I've been reading stuff on here for a while... not sure if I've posted b4 or not??

I've searched for the answer, and come up w/ a lot of possibilities.. but first, the situation:

I've got a 95 Z28 A4 w/ 49K miles.. I only noticed the problem say 4-5K miles ago..

I'm running down the hwy at 80 or so and punch it... it will take off like a scalded ape, but then bap bap bap... hesitate, hesitate, bap bap... etc... until I let out of the gas..(pretty unnerving)

noises/feel are from the front of the car, not the exhaust (muffler) end..

Happens sometimes when I pass someone on 2 lane country road... starting at say 60, and going to 85-90?? (I'm not sure of the RPMs it starts at tho??)

Looking for some ideas where to start..

Car is pretty much stock except for TB bypass and Home Made FIPK w/ a K&N filter...and new fuel filter (old one seemed ok after removal tho).. and a couple of bottles of injector cleaner..

Oh.. The possibilities I've found via search are:
fuel pump
water in fuel
Loose ground near coil - cost: $0
ECM sensor for coolant (in front of water pump) - cost $7
plugged CAT (not sure??? only happens at WOT)
injectors plugged
vacuum leak
valve springs
knock retard... bad lifter(s)... worn lobe on cam

check ground btn battery and passenger fender...(would think the car would run bad at other times???)

LT4 chip

Thanks for any input..

John T

 

oh... just remembered..

Coil wire came off (twice) in that time... Replaced once by place I had it towed to... 2nd time by me... (not sure it was the same end of that wire tho)..

maybe something there??? (I'm not really sure what to look for tho)..

 

I would start by changing your plugs, wires, and coil.


Mine did something similiar and it ened up being the coil.

 

I had this problem, but it was down low, not WOT. Well lets think outside the box....if it happens at WOT, car requires more air/fuel...if I were you, after i verified the plugs, wires, coil was good. I would hook up a normal fuel pressure tester to the shrader valve, put it through the cowl area, close the hood and tape it to the windsheild (I did this) and give her a run, stock FP is around 43 i belive...see what she does when the rpms start climing. If that checks out fine, check for a vacume leak. You prob have the stock elbow, check underneed if its bent and not sealing around the whole throttle body. Your saying your hearing noises under the hood when your up that high, possibly it could be knock and the pcm is retarding the timing...get a cable and datamaster and give it a shot, see if u get any knock retard....let us know... O yea, and pull your maf out and clean it with eletric parts cleaner for the hell of it...