Ever since I got my GIAC about 2 weeks ago my car has been missing a little when I give it hard throttle. I changed my spark plugs with the NGKs that were recommended on here and gapped them to .028. I also found a little leak where my intake goes into the airbox and I fixed that. So far neither one of these has worked. The missing seems like it's getting worse and my gas mileage is like 15mpg. I know that something isn't right but I don't know what else to try. I almost have my boost guage hooked up (long story) but I can't notice any performance loss except for the missing. Any ideas? Thanks!

Oh...I have a B5 - 98.5 1.8T.

 

Are you getting a bad idle?

You may want to do a TBA (Throttle body alignment)

 

It idles very well actually. I sometimes feel just a little vibration from my snub but nothing aside from that. Thanks. Is there a write up for the TBA?

 

I think ( remember that word it THINK) you get in your car , turn the key the the ON position and wait there... it should align itself... best one to do is the VAG-COM one ofcourse

 

Oh yeah...duh...I knew that. I have a vag-com too and I think there are instructions on the ross tech site. Anyway thanks. If anyone has any other suggestions, I'm listening.

 

Coil Packs.

 

Check for fault codes.. If you have any that could cause it to run that way. You may have gotten some codes when the ecu was adapting to the new software, clear the codes do tba and see what happens... You got a better DV right at least 710n?

 

I checked codes and only had one that wasn't engine related. I have a 710n. It's also been making a much louder noise in the past week...like the turbo is spooling louder. I had a previous post about that too but I still can't figure it out. This is starting to suck [&:].

 

If you have a miss (misfire) you will get a code eventually.

Is the 710N installed with the non vacuum side in the turbo outlet hose? If not, you may be feeling a surge not a miss.

To aid in diagnosing a misfire try driving up a steep hill slowly and let your car struggle a little. 99% of the time this will make a misfire really noticeable and you won't be under alot of boost which will help you rule out a boost issue.

15 MPG is really bad, you do have a problem. I get just over 24...entirely city driving.

Does the '98 have plug wires or do the coil packs sit on top of the plugs? I can't remember when Audi got rid of the wires.

 

2nd that if you have a VAG try switching coilpacks to a different cylinder see if the misfire goes to the other cylinder then you have found your problem