kibZ28

got my car dynoed today , everytime we made a pull it kept leaning out very badly. we couldnt figure out what it is and still havent. it always spikes at the same rpm too. because it start out pulling like he wanted then just all of a sudden goes lean and the car sputters and hesitates. the car will hold idle too high for a couple of seconds then comes back down. we spent about 2 hours on the dyno and came up with nothing. it happens around the 4000rpm mark. any suggestions would b helpful.

JRC2000SS

what size injectors do you have? what mods have been done to the car? a4 or m6?

kibZ28

stock injectors. i have slp underdrive, slp flowpac, slp maf, 80mm TB, flowmaster catback, M6 and diablosport predator

we used HP on the dyno. we used both but final tune will b with HP
the first pull the car did 300 exactly with being really lean then we coulndt go anywhere from there but backwards
checked alll wiring grounds etc.
i'm goin to do the plugs and fuel filter this weekend cuz i go back friday

matt3383

iTrader: (3)

could there be something restricting the fuel? I dont know if a partially clogged filter or a weak pump could cause this or not. Just a thought

massls1guy

iTrader: (9)

I agree with Matt3383.

Have you scanned it for any codes?

There also have been a few posts about MAFs going bad. With your current mods a bigger MAF won't give any gains anyway so I would put the stock MAF back on and see if it helps.

WS6FirebirdTA00

iTrader: (33)

It is the MAF, ditch that POS and put the stocker back on.

You NEED to retune after mods like that (Predator won't cut it). Running lean can cause knock, knock can cause the motor to go.

Ryne @ CMS

iTrader: (10)

i agree

vaticano

iTrader: (8)

Ditch the MAF

twelver12

iTrader: (3)

definately the MAF aftermarket MAFs arent worth a crap i dont care how much you payed for it it doesn work and thats all your car is going to do every time you run it, i made the same mistake and so have thousands upon thousands of others so your not alone, get ported ends for it or sumthin just dont ever use the aftermarket electronics

twelver12

iTrader: (3)

in fact i almost guarantee if you put the stock MAF back on it you can tune another twenty hp out of it, my tuner does it quite often he has a drawer of MAFs off of customers vettes they get all bent out of shape when he tells them to ditch it but dont have a problem with the idea after the numbers back him up, i have the slp also its sittin in its box in my room i bought it and learned about it the day after i had ordered it and never installed it

Slowhawk

iTrader: (12)

I've seen alot of bad SLP MAF's do exactly what you describe. It's easy to see if your scanning MAF frequency.

WS6FirebirdTA00

iTrader: (33)

I retuned a car with the SLP MAF which they say does not need tuning, the car was 18% lean around 500 RPM. It was ridiculous.

Once the frequency goes about 5000 Hz the car starts to lean out considerably, which would mean most high load and all WOT fueling will be very lean.

kibZ28

thanks alot guys tha'ts also what my dyno guy said and i've heard that before i'm going to change it today anyway thanks again
changed stock MAF and does the same thing????

9sec93

iTrader: (67)

my car is doing the same exact thing and i have a stock maf from an LT1 car. just got it running so i havent found what is causing it yet. if i figure it out i will post it up.

twelver12

iTrader: (3)

was it tuned with the stock MAF again?