Ok, first off, did a search. The car has been pretty good for a while. Here in FL, I used the AC for an extended period of time yesterday and noticed the car runs very very poorly with the ac on - 2004, 6 speed, 40k miles, mid-grade/high-grade gas.

Conditions:
AC has to be on for at least 10 minutes straight
Car sputters especially at 5-6k, sometimes even jerky
At this point, accelerates very poorly, at 5th gear at 72mph I floor it and car goes no where and climbs 1mph slowly, could not even keep up with the flow of traffic- a speeding corolla in front of me. (I should proly drop it down a gear but it should move fine as I remember it to w/o ac)
Coolant light blinks but turns off (coolant level is fine)
It feels like something is clogged, like not enough gas or air. Checked my Green air filter and is clean
Last time i took it to the dealer, they checked everything including cat and could not duplicate this- A waste of my time

Anyone have any experience with this? Any ammo I can go to the dealer with? I don't want to keep going and have them tell me everything is ok. I didn't think the AC was connected at all with the car. Thanks in advance

 

The AC compressor is driven off the accessory belt on the motor. When you turn on the AC the compressor a clutch in the compressor makes the pulley spin the internals presenting significantly more load to the car's motor. Thats why it affects the motors performance.

 

I still think it's your Cat or a bad batch of gas.

So, are you sure it runs fine and never repats the same condition with the AC off?

When were your plugs replaced?

Did you ask the dealer to pull the codes off your car? if coolant link blinks and then goes off....you may have another problem that they can pick up if the read the error codes stored in memory.

 

Misunderstood your point, I thought that you were under the impression that the AC didn't impact the performance of the car. Re-reading it seems that you seem mean the problems aren't necessarily a result of the AC.

I had 1 skunky tank of gas produce some horrific results, ie hesitation rough idles etc. Also, prior to the oil foaming recall I had a vaccum leak from one of the fittings on the intake. That caused a seriously rough idle, threw a CEL and had high rpm hesitation. I've yet to have a coolant light. I've also had a cat go bad and produce the same crap results in performance. Same with plugs. All caused hesitation and or sputtering at high rpm along with nasty rough idles and the occasional CEL.

One final note, the first dealer I took my car to said the cat was fine along with my intake issue. Dissatisfied, I changed dealers and the second one replaced the cat and intake tube while performing all the tsbs related to emmissions etc. So don't neccessarily rely on trusting one dealership.

 

Yeah I very recently noticed a huge drop in performance and sputtering at the 6k range (someone said that's the area where the auxiliary ports open up). Pretty much it would struggle through the entire power band and then jerk really hard when I shifted. I couldn't even pass a truck on a curvy mountain (two-lane) road!! I figured the damn starter was messing up again and fouled the plugs like what happened last time.

Took it in for 15k maintenance and turns out the Cat was badly clogged so they are having a replacement ordered. Spark plugs were fine they said. So until they get the new Cat installed I'm stuck in this bottom of the line Kia Rio rental... all I can say is I miss my Rx-8 BADLY.

 

Thanks for the feedback. It seems like only when the AC is on. They did change out the starter and updated plugs early this year. I will have them look at the codes and recheck the cat.I will try a different brand of gas other than my shell also. I will leave an update when I find something out.

 

Since it is the summer and more than just Florida gets hot, I was wondering if anyone else's 8 runs poorly after the AC has been on for a while? This happens mostly at 5-7k 2nd gear. Also, when I am on 5th and 75 mph I floor it and it barely moves. I try the same with the AC OFF, and she runs like a champ.

The care is a lease ending this year and I was seriously thinking of keeping her, but when I go to the dealer again in Sept and there is still no fix, I think she is going back. Who knows- maybe get another 8 but how can you trust a car that 2 dealers cannot fix?

 

From tampa too. When I have my ac on it sputters when idling. Shut off on me twice. when I turn off a/c runs fine. will have checked at next oil change. No problems at higher rpms with a/c on.

 

Even on a motor like the ren the A/C compressor shouldn't put on such a load that the car can't run. I'm thinking your cat is probably partially clogged and that maybe the additional load caused by running the A/C causes the partial clog to temporarily get worse. But I'm just pulling that one outta nowhere so don't bank on it...

 

The engine load goes from 34% to 45%, at idle, when the AC kicks in. The RPMs take a short dip and come back to the same 840 when AC kicks in.

PS This is for 4AT, not sure about 6MTs

 

Any more suggestions about the AC compressor? Is there anything that can be done to reduce the engine load?

 

With my A/C on I can tell a small difference in performance and it idles a little rough, but that is true with a lot of cars . My loss of power problem was that the inlet air valve was not opening enough. After the dealer replaced the switch that tells the air valve to open fully at about 6k rpm , she runs great again. My initial problem was a almost total loss of power. I could mash the gas to the floor and gain no speed at all , except down hill. It was like a log was tied behind me. I am somewhat confused about bxb40's post that said the engine load is 45% at idle. By engine load do you mean 45% of available power? Someone enlighten me.

 

I doubt if it is the load of the compressor. As someone else stated, the load is not that great -- heck the car will idle with the compressor running; don't think it's much compared to horsepower generated at 7000 rpm. Plus, the compressor will cut out at wide-open-throttle anyway.

I'd suspect a heat problem. When the AC runs, the radiator receives warm air that has already taken on heat from the AC coils.

One of the symptoms of the engine failures is loss of power in hot conditions. I hope that's not your problem but you should have the dealer check it out based on that. You can find the test procedure on the forum -- involved running the car with AC and defined rpm/time period, then attempting performance acceleration. I'd try running that test and see how the car reacts.

 

plugs
coils
cat
motor.

in that order.. make sure you have the last recall done. and correctly..

beers

 

Plugs? nah
coils? nah,
cat? maybe
motor? nah
I don't mean to come off as too strong, but I think people need to be more careful telling someone they probably need a new motor every time they have and issue with this car. If you have an engine problem with a piston engine, and lots of folks do, the dealers just repair the problem whether it is top end or bottom end. I may be wrong but it seems to me that most of the mazda dealers mechanics don't have the skills or tools to repair a rotary engine, other than the components on the outside of the engine. So if the problem is internal they just replace the engine short block.

 

really,

my troubleshooting here it been pretty good... and you do not understand why they just dont rebuild the motor at the dealer...

well you got me...

beers

 

I did not say that a blown motor was "probable", only that loss of power which manifests at high temperature was one of the symptoms. There was a big recall for this issue and the OP needs to be aware and make sure that possibility is properly addressed by the dealer instead of saying "can't duplicate".

As far as repairing engine internals -- what do you suggest? There are only a couple of moving parts. Repair is relacing a plethora of seals and complex machining of surfaces. Labor intensive and far better done by someone with lots of experience in the process rather than a shop mechanic who might only do 1 or 2 per year. Not to mention the cost of deploying the specialized equipment used. Mazda prefers it to be done in a dedicated facility and by technicians that specialize in the process.

 

I didn't mean to misquote you on the blown engine probability. I guess I have read too many post that the first thing that was said was , uh oh you need a new engine! You said exactly what I was trying to say about dealers not rebuilding the rotary. The mechanics don't have the skills and tools to rebuild the rotary internals. So they replace the engine.

 

you miss the point that it is more cost effective to just replace the short block.


beers

 

Yes I get the point. And yes you are correct about not being cost effective. Even if the dealers had the tools and specialize machines to do the complex machining of the block , the mechanics still would not have the skills and experience to do the work. The techs I have spoken with at the dealers near me know very little about the rotary. I have had them tell me some weird things about the engine. So then I go do some research on this forum and the various rotary websites and find out otherwise.