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Replaced air filter... Car stopped running right.

1K views 11 replies 6 participants last post by  PearlWhiteR/T 
#1 ·
I'm really new to this car. (3000gt vr4)
The car has 16k original miles and is bone stock. I'm going over the car just making sure fluids are fresh ect... I purchased a k&n air filter kit the cone type where you remove the oem air box. Installed it. Now the car won't run right. It sounds like a wrx, not smooth like its not firing on all cylinders. I tested the harness to the maf and everything is good. I went out and bought a new maf 3.0 gm and a translator. The car runs exactly the same which means both maf were good and my new setup will work once I find out what the real problem is.
I'm beginning to think its a coincidence it stopped working the same time I changed the air cleaner. I tried disconnecting the battery. I'm stumped. :(
 
#2 ·
What? Why not just put the oem filter back on rather than going 3 inch gm and maf if you think it was the air filter. Edit: unless your plan was to get those 2 items anyways haha

I highly doubt changing the filter caused this problem. Probably like you said, coincidence or you unplug something and forgot to put it back on.

Ive had my old sl sound like a wrx when it wasnt having all the cylinders firing. I replaced the ptu for that situation. Yours could vary. There will be more experienced members to help you when they come on and see your post.

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#3 ·
Probably an air leak in the intake system system at the plenum. It is easy to clamp things together and still have a leak where the hoses don't mate properly. A leak after the MAF will cause the computer to search around to find the right air fuel mixture and make your car die or run like crap. If you don't find a leak put the oem set-up back on to rule out other causes. I am guessing it is not a coincidence.
 
#4 ·
I'm sure its not the air filter. I thought I perhaps was too rough with the maf. It runs somewhat smooth when cold but when its at operating temperature its war rougher. I'll look into the ptu. Thanks for responding. Any help is good help!
 
#5 ·
Its not leaking between the maf and throttle body. The maf is now pretty close to the throttle body. I'm using a split y pipe to hold the 3.0 maf. The problem was the same even after only one hose clamp right behind the stock maf was removed and tightened. What engine problem could cause it to run rougher once at operating temperature?
 
#11 ·
When your car or nearly any modern car starts up it is in limp mode. Limp mode keeps it running until the car warms up and all of the inputs reach steady state. After this mode the idle will drop and the computer will start using all of the sensors to control idle, air fuel mixture, emissions etc. If any of the inputs are not within the range of normal the computer tries to adjust things until it is normal. This causes it to sound rough.

So anything like an air leak, bad sensor, clogged cat, loose wire, weak ground could mess up the computer and cause it to keep changing things. Sensors and wires usually show up as an error code. Vacuum leaks and intake links may not show up as an error code. Try disconnecting the maf sensor and see if it wont go back into limp mode.
 
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