Odd Rev Hang Post CAI Install

[JWalk]

Hello everyone, wondering if someone may be able to assist.

A couple of days ago I installed the Injen Evolution Cold Air Intake and did a full sound tube delete on my manual GT. During installation I disconnected the battery and reconnected it when all was said and done. I started the car and let it idle for a few minutes to allow the computer to sort out the new set up and to get the exhaust to stop burbling. Since this installation I have noticed that the car is driving very differently. My revs are hanging and the car doesn't seem to decelerate, or engine brake, when I press in the clutch. When upshifting, the revs stay high and don't fall like they used to, causing my shifts to either be delayed or to be very jumpy. The same happens when I downshift and rev match, the revs hang too high and the shifts end up rough.

I have installed CAIs on other cars and am used to them barely affecting performance, and certainly not in a negative way. I checked to see if there was a vacuum leak and couldn't find any sign that there was one (vacuum holds at about 16.9 at idle). Does anyone have an idea what could be going on? Do I need to get the car to relearn idle somehow? Thank you in advance for any assistance you can offer!

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[markmurfie]

Dumb question maybe... Did you plug the hole in the intake tube the sound tube came out of? If so how, was it air tight?

another possible dumb one... you reconnect the MAF sensor?

 

[JWalk]

Dumb question maybe... Did you plug the hole in the intake tube the sound tube came out of? If so how, was it air tight?

another possible dumb one... you reconnect the MAF sensor?

Haha after the amount that I've scratched my head on this I don't that there are any dumb questions. The Injen doesn't have a hole for the sound tube, it comes with a cap to plug the remaining tube connected to the firewall, but I removed that too. And yep, MAF has been reconnected and double checked.

 

[markmurfie]

Can you post pictures of different angles of the connection at the TB?

 

[SVT Wylde]

That's very odd. I didn't have any issues like that when I installed mine. The engine idled a little rough for the first few minutes after initial start up but then she smoothed right out. I did not disconnect the battery but that shouldn't make a huge difference.

I would disconnect the battery, then turn on the headlights momentarily to drain any residual power from the ECU. While the battery is disconnected, double check all of your connections. Especially the one at the throttle body and at the inlet to the cold air box making sure there are no gaps. Check all of your connections on the intake tube as well. Take them off and make sure they click when they go back into place. Reconnect the battery and go for a drive and see what happens.

 

[JWalk]

I rechecked the connections and everything seems ok. The crank case line doesn't seem to click into place very well and one of my vacuum line retainer clips broke but I have it zip tied down pretty well until I can pick up a new one. The crank case line lightly clicks on but you can pull it off without too much force, but it seems to be seated pretty well. Going out for a test drive to report back. See below for pictures of connection at throttle body.

 

[JWalk]

So after a test drive my car still drives strangely. The rpms either don't drop when I press in the clutch or they drop extremely slowly. When engaged in 3rd gear pulling into a parking lot I took my foot off the gas pedal and the car maintained rpms and helped about 20 mph not dropping until I pressed in the clutch and shifted out of gear. I'm not sure what else to check.

 

[SVT Wylde]

Have you tried resetting the ECU for a second time?

 

[JWalk]

Have you tried resetting the ECU for a second time?

Yea, I disconnected the battery again while rechecking the connections. I also tried spraying some starter fluid around the vacuum connectors to test for a leak to no avail.

 

[markmurfie]

This is a no tune required intake. Do you have a custom tune on your car?

 

[JWalk]

This is a no tune required intake. Do you have a custom tune on your car?

Nope I'm not running any tune. All stock except the cai and exhaust.

 

[SVT Wylde]

I would remove the Injen and go back go the stock box and see what happens. You might see something wrong in the process or narrow it down to a problem with the intake. That rev hang would drive me crazy.

Did you buy the intake new with the no tune insert installed?

 

[350sexZ]

I had a very similar problem. It turned out to be a bad maf. Mine didn't happen right away tho it was a couple months down the road. Only because my filter came off and crap messed up the sensor. Try stock intake if it still does it. I'd change maf

 

[JWalk]

Thank you everyone for the help so far. I checked the MAF today and cleaned it, also checked again for leaks with a second set of eyes/ears. Revs seem a little better afterwards but still hangs up a bit. I'm probably going to drive it for a few more days and see if it shapes up. Otherwise I will probably go back to the stock box and see if there is any change. Pretty frustrating so far, hopefully it sorts itself out.

 

[Keith_PDX]

You've failed to answer the question regarding the insert and the no-tune version. Is it a no-tune with maf insert?

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