AC= Big Block fuel mileage and NO POWER! [Archive] - Forum


View Full Version : AC= Big Block fuel mileage and NO POWER!

08-09-2009, 10:15 PM
now i know turning on your AC is going to kill power and mileage a little bit. But this is like i just attached a 10,000 pound trailer to my car when i turn it on. I need to give it WAAAY more throttle to get nowhere basically. If i run into a decent hill, i need to turn it off so i dont lose all my speed. I dont hear a belt squealing or anything, so my thought isnt that i have a bad compressor or clutch on it.

I almost never use my ac, but today was almost 100 degrees so i wanted it. Blows cold as ice, but robs way too much power and mileage. Or is this just how this car is? Let me know your ideas and ill see what i can do.

08-09-2009, 10:49 PM
I do notice a slight drop in power when running the A/C but it shouldn't affect your mileage too terribly bad. Actually, on the highway at least, it's often better for mileage than having your windows open. If you're seeing huge power drops with it on then something is amiss.

08-09-2009, 11:14 PM
i used to notice it too quite a bit so i never used it unless i absolutely had to :/. i also noticed the significant (watch the needle drop) mpg hit as well. maybe its just a GA thang.

08-09-2009, 11:17 PM
I notice very little difference with mine on. I can hear it load the engine a bit at idle, but thats normal when you place more drag on the engine at such low rpm. At cruising rpm I don't even notice it, and when you go into PE mode the pcm disengages the compressor clutch so you won't lose any power under heavy acceleration.

08-10-2009, 01:49 PM
maybe im just special then. If the darn compressor assembly wasnt so expensive i would just replace it..

To give you an idea. i went about 20 miles of mixed high and minimal city. Most the time cruising at 50ish. And i used a smidge over 1/8th tank according to the gauge. Thats WAAAAAY to much to me. Considering i can make that same trip ( to work and back) twice before i begin to notice a difference in the position, let alone that much lost.

08-10-2009, 01:58 PM
Something definitely sounds amiss there

08-10-2009, 02:25 PM
yea, thats what im saying. The engine is SUPER loaded which is where the poor mileage and no power comes from. If its off the car runs great. But whats strange to me, is that the RPM's at idle are no different with the AC on or off.

08-10-2009, 02:54 PM
How many miles and when was the last tune up / service to anything related to the engine?

08-10-2009, 04:56 PM
i did a full tuneup not even 5k ago. Plugs, wires, oil, PCV, and O2 sensors. Air filter i did about 10k. brakes i did about 10k as well, so they arent dragging or anything.

Im half considering getting a used 3.4 out of a junkyard and rebuilding it with some MILD performance parts.. that way ive got some power plus a new engine to tinker with. Shouldnt give me problems like this one. lol

08-10-2009, 06:08 PM
fuel filter?

08-10-2009, 07:01 PM
yea, did that too. I always forget that.

08-10-2009, 11:08 PM
take the belt off and make sure the ac clutch pulley spins freely or if the bearings have seized

08-11-2009, 12:35 AM
I don't care about mpg as long as my a/c works. Windows never go down in my car. Today was a hot one, 105 and what felt like 100% humidity. But getting back to the topic. You have the a/c going, both rad fans are running on high to cool the car and you. Also their is a insane amount of heat under your hood. If your car is not use to running under said loads it will feel dead. Drive around with the a/c on for a little so your car can learn how to work under the load.

The worst mpg I got was 14mpg last summer. And i have 2.4. But as the days went on I was able to get 18mpg.

08-11-2009, 03:50 PM
Well i just landed a new job, so this car is gonna be gone in the next year. And since summer is cooling down, i will just deal with it.

08-13-2009, 02:35 PM
ok this isnt AC related. The car shudders and barely moves under acceleration untill it hits about 2000 rmps or more. and if it gets over 3500 there is a TERRIBLE rattle and screaching sound. Ideas?

Still no power, in fact its wayyy less now since when i posted. And its not throwing a single code..

08-13-2009, 02:51 PM
ok this isnt AC related. The car shudders and barely moves under acceleration untill it hits about 2000 rmps or more. and if it gets over 3500 there is a TERRIBLE rattle and screaching sound. Ideas?

Still no power, in fact its wayyy less now since when i posted. And its not throwing a single code..

Have you checked your belt and tensioner? Its possible that the belt it being ratcheted down super tight causing excess drag on the engine.

08-13-2009, 02:53 PM
well my EGR is deffinatly leaking. but im not going to waste my time and money replaceing that if i have bigger fish to fry. Think it could be causeing the rattle somehow?

