letS4nicate

I was having this problem with APR chip installed. I put back my original ecu and brought car in for service. They could not find anything wrong with my car after doing a full analysis. Car seems to drive fine (albeit seemingly slow as hell with the stock ecu) with no hesitation or power loss. I reinstalled APR ecu and I'm back to random hesitation, roughness, and intermittant power loss. Any ideas?

Psyence

Put in some high octane and see what happens

frank

also did you accidentally, select the 100 Octnae mode?

NASA racer

I should link this permanently.

The S4 has a turbocharged engine...this results in high cylinder temperatures and pressures. Now Octane is the measure of a fuel's resistance to pre-ignition. ONE of the reasons that euro cars are slightly detuned for the US is because our gas sucks s**t (especially in california). They set the ECU to a boost and ignition timing sequence which is not likely to induce preignition under most forseeable circumstances.

Now, when you chip...you are throwing that out the window so are MUCH closer to pre-ignition. You running the 100 octane program on 93 octane gas? The timing and boost advance but the MOMENT the sensors detect pre-ignition the timing is cut to 0 so the engine is essentially shut off...as SOON as it can, the ECU will give you timing again so the engine will "surge"...the tach will hesitate and the car WILL be slow because you can't make full power.

Use the VERY best gas you can find at ALL TIMES with a chipped car. If in doubt...fill up with 100 octane pump gas (available at some stations) and try THAT.

I also contend that you should NEVER go to a dragstip without using 100 octane gas...once you enter the gates, your car will be heatsoaked and driven hard for short periods with no decent air circulation to cool it...MANY of the crappy times I've seen are probably due to the gas.

By comparison...my old chipped tip S4 did 14.7 with pump gas and 13.8 with 100 octane...the pump gas just couldn't cut it that day.

letS4nicate

I didn't order any of the options with my chip and use 93 octane gas.

letS4nicate

How high do I need? I'm in Boston and don't see anything higher than 94.

letS4nicate

thanks for the info. very interesting.

NASA racer

it happened to me dramatically once. I wasn't paying attention and inadvertently put REGULAR gas in my car! (this was the chipped tip).

Find an empty stretch of road...get the car well warmed up and stop on this stretch of road idling for a couple of minutes...then concentrate and watch the tach and get your butt sensors tuned and do a couple of WOT acceleration runs.

If the tach hits about 3krpm then starts hesitating (accompanied by the same feeling in your butt sensors) that's almost CERTAINLY preignition.

The BEST thing is if you know someone with a VAG tool...have them ride with you and watch the timing...under WOT it'll dramatically advance to something like 55 degrees then suddenly hit 0 then got up then hit 0...corresponding to the preignition.

It's good that it can do that...preignition is REALLY HARD on your cylinders, valves and spark plugs. The ECU is protecting your engine while asking for BETTER GAS. Since you don't have much choice in octane (short of race gas) try different stations.

Psyence

and you're running in regular "chipped" mode and not the race mode (which requires 100 octane), there is either something else wrong with the car or APR's tuning.

Try to find some 100 octane (unleaded) and use that with the regular chipped program. If that fixes it then APR has some explaining to do...