996TT X50 running issues
Had a freind bring by his 996TT that was having some odd boost and running issues. Erratic boost now and again, and then the CEL came on. CEL was due to the MAF sensor, which I replaced and took out for a test run. A lot of times erratic boost levels are due to bad MAF sensors. Unfortunately, we had two issues here. The other major cause of boost issues are spark plugs. On my test run, the CEL started blinking after a quick run, indicating a misfire. Turns out the #4 cylinder had stored a pending code, so time for plugs. With the odometer at 25k miles, and on the original plugs, it was time. If you can get 30k out of a set of plugs on a 996TT or 997TT you are doing good, so it wasn’t surprising.
This was also a car that I modified at Imagine Auto. I had installed Bilstein PSS9’s, high flow exhaust, headers, EVOMS intake, and programming. With the K24’s from the X50 package, that was about the equivalent of our 600hp kit, which is by far my favorite and most reliable kit. There is no substitute!
First off I wanted to check a couple of common causes of boost loss. First is the diverter valves. They checked out to be ok.
Next I wanted to make sure the wastegates were operating correctly, so I manually activated them and they worked fine.
New spark plugs. I pulled the original Beru plugs out. Updated to the new heat range plugs.
Rear bumper off to get to the plugs.
And the driver’s side intercooler off.
Here you can see the end of the existing plugs, pretty well shot.
Where the coil packs sit. Note: It is highly recommended to replace the coilpacks with the updated 997TT coil packs when doing plugs, as they are prone to failure which will also cause a misfire. You might throw plugs in and put everything back together (you must to start the car), and find the misfire is still there due to the plugs. I made sure to move the coil pack from #4 to another cylinder so if we did see a misfire still, it would have moved to a different cylinder (in this case the #6 cylinder where I put it). The downside is you will drop about $400 to update the coil packs. If you are paying dealer labor rates, you don’t want to pay to go back in there to replace coil packs.
Got everything back together and she ran like a champ. It was hard to put back in the garage.