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Hey Everybody,

This might be a fun one to figure out.

Last week I took a road trip with the family. Destination was about 280 miles. About 2/3 the way up, I started to notice a greater than normal turbo lag. I could be cruising at 65-75 mph, let off the throttle, apply throttle, and there would be a delay, then after a second or so with no increase in throttle, it would finally accelerate. Never noticed any visible smoke. After exiting the freeway, starting out in first gear, I noticed a definite hesitation from idle to around 1800 rpm. After 1800 or so, it runs fine. It also had a noise associated with it that I could hear happen twice before acceleration felt normal. It sounded like the Intake Flap opening and closing, but louder (obviously because I could hear it over the engine). The same type of hesitation happens in every gear. I did not have a VCDS with me, but I did have a Blue-Point Scan Tool, which I connected, and no codes showed up. Took it to a Stealership, and the tech and I took it for a test drive. He could feel the hesitation in it, so they took the car in the shop. An hour later he came and told me that they could not find anything wrong with it, except that the EGR Cooler is beginning to leak. Fortunately, they didn't charge me anything for looking at it, so that was cool.

Now, I did get a VCDS, and now I'm just trying to figure out what the problem is. However I am totally new to using it, so I need some help figuring out what to look for. I used to be able to accelerate smoothly from idle to 2000 RPM, and everything felt good. Now it just kinda lurches until 1800 or so, then it's all good from there.

I've looked through the MAF Sensor troubleshooting, and just took a peek at it, found that at idle it was averaging around 400. The VCDS said that at idle it should be in between 150-300 I think. So possibly a MAF Sensor problem?

Just today I did adjust the cam timing, VCDS showed that it was running at -2.0, so I adjusted it to +1.0. Also, I did perform a camshaft inspection, and fortunately, everything looks good there.

Almost forgot, this issue is more noticeable when the Air Conditioning is being used.

Suggestions?
 

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It does not seem like the MAF is bad although it's possible. Go for a drive and have a helper look at the values. After all, the prob is at speed not idle. Also look at boost requested and.or boost actual. This is the MAP manifold pressure.

It is possible there is a problem with the intake flap, the gears are plastic and can strip. It moves based off EGR regulation. If EGR cooler is leaking gases, do you see soot stains? It is possible that your first hunch is right and that the throttle is moving in response to unexpected EGR and MAF values due to the gases leaking out.
 

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Discussion Starter #3
I have checked to see if the intake flap is moving by using the VCDS, it seems to be operating correctly. However, there is some carbon buildup on the face of the flap. I noticed it by visual inspection when I checked the camshaft for wear. But inside the intake manifold looked ok.

My brother is coming to visit tomorrow, so I'll see if he can help me do some data logging. Is is possible that the intake flap is closing and opening during acceleration for some reason? I wouldn't think so, but I'm a bit at a loss at this point. When does the flap close? During engine shut down? Or while running under certain conditions?
 

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I believe it closes during shut down, during self calibration (if you turn the engine on and off you can hear it move, the high pitched whining sound), and moves somewhat for EGR metering. It does not shut down during running or else it would choke the engine.

I don't know the range since I've never bothed to datalog it.
 

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My car just started to have the exact same symptoms. 1800 rpm and above it is fine, anything below that rpm and the lag is terrible.
 
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