08-13-2009, 02:59 PM
Its possible. Could be a cause for your power issues. Is the EGR itself leaking or is it the tube that takes the exhaust up from the headers?

08-13-2009, 03:06 PM
im thinkin EGR itself. I dont see how the tube would be effected. Only time it has ever moved is when i did the LIM. I messed around with it a bit when i got to work before i went in. When i move the throttle when parked by hand there is deffinatly a leak around there.

08-13-2009, 06:50 PM
we have deduced that the leak is from VERY CLOGGED CAT!! There is almost NO exhause flow at the tail pipes. We compared to my dads Lumina with a 3.1 ( which should have less right?) and it was WAAAAAAY more. Imagine taking a desk fan and putting it on low, thats about all i was getting. When he would rev it up a bit i heard a loud rattle ( heres the sorce) and it was directly below me. So i looked under the car to see the cat shakin about like it was about to explode..

so im going to replace that most likely. Whats stock size for the pipe? 2 1/4?

08-15-2009, 02:13 PM
Well. 250 bucks later i have a whole new pipe and cat. All one piece and fits with no extra work. Sounds waaay deeper and smoother. No more rough acceleration. Power is back, even more so than when i first bought it. I will update with gas mileage as a few days pass by.

Again, not bragging so much, just filling in the empty holes for people who know what the search is all about.. lol

on another note.. Since i bought the car, when i would go WOT i would notice a pinging noise. I thought it was just valvetrain noise and nothing to really worry about. But that is now gone as well. Which means it was probably thousands of little tiny explosions in my manifolds making that noise. Because the valvetrain is totally silent it appears. And my AC dosent drain my power at all really. Blows cold, silent, and still have decent get up and go. All SEEMS well in the world of my GA at the moment. Pray that it keeps up.

08-15-2009, 08:03 PM
Again, not bragging so much, just filling in the empty holes for people who know what the search is all about.. lol

good thing to do. :applause:

08-15-2009, 10:41 PM
Thats what i think. im a member on 2 or 3 Camaro forums and ive answered the infamous " LS1 into a third gen" question no less than a dozen times.. Let alone the ones i didnt even answer.

08-18-2009, 04:24 PM
So far mileage is slowly returning. I figure the engine has to "relearn" a few things since it was running so poorly for so long. but ive got almost 100 miles on about the first quarter. But this car takes awhile to get through the first half then it drops pretty quick. NO its no a scientific results type of thing going here, just joe blow watching gauges.

Dosent help that ive been romping on it a little bit, im fairly impressed with the power of that little V6

08-18-2009, 05:27 PM
heh i remember that too; it seems as though you are doing REALLY good then it like drops like a rock...

08-18-2009, 06:27 PM
My car does it too. I think gm put the sending unit in a wonky place in the tank.

08-18-2009, 10:01 PM
yea. i wish they would do it some other way than a float. Or if it is, have it send varying currents depending on its TRUE level.

08-18-2009, 10:41 PM
dont "they" say though that the only accurate parts of gas gauges are the top 1/4 and the bottom 1/4?

08-19-2009, 02:05 AM
Full to 3/4 and 1/4 to E. I'm a optimism. I hate after drving my GA hard and cutting it off. Then start it back up to see my gas has drop about 3 clicks.

08-19-2009, 04:04 PM
lol at least I don't feel so unique now.
Mine always did that...

It would stay past F for about 50 miles, then another 50 miles from 3/4 to F... then soon after that it would just fall off.

08-20-2009, 07:42 AM
hey, mine does that.... glad to know im not alone

08-22-2009, 09:55 AM
Ok well its been a week. Car continues to run great. Gas mileage seems to have improved. Though its still nothing to brag about. ( anybody run those E3 spark plugs in this car?) Give that some more time maybe. I got under replace it and noticed a small oil leak had started. When i got under to recheck the bolts and make sure none come loose from the heating and cooling, and the leak was gone. Im guessing from getting rid of the excess crank case pressure built up from the exhaust fighting that old cat so hard.

For those of you who remember my high idle woes.. that is 100% gone now. After replacing nearly every sensor that deals with either idle or the injection, It turned out to be a combination of the IAT sensor and its pigtail from the harness. But it would still idle somewhat high sometimes. Since i did the cat, smoooooooth idle and its low like it should be at a stop in gear.

Next fix: strange squeak with brakes even though they are allmost brand new..

08-27-2009, 11:01 PM
My gauge stopped working a long time ago, but I finally got this because I was tired of running out of gas...

Product website...

This thing displays a **** ton of information.