Hey guys,

Tried searching, seems there's about a million threads that I sorted through. This one is werid. I installed a RB header and presilencer into an Apexi N1 cat-back after that I get this problem:

The car seems like is misses under a load like in 3rd and 4th and 5th around 2-4k rpms. It vibrates really bad inside the cabin, almost like the timing is off, but then when you give it WOT it seems to almost dissapear. 1st and 2nd seem decent at WOT.

Idles fine a little high and bounces around 1-1.2k but it's always done that. This huge vibration issue just started after the exhaust install. It's not related to how loud it is, the engine actually feels like it's missfiring. I also notice a 10 degree jump in water temp (I have an aftermarket guage) when I give it like 20% throttle in 3rd around 3,000 rpms and this noise vibration kicks in. When I let off the gas the temp goes back down or if I'm at WOT the temp will not go up.

The only thing I can think of is running lean maybe because the motor is streetported with an intake, so the full exhaust is finally letting the engine breath, but at part throttle situations it's just not getting enough fuel? It seems to have the same vibs at 3-4k rpms when off the gas as well.

ANY ideas? I'll be looking at the timing and 6 ports (they are activated using an RPM switch and the S5 system, it's an entire S5 motor)

 

Anyone else have any ideas?

 

bad water seal.......maybe?

 

nah, it's fresh rebuild..

 

Check the connectors on you secondary injectors, and the secondary injectors.

The cheap plastic snaps on the secondarys on my '87 are broken, so I as soon as I feel the vibration over 3800 RPM, I know they are loose. I unplug and re-plug them and the problem goes away.

Also, check the ECU for cold solder joints.

Just because of the RPM deal, it really sounds like the secondaries.


<edit - re-read the original post>


Z

 

Hmm we'll have to check that, I can't see why they would go goofy with the exhaust install, but it's worth a shot.

 

not getting any codes? my exhaust likes to mess with my boost sensor's outputs & throws a code when I'm on it- doesn't affect performance, though...

 

Dont think so. I'll look into it. This is an N/A btw...

 

I would start to trace back over everything you did during your instillation. Did you hook connectors back up? Did you have to remove anything to get the old exhaust manifold off (like the ACV for space) and not re-install it properly. I would start to trace back over your car and look for something missing. Sounds like something is disconnected.

- Dana

 

Thats hella weird that it did that after an exhaust install.. perhaps listen to dana, thats what i was thinking as well

 

what did you disconnect to get the header on (wires and such)?

 

When was the last time you did a complete tuneup? The bouncing idle is classic of a misadjusted/bad TPS...