cosmo vyss

I have a slight hestitation,splutter, whilst at lean cruise with in about the 7% to 10% throttle opening. The best way to explain it would be sailing a yatch abd the air drops from the sails ever so slightly and then returns to the air volume. Another way of describing it would be going for a walk and you are cruising along and a stiff breeze hits you for a split second then goes away. The symptoms are only at the part throttle and it seems to be highlighted more when coasting down a hill. I would even say a slight bork could be used to describe it.

The car recently has a 220 cam and patriot ls6 cnc ported heads and YT roller rockers fitted. The problem wasn't there b4 the heads,cam and YT were fitted. The car has been mafless tuned and logged and it didn't provide any real information in resolving the issue. We tried more fuel,timing etc and no matter what we did it didn't fix the problem. So the tune has been ruled out.

The hestitation/splutter is only so very slight and is not like a major misfire.

The car is a 2004 LS1 5.7. The same as your 2004 GTO i think. Cars mods are listed below.

So far in the hunt to resolve this issue I have replaced leads/plugs, 02 sensors, fuel filter. Clean throttle body and all its components.

I thinks it may be mechanical. I thought it may be valve float or something? Could having .650 valve springs be too much spring for a .580 lift cam? Could it be the spings are not seated correctly?

I really have no idea how to fix this and any help would be greatly appreciated.


Cheers
JB

220/220/112 .581 .581 Comp Cam XER Lobes
Patriot CNC ported stage 2 LS6 heads
7.425 comp push rods
yella terra 1.7 roller rockers
tba 78mm throttle body
Di Fillipo 1 5/8 headers hpc coated and high flow cats into dual 2 1/2 zorts
orsome otr

conan

iTrader: (5)

Do you run a K/N air filter? If so could be a over oil problem and the MAF has some oil on it.

cosmo vyss

The car is mafless tuned (speed density) so no maf to foul up. Yes it does have a K/N filter and its in the orsomme otr. I have checked it and there isn't to much oil on it.

Thanks for replying

JB

tatasta

iTrader: (24)

Is it an A4 with a stall?

cosmo vyss

No car is a 6 speed manual. Trying to work out what is causing this is driving me nuts.

JB

Black94Z28

iTrader: (12)

i have pretty much a bone stock 99 ta with the same problem with auto trans/no stall and its driving me nuts, i put in to fix this, k and n filter, royal purple oil change, and seafoamed the car. still doing it. idk i descreened my maf and had my throttle body ported and polished, but otherwise a stock ls1

cosmo vyss

I am surprised more ppl have not had this problem b4 with a cam or even without one. There must be a simple solution for this. Has yours been doing it for long?

I am going to re-check for vacuum leaks and then double check all the other connections.

JB

cosmo vyss

There must be someone who has had this problem and got it resolved.

JB

Black94Z28

iTrader: (12)

Mine just started maybe 2 weeks ago? its annoying, hopefully its something easily fixable

McCs WS6

iTrader: (2)

maybe the map sensor??

84ls1_transam

iTrader: (11)

Is it just me? It takes me way to long to figure out what you are trying to say when you spell stuff wrong.

cosmo vyss

Don't know. I didn't make that many mistakes ( typo's).

JB

cosmo vyss

If it was the map sensor, then wouldn't I have the problem everywhere and not just at part throttle? Is there a way to check the map sensor is functioning correctly?

dadem0n

Cam surge = tune problem.

Who tuned it?