

Hello,
I am having the same exact problem that you are describing. I put a tune-up on my Astro in May and had a small vacuum leak fixed. It ran fine for a few weeks and then started acting up again. The code kicked out a 'multi-cylinder mis-fire' and so the mechanic told me to put a tune up on it. I replaced the plugs from Bosche to AC Rapidfire and it seemed to help for about a week and it started all over again. He again told me to put a tune up on it so I went and bought new plugs/wires/cap/rotor from the dealer ($181) and just replaced them all again yesterday. It is not missing anymore at the moment but the vacuum problem is still there where the engine is under torque and the AC blower kicks off. I pulled my camper today and the blower kicked off more than it was on. I am almost convinced that the who problem is vacuum related. I just don't know how to track down the vacuum leak. If you find out anything, please post and I'll do the same. Thanks!

Carl.

[Kings-x59]

Does the fan actually stop blowing, or does air just stop coming out the vents? If the fan stops blowing it's an electrical issue. if you can still hear the fan blowing, but the air stops it's a vacuum issue. The dampers in the ductwork are vacuum operated. A vacuum leak will cause the engine to run poorly. Since you have both symptoms it probably is a vacuum leak.
As the engine become hotter under load, the vacuum hoses become more pliable and leaks can be intermittant. You can purchase a vacuum tester for not to much money, or you can take the poorboy's approach (mine) and pull each hose loose from its fitting, one end at a time. Just looking at the hoses in place doesn't always find the problem. For example the vacuum hose from my map sensor had a small split in the TBI end of the hose, on the inside. The split didn't show on the outside of the hose. When the engine got good and warm the hose started sucking air and my map sensor coded.
Start with the hoses connected to the AC vacuum chamber. On my old '89, the AC vacuum chamber is an arms length down by the passenger side wheel well, from inside the van. It's one of those hose fitting you can see with a flashlight, or you can get your hand on it, just barely, but you can't do both at the same time. Expect to get greasy.
There isn't any silver bullet solution to this process, only the patience of water solves the problem. Good luck, and happy wrenching.