So my old battery stopped holding charge and I dropped a new one in tonight. I drove my car for a about a half hour and noticed the car would break up when I got into boost, especially in the higher gears. It's fine when I slowly accelerate, but when I get on it, all I feel is just some knocking from the rear. I think I may even heard a "pop" or two in the rear. Any advice?

 

Well there is the possibility the alternator is not working fully and the car runs fine until the battery runs down.

I came across a Cayenne in the dealership the other day. The tech told me the engine would start and run just fine -- idling in the service bay -- for about 5 minutes then various system warning lights would come on alarms would sound then the engine would die.

After letting the vehicle sit a while with the ignition switched off the tech reported he was able to repeat this behavior.

The diagnosis was the alternator was ok for a while -- a few minutes -- then it would stop working and the car's electrical system was powered by battery alone which is not up to this task and the behavior just before the engine died was the result of this.

 

Which would also explain why he had to replace the battery in the first place. It may very have not been in bad shape, but having a bad alternator would be masked by the battery "not holding a charge". It wasn't holding a charge because it wasn't receiving a charge by the alternator. Just another idea to re-enforce getting that alternator looked at.

Cheers
Mikey

 

If you do think its the alternator pull it and test it first. They are kinda pricey. Also if your car is a 6 speed I personally had the pulley of the alternator fail as it has a slip feature built in to be more forgiving to the other pulleys when you shift gears. Autos don't have this. The other I heard lots about running through my alternator issue is the grounding strap for the motor being rusty or frayed or just loose causing bad charging issues. What does you dash gauge read? When mine went the gauge would suddenly drop when I pulled up to a light. If I slightly revved it I could make it return to normal sometimes which lead me to the failed pulley.
Good luck.

 

Well I actually noticed last night when I started the car with a new battery, I heard perpetual squeaking. This would make perfect sense that a belt was making that noise. It went away though after I drove it last night though. Today I've been driving for a little and the car seems to be fine. I didn't get on it extremely hard cause it's raining, but I got into the Turbos for sure.

It just seems to unlikely that a problem would spring up at the same exact time I put in a new battery :P

 

Oh for sure. These cars do weird things sometimes.
The belt squeaking can happen simply because its raining heavy or you just washed it as the hood is like a big BBQ grill. I live in Vancouver and it rains here all the freakin time so I definitely hear that squeak periodically from time to time. Nothing to worry about.

 

My dash reads at about 13.5. The car is still actually breaking up in high RPMs, any advice??

 

Plugs or coils, possibly MAF.
Get a durametric, and post the codes. You might not have a cel on the dash but there could still be codes.

 

Alright so I just went for a nice long drive. As usual, it starts to really break up at the high RPMs and even back fires with a loud "pop" once in a while. Occasionally though, the car clears, but not for long. Best part though is that the CEL starts blinking, but then it goes off. Then it goes back on, etc.

 

From my experience, when I had my car in stock form it ran great, after I flashed it all of a sudden I'd have exactly what you describe. When hitting high boost the car would sputter, miss fire as well as back fire.
I pulled the plugs out and replaced them with what epl recommended as well as what gap to run. My coils looked fine, no cracks etc.
Unfortunately I can't remember what that was as it was a couple of years ago but I'm sure doing a search you could find it.
This fixed my problem and the car has run strong ever since.
They recommend changing the plugs at 30k miles, less if your flashed.
That would be my recommendation, bit of a pain to change but cheap.
You can find DIY for this in the knowledge section on the site.
Good luck.

 

Well the thing is that my car has had a GIAC chip and its ran absolutely fine with it. It's had it for thousands of miles. Only when I changed the battery did this problem come up. I'm thinking when I did change the battery, maybe a micro-short caused one of the coils to stop working.

Is it possible the new battery may be causing the chip to malfunction? I notice that once in a while I build a large amount of boost in the low RPMs.

 

The best help you could be to yourself if you want to chase down problems is buy yourself a Durametric tool.

Really anything anyone could tell you is not really and thing close to a definitive answer.

Do yourself a favor and spend the < $300.00 for even the basic kit. A car that is doing what you describe could be going quite lean or even rich at times. Both of which can cause more expensive damage to your car.

http://www.durametric.com/buyus.aspx

 

Yup! Need codes.

 

If you live in the SF Bay Area, I have a Pro version of the Durametric with unlimited VIN's, you can plug into your TT free of charge.

 

I really appreciate the generosity, but I live in Philadelphia!!