Slight Jerk Around 65mph

[SA56]

I just installed the RTR front grille on my GT and now it has a slight jerk to it when I'm on the freeway. The car ran great before the grille install. It still idles fine and drives fine on city streets. No CEL's but I have noticed the AFR bouncing between 12 and 17 when the jerk is occurring. Does this have anything to do with the new grille or is something else wrong?

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[clicklogical]

Is your grill blocking your intake in any way?

 

[SA56]

Is your grill blocking your intake in any way?

Definitely not blocking the intake in any way. I'm starting to wonder if the car is just trying to get used to the massive amount of air being pulled in now due to the larger opening on the grille. I watched the vacuum gauge on the freeway today and noticed the needle constantly going back and forth between 10 to 15in-hg and even sometimes as much as 20in-hg. Thats when the jerk is really noticeable. By the way, this is also with cruise control set at 65mph on level ground. It doesn't seem to do it when cruising at 35mph though. I emailed Steeda about it to see if they can send me a new tune that would fix the problem. Hopefully they have good news!

 

[GT Pony]

Did you mess around with the intake system at all ... removed and reinstalled as part of the grill mod? Sounds like a possible intermittent vacuum leak.

 

[SA56]

Did you mess around with the intake system at all ... removed and reinstalled as part of the grill mod? Sounds like a possible intermittent vacuum leak.

I did not touch any part of the intake system when I removed the front bumper. I gave the engine bay a quick once-over today and found nothing loose or not connected. I'll try to find some time to look at it again tomorrow if possible.

 

[moffetts]

Do you become a huge jerk at like 120?

 

[clicklogical]

Definitely not blocking the intake in any way. I'm starting to wonder if the car is just trying to get used to the massive amount of air being pulled in now due to the larger opening on the grille. I watched the vacuum gauge on the freeway today and noticed the needle constantly going back and forth between 10 to 15in-hg and even sometimes as much as 20in-hg. Thats when the jerk is really noticeable. By the way, this is also with cruise control set at 65mph on level ground. It doesn't seem to do it when cruising at 35mph though. I emailed Steeda about it to see if they can send me a new tune that would fix the problem. Hopefully they have good news!

If the new grill is allowing for more volume of air, then yes, you probably need your tune adjusted.

 

[SA56]

If the new grill is allowing for more volume of air, then yes, you probably need your tune adjusted.

I got in touch with Matt from Steeda and he seems to think there is turbulence being built up in the airbox and around the MAF sensor. His suggestion is to block off the intake from the grille to fix the problem. Any ideas on how to do this in an inconspicuous way?? Also, it sounds like this issue only comes up when you pair the RTR Grille with the Roush Cold Air Intake w/o Venturi Tube w/ 91+ Octane Tune. I can't find anyone else talking about this issue anywhere on the web. Any suggestions would be very much appreciated!

 

[keltymd]

Maybe put some screen at the inlet. on a lot of older cars just before the MAF they have a section of screen to clean up the flow a bit you could put some just inside the inlet before the filter box inside the tube.

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