Nat, this is a sign that your intake manifold vacuum is decreasing when you are asking the engine for maximum power. This will happen on any engine, but if the engine is worn, the effect will be much more severe. If you have a vacuum gauge, temporarily disconnect one of the hoses from a vacuum fitting on the intake manifold and measure the vacuum at idle. Depending on your altitude, the ideal reading should be around 21 in. Hg.; lower at higher altitude by about 1 in. Hg. for each 1000 feet (Less air pressing down, you know!). If your vacuum at idle is OK, you don't have a serious vacuum leak. If it is a bit low, your engine is in need of a run on an engine analyzer to find the cause. I've forgotten how many miles on this car, but if it is up in the 6 digit area, this is to be expected. In other words, what you experience is not a malfunction other than a sign of a worn engine. If you don't have a vacuum gauge, you can try the poor man's check for a vacuum leak as follows: with the engine fully warm and idling peacefully, slowly restrict air flow into the air cleaner with your hand, very slowly increasing the restriction until you hear the engine either speed up or slow down. If it speeds up at all, it has a lean mixture at idle, which could be a misadjusted carburetor idle mixture control, or it could be a vacuum leak. If it just slows down as you restrict the air flow, you don't have a vacuum leak. Dick Benjamin -----Original Message----- From: mailing-list-owner@xxxxxxxxxxxxxxxx [mailto:mailing-list-owner@xxxxxxxxxxxxxxxx] On Behalf Of Nat Hall Sent: Wednesday, May 17, 2006 8:28 PM To: mailing-list@xxxxxxxxxxxxxxxx Subject: IML: odd vaccum-related behavior (82 Imperial) I haven't had a chance yet to play with finding out why my carb-converted '82 isn't passing the smog test, but in the meantime I've noticed something very odd. On hard acceleration, like on a freeway on-ramp with almost-full-throttle to full-throttle acceleration, if my A/C is on blowing out the dash panel vents, air flow direction will temporarily switch to blow exclusively from the floor vents (isn't this the "default" position?). Since the air flow direction of the climate control system is a vaccum assisted/controlled system, it seems to me like this is a result of a lack of vaccum. This is reproducable 100% of the time and has happened many times over the last week. As soon as my desired cruising speed is reached, and I ease off the accelerator, the airflow direction will quickly return to the dash vents. I have to believe this is not normal. Is this a result of a vaccum leak somewhere? If so, could this be a cause of my emissions test failure? ------------------- Nat Hall 1982 Imperial Coupe ------------------- ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm ----------------- http://www.imperialclub.com ----------------- This message was sent to you by the Imperial Mailing List. Please reply to mailing-list@xxxxxxxxxxxxxxxx and your response will be shared with everyone. Private messages (and attachments) for the Administrators should be sent to webmaster@xxxxxxxxxxxxxxxx To UN-SUBSCRIBE, go to http://imperialclub.com/unsubscribe.htm