hesitation in 1st

[Jovan Ceklaj]

This problem has me kinda stumped.  When I'm running higher boost (16+) my car starts bucking at around 4000 rpm....here's the kicker, it's only in 1st gear.  If I run lower boost it doesn't happen; if I'm in other gears, it doesn't happen.  It's pretty frustrating.  Also, when I launch, it just falls flat on it's face.  

I figured it was plug wires, so I replaced them with some NGKs and no dice. Timing gets pulled, so I also figured my fuel curves were wrong, but then it wouldn't only happen in first gear.

Stumped :? .  Suggestions?

[Andrew Steele]

you replaced the wires, did you look at the plugs?

It's odd that it only happens in 1st gear... might be MAF?  1st gear there's not much air cirulation (fan wash) from outside elements.  This is the first time you're running all your new shit with warm(er) temp's.  Does the care shit itself in first when she's cold? hot? both?

[Vlad Busta]

Could it be that the ferosity of your launch causing the knock sensor to pick up something other than real knock?

Try tightening up your knock sensor to see if that helps.  Or maybe the black goo is leaking out of it indicating that you might need a new one.

I only used to get knock in first gear when I used the studder box.  But now I have knock in all gears above 4000 RPM at WOT.  Hope to fix that on the weekend though.

Later, Vlad.

[Jovan Ceklaj]

Andrew, I didn't check the plugs, I guess I'll get on that first.  It couldn't be fanwash, because my MAF is tucked way in where the stock UICP is, plus that doesn't make much sense to happen ALL the time in 1st .

Vlad, it happens whether I launch or not, even from a roll.  I get knock when I use the studder box as well, but it's only when it's at the line.  Wouldn't tightening the knock sensor make the thing more sensitive though?

[Vlad Busta]

Sorry about that Jovan, yeah loosen it if it is on there really tight.  But do check if you feel any black goo leaking out of it.

[John Hartman]

my thoughts, for what they are worth, are this.

1st gear has alot less load on the system.  I don't see full boost in 1st gear.  

Or, and I just had this thought.  In 1st, our cars really transfer alot of weight to the rear of the car, and rather harshly, especially on a stutterbox launch.  So, my thought is what about a connection somewhere (fuel, air or electrical) that is being loosened up by the dramatic motion of a 1st gear romp?

again, just some thoughts, but being that YOU are stumped, I figure all the conventional stuff has been explored, and it was time to think outside the bun.

[Mike Meron]

lifter tick?

[Kimyee Lai]

Check your plugs...also, does it happen repeatedly in 1st, ie. back to back 1st gear runs?  Does it go away if you lift slightly?  The only thing I could think of is that you might get more of a boost spike in 1st...

[Jovan Ceklaj]

thanks for all the ideas guys.

Kimyee, it happens consistently.  EVERY pull ends up bucking around and yeah, it stops if I lift off of it but that's not fast  :laugh:  

John, the only reason why I don't think it could be anything loosening is because it only happens in 1st.  I don't forsee it loosening and retightening in 2nd

Mike, I guess we'll have to do something about that, won't we? :wink:

[John Hartman]

what I mean is, a connection, pipe or line of some sort gets flexed causing a lost connection/air leak etc for that brief moment when the car is really stressed, and in the other gears, it doesnt hit as hard.  Once you shift, the part goes back to the way it was.

but again, its just a thought.

[Marty van den Bosch]

Acts like MAF over run but in one gear...
Odd how it is just in first.

To eliminate anything MAF related, you can swing by and we can toss mine on your car if you like - it has been opened alot with John's help and runs my evo at 15psi (high flow)

We could log with my laptop too

[John Hartman]

Jovan is running a 2g maf.

[Marty van den Bosch]

Jovan is running a 2g maf.

DOH !  :oops:

[Jack Palmer]

i wonder if you are getting the same problem as me..i get it in all 3 gears though... and i have no idea or any experience to diagnosis it. but if you find out what it is please post it cause i'd be willing to look into it on mine.

[Matt Demick]

Me too    don't know what it is. what does ur A/F gauge say?