Need some help. I have a 2003 Stype 6cyl. with 74K mi on it. To be honest I was late for work one morning when this problem occured. I had pushed the car and was doing between 100-110mph for about a 20mi stretch of highway, never noticed a problem until I arrived at work and the engine light pops up and restricted performance message appears. I have had the codes read at autozone. I got a p0171 message. The only thing I am noticing is that the car idles rough but not terrible, and it will hesitate if I am getting on the highway and punch the accelerator. If I back off and gradually increase the pressure on the pedal it accelerates just fine.
I have cleaned out the MAF sensor area, disconnected the MAF and reconnected. Still no change.

Any ideas as to the potential causes, My thoughts have been that it may be a misfire, so plugs, wires coils was going to be one of the replacements for it, but i found it weird that the symptom is only present with hard acceleration and minor idling changes.

Any info is greatly appreciated.


Matt

 

I don't think its a K&N filter, I just purchased in Feb of this year and was told that they don't require any maintenance for 5K I am approaching this now, so I can certainly replace the filter and replace the MAF 80 bucks and see what that does. Any suggestion on cleaning agent?

 

So in my line of work(medicine) there is nothing that compares to an old fashioned physical exam. No matter what the problem is, no amount of technology can replace a set of human senses like the ears and eyes.
I say this because after going and buying a new MAF for my S Type, I hear a loud hissing from under hood near the throttle body. Of course this is after I had replaced the sensor. There I found a connecting tube from the throttle body to another airtube leading toward the firewall that had a large hole in it. I plug it and magically, my car begins to idle fine. Trouble is that by the time I found it, it was 1030 at night and all dealers are closed. Luckily I found some hi temp fiberglass muffler repair tape. Couple of hose clamps and the tape and it is running fine till I can get to the dealer to buy the replacement piece. I am sure they will charge me 75 bucks for the hose.

 

At 60,000 miles my idle went rough, engine light on and when I accelerate it "chugs". A mechanic I trust did a vacuum check and I have two leaks, which is causing a lean burn fuel issue, hence the poor idle and acceleration. Regretfully the vacuum leak is in a lower gasket and the that costs some money to fix -- $500. Have someone do a vacuum check. There's some good info online about how to diagnose.