I have a 08 with roughly 30k. Over the years I've experienced a "stutter" under WOT. This only happens when I am cruising around 60-70mph in 5th or 6th gear and stomp on the accelerator. Then as boost is building, there's a stutter for 2-3 seconds. I do feel it in the pedal. It does smooth out after a bit. I've searched all the forums and only come across similar issues but with 944 and panamara vehicles.

Car runs fine otherwise. No codes no rough idle. This happened a few years back. Didn't bother me as I rarely go wot. I had a tune up at the dealer and plugs changed. It still did it. Few month ago, suffered a crack coolant pipe. As the engine was out, Indi said to change the plugs again and also changed the gas filter. He inspected the clutch and said it appeared fine. I am also good with wrenching and cleaned the two MAFs and air filter.

As the stutter/slipping is still occurring I am wondering if there are other areas which could be looked at. Thanks for any ideas

 

Sounds like you have no boost leaks - coils and plugs all sorted

I would try to hook up a fuel pressure gauge and test fuel pressure to make sure it is not falling down

I would do another pressurized boost leak test also

I would not start throwing sensors at the car unless you are looking at data logs and are seeing a problem with a sensor reading

Finally - this is a long shot but I had a car years ago that exhibited a similar problem which was very hard to track down and it turned out that it was a loose plate in the battery - on the dyno the car ran fine - as soon as the car hit any G force in acceleration on the street it would miss fire - very hard to diagnose - just swapping batteries with another car solved the problem

 

Is it stock or has a tune? 60-70mph in 5th or 6th is fairly low rpm and it might be some knock happening on tip-in which ccould be seen in a datalog. If you have access to durametric or cobb then a datalog would be helpful especially if it's a repeatable issue.

 

That's very strange because it's a electronic throttle??

 

That is very strange indeed

I would log the TPS signals you are getting when this event is occurring see if they are giving you 100% WOT

Any issues in the pedal should result in immediate limp mode

 

 

Good catch - stupid me me I saw he was changing the plugs at the stealership twice I ASSumed he had also changed / updated the coils

If he did not update the coils then that would be a very good chance of being the problem

 

Thanks all. The coils hadn't been changed with either spark plug swap. Would the engine need to be dropped in order to replace the coils which are difficult to reach?

 

Engine does NOT need to be dropped. Only about 2 coils are more difficult to get to. Look at my DIY, and you can see clear pics and instructions that will at least help you understand what is involved...Here is a Link

Good luck,
DC

 

Thanks Rock. Appreciate your help